CN109064071A - A kind of secondary system of intelligent substation methods of risk assessment based on shielding failure - Google Patents
A kind of secondary system of intelligent substation methods of risk assessment based on shielding failure Download PDFInfo
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Abstract
The invention discloses a kind of secondary system of intelligent substation methods of risk assessment based on shielding failure; it includes; S1: collecting the reliability data of secondary device in each protection system of intelligent substation, analyzes the failure scenario of each protection system, obtains the probability of happening of every kind of failure scenario；For every kind of failure scenario, the reliability in time index of corresponding electrical main connecting wire is calculated；According to the probability of happening and reliability in time index of protection every kind of failure scenario of system, the extraordinary failure risk or stoppage in transit failure risk of the protection system are calculated；The failure risk of other each protection systems is calculated, the integrated operation risk that whole station respectively protects system is obtained.The present invention comprehensively considers shielding failure probability, loses load, the failure-frequency relative value of main electrical scheme these three indexs, the risk indicator of establishing protective failure, the integrated risks of secondary system of intelligent substation under the different protection systemic effects of quantitative analysis.
Description
Technical Field
The invention relates to the technical field of intelligent substations, in particular to a secondary system risk assessment method of an intelligent substation based on protection failure.
Background
The intelligent substation plays important roles in voltage transformation, electric energy collection and distribution, voltage control and the like, and is an important link of an intelligent power grid. The IEC 61850-based intelligent substation has new characteristics of digitization, information network sharing, standardization and the like. The addition of new equipment such as a merging unit, an intelligent terminal and a switch increases factors and links influencing the reliability of a secondary system of the intelligent substation. The reliability research of the secondary system of the intelligent substation is paid attention by people. The historical data of the north american power reliability committee indicates that only 25% of blackout incidents and protections of power systems are not directly linked. In Shenzhen of 2012, "4.10" power failure event originated from the consecutive failure of primary power equipment, and incorrect actions of the protection system become important factors for triggering and propagating disturbance. Therefore, the reliability evaluation of the secondary system of the intelligent substation is particularly important.
In the existing literature, a network model of a secondary system is abstracted according to a physical structure of an intelligent substation, reliability of the secondary system is evaluated, and weight of equipment is mainly considered, but weight of each interval function in the secondary system is not considered. The prior document establishes a five-state space model of a dual relay protection system under 4 working conditions, reveals the relationship between the reliability of the protection system and the adjacent state conversion, but the model does not consider the reliability of related equipment. Reliability evaluation of a relay protection system of a new generation of intelligent substation is researched, and influence of the relay protection system on a primary system is not considered. The literature discusses the possible risks and failure consequences of each link of the protection function, and provides a risk assessment scheme of the primary and secondary system fusion. However, the secondary system risk index in the existing literature mainly considers the load loss amount, and the research on the influence of the failure of the protection system on the primary system and the consequences of the failure of the protection system is not deep enough.
The primary system risk assessment is already developed, but the secondary system risk assessment research is still in a research stage because people do not agree on relay protection failure consequences, the consequences caused by the principle failure of a protection system and the hardware failure are greatly different, the protection operation risk is derived from the probabilistic incorrect action behavior of the system, and the protection failure consequences are finally reflected by the primary system. Considering the actual effects of misoperation and refusal of the protection system, the risk assessment of the secondary system is not limited to the protection category, and is extended to the primary system, and reasonable indexes are selected to assess the operation risk of the secondary system by combining the consequences of the primary system and the secondary system.
Disclosure of Invention
In view of the above defects in the prior art, the present invention aims to provide a method for evaluating the risk of a secondary system of an intelligent substation based on protection failure, which comprehensively considers three indexes, namely, the probability of protection failure, the load loss amount and the fault frequency relative value of a main wiring, constructs a risk index of protection failure, and quantitatively analyzes the comprehensive risk of the secondary system of the intelligent substation under the action of different protection systems.
The invention aims to realize the technical scheme, and the intelligent substation secondary system risk assessment method based on protection failure comprises the following steps:
s1: collecting reliability data of secondary equipment in each protection system of the intelligent substation, analyzing failure situations of each protection system, and obtaining the occurrence probability of each failure situation;
s2: calculating a real-time reliability index of the corresponding main electrical wiring according to each failure situation;
s3: calculating the abnormal failure risk or outage failure risk of the protection system according to the occurrence probability and real-time reliability index of each failure situation of the protection system;
s4: and calculating the failure risk of other protection systems to obtain the comprehensive operation risk of all the protection systems in the total station.
