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Review and prospect of hidden failure: protection system and security and stability control system

Review and prospect of hidden failure: protection system and security and stability control system J. Mod. Power Syst. Clean Energy (2019) 7(6):1735–1743 DOI 10.1007/s40565-015-0128-9 Review and prospect of hidden failure: protection system and security and stability control system 1 1 1 2 3 Lili ZHAO , Xueming LI , Ming NI , Tianyu LI , Yameng CHENG Abstract With the construction of the ‘‘3-level, 3-vertical- Keywords Relay protection, Security and stability line, and 1-circle’’ power backbone in China, it’s stricter and control device, Hidden failure, Coordination stricter on relay protection system and security and stability control system (SSCS) for reliable power transmission. Lots of blackouts in the world had happened, one main reason for 1 Introduction which is the hidden failures of relay protection system or SSCS. Much work had been done about the hidden failure of In China, a ‘‘3-level, 3-vertical-line, and 1-circle’’ power relay protection, including classification, probability model, backbone will be formed in the future, where the ultra-high- analysis methods of effects on power grid, and monitoring voltage (UHV) AC and DC transmission projects have been measures, which was summarized in the paper. The opera- built, to help transferring power energy from large-scale tion experiences of SSCS indicated that there might be energy bases to the major load centers. In order to ensure the hidden failures in five links of the security and stability security and reliability of power transmission, the protection control device (SSCD), e.g. measuring, control strategy, system and security and stability control system (SSCS) must setting, communication and voting pattern. In addition, the be highly reliable, being its strong backing. Committed to coordination hidden failure among relay protection system, reducing the failure losses as best as possible by taking dif- SSCS, and power plant’s parameters related to the power ferent control measures, the antecessors of China’s elec- grid was pointed out for more attention. In the future, tricity proposed the concept of three-defense lines with relay amounts of work will be expected to be conducted on hidden protection system and SSCS respectively lying in the first failure: model building, assessment methods, application of and second defense lines (See Fig. 1 [1]). So the reliability of research achievements, operation management of secondary the relay protection system and the SSCS plays an important equipment, and coordination problem between the relay role in the stability control of power system. However, protection system and the SSCS. because of technology limitations, miss-operations, weak CrossCheck date: 4 February 2015 management system of maintenance etc., there can be defects, great or minor, in relay protection and security and Received: 3 December 2014 / Accepted: 16 April 2015 / Published stability control device (SSCD), leading to hidden failures online: 4 June 2015 The Author(s) 2015. This article is published with open access at and security risks if not found in time. Springerlink.com Hidden failures are caused by the device’s defects or & Lili ZHAO human factors, bound to weakening the device’s reliability. zhaolili@sgepri.sgcc.com.cn They produce no immediate action on the device and power system in a normal operating environment, and only Nari Technology Development Limited Company, Nanjing 211106, Jiangsu, China possibly are triggered in an abnormal pressure state, e.g. grounded short-circuit fault, load-flow reversion and great Nanjing University of Posts and Telecommunications, Nanjing 210046, Jiangsu, China drop of voltage or a harsh operating environment. Obviously hidden failures are covert, once triggered, Jiangsu Electric Power Research Institute, Nanjing 210093, leading the improper operation of relay protection and Jiangsu, China 123 1736 Lili ZHAO et al. Recovery secondary equipment, hoping to provide some reference for Black start control the future research in this field. Remove Operate Fault Lose Large-scale faulty + + + normally occurs stability blackout component 2 Analysis of relay-protection hidden failures Out-of-step separation, Automatical Stability control Action of relay Frequency emergency preventative generator tripping protection control, 2.1 Classification of protection hidden failures or load shedding control or Voltage emergency (the first line (the second line adjustment by of defense) control dispatch center of defense) (the third line of defense) Since the concept of relay-protection hidden failures [5] was put forward for the first time in 1994, the influence of Fig. 1 The stability control and the three-defense lines power system relay-protection hidden failures with its research has been in China paid more and more attention. The protection hidden fail- ures are classified in different ways, which are generally based on the causes of the hidden failures [6, 7], protection SSCD, which possibly cause cascading failure of power element functionality defect (PEFD) [8], and the dynamic system with huge losses of load and power supply, even and static characteristics of relay protection devices [9]. blackouts, and further bring about a great loss of the The detail of the three ways is as follows: national economy. Although hidden failures are uncovered by some other events in a quite low probability, they might 1) Classification based on the causes of the hidden break through the first and second defense lines of China’s failures. It divides hidden failures into five ones: a. power system once triggered, which can’t be ignored for hidden failures caused by hardware faults, such as the profound impact on power grids and society. damages or defects of device elements; b. hidden failures caused by system errors of protection soft- Hidden failures of relay protection caused many black- outs of power systems, i.e. the WSCC blackout in 1994 [2], ware, such as logic errors of protection principle and the ‘‘814’’ Blackout in America and Canada in 2003, the version errors of software; c. hidden failures caused by large-scale power failure in Brazil in 2011 [3], and the protection setting values, such as improper settings power failure in Indonesia in 2012. Blackout accidents and man-made setting errors; d. hidden failures caused resulted from hidden failures of SSCD have also happened by natural environment, like bad climatic conditions or many a time, such as the two WSCC blackouts in 1996 [2] storm disasters; e. hidden failures caused by improper and the large-scale power failure in 2009 [4]. What’s more, manual operation or ill maintenance. the ‘‘71’’ accident of Central China (Henan) Power Grid in 2) Classification based on PEFD. It consists of hidden 2006 is evoked by hidden failures of both relay protection failures caused by hardware faults (PEFD-A) and by devices and security control devices. human errors and protection settings (PEFD-B). Study of hidden failure holds great significance for 3) Classification based on the dynamic and static charac- ensuring security and stability of power grid, people’s teristics of relay protection devices. It divides hidden lives, and national development, including the mechanism failures of protection devices into dynamic hidden of hidden failure’s impact on power systems and the hidden failures and static hidden failures. The static character- failure monitoring approaches. Large amounts of studies istic of protection devices is that if the protection device and discussions about protection hidden failure have been doesn’t fulfill the starting conditions, it will only do done at home and abroad. This paper reviews these work electric-parameter measurement and calculation or do and summarizes issues related with protection hidden data collection and start judgment; while the logic failures: classification methods, probability model, research comparison and tripping output are not in consideration, methods and monitoring measures. The possible hidden- mainly with the hardware devices, mutual-inductor failure risks of SSCD are presented based on the knowl- measurement circuit, connecting cables, terminals, pre- edge of the devices’ characteristics and operating experi- process circuit of relay protection, sampling and sam- ence. It also briefly analyzes the influence of hidden pling-value calculation. The hidden failures in these failures caused by cooperation problem among relay pro- links are called static hidden failures. Dynamic charac- tections, SSCSs, and parameters of power plants in oper- teristic of protection is that when the protection meets ation related to the power grid. Last but not least, it with the starting conditions, the fault parameters will be proposes prospects on hidden-failure research, including measured and logic comparison will be done, mainly modeling, risk evaluation methods, research result appli- with links of measurement, calculation, and blocking- cation, the coordination problem hiding between the relay signal inspection. The hidden failures in these links are protection and the SSCS, and operation management of called dynamic hidden failures. 123 Review and prospect of hidden failure: protection system and security and stability control… 1737 Although the three classification methods of hidden operation mode at that time. Throughout all processes of failures appear different, all of them think over the clas- protection hidden failure modeling, there are two ideas. sification from hardware and software, and then classified One which is often used is to work out hidden failure hidden failures by considering detailed factors like human probability of relay protection devices and how it changes behaviors and design defects of devices. with the electric parameters (voltage, current, and line power flow) by taking the equipment’s software/hardware 2.2 Probability models of hidden failures of relay and control scheme into account. The other one is to work protection system out hidden failure probability by considering the relay protection as a whole. These modeling processes only The probability of relay-protection hidden failure is the reflect the consequences of human negligence or errors, first problem to be solved during the research, which can be production quality of devices, equipment management & solved now mainly by probability statistical method and maintenance, etc., but don’t embody how these factors probability model method. The probability value obtained affect protection hidden failure probability. The problem is by probability statistical method is a fixed value, which can worth thinking over, and if solved will help reduce human be used to evaluate the cascading failure risk caused by negligence or errors, perfect the devices, and improve the hidden failures, but can’t reflect the change of hidden coordination between devices and power grid. failure probability value along with the real-time operating- condition such as line power flow, bus voltage, and system 2.3 Effects and research methods of hidden failures frequency. By the probability model method, the hidden failure probability of a particular protection system or a The relay protection’s failure actions or malfunctions particular protection scheme can be worked out under caused by its hidden failures weaken the reliability of different operating conditions. So far, 4 probability models protection system. When the power grid is abnormal, the of relay protection hidden failure have been proposed: triggering of relay-protection hidden failures may result in hidden failure probability model of zone III transmission- N-2 events [16], even cascading failures, which increases line distance protection [10, 11], hidden failure probability the insecurity and instability, bringing load isolation, model of over-current protection [12], hidden failure power-supply isolation, out-of-step separation and even probability model of line protection considered over-flow overall instability. [13], and hidden failure probability model of generator Lots of risk assessment methods have been proposed for protection considered terminal-voltage [14]. The hidden quantifying the influence severity of relay-protection hid- failure probability value of zone III transmission-line dis- den failures on power system. Risk assessment methods which are the most used in assessing reliability are devel- tance protection is decided by the impedance seen by protection devices; the hidden failure probability of over- oped and improved on the basis of certainty analysis current protection devices is related to the magnitude of methods and probabilistic analysis methods [17]. So they line current; the hidden failure probability of line protec- synthesize technical economics and quantitative eco- tion considered over-flow is related to the magnitude of nomics. The risk assessment methods analyze relay pro- active line-load-flow; the hidden failure probability of tection reliability in terms of risk, mainly by Markov, event generator protection considered terminal-voltage is related tree and fault tree. The output risk indicators of device to the magnitude of generator’s terminal voltage. The [15] level separately are failure rate and availability of a device, catalogued protection’s failure to operation and second- risks of load isolation & power-supply isolation, and the type mal-operation as hidden failures in consideration of margin of interface transmission. In addition, the risk the types of relay protection failures. Taking the proba- indicators of primary-system level that is security & sta- bility obtained from the above hidden-failure probability bility indicators can also be obtained by event tree analysis models as the probability of protection’s second-type mal- method. The risk indicators of primary-system level operation, a general hidden failure probability model is including grid separation risk and integrated risk can be built on the basis of Markov, in which the protection sys- obtained by fault tree analysis method. tem involves protective devices with associated circuit The three analysis methods, i.e. Markov, event tree and breakers. fault tree, have different characteristics of application in Among the factors that result in hidden failures of relay the effect analysis of relay-protection hidden failures on protection equipment, there is no lack of human negligence power grid. Compared with the probability method, Mar- or errors, production quality of devices, devices manage- kov is more applicable to the relay protection system that is ment & maintenance, etc. These factors usually have a repairable system [18, 19]. Currently, the probabilistic effects on the fitness of software/hardware system and statistical method is often used to build hidden failure control scheme of the secondary equipment to the grid probability models of relay-protection, in terms of the state 123 1738 Lili ZHAO et al. change of power system, like load-flow transfer. But it is constant. Submission of a manuscript implies: that the not as accurate as Markov method in assessing the hidden work described has not been published before; that it is not failure probability of protection. However, Markov method under consideration for publication anywhere else; that its needs lots of samples to ensure the accuracy of Markov, publication has been approved by all co-authors, if any, as which must bear a heavy computation burden. In Markov well as by the responsible authorities—tacitly or explic- method, the event’s current state depends only on the last itly—at the institute where the work has been carried out. state, while event tree obeying the time sequence starts from the primary event, reasons out possible outcomes and 2.4 Monitoring method of hidden failures identify the hazard source. For an example, based on the analysis of the hidden failure triggering conditions of relay- In recent years, many researches on protection-system protection by event tree, it starts from a certain initial event hidden failure have been done, i.e. researches on protection and reason out the malfunction probability model of system reliability modeling and influence of protection associated relay-protection under different contingences devices on Power System’s reliability. Research on the [20]. However, the event tree requires confirming object monitoring and control of protection hidden failure is also firstly, which demands thorough knowledge of the system involved [7], which is aimed at taking precautionary structure, occurrence & probability of relevant accidents measures against hidden failures to avoid serious cascading and the severity of consequences caused by accidents. of power system. A technology embodiment for the mon- Similar to the analysis by event tree, the analysis by fault itoring and control system against relay-protection hidden tree is intuitively, straightforward, clear and logical. E.g., failures [27] was proposed by AG Phadke and JS Thorp of the dynamic process of the cascading resulted from relay- Virginia Tech in 1995, but it was not applied in industry protection hidden failures is analyzed by fault tree so as to since the technology was not mature enough. In 2004, a find out the line or generator protection ‘‘pre-malfunction monitoring system was developed against hidden failures set’’ [21] (the ‘‘pre-malfunction set’’ means the set of line by the wide-area protection system, however was of poor or generator protection associated with the removed reliability and the cost was high [28]. The detection of lines). hidden failures depends on the running state of Power Aside by the above methods, certainty method, proba- System [29]. The off-line detection which is widely used bility method and risk method, protection reliability is now can’t meet with the requirements, high security, high analyzed by other methods such as GO method [22] and the reliability and real time, and is unable to do an exhaustive importance analysis on relay-protection hidden failures detection for hidden failures. Therefore, new methods based on risk assessment [23]. The importance analysis on should be worked out for on-line detection. That off-line setting value is improper is main contrib- relay-protection hidden failures is derived from the element importance analysis which is an important approach for utor to hidden defects of protection settings. The off-line system reliability analysis. Its purpose is to identify the key setting values are mostly set and modified manually, thus elements that have crucial effect on system’s reliability so easily result in security risks. Particularly, off-line settings as to objectively increase the overall reliability of the if have not been modified for a long time, will deteriorated system at low cost [24]. the performance of devices, and may be not adapt to the The influence of protection hidden failures on system real-time operation mode of power grid. One of the solu- can also be analyzed by simulation. Monte Carlo [25] and tions to get over off-line setting defects is on-line setting Importance Sampling [26] are important tools for simula- [30] for protection devices. An online intelligent early tion analysis. Monte Carlo, the simulation method in warning system of protective relaying [31] was developed probability method, take advantage of the comprehensive and applied to the power grid of some domestic province. statistical data of power system state, to calculate the Based on the warning system Scholars at home checked reliability indicators of a certain period of time, and can’t setting hidden defects of protection online, and assessed the be fit to analyzing the frequency and probability of events risk brought by these defects for the weak links of pro- that do not often occur. Based on whether the simulation tection hidden failures. The early warning system sent periods are a sequence, the Monte Carlo method can be signals about these weak links and associated measures divided into Monte Carlo method with time sequence and could be taken timely for the security of power grid. Monte Carlo method without time sequence. The impor- The hidden failures of protection system are proved to be tance sampling method does not use the primary proba- the key contributors to the wide-area disturbance [32]. bility of hidden failure model; instead, in order to increase Identifying the key lines affected by hidden failures [33] the probability of cascading, it does simulation with a and taking associated measures can inhibit cascading probability value greater than the primary probability under development and reduce blackouts. Thus, some researches the premise that the mean of probability value remains built pre-malfunction sets of lines where protection hidden 123 Review and prospect of hidden failure: protection system and security and stability control… 1739 failures might be triggered. But these pre-malfunction sets 2) Strategy are only sets of lines connected with the primary fault line A SSCD is the implementation medium of various and the researches didn’t analyze the cause of line protec- control measures. The ways of carrying out its control tion malfunctions systematically from the point of the strategies usually include off-line decision and on-line pre-decision. If control strategies cannot fit the real- essence of hidden failures, which lead to the obtained pre- malfunction sets incomplete. This problem has got solved in time operation mode of power grid, malfunction of the SSCS including over-shedding, under-shedding and [34] that firstly put the protection hidden failures as a part of contingencies constituted by different accidents, secondly mal-shedding will take place, further expanding the accidents in power grid [38]. exposed the hidden risks of cascading during selecting N–k contingencies, and last found out vulnerable lines and the 3) Setting key protection. The hidden failure monitoring of other The correctness of setting in device determines the equipment like control circuit in high voltage circuit efficiency of device and whether the monitored object breaker in protection system is to check hidden failures by can make right judgment about the type of faults as reverse point-by-point investigation method [35]. fast as faults occur. Unreasonable or incorrect settings impair the security of the SSCD and the stability of power system [39]. For instance, in the ‘‘71’’ Accident of Central China Power Grid, the mismatching 3 Analysis of hidden failures of SSCD between a setting and the real-time operation mode of power grid led to action failure of the security & SSCDs widely used in China are the second defensive stability control devices in Songshan substation and line [36] which is aimed at ensuring security, stability and finally expended the accident. reliability of power system. The SSCDs of multiple power 4) Communication plants or substations communicate with each other, con- Generally, how to configure a SSCD in the power grid stituting a SSCS with a hierarchical classification of control