Further, risk assessment index calculation of the intelligent substation protection system is also included, and the calculation process is as follows:
risk of operation R of a certain protection system jj：
In the formula, RjRepresenting the risk of the protection system j, n being the number of failure scenarios, pjiIs the probability of occurrence of the i-th failure scenario of the protection, SjiIs the loss of load, D, brought by the i-th failure scenario of the protectionjiIs the relative value of the main wiring fault frequency under the ith failure situation of the protection;
defining a comprehensive operational risk R of a total station protection systemsAnd then, the sum of the operation risks of all protection systems of the total station is as follows:
in the formula, RLiIs a line LiR of the protection systemBjIs a bus BjR of the protection systemTkIs a main transformer TkL, m and n are the number of corresponding protection systems in the intelligent substation.
Further, the reliability data of the secondary devices in each protection system of the intelligent substation collected in step S1 includes reliability data of the protection device, the merging unit, the intelligent terminal, the optical fiber, and the switch;
and collecting the steady-state probability of each device based on the Markov process according to the data, wherein the collection process is as follows:
calculating a state transition matrix R of a certain element:
the steady-state probability of an element in each state is represented by a 3-dimensional column vector P, and the matrix R and the vector P satisfy the following equation:
in the formula, PiThe ith dimensional column vector P corresponding to the element.
Further, before collecting the reliability data of step S1, the following reasonable assumptions and simplifications are included:
1) because the failure rate of each element is very low, the condition that two or more elements simultaneously fail is not considered;
2) the failure processes of the elements are independent; the protection system relates to a merging unit, an intelligent terminal, a protection device and the like, and each element failure is an independent individual behavior;
3) assuming that the voltage/current transformers all work normally;
4) two sets of protection systems at the same interval are independent and do not influence each other;
5) if the main protection refuses to be operated, the backup protection successfully operates and removes the fault;
6) if the circuit breaker fails, the fault is removed by failure protection;
7) information delay is not considered; the communication performance of the existing transformer substation meets the most severe time delay limit.
Further, the reliability data in step S1 includes reliability data of a single protection system, and the connection relationship of the reliability data of the single protection system tested is as follows:
the bus merging unit MU1 is connected with the line merging unit MU2 through a first optical fiber FB 1;
the line merging unit MU2 is connected with the line protection PL through a second optical fiber FB 2;
the line protection PL is connected with a line intelligent terminal IL through a third optical fiber FB 3;
the line intelligent terminal IL is connected with a spacing switch SW1 through a fourth optical fiber FB 4;
the interval switch SW1 is connected with the central switch SW2 through a fifth optical fiber FB 5;
the central switch SW2 is connected to the bus differential protection via a sixth optical fiber FB 6.
Further, the reliability data of the single protection system comprises: the steady state false action rate, the steady state rejection probability and the steady state availability; wherein,
single-set protection systemThe steady state error rate of the system is Pwu，Pwu＝2PMU_W+PPL_W+PIL_W；
The steady-state failure probability of the single set of protection is Pju，Pju＝2PMU_J+PPL_J+PIL_J+3PFB_J；
The steady-state availability of a single protection system is a, a is 1-Pwu-Pju。
Further, in step S1, the reliability data of the secondary device in each protection system of the intelligent substation includes reliability analysis data of the protection failure on the main connection line, and specifically includes:
(1) the line has no fault, and the line protection system malfunctions;
(2) when a line fails, the two sets of protection systems refuse to operate simultaneously;
(3) when a line fails, the incoming line breaker fails;
(4) the protection system works normally, and the breaker is normally tripped.
Due to the adoption of the technical scheme, the invention has the following advantages: on the basis of the existing secondary system reliability research results, the method firstly adopts the Markov process to research the steady-state availability, the false operation rate and the failure rate of each secondary device in the intelligent substation, and then researches the influence of protection false operation or failure operation on the reliability index of the primary system main wiring. The three indexes of the protection failure probability, the loss load and the fault frequency relative value of the main wiring are comprehensively considered, the risk index of the protection failure is constructed, and the comprehensive risk of the secondary system of the intelligent substation under the action of different protection systems is quantitatively analyzed.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Drawings
The drawings of the invention are illustrated as follows:
fig. 1 is a schematic flow chart of an intelligent substation secondary system risk assessment method based on protection failure.
FIG. 2 is a state transition diagram for a three-state element.