should take control range and functions to be achieved scheme like Electric Power Alarming and Coordinated of the device and power system planning into consid- Control System (EACCS). The EACCS in Jiangsu Pro- eration. In order to achieve large-scale stability vince of China has a typical control structure of 4-hierar- control, SSCDs of multiple plants are usually config- chy, dispatch center station-control station—control ured as a SSCS via communication channel and substation—implementation station from top to bottom. communication interface equipment, and work coop- Since the SSCS takes charge of a regional power grid, once eratively, to achieve the regional security and stability it goes wrong, enormous losses will take place, which has control. However, in the communication progress been proved by the ‘‘730’’ Load-Shedding Fault in between SSCDs, the reception and execution of Zengcheng in Guangdong province of China in 2004 and commands in the SSCS are affected by error codes, the ‘‘71’’ Accident of Central China Power Grid in 2009. unstable transmission in communication channel, not- The losses are so huge that it cannot wait to conduct in-time information transfer. It brings about that the researches on the hidden failures in SSCDs and associated strategy cannot be executed at right time or security & effects on the power grid. control devices cannot act properly, resulting in more According to the accident experiences in power grids serious accidents. On July 30, 2004, the security and and the structure of the SSCS, the hidden failures of the stability control subsystem of Zengcheng, Guangdong SSCD are described in five links: measuring, strategy, mal-operated with 714 MW load shedding for the setting, communication, and voting pattern. reason that communication codes were error and there 1) Measuring were loopholes in the communication module and the CT and PT are used for the measuring of electric verification links. parameters by the SSCD. The break-line accidents of 5) Voting pattern PT are easy to take place and remain hidden until Redundancy design is introduced into enhance the triggered by other events; the remaining current of CT security and reliability of the SSCS. The voting pattern second winding can influence the judgment of SSCD determines the characteristics of the malfunction [37]. In addition, that the chip of measuring circuit prevention of a SSCS, so in the process of redundancy goes wrong will influence the accurate of measured design it needs to consider the type of voting pattern of values which reflect electric information, easily result- control outlet logic in a SSCS. There are mainly three ing in incorrect judgment and malfunction of the types of voting patterns, e.g. ‘‘2 out of 3’’ pattern, ‘‘2 SSCD. out of 2’’ pattern, and ‘‘1 out of 2’’ pattern. 123 1740 Lili ZHAO et al. In the ‘‘2 out of 3’’ pattern, only when at least two of differential protection (BDP) block each other. The hidden three sets of SSCDs act can the outlet action be permitted. defect remains undetected by the occurrence of a single This will prevent malfunctions of the SSCS that are caused simple fault, but when complicated failures occur and by hidden failures in any one of the three sets of SSCDs. cannot be identified by the judgment circuit of the relay But this pattern is the least adopted because of high cost, protection for the coordination hidden defect between wiring complexity, operation and maintenance difficulty, BCASP and BDP [42], serious failures may follow. etc. In the ‘‘2 out of 2’’ pattern, the outlets of the two sets of 4.2 Coordination hidden failures between SSCSs SCCDs are connected serially, so the outlet tripping can be achieved only when both of the two sets of devices act. The conventional SSCS takes charge of the stability of a This will effectively prevent malfunctions of the system regional power grid, usually restricting the control range in caused by hidden failures in either one of the two sets and a provincial grid. Distributed in a regional power grid, the ensure the reliability of the system. However, if neither of early SSCS made decisions independently and took the 2 sets acts for their hidden failures, tripping pulse will appropriate measures against failures listed in the control not be transferred to the ultimate executive and then action strategy. With the development of EHV AC/DC transmis- failures of the SSCS will come into being. sion network, strong electrical connection will be estab- The ‘‘1 out of 2’’ pattern is the most adopted at present. lished between regional power grids. It may occur that the In this pattern, if either set of SSCDs acts, the outlet will be operation of some SSCS in region A becomes a disturbance permitted [40]. This can prevent action failures that are to the SCCS in region B, though the operation is correct for caused by failures of either set of SSCDs, but it cannot the stability problems caused by faults in region A [35]. For prevent the mal-operation of the SSCS for hidden failures example, the rapid and large-scale transfer of load flow in the SSCDs. Various measures of preventing mal-oper- caused by generator tripping or separation in region A can ation have to be taken to ensure the reliability of a SSCS. lead to action failures, malfunctions or unexpected actions of the SSCS in region B. Therefore, in order to prevent such hidden failures, the coordination between SSCSs in 4 Analysis of coordination hidden failures of relay different regions must be considered and attached impor- protection system and SSCS tance to. Among reasons of blackouts, there are also coordination 4.3 Coordination hidden failures among relay hidden failures, which may lie between relay protections, protection, SSCS and parameters of power between SSCSs, between the relay protection system and plants related to power grid the SSCS, or among power plants’ parameters related to the grid, relay protection system and SSCS, affecting the It also should be paid attention to that whether it’s security of power grids, sometimes even deadly. coordinate among relay protections, the SSCS and parameters of power plants related to power grid. The 4.1 Coordination hidden failures between relay incoordination among the three was also looked on as one protections of contribute factors to some blackouts by some experts. The consequences resulted from the coordination problem What a relay protection cares about is the element in had been proved by the WSCC 2 blackouts of United States power grid and relay protections make decisions all alone in 1996 [2], the ‘‘814’’ Blackout in America and Canada in [41], which make the coordination between relay protec- 2003 [43], and the Italian blackout in 2003 [44]. The series tions poor. of accidents alarm that close attention should be paid to the The poor coordination between relay protections mainly coordination hidden failures between the relay protections results from the unreasonable setting matching between and the SSCS, or among parameters of power plants related one protection and its lower protection [20], i.e., that zone to power grid, the relay protection and the SSCS. With the II or zone III setting of distance protection doesn’t satisfy large scale new energy connected to power grid in China, the selectivity results in the disharmony cooperation the grid-connected control and protection of wind energy between a main protection and its associated backup pro- generation and photovoltaic power generation brings a new tection or its lower protection. The hidden defects of challenge to the relay protection system and the SSCS. The cooperation between relay protections may be caused by operating experience about new energy indicates that the other factors like design schemes. i.e., there exists a tripping accident of large-scale wind turbine generators in coordination hidden defect in the design scheme that the Northwest China Power Grid in 2011 was caused by hidden bus couple auto-switch protection (BCASP) and bus coordination problem among the feeder protection, SVC/ 123 Review and prospect of hidden failure: protection system and security and stability control… 1741 SVG and the grid-connected protection of wind turbines. new input to assess risk online and analyze the security Moreover, that large-scale new energy is connected to the of power grid, which will be a new trend to study power grid in centralization brings new challenges to the hidden failures. The modeling and analysis of hidden adaptability of various criterions of the SSCS. Among failures in the relay protection and SSCS need the support of large amounts of operating data, but the these challenges the criterion for fault trip and control measures may become invalid. Therefore, there is necessity categorization of operating data is not complete, and the expert knowledge is of ambiguity and uncertainty. to study hidden failures caused by generator-power grid coordination problem; otherwise a tiny accident could lead To acquire adequate data it needs to reinforce the unified management of the monitoring and accident to instability and large scale blackouts of power grid. record of secondary system. However that’s not enough. New methods should also be explored simul- taneously to evaluate the risk of hidden failure under 5 Conclusions the condition of data deficiency. 3) Coordination hidden failure of the relay protection and By summarizing and analyzing the research on hidden the SSCS. Although the coordination problem between failures of the relay protection and the SSCS, the author relay protections has been concentrated on, research thinks that the further research on hidden failures of the on the coordination problem is still relatively deficient relay protection and the SSCS in the future should be and requires further studies. Furthermore, after the conducted as follows: separation of power grid and power plants, the 1) Hidden failure modeling. So far, most are hidden coordination problem among the relay protection, the failure probability model of over-current protection SSCS and parameters of power plants related to power and distance protection, current differential protection grid has been gradually becoming outstanding, which which is often used as main protection seldom has to be paid attention to since it is a big threat hiding included. Research on hidden failure in SSCS is just in the operation of power grid. 4) Application of hidden failure research. The achieve- in its infancy. It will be a key to build a proper probability model of hidden failure in the SSCS. The ments of hidden failure research should be helpful to control scheme of the SSCS is a distributed control enrich the collection of contingencies and pre-decision scheme and more complicated than that of the relay system, and strengthen the prevention and emergency protection. During the model building of hidden control system. Simultaneously, it should also be failure in the SSCS, it has to consider the effect of helpful to identify the coordination hidden failures action failures or malfunctions of devices caused by between different controls on security and stability of hidden failures not only on protected elements and the power system, and find out the weak links of power neighboring elements, but also on the area charged by system. Then associated measures can be taken timely the SSCS. So inevitably it is more complicated to to enhance the security and reliability of power system. build hidden failure model of the SSCS. The proba- 5) Operation management of secondary equipment. bility and severity of consequences