Fig. 3 is a structural diagram of a single set of 220kV line protection system in a "direct sampling and direct jumping" mode.
Fig. 4 is a reliability block diagram of a single protection system for a 220kV line.
Fig. 5 is an electrical structure schematic diagram of a 220kV typical substation.
Detailed Description
The invention is further illustrated by the following figures and examples.
Example, as shown in fig. 1; a risk assessment method for a secondary system of an intelligent substation based on protection failure comprises the following steps:
s1: collecting reliability data of secondary equipment in each protection system of the intelligent substation, analyzing failure situations of each protection system, and obtaining the occurrence probability of each failure situation;
s2: calculating real-time reliability indexes of corresponding main electrical wiring, such as relative values of main wiring fault frequency, aiming at each failure situation, and obtaining corresponding load loss by using corresponding simulation tools;
s3: calculating the abnormal failure risk or outage failure risk of the protection system according to the relative values of the occurrence probability, the load loss amount and the main wiring failure frequency of each failure situation of the protection system;
and S4, calculating the failure risk of other protection systems, and obtaining the comprehensive operation risk of the protection systems in the total station, and finally obtaining the proportion β of the failure risk of the protection system in the comprehensive operation risk of the total station protection system.
According to the definition of IEEE, risk is a composite manifestation of probability and outcome. The risk assessment of the existing intelligent substation secondary system mostly adopts load indexes as failure consequences.
Protection system malfunction or error, line normal shutdown, and abnormal shutdown all result in loss of delivered power. Protection maloperation or refusal operation not only brings loss of load, but also changes the structure of the main wiring and influences the reliability index of the main wiring. Considering that the protection system serves the safe and reliable operation of the primary equipment, the risk assessment of the intelligent substation protection system should relate the risk consequences of the protection system to the reliability changes of the main wiring. Aiming at each protection system in the intelligent substation, the invention mainly discusses the influence of the failure of the protection systems on the continuous power supply capability and the operation reliability of the secondary side bus, and the loss load represents the influence of the protection action on the power transmission quantity of the main wiring. Two parameters of the load loss amount and the real-time fault frequency relative value of the main wiring are adopted to comprehensively reflect the failure consequence of the power system under the condition of failure protection.
Incorrect operation of the protection system also poses additional risks to the operation of the grid. The risk evaluation of the intelligent substation does not consider the risk of the normal protection and removal of a certain equipment fault, and mainly examines the abnormal failure risk when the protection is abnormally failed and the shutdown failure risk when one set of double-set protection equipment is shutdown and the other set of double-set protection equipment is failed.
Risk of operation R of a certain protection system jj：
In the formula, RjRepresenting the risk of the protection system j, n being the number of failure scenarios, pjiIs the probability of occurrence of the i-th failure scenario of the protection, SjiIs the loss of load, D, brought by the i-th failure scenario of the protectionjiIs the relative value of the main wiring fault frequency (the ratio of the main wiring fault frequency after failure to the main wiring fault frequency during normal operation of the protection) under the ith failure situation of the protection. The operation risk of the protection system is specifically divided into an abnormal failure risk and an outage failure risk.
The abnormal failure risk of a certain protection system refers to the risk brought by the fact that a certain protection system does not normally act (refuses to act) when a power grid fails or the power grid does not fail and the action (misoperation) of the certain protection system occurs.
For a protection system with a dual configuration, the shutdown failure risk of a certain protection system refers to the risk that one protection system is normally and periodically overhauled or quits due to a fault while the other protection system is abnormally failed in the operation process of the dual protection system.
Defining a comprehensive operational risk R of a total station protection systemsThe total station protection system running risk sum is the sum of the running risks of all the protection systems when the protection systems between a power supply inlet wire and a load side bus are abnormal:
in the formula, RLiIs a line LiR of the protection systemBjIs a bus BjR of the protection systemTkIs a main transformer TkI, m, n are the number of corresponding protection systems in the intelligent substation of fig. 5.
The method comprises the steps of calculating abnormal failure risks of failure of each protection system, calculating outage failure risks caused by abnormality of the other protection system after one protection system exits for the protection systems with a certain double configuration, calculating abnormal risks of the other protection systems, adding the risks of all the protections to obtain the comprehensive risks of the total-station protection system, and dividing the abnormal failure risks or the outage failure risks of the protection systems by the comprehensive risks of the total-station protection system to obtain the proportion β of the failure risks of the protection systems to represent the influence of the failure of the protection systems on the comprehensive risks of the total-station protection system.