caused by different Human factors are also contributors to hidden failures hidden failures might be different and should be taken of the relay protection and the SSCS. The limitation of into account to assess the effects of hidden failures. testing-personnel quality and testing technology could The outcome of the assessment should be taken as one bring about hidden failures for ignorance of some of considerations in building probability model of defects in devices. So it should be done to obey hidden failures in secondary equipment. Work in the relevant electric regulations strictly, to update these field is underway and the details will be introduced in regulations with the development of power grid, and to follow-up articles. reinforce the management of the links like debugging, 2) Risk assessment of hidden failure. As members of operation & maintenance, and setting. Then some secondary equipment, relay protections and SSCDs are hidden dangers can be avoided and series accidents a part of operational risk sources of power grid. Until evoked by tiny problems can be reduced as much as now, the severity assessment of the effect of hidden possible. Though action criterions for relay protections failures in the relay protection on power grid is and SSCDs have been established based on the generally carried out based on the point of risk. operating characteristics of the power grid, these According to the ideas of risk assessment proposed in criterions can’t be adapt to the operating characteristics the research with achievements, such as research on of power grids forever and need to be updated timely. A power grid faults caused by lighting [45], hidden device itself has to be faced with many operation failures of secondary equipment will be treated as a problems such as harsh operating environment and 123 1742 Lili ZHAO et al. [13] Sun YZ, Cheng L, He J (2012) Power system operational reli- aging of components resulted from device’s long time ability theory. Tsinghua University, Beijing operation, possibly becoming contribute factors to [14] Cheng YM, Chen X, Ren JF, Li XM (2013) Study on hidden hidden failures too. So in order to reduce accidents failure of relay protection in power system. In: Paper presented rd caused by devices’ hidden failures as much as possible at 2013 IEEE 3 annual international conference on cyber technology in automation, control and intelligent systems strict supervision and early warning should be done (CYBER), Grand Metropark Hotel Nanjing and Nanjing with the condition-based maintenance date of sec- University of Science and technology (NJUST), 26–29 May ondary equipment. [15] Wu X, Zhang JH, Wu LW et al (2012) Method of operational risk assessment on transmission system cascading failure. Proc Acknowledgements This work is supported by State Grid Corpo- CSEE 32(34):74–82 (in Chinese) ration of China, Major Projects on Planning and Operation Control of [16] De La Ree J, Elizondo DC (2004) A methodology to assess the Large Scale Grid (SGCC-MPLG003-2012). impact of hidden failures in protection schemes. IEEE PES Power Syst Conf Expo 3:1782–1783. doi:10.1109/PSCE.2004. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://cre- [17] Guo CX, Lu HB, Yu B et al (2013) A survey of research on ativecommons.org/licenses/by/4.0/), which permits unrestricted use, security risk assessment of secondary system. Power Syst distribution, and reproduction in any medium, provided you give Technol 37(1):112–118 (in Chinese) appropriate credit to the original author(s) and the source, provide a [18] Wang SC (2005) Markov model for reliability analysis of dual- link to the Creative Commons license, and indicate if changes were redundant relays. Relay 33(18):6–10 (in Chinese) made. [19] Chen SH, Ma BY, Lei Y et al (2007) Integrative and quantitative calculation of reliability for relay protection system. Autom Electr Power Syst 31(15):111–115 (in Chinese) [20] Wu WC, Lv Y, Zhang BM (2009) On-line operating risk assessment of hidden failures in protection system. Proc CSEE References 29(7):78–83 (in Chinese) [21] Chen WH, Jiang QY, Cao YJ (2006) Risk assessment of power [1] Xiao SJ (ed) (2011) Control technology of security and stability system cascading failures considering hidden failures of pro- in power system. China Electric Power Press, Beijing (in tective relayings. Power Syst Technol 30(13):14–19 (in Chinese) [22] Wang C, Gao P, Xu Z et al (2007) Application of GO Chinese) [2] He DY (1998) The successive ponderation (layers-built analysis) methodology in reliability assessment protective relays. Autom over U.S. WSCC two outages in 1996. Electr Power 31:37–40 Electr Power Syst 31(24):52–56 (in Chinese) (in Chinese) [23] Huo C, Zhang PC, Liao XH (2008) Analytic method for relay [3] Lin WF, Sun HD, Tang Y et al (2010) Analysis and lessons of protection importance with consideration of hidden failures. East the blackout in Brazil power grid on November 10, 2009. Autom China Electr Power 36(3):63–65 (in Chinese) Electr Power Syst 34(7):1–5 (in Chinese) [24] Kececioglu D (1991) Reliability engineering handbook, vol 2. [4] Lin WF, Tang Y, Sun HD et al (2011) Blackout in Brazil PTR Prentice Hall, Englewood Cliffs power grid on February 4, 2011 and inspirations for stable [25] Chen J et al (2005) Cascading dynamics and mitigation operation of power grid. Autom Electr Power Syst 35(9):1–5 assessment in power system disturbances via a hidden failure (in Chinese) model. Electr Power Energy Syst 27:318–326 [5] Tamronglak S (1994) Analysis of power system disturbances [26] Bae K, Thorp JS (1999) A stochastic study of hidden failures in due to relay hidden failures. Dissertation, Virginia Polytechnic power system protection. Decis Support Syst 24:259–268 State University [27] Phadke AG, Horowitz SH, Thorp JS (1995) Anatomy of power [6] Zhang XS, Wang HF, Huang XM et al (2011) Discussion on system blackouts and preventive strategies by rational supervi- hidden failures in relay protection system. Electr Power Constr sion and control of protection systems. ORNL/Sub-89-SD630C/ 32(2):47–51 (in Chinese) 1. Oak Ridge National Laboratory, Oak Ridge [7] Zhang JJ (2012) Research on hidden failures related issues of [28] Huang J (2004) Adaptive wide area protection of power system. relay protection system. Dissertation, HeFei University of Dissertation, Iowa State University Technology (in Chinese) [29] Sun X (2009) Research on the detection of hidden failure in [8] Xu J (2011) Analysis and research on complex power system relay protection and risk analysis. Dissertation, Chongqing cascading failures considering hidden failure of protection. University (in Chinese) Dissertation, China Electric Power Research Institute (in [30] Duan XZ, Yang ZL, Cheng Xiao (2005) Performance analysis of Chinese) relay settings determined according to off-line calculation and [9] Wang ST (2010) Research on the monitoring methods of hidden on-line calculation. Autom Electr Power Syst 29(19):58–61 (in failures in relay protection. Dissertation, Chongqing University Chinese) (in Chinese) [31] Lv Y, Sun HB, Zhang BM et al (2005) Research and devel- [10] Yang MY, Tian H, Yao W (2010) Analysis of power system opment of an online intelligent early warning system of pro- cascading failure based on hidden failures of protective relaying. tective relaying. Autom Electr Power Syst 30(4):1–5 (in Power Syst Prot Control 38(9):1–5 (in Chinese) Chinese) [11] Bae K, Thorp JS (1998) An importance sampling application: [32] Bae K, Thorp JS (1999) Hidden failures in protection systems 179 bus WSCC system under voltage based hidden failures and and their impact on wide-area disturbances. Decis Support Syst relay operation. Decis Support Syst 24:259–268 24:259–268 [12] Yu XB, Singh C (2004) A practical approach for integrated [33] Wang H, Thorp JS (2001) Optimal locations for protection power system vulnerability analysis with protection failures. system enhancement: a simulation of cascading outages. IEEE IEEE Trans Power Syst 19(4):1811–1820 Trans Power Deliv 16(4):528–533 123 Review and prospect of hidden failure: protection system and security and stability control… 1743 [34] Xu J, Bai XM (2012) Power systems N-k contingency analysis in defence measures. Autom Electr Power Syst 29(8):1–4 (in consideration of protection hidden failure. Proc CSEE Chinese) 32(1):108–114 (in Chinese) [45] Xie YY, Xue YS, Wang HH (2013) Space–time early-warning [35] Cui Y, Wang C, Yang JH et al (2011) Inspection and repair of power grid fault probability by lightning. Autom Electr Power method for hidden faults of control circuit in high voltage circuit Syst 37(17):44–51 (in Chinese) breaker. High Volt Appar 47(12):96–99 (in Chinese) [36] Song JH, Li XM, Ji CA et al (2005) Current situation devel- opment prospect of security and stability control equipment. Lili ZHAO was born in Jiangsu, P.R. China, in 1988. She is an Autom Electr Power Syst 29(23):91–96 (in Chinese) engineer of Nari Technology Development Limited Company. Her [37] Zhang Y, Li JS, Huang H et al (2009) Improvement of line trip research interests include control technology about security and criterion of power system security and stability control equip- stability of power system. ment. South Power Syst Technol 3(3):74–76 (in Chinese) [38] Wang W, Chen J, Yu R et al (2012) Analysis of non-fault Xueming LI was born in Jiangsu, P.R. China, in 1965. He is a tutor in tripping criterion operation for area-based stability control State Grid Electric Power Research Institute and a senior engineering device. Power Syst Prot Control 40(2):120–124 (in Chinese) of Nari Technology Development Limited Company. His research [39] Cai M, Sun GH, Wu XC et al (2007) Analysis and application of interests include control technology about security and stability of AC fault criterion in power system stability control. Autom power system. Electr Power Syst 31(8):46–51 (in Chinese) [40] Zhu JJ, Huang ZY, Hong J et al (2011) Analysis on Shanghai Ming NI was born in Jiangsu, P.R. China, in 1969. He is a tutor in grid security and stability control device. Power Energy Hohai University and a chief expert of China. His research interests 32(3):190–193 (in Chinese) include control technology about security and stability of power [41] You JX, Wu R, Ye K et al (2011) Analysis of a blackout system, power system planning, and automation of power system. escalation caused by hidden failure lying in blocking logic between auto-switching protection and bus differential protec- Tianyu LI was born in Jiangsu, P.R. China, in 1992. He is a student tion. Autom Electr Power Syst 35(7):102–107 (in Chinese) of Nanjing University of Posts and Telecommunications. His research [42] Begovic M, Novosel D, Karlsson D et al (2005) Wide-area interests include stability analysis and control of power system. protection and emergency control. Proc IEEE 93(5):876–891 [43] Yin YH, Guo JB, Zhao JJ et al (2003) Preliminary analysis of Yameng CHENG was born in Jiangsu, P.R. China, in 1989. Her large scale blackout in interconnected North America power grid work is in Jiangsu Electric Power Research Institute. Her research on August 14 and lessons to be drawn. Power Syst Technol interests include automation of power system. …. 27(10):8–11 (in Chinese) [44] Fu ST (2005) Summary on power system security problems on 2004 IEEE PES Meeting and recommendation for developing http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Modern Power Systems and Clean Energy Springer Journals

Review and prospect of hidden failure: protection system and security and stability control system