Firstly, calculating the steady-state probability of each device based on Markov process
The reliability data of each secondary device in the intelligent substation, such as a protection device, a merging unit, an intelligent terminal, an optical fiber and a switch, are shown in table 1. The system failure state caused by the fault of each device is different according to different links of the device in the system. For elements such as optical fibers, exchangers and the like used in an information transmission link, when information is lost, the protection system can only refuse to operate without generating misoperation; if faults occur to elements such as a merging unit, a protection device, an intelligent terminal and the like used in the links of data generation, judgment, execution and time service, system misoperation and system refusal can be caused. In the analysis process, the failure mode of the equipment is divided into two states of failure and misoperation, and the steady-state misoperation probability and the steady-state failure probability are considered to be respectively half of the total failure probability. The average repair time of all secondary devices is unified to 24h, and the repair rate mu is 1/(24/8760) ═ 365 times/year. Failure and repair of secondary equipment follows an exponential distribution.
TABLE 1 reliability data of each secondary device of intelligent substation
| Name of element | Failure rate | Rate of motion rejection | Rate of false activation |
| Protective device | 0.0067 | 0.0033 | 0.0033 |
| Intelligent terminal | 0.0067 | 0.0033 | 0.0033 |
| Merging unit | 0.0067 | 0.0033 | 0.0033 |
| Optical fiber | 0.0010 | 0.0010 | / |
| Switch | 0.0200 | 0.0200 | / |
And (3) solving the steady-state probability value of each secondary device in each state by using a Markov process, wherein a transition diagram among three states of the secondary device is shown in FIG. 2.
In FIG. 1, A is a normal operation state, B is a class I failure state, C is a class II failure state, and λ1、λ2、λ3Are respectively fromTransition probabilities, μ, from state A to state B, from state A to state C, and from state B to state C1、μ2、μ3The transition probabilities from state B to state a, from state C to state a, and from state C to state B, respectively, the state transition matrix R of the element is obtained from fig. 2:
the steady-state probabilities of the elements in each state are represented by a 3-dimensional column vector P, the matrix R and the vector P satisfy the following equation,
in this embodiment, the protection IED is taken as an example to describe a solving process of the secondary device steady-state probability.
In FIG. 2, state A corresponds to its normal state, state B corresponds to its malfunction state, state C represents its malfunction state, λ1＝0.0033，λ2＝0.0033，λ3＝0，μ1＝μ2＝365，μ30, state transition matrix R:
and due to P1+P2+P31, the following system of linear equations is obtained:
the system of equations is solved for the purpose of,obtaining the steady-state probabilities of the protection IED in each state as P1＝0.99998192，P2＝0.00000904，P3＝0.00000904。
And calculating the steady-state probability, the steady-state motion rejection rate and the steady-state false motion rate of each state of other secondary equipment in the same way, and referring to the table 2. The steady state probabilities of the table are close to the reliability calculations of the relevant literature.
TABLE 2 Steady-State probability tables for Secondary devices
Each protection system in the intelligent substation is composed of a protection device, an intelligent terminal, a merging unit and the like, the reliability index of each secondary device is obtained firstly, and the following reasonable assumptions and simplifications are made before the reliability index of each protection subsystem is solved:
1) since the failure rate of each element is very low, the situation that two or more elements fail at the same time is not considered.
2) The failure processes of the elements are independent of each other. The protection system relates to a merging unit, an intelligent terminal, a protection device and the like, and the failure of each element is an independent individual behavior.
3) It is assumed that the voltage/current transformers all work normally.
4) Two sets of protection systems at the same interval are independent and do not influence each other.
5) If the primary protection is refused, the backup protection will act successfully and remove the fault.
6) If the circuit breaker fails, the fault is removed by the failure protection.
7) Without regard to information latency. The communication performance of the existing transformer substation meets the most severe time delay limit.
As shown in fig. 4, according to the working principle of each protection, the function decomposition of IEC61850, and the reliability block diagram method, the reliability block diagrams of the subsystems such as line protection, bus protection, main transformer protection, etc. are given, and then the reliability indexes thereof are solved.
The 220kV line protection system is mainly completed by equipment such as a bus merging unit MU1, a line merging unit MU2, line protection equipment PL and a line intelligent terminal IL, wherein the line protection equipment PL sends a starting failure signal to busbar differential protection equipment PM through an interval switch SW1 and a central switch SW 2. The steady-state false operation rate, the steady-state failure probability and the steady-state availability of the single protection system can be solved according to the reliability block diagram of the single protection system of the 220kV line.