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Copyright © 2015 by The Author(s)
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Energy; Energy Systems; Renewable and Green Energy; Power Electronics, Electrical Machines and Networks
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J. Mod. Power Syst. Clean Energy (2019) 7(6):1735–1743 DOI 10.1007/s40565-015-0128-9 Review and prospect of hidden failure: protection system and security and stability control system 1 1 1 2 3 Lili ZHAO , Xueming LI , Ming NI , Tianyu LI , Yameng CHENG Abstract With the construction of the ‘‘3-level, 3-vertical- Keywords Relay protection, Security and stability line, and 1-circle’’ power backbone in China, it’s stricter and control device, Hidden failure, Coordination stricter on relay protection system and security and stability control system (SSCS) for reliable power transmission. Lots of blackouts in the world had happened, one main reason for 1 Introduction which is the hidden failures of relay protection system or SSCS. Much work had been done about the hidden failure of In China, a ‘‘3-level, 3-vertical-line, and 1-circle’’ power relay protection, including classification, probability model, backbone will be formed in the future, where the ultra-high- analysis methods of effects on power grid, and monitoring voltage (UHV) AC and DC transmission projects have been measures, which was summarized in the paper. The opera- built, to help transferring power energy from large-scale tion experiences of SSCS indicated that there might be energy bases to the major load centers. In order to ensure the hidden failures in five links of the security and stability security and reliability of power transmission, the protection control device (SSCD), e.g. measuring, control strategy, system and security and stability control system (SSCS) must setting, communication and voting pattern. In addition, the be highly reliable, being its strong backing. Committed to coordination hidden failure among relay protection system, reducing the failure losses as best as possible by taking dif- SSCS, and power plant’s parameters related to the power ferent control measures, the antecessors of China’s elec- grid was pointed out for more attention. In the future, tricity proposed the concept of three-defense lines with relay amounts of work will be expected to be conducted on hidden protection system and SSCS respectively lying in the first failure: model building, assessment methods, application of and second defense lines (See Fig. 1 [1]). So the reliability of research achievements, operation management of secondary the relay protection system and the SSCS plays an important equipment, and coordination problem between the relay role in the stability control of power system. However, protection system and the SSCS. because of technology limitations, miss-operations, weak CrossCheck date: 4 February 2015 management system of maintenance etc., there can be defects, great or minor, in relay protection and security and Received: 3 December 2014 / Accepted: 16 April 2015 / Published stability control device (SSCD), leading to hidden failures online: 4 June 2015 The Author(s) 2015. This article is published with open access at and security risks if not found in time. Springerlink.com Hidden failures are caused by the device’s defects or & Lili ZHAO human factors, bound to weakening the device’s reliability. zhaolili@sgepri.sgcc.com.cn They produce no immediate action on the device and power system in a normal operating environment, and only Nari Technology Development Limited Company, Nanjing 211106, Jiangsu, China possibly are triggered in an abnormal pressure state, e.g. grounded short-circuit fault, load-flow reversion and great Nanjing University of Posts and Telecommunications, Nanjing 210046, Jiangsu, China drop of voltage or a harsh operating environment. Obviously hidden failures are covert, once triggered, Jiangsu Electric Power Research Institute, Nanjing 210093, leading the improper operation of relay protection and Jiangsu, China 123 1736 Lili ZHAO et al. Recovery secondary equipment, hoping to provide some reference for Black start control the future research in this field. Remove Operate Fault Lose Large-scale faulty + + + normally occurs stability blackout component 2 Analysis of relay-protection hidden failures Out-of-step separation, Automatical Stability control Action of relay Frequency emergency preventative generator tripping protection control, 2.1 Classification of protection hidden failures or load shedding control or Voltage emergency (the first line (the second line adjustment by of defense) control dispatch center of defense) (the third line of defense) Since the concept of relay-protection hidden failures [5] was put forward for the first time in 1994, the influence of Fig. 1 The stability control and the three-defense lines power system relay-protection hidden failures with its research has been in China paid more and more attention. The protection hidden fail- ures are classified in different ways, which are generally based on the causes of the hidden failures [6, 7], protection SSCD, which possibly cause cascading failure of power element functionality defect (PEFD) [8], and the dynamic system with huge losses of load and power supply, even and static characteristics of relay protection devices [9]. blackouts, and further bring about a great loss of the The detail of the three ways is as follows: national economy. Although hidden failures are uncovered by some other events in a quite low probability, they might 1) Classification based on the causes of the hidden break through the first and second defense lines of China’s failures. It divides hidden failures into five ones: a. power system once triggered, which can’t be ignored for hidden failures caused by hardware faults, such as the profound impact on power grids and society. damages or defects of device elements; b. hidden failures caused by system errors of protection soft- Hidden failures of relay protection caused many black- outs of power systems, i.e. the WSCC blackout in 1994 [2], ware, such as logic errors of protection principle and the ‘‘814’’ Blackout in America and Canada in 2003, the version errors of software; c. hidden failures caused by large-scale power failure in Brazil in 2011 [3], and the protection setting values, such as improper settings power failure in Indonesia in 2012. Blackout accidents and man-made setting errors; d. hidden failures caused resulted from hidden failures of SSCD have also happened by natural environment, like bad climatic conditions or many a time, such as the two WSCC blackouts in 1996 [2] storm disasters; e. hidden failures caused by improper and the large-scale power failure in 2009 [4]. What’s more, manual operation or ill maintenance. the ‘‘71’’ accident of Central China (Henan) Power Grid in 2) Classification based on PEFD. It consists of hidden 2006 is evoked by hidden failures of both relay protection failures caused by hardware faults (PEFD-A) and by devices and security control devices. human errors and protection settings (PEFD-B). Study of hidden failure holds great significance for 3) Classification based on the dynamic and static charac- ensuring security and stability of power grid, people’s teristics of relay protection devices. It divides hidden lives, and national development, including the mechanism failures of protection devices into dynamic hidden of hidden failure’s impact on power systems and the hidden failures and static hidden failures. The static character- failure monitoring approaches. Large amounts of studies istic of protection devices is that if the protection device and discussions about protection hidden failure have been doesn’t fulfill the starting conditions, it will only do done at home and abroad. This paper reviews these work electric-parameter measurement and calculation or do and summarizes issues related with protection hidden data collection and start judgment; while the logic failures: classification methods, probability model, research comparison and tripping output are not in consideration, methods and monitoring measures. The possible hidden- mainly with the hardware devices, mutual-inductor failure risks of SSCD are presented based on the knowl- measurement circuit, connecting cables, terminals, pre- edge of the devices’ characteristics and operating experi- process circuit of relay protection, sampling and sam- ence. It also briefly analyzes the influence of hidden pling-value calculation. The hidden failures in these failures caused by cooperation problem among relay pro- links are called static hidden failures. Dynamic charac- tections, SSCSs, and parameters of power plants in oper- teristic of protection is that when the protection meets ation related to the power grid. Last but not least, it with the starting conditions, the fault parameters will be proposes prospects on hidden-failure research, including measured and logic comparison will be done, mainly modeling, risk evaluation methods, research result appli- with links of measurement, calculation, and blocking- cation, the coordination problem hiding between the relay signal inspection. The hidden failures in these links are protection and the SSCS, and operation management of called dynamic hidden failures. 123 Review and prospect of hidden failure: protection system and security and stability control… 1737 Although the three classification methods of hidden operation mode at that time. Throughout all processes of failures appear different, all of them think over the clas- protection hidden failure modeling, there are two ideas. sification from hardware and software, and then classified One which is often used is to work out hidden failure hidden failures by considering detailed factors like human probability of relay protection devices and how it changes behaviors and design defects of devices. with the electric parameters (voltage, current, and line power flow) by taking the equipment’s software/hardware 2.2 Probability models of hidden failures of relay and control scheme into account. The other one is to work protection system out hidden failure probability by considering the relay protection as a whole. These modeling processes only The probability of relay-protection hidden failure is the reflect the consequences of human negligence or errors, first problem to be solved during the research, which can be production quality of devices, equipment management & solved now mainly by probability statistical method and maintenance, etc., but don’t embody how these factors probability model method. The probability value obtained affect protection hidden failure probability. The problem is by probability statistical method is a fixed value, which can worth thinking over, and if solved will help reduce human be used to evaluate the cascading failure risk caused by negligence or errors, perfect the devices, and improve the hidden failures, but can’t reflect the change of hidden coordination between devices and power grid. failure probability value along with the real-time operating- condition such as line power flow, bus voltage, and system 2.3 Effects and research methods of hidden failures frequency. By the probability model method, the hidden failure probability of a particular protection system or a The relay protection’s failure actions or malfunctions particular protection scheme can be worked out under caused by its hidden failures weaken the reliability of different operating conditions. So far, 4 probability models protection system. When the power grid is abnormal, the of relay protection hidden failure have been proposed: triggering of relay-protection hidden failures may result in hidden failure probability model of zone III transmission- N-2 events [16], even cascading failures, which increases line distance protection [10, 11], hidden failure probability the insecurity and instability, bringing load isolation, model of over-current protection [12], hidden failure power-supply isolation, out-of-step separation and even probability model of line protection considered over-flow overall instability. [13], and hidden failure probability model of generator Lots of risk assessment methods have been proposed for protection considered terminal-voltage [14]. The hidden quantifying the influence severity of relay-protection hid- failure probability value of zone III transmission-line dis- den failures on power system. Risk assessment methods which are the most used in assessing reliability are devel- tance protection is decided by the impedance seen by protection devices; the hidden failure probability of over- oped and improved on the basis of certainty analysis current protection devices is related to the magnitude of methods and probabilistic analysis methods [17]. So they line current; the hidden failure probability of line protec- synthesize technical economics and quantitative eco- tion considered over-flow is related to the magnitude of nomics. The risk assessment methods analyze relay pro- active line-load-flow; the hidden failure probability of tection reliability in terms of risk, mainly by Markov, event generator protection considered terminal-voltage is related tree and fault tree. The output risk indicators of device to the magnitude of generator’s terminal voltage. The [15] level separately are failure rate and availability of a device, catalogued protection’s failure to operation and second- risks of load isolation & power-supply isolation, and the type mal-operation as hidden failures in consideration of margin of interface transmission. In addition, the risk the types of relay protection failures. Taking the proba- indicators of primary-system level that is security & sta- bility obtained from the above hidden-failure probability bility indicators can also be obtained by event tree analysis models as the probability of protection’s second-type mal- method. The risk indicators of primary-system level operation, a general hidden failure probability model is including grid separation risk and integrated risk can be built on the basis of Markov, in which the protection sys- obtained by fault tree analysis method. tem involves protective devices with associated circuit The three analysis methods, i.e. Markov, event tree and breakers. fault tree, have different characteristics of application in Among the factors that result in hidden failures of relay the effect analysis of relay-protection hidden failures on protection equipment, there is no lack of human negligence power grid. Compared with the probability method, Mar- or errors, production quality of devices, devices manage- kov is more applicable to the relay protection system that is ment & maintenance, etc. These factors usually have a repairable system [18, 19]. Currently, the probabilistic effects on the fitness of software/hardware system and statistical method is often used to build hidden failure control scheme of the secondary equipment to the grid probability models of relay-protection, in terms of the state 123 1738 Lili ZHAO et al. change of power system, like load-flow transfer. But it is constant. Submission of a manuscript implies: that the not as accurate as Markov method in assessing the hidden work described has not been published before; that it is not failure probability of protection. However, Markov method under consideration for publication anywhere else; that its needs lots of samples to ensure the accuracy of Markov, publication has been approved by all co-authors, if any, as which must bear a heavy computation burden. In Markov well as by the responsible authorities—tacitly or explic- method, the event’s current state depends only on the last itly—at the institute where the work has been carried out. state, while event tree obeying the time sequence starts from the primary event, reasons out possible outcomes and 2.4 Monitoring method of hidden failures identify the hazard source. For an example, based on the analysis of the hidden failure triggering conditions of relay- In recent years, many researches on protection-system protection by event tree, it starts from a certain initial event hidden failure have been done, i.e. researches on protection and reason out the malfunction probability model of system reliability modeling and influence of protection associated relay-protection under different contingences devices on Power System’s reliability. Research on the [20]. However, the event tree requires confirming object monitoring and control of protection hidden failure is also firstly, which demands thorough knowledge of the system involved [7], which is aimed at taking precautionary structure, occurrence & probability of relevant accidents measures against hidden failures to avoid serious cascading and the severity of consequences caused by accidents. of power system. A technology embodiment for the mon- Similar to the analysis by event tree, the analysis by fault itoring and control system against relay-protection hidden tree is intuitively, straightforward, clear and logical. E.g., failures [27] was proposed by AG Phadke and JS Thorp of the dynamic process of the cascading resulted from relay- Virginia Tech in 1995, but it was not applied in industry protection hidden failures is analyzed by fault tree so as to since the technology was not mature enough. In 2004, a find out the line or generator protection ‘‘pre-malfunction monitoring system was developed against hidden failures set’’ [21] (the ‘‘pre-malfunction set’’ means the set of line by the wide-area protection system, however was of poor or generator protection associated with the removed reliability and the cost was high [28]. The detection of lines). hidden failures depends on the running state of Power Aside by the above methods, certainty method, proba- System [29]. The off-line detection which is widely used bility method and risk method, protection reliability is now can’t meet with the requirements, high security, high analyzed by other methods such as GO method [22] and the reliability and real time, and is unable to do an exhaustive importance analysis on relay-protection hidden failures detection for hidden failures. Therefore, new methods based on risk assessment [23]. The importance analysis on should be worked out for on-line detection. That off-line setting value is improper is main contrib- relay-protection hidden failures is derived from the element importance analysis which is an important approach for utor to hidden defects of protection settings. The off-line system reliability analysis. Its purpose is to identify the key setting values are mostly set and modified manually, thus elements that have crucial effect on system’s reliability so easily result in security risks. Particularly, off-line settings as to objectively increase the overall reliability of the if have not been modified for a long time, will deteriorated system at low cost [24]. the performance of devices, and may be not adapt to the The influence of protection hidden failures on system real-time operation mode of power grid. One of the solu- can also be analyzed by simulation. Monte Carlo [25] and tions to get over off-line setting defects is on-line setting Importance Sampling [26] are important tools for simula- [30] for protection devices. An online intelligent early tion analysis. Monte Carlo, the simulation method in warning system of protective relaying [31] was developed probability method, take advantage of the comprehensive and applied to the power grid of some domestic province. statistical data of power system state, to calculate the Based on the warning system Scholars at home checked reliability indicators of a certain period of time, and can’t setting hidden defects of protection online, and assessed the be fit to analyzing the frequency and probability of events risk brought by these defects for the weak links of pro- that do not often occur. Based on whether the simulation tection hidden failures. The early warning system sent periods are a sequence, the Monte Carlo method can be signals about these weak links and associated measures divided into Monte Carlo method with time sequence and could be taken timely for the security of power grid. Monte Carlo method without time sequence. The impor- The hidden failures of protection system are proved to be tance sampling method does not use the primary proba- the key contributors to the wide-area disturbance [32]. bility of hidden failure model; instead, in order to increase Identifying the key lines affected by hidden failures [33] the probability of cascading, it does simulation with a and taking associated measures can inhibit cascading probability value greater than the primary probability under development and reduce blackouts. Thus, some researches the premise that the mean of probability value remains built pre-malfunction sets of lines where protection hidden 123 Review and prospect of hidden failure: protection system and security and stability control… 1739 failures might be triggered. But these pre-malfunction sets 2) Strategy are only sets of lines connected with the primary fault line A SSCD is the implementation medium of various and the researches didn’t analyze the cause of line protec- control measures. The ways of carrying out its control tion malfunctions systematically from the point of the strategies usually include off-line decision and on-line pre-decision. If control strategies cannot fit the real- essence of hidden failures, which lead to the obtained pre- malfunction sets incomplete. This problem has got solved in time operation mode of power grid, malfunction of the SSCS including over-shedding, under-shedding and [34] that firstly put the protection hidden failures as a part of contingencies constituted by different accidents, secondly mal-shedding will take place, further expanding the accidents in power grid [38]. exposed the hidden risks of cascading during selecting N–k contingencies, and last found out vulnerable lines and the 3) Setting key protection. The hidden failure monitoring of other The correctness of setting in device determines the equipment like control circuit in high voltage circuit efficiency of device and whether the monitored object breaker in protection system is to check hidden failures by can make right judgment about the type of faults as reverse point-by-point investigation method [35]. fast as faults occur. Unreasonable or incorrect settings impair the security of the SSCD and the stability of power system [39]. For instance, in the ‘‘71’’ Accident of Central China Power Grid, the mismatching 3 Analysis of hidden failures of SSCD between a setting and the real-time operation mode of power grid led to action failure of the security & SSCDs widely used in China are the second defensive stability control devices in Songshan substation and line [36] which is aimed at ensuring security, stability and finally expended the accident. reliability of power system. The SSCDs of multiple power 4) Communication plants or substations communicate with each other, con- Generally, how to configure a SSCD in the power grid stituting a SSCS with a hierarchical classification of control should take control range and functions to be achieved scheme like Electric Power Alarming and Coordinated of the device and power system planning into consid- Control System (EACCS). The EACCS in Jiangsu Pro- eration. In order to achieve large-scale stability vince of China has a typical control structure of 4-hierar- control, SSCDs of multiple plants are usually config- chy, dispatch center station-control station—control ured as a SSCS via communication channel and substation—implementation station from top to bottom. communication interface equipment, and work coop- Since the SSCS takes charge of a regional power grid, once eratively, to achieve the regional security and stability it goes wrong, enormous losses will take place, which has control. However, in the communication progress been proved by the ‘‘730’’ Load-Shedding Fault in between SSCDs, the reception and execution of Zengcheng in Guangdong province of China in 2004 and commands in the SSCS are affected by error codes, the ‘‘71’’ Accident of Central China Power Grid in 2009. unstable transmission in communication channel, not- The losses are so huge that it cannot wait to conduct in-time information transfer. It brings about that the researches on the hidden failures in SSCDs and associated strategy cannot be executed at right time or security & effects on the power grid. control devices cannot act properly, resulting in more According to the accident experiences in power grids serious accidents. On July 30, 2004, the security and and the structure of the SSCS, the hidden failures of the stability control subsystem of Zengcheng, Guangdong SSCD are described in five links: measuring, strategy, mal-operated with 714 MW load shedding for the setting, communication, and voting pattern. reason that communication codes were error and there 1) Measuring were loopholes in the communication module and the CT and PT are used for the measuring of electric verification links. parameters by the SSCD. The break-line accidents of 5) Voting pattern PT are easy to take place and remain hidden until Redundancy design is introduced into enhance the triggered by other events; the remaining current of CT security and reliability of the SSCS. The voting pattern second winding can influence the judgment of SSCD determines the characteristics of the malfunction [37]. In addition, that the chip of measuring circuit prevention of a SSCS, so in the process of redundancy goes wrong will influence the accurate of measured design it needs to consider the type of voting pattern of values which reflect electric information, easily result- control outlet logic in a SSCS. There are mainly three ing in incorrect judgment and malfunction of the types of voting patterns, e.g. ‘‘2 out of 3’’ pattern, ‘‘2 SSCD. out of 2’’ pattern, and ‘‘1 out of 2’’ pattern. 123 1740 Lili ZHAO et al. In the ‘‘2 out of 3’’ pattern, only when at least two of differential protection (BDP) block each other. The hidden three sets of SSCDs act can the outlet action be permitted. defect remains undetected by the occurrence of a single This will prevent malfunctions of the SSCS that are caused simple fault, but when complicated failures occur and by hidden failures in any one of the three sets of SSCDs. cannot be identified by the judgment circuit of the relay But this pattern is the least adopted because of high cost, protection for the coordination hidden defect between wiring complexity, operation and maintenance difficulty, BCASP and BDP [42], serious failures may follow. etc. In the ‘‘2 out of 2’’ pattern, the outlets of the two sets of 4.2 Coordination hidden failures between SSCSs SCCDs are connected serially, so the outlet tripping can be achieved only when both of the two sets of devices act. The conventional SSCS takes charge of the stability of a This will effectively prevent malfunctions of the system regional power grid, usually restricting the control range in caused by hidden failures in either one of the two sets and a provincial grid. Distributed in a regional power grid, the ensure the reliability of the system. However, if neither of early SSCS made decisions independently and took the 2 sets acts for their hidden failures, tripping pulse will appropriate measures against failures listed in the control not be transferred to the ultimate executive and then action strategy. With the development of EHV AC/DC transmis- failures of the SSCS will come into being. sion network, strong electrical connection will be estab- The ‘‘1 out of 2’’ pattern is the most adopted at present. lished between regional power grids. It may occur that the In this pattern, if either set of SSCDs acts, the outlet will be operation of some SSCS in region A becomes a disturbance permitted [40]. This can prevent action failures that are to the SCCS in region B, though the operation is correct for caused by failures of either set of SSCDs, but it cannot the stability problems caused by faults in region A [35]. For prevent the mal-operation of the SSCS for hidden failures example, the rapid and large-scale transfer of load flow in the SSCDs. Various measures of preventing mal-oper- caused by generator tripping or separation in region A can ation have to be taken to ensure the reliability of a SSCS. lead to action failures, malfunctions or unexpected actions of the SSCS in region B. Therefore, in order to prevent such hidden failures, the coordination between SSCSs in 4 Analysis of coordination hidden failures of relay different regions must be considered and attached impor- protection system and SSCS tance to. Among reasons of blackouts, there are also coordination 4.3 Coordination hidden failures among relay hidden failures, which may lie between relay protections, protection, SSCS and parameters of power between SSCSs, between the relay protection system and plants related to power grid the SSCS, or among power plants’ parameters related to the grid, relay protection system and SSCS, affecting the It also should be paid attention to that whether it’s security of power grids, sometimes even deadly. coordinate among relay protections, the SSCS and parameters of power plants related to power grid. The 4.1 Coordination hidden failures between relay incoordination among the three was also looked on as one protections of contribute factors to some blackouts by some experts. The consequences resulted from the coordination problem What a relay protection cares about is the element in had been proved by the WSCC 2 blackouts of United States power grid and relay protections make decisions all alone in 1996 [2], the ‘‘814’’ Blackout in America and Canada in [41], which make the coordination between relay protec- 2003 [43], and the Italian blackout in 2003 [44]. The series tions poor. of accidents alarm that close attention should be paid to the The poor coordination between relay protections mainly coordination hidden failures between the relay protections results from the unreasonable setting matching between and the SSCS, or among parameters of power plants related one protection and its lower protection [20], i.e., that zone to power grid, the relay protection and the SSCS. With the II or zone III setting of distance protection doesn’t satisfy large scale new energy connected to power grid in China, the selectivity results in the disharmony cooperation the grid-connected control and protection of wind energy between a main protection and its associated backup pro- generation and photovoltaic power generation brings a new tection or its lower protection. The hidden defects of challenge to the relay protection system and the SSCS. The cooperation between relay protections may be caused by operating experience about new energy indicates that the other factors like design schemes. i.e., there exists a tripping accident of large-scale wind turbine generators in coordination hidden defect in the design scheme that the Northwest China Power Grid in 2011 was caused by hidden bus couple auto-switch protection (BCASP) and bus coordination problem among the feeder protection, SVC/ 123 Review and prospect of hidden failure: protection system and security and stability control… 1741 SVG and the grid-connected protection of wind turbines. new input to assess risk online and analyze the security Moreover, that large-scale new energy is connected to the of power grid, which will be a new trend to study power grid in centralization brings new challenges to the hidden failures. The modeling and analysis of hidden adaptability of various criterions of the SSCS. Among failures in the relay protection and SSCS need the support of large amounts of operating data, but the these challenges the criterion for fault trip and control measures may become invalid. Therefore, there is necessity categorization of operating data is not complete, and the expert knowledge is of ambiguity and uncertainty. to study hidden failures caused by generator-power grid coordination problem; otherwise a tiny accident could lead To acquire adequate data it needs to reinforce the unified management of the monitoring and accident to instability and large scale blackouts of power grid. record of secondary system. However that’s not enough. New methods should also be explored simul- taneously to evaluate the risk of hidden failure under 5 Conclusions the condition of data deficiency. 3) Coordination hidden failure of the relay protection and By summarizing and analyzing the research on hidden the SSCS. Although the coordination problem between failures of the relay protection and the SSCS, the author relay protections has been concentrated on, research thinks that the further research on hidden failures of the on the coordination problem is still relatively deficient relay protection and the SSCS in the future should be and requires further studies. Furthermore, after the conducted as follows: separation of power grid and power plants, the 1) Hidden failure modeling. So far, most are hidden coordination problem among the relay protection, the failure probability model of over-current protection SSCS and parameters of power plants related to power and distance protection, current differential protection grid has been gradually becoming outstanding, which which is often used as main protection seldom has to be paid attention to since it is a big threat hiding included. Research on hidden failure in SSCS is just in the operation of power grid. 4) Application of hidden failure research. The achieve- in its infancy. It will be a key to build a proper probability model of hidden failure in the SSCS. The ments of hidden failure research should be helpful to control scheme of the SSCS is a distributed control enrich the collection of contingencies and pre-decision scheme and more complicated than that of the relay system, and strengthen the prevention and emergency protection. During the model building of hidden control system. Simultaneously, it should also be failure in the SSCS, it has to consider the effect of helpful to identify the coordination hidden failures action failures or malfunctions of devices caused by between different controls on security and stability of hidden failures not only on protected elements and the power system, and find out the weak links of power neighboring elements, but also on the area charged by system. Then associated measures can be taken timely the SSCS. So inevitably it is more complicated to to enhance the security and reliability of power system. build hidden failure model of the SSCS. The proba- 5) Operation management of secondary equipment. bility and severity of consequences caused by different Human factors are also contributors to hidden failures hidden failures might be different and should be taken of the relay protection and the SSCS. The limitation of into account to assess the effects of hidden failures. testing-personnel quality and testing technology could The outcome of the assessment should be taken as one bring about hidden failures for ignorance of some of considerations in building probability model of defects in devices. So it should be done to obey hidden failures in secondary equipment. Work in the relevant electric regulations strictly, to update these field is underway and the details will be introduced in regulations with the development of power grid, and to follow-up articles. reinforce the management of the links like debugging, 2) Risk assessment of hidden failure. As members of operation & maintenance, and setting. Then some secondary equipment, relay protections and SSCDs are hidden dangers can be avoided and series accidents a part of operational risk sources of power grid. Until evoked by tiny problems can be reduced as much as now, the severity assessment of the effect of hidden possible. Though action criterions for relay protections failures in the relay protection on power grid is and SSCDs have been established based on the generally carried out based on the point of risk. operating characteristics of the power grid, these According to the ideas of risk assessment proposed in criterions can’t be adapt to the operating characteristics the research with achievements, such as research on of power grids forever and need to be updated timely. A power grid faults caused by lighting [45], hidden device itself has to be faced with many operation failures of secondary equipment will be treated as a problems such as harsh operating environment and 123 1742 Lili ZHAO et al. [13] Sun YZ, Cheng L, He J (2012) Power system operational reli- aging of components resulted from device’s long time ability theory. Tsinghua University, Beijing operation, possibly becoming contribute factors to [14] Cheng YM, Chen X, Ren JF, Li XM (2013) Study on hidden hidden failures too. So in order to reduce accidents failure of relay protection in power system. In: Paper presented rd caused by devices’ hidden failures as much as possible at 2013 IEEE 3 annual international conference on cyber technology in automation, control and intelligent systems strict supervision and early warning should be done (CYBER), Grand Metropark Hotel Nanjing and Nanjing with the condition-based maintenance date of sec- University of Science and technology (NJUST), 26–29 May ondary equipment. [15] Wu X, Zhang JH, Wu LW et al (2012) Method of operational risk assessment on transmission system cascading failure. Proc Acknowledgements This work is supported by State Grid Corpo- CSEE 32(34):74–82 (in Chinese) ration of China, Major Projects on Planning and Operation Control of [16] De La Ree J, Elizondo DC (2004) A methodology to assess the Large Scale Grid (SGCC-MPLG003-2012). impact of hidden failures in protection schemes. IEEE PES Power Syst Conf Expo 3:1782–1783. doi:10.1109/PSCE.2004. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://cre- [17] Guo CX, Lu HB, Yu B et al (2013) A survey of research on ativecommons.org/licenses/by/4.0/), which permits unrestricted use, security risk assessment of secondary system. Power Syst distribution, and reproduction in any medium, provided you give Technol 37(1):112–118 (in Chinese) appropriate credit to the original author(s) and the source, provide a [18] Wang SC (2005) Markov model for reliability analysis of dual- link to the Creative Commons license, and indicate if changes were redundant relays. Relay 33(18):6–10 (in Chinese) made. [19] Chen SH, Ma BY, Lei Y et al (2007) Integrative and quantitative calculation of reliability for relay protection system. Autom Electr Power Syst 31(15):111–115 (in Chinese) [20] Wu WC, Lv Y, Zhang BM (2009) On-line operating risk assessment of hidden failures in protection system. Proc CSEE References 29(7):78–83 (in Chinese) [21] Chen WH, Jiang QY, Cao YJ (2006) Risk assessment of power [1] Xiao SJ (ed) (2011) Control technology of security and stability system cascading failures considering hidden failures of pro- in power system. China Electric Power Press, Beijing (in tective relayings. Power Syst Technol 30(13):14–19 (in Chinese) [22] Wang C, Gao P, Xu Z et al (2007) Application of GO Chinese) [2] He DY (1998) The successive ponderation (layers-built analysis) methodology in reliability assessment protective relays. Autom over U.S. WSCC two outages in 1996. Electr Power 31:37–40 Electr Power Syst 31(24):52–56 (in Chinese) (in Chinese) [23] Huo C, Zhang PC, Liao XH (2008) Analytic method for relay [3] Lin WF, Sun HD, Tang Y et al (2010) Analysis and lessons of protection importance with consideration of hidden failures. East the blackout in Brazil power grid on November 10, 2009. Autom China Electr Power 36(3):63–65 (in Chinese) Electr Power Syst 34(7):1–5 (in Chinese) [24] Kececioglu D (1991) Reliability engineering handbook, vol 2. [4] Lin WF, Tang Y, Sun HD et al (2011) Blackout in Brazil PTR Prentice Hall, Englewood Cliffs power grid on February 4, 2011 and inspirations for stable [25] Chen J et al (2005) Cascading dynamics and mitigation operation of power grid. Autom Electr Power Syst 35(9):1–5 assessment in power system disturbances via a hidden failure (in Chinese) model. Electr Power Energy Syst 27:318–326 [5] Tamronglak S (1994) Analysis of power system disturbances [26] Bae K, Thorp JS (1999) A stochastic study of hidden failures in due to relay hidden failures. Dissertation, Virginia Polytechnic power system protection. Decis Support Syst 24:259–268 State University [27] Phadke AG, Horowitz SH, Thorp JS (1995) Anatomy of power [6] Zhang XS, Wang HF, Huang XM et al (2011) Discussion on system blackouts and preventive strategies by rational supervi- hidden failures in relay protection system. Electr Power Constr sion and control of protection systems. ORNL/Sub-89-SD630C/ 32(2):47–51 (in Chinese) 1. Oak Ridge National Laboratory, Oak Ridge [7] Zhang JJ (2012) Research on hidden failures related issues of [28] Huang J (2004) Adaptive wide area protection of power system. relay protection system. Dissertation, HeFei University of Dissertation, Iowa State University Technology (in Chinese) [29] Sun X (2009) Research on the detection of hidden failure in [8] Xu J (2011) Analysis and research on complex power system relay protection and risk analysis. Dissertation, Chongqing cascading failures considering hidden failure of protection. University (in Chinese) Dissertation, China Electric Power Research Institute (in [30] Duan XZ, Yang ZL, Cheng Xiao (2005) Performance analysis of Chinese) relay settings determined according to off-line calculation and [9] Wang ST (2010) Research on the monitoring methods of hidden on-line calculation. Autom Electr Power Syst 29(19):58–61 (in failures in relay protection. Dissertation, Chongqing University Chinese) (in Chinese) [31] Lv Y, Sun HB, Zhang BM et al (2005) Research and devel- [10] Yang MY, Tian H, Yao W (2010) Analysis of power system opment of an online intelligent early warning system of pro- cascading failure based on hidden failures of protective relaying. tective relaying. Autom Electr Power Syst 30(4):1–5 (in Power Syst Prot Control 38(9):1–5 (in Chinese) Chinese) [11] Bae K, Thorp JS (1998) An importance sampling application: [32] Bae K, Thorp JS (1999) Hidden failures in protection systems 179 bus WSCC system under voltage based hidden failures and and their impact on wide-area disturbances. Decis Support Syst relay operation. Decis Support Syst 24:259–268 24:259–268 [12] Yu XB, Singh C (2004) A practical approach for integrated [33] Wang H, Thorp JS (2001) Optimal locations for protection power system vulnerability analysis with protection failures. system enhancement: a simulation of cascading outages. IEEE IEEE Trans Power Syst 19(4):1811–1820 Trans Power Deliv 16(4):528–533 123 Review and prospect of hidden failure: protection system and security and stability control… 1743 [34] Xu J, Bai XM (2012) Power systems N-k contingency analysis in defence measures. Autom Electr Power Syst 29(8):1–4 (in consideration of protection hidden failure. Proc CSEE Chinese) 32(1):108–114 (in Chinese) [45] Xie YY, Xue YS, Wang HH (2013) Space–time early-warning [35] Cui Y, Wang C, Yang JH et al (2011) Inspection and repair of power grid fault probability by lightning. Autom Electr Power method for hidden faults of control circuit in high voltage circuit Syst 37(17):44–51 (in Chinese) breaker. High Volt Appar 47(12):96–99 (in Chinese) [36] Song JH, Li XM, Ji CA et al (2005) Current situation devel- opment prospect of security and stability control equipment. Lili ZHAO was born in Jiangsu, P.R. China, in 1988. She is an Autom Electr Power Syst 29(23):91–96 (in Chinese) engineer of Nari Technology Development Limited Company. Her [37] Zhang Y, Li JS, Huang H et al (2009) Improvement of line trip research interests include control technology about security and criterion of power system security and stability control equip- stability of power system. ment. South Power Syst Technol 3(3):74–76 (in Chinese) [38] Wang W, Chen J, Yu R et al (2012) Analysis of non-fault Xueming LI was born in Jiangsu, P.R. China, in 1965. He is a tutor in tripping criterion operation for area-based stability control State Grid Electric Power Research Institute and a senior engineering device. Power Syst Prot Control 40(2):120–124 (in Chinese) of Nari Technology Development Limited Company. His research [39] Cai M, Sun GH, Wu XC et al (2007) Analysis and application of interests include control technology about security and stability of AC fault criterion in power system stability control. Autom power system. Electr Power Syst 31(8):46–51 (in Chinese) [40] Zhu JJ, Huang ZY, Hong J et al (2011) Analysis on Shanghai Ming NI was born in Jiangsu, P.R. China, in 1969. He is a tutor in grid security and stability control device. Power Energy Hohai University and a chief expert of China. His research interests 32(3):190–193 (in Chinese) include control technology about security and stability of power [41] You JX, Wu R, Ye K et al (2011) Analysis of a blackout system, power system planning, and automation of power system. escalation caused by hidden failure lying in blocking logic between auto-switching protection and bus differential protec- Tianyu LI was born in Jiangsu, P.R. China, in 1992. He is a student tion. Autom Electr Power Syst 35(7):102–107 (in Chinese) of Nanjing University of Posts and Telecommunications. His research [42] Begovic M, Novosel D, Karlsson D et al (2005) Wide-area interests include stability analysis and control of power system. protection and emergency control. Proc IEEE 93(5):876–891 [43] Yin YH, Guo JB, Zhao JJ et al (2003) Preliminary analysis of Yameng CHENG was born in Jiangsu, P.R. China, in 1989. Her large scale blackout in interconnected North America power grid work is in Jiangsu Electric Power Research Institute. Her research on August 14 and lessons to be drawn. Power Syst Technol interests include automation of power system. …. 27(10):8–11 (in Chinese) [44] Fu ST (2005) Summary on power system security problems on 2004 IEEE PES Meeting and recommendation for developing

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Journal of Modern Power Systems and Clean Energy – Springer Journals

Published: Jun 4, 2015

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