The steady state fault rate of the single set of protection system is Pwu，Pwu＝2PMU_W+PPL_W+PIL_W。
The steady-state failure probability of the single set of protection is Pju，Pju＝2PMU_J+PPL_J+PIL_J+3PFB_J。
The steady-state availability of a single protection system is a, a is 1-Pwu-Pju。
For a 220kV line duplicate protection system (if no special description exists, the '220 kV line protection system' refers to a duplicate protection system later), a fault cannot be protected and removed only when two sets of protection simultaneously refuse. Recording the power failure rate of the 220kV duplex protection system as PPaper reject，PPaper reject＝Pju1Pju2Wherein P isju1、Pju2The failure rates of the protection systems of the A set and the B set are respectively.
At least one set of protection system works normally and the other set does not malfunction, so that the protection system can be considered to work normally, and the stability of the dual protection system is recorded
The state probability is A, A ═ a1a2+a1Pju2+a2Pju1. Wherein, a1、a2The steady-state availability, P, of the protection systems of the set A and the set B, respectivelyju1、Pju2The steady state rejection rates of the protection systems of the A set and the B set are respectively.
The steady state error rate of the dual protection system is PError of＝1-A-PPaper reject。
The reliability index calculation results of the dualized 220kV protection system are shown in table 3. The availability of the 220kV line protection system is 0.999932, which is closer to the availability 0.999892679 in the prior art, and the calculation method is more accurate and reasonable.
TABLE 3 reliability of 220kV protection system in duplexed configuration
Second, analysis of influence of protection failure on reliability of main wiring
The effect of the protection system on the main wiring is embodied by the correct action and the incorrect action of protection respectively, and the incorrect action comprises two states of protection misoperation and protection refusal action. The changes brought to the main electrical wiring structure by failure (malfunction and refusal) of the protection system need to be analyzed, and then the influence of the reliability of the corresponding main wiring is analyzed.
For the typical intelligent substation electrical main connection shown in fig. 5, taking the protection system of the 220kV line a as an example, the influence of the protection failure on the reliability of the main connection is studied.
When a line is in fault and normal operation is protected, a power supply path is searched from a power supply of an electric main connection line to a certain feeder line to form minimum path sets, non-intersection processing is performed on each minimum path set by using a 'delete leave' algorithm, and reliability indexes of the main connection line when normal operation is protected are obtained through calculation and are shown in table 4.
TABLE 4 reliability index of main wiring during normal operation of protection
| Availability Ps | Degree of unavailability Qs | Frequency of failure fs | Failure rate λs | Mean Time Between Failures (MTBF)s(year) |
| 0.999764 | 0.000236 | 0.126919 | 0.126949 | 7.879017 |
Then, considering the reliability index of the main wiring under the condition of the protection failure of the 220kV line A, the following situations are divided:
1) line A has no fault, and the 220kV line protection system malfunctions
The 220kV line has no fault, when the rated delay of the software parameters in the merging unit is set to be wrong before leaving a factory, the sampling delay of the merging unit is asynchronous, and then protection misoperation is caused, however, the 220kV line protection sends a reclosing signal while sending a tripping signal to the intelligent terminal, and the latter reclosing can cut off transient faults. However, it is not excluded that the line a is mistakenly cut with a very small probability, and the structure of the main wiring is changed, and the reliability index of the main wiring at this time is obtained by using the "delete leave" algorithm as shown in table 5.
Comparing table 4 and table 5, it can be found that the real-time availability of the main electrical connection line is reduced from 0.999764 to 0.999763 due to line protection misoperation, the fault frequency is increased from 0.126919 to 0.127480, and the increasing proportion is 0.442%, so that the influence on the power supply capacity of the main connection line of the whole substation is small, because the intelligent substation has 4 power inlet lines, and the redundancy is high.
Real-time reliability of main wiring under meter 5220 kV line protection maloperation
| Availability ratio Ps | Rate of unavailability Qs | Frequency of failure fs | Failure rate λs | Mean time between failure MTBFs(year) |
| 0.999763 | 0.000237 | 0.127480 | 0.127510 | 7.844357 |
2) When the line A has a fault, the two sets of protection simultaneously refuse to operate
For high-voltage transmission lines of 220kV and above, two sets of mutually independent main protections are provided. The dual configuration protection system basically prevents the main protection from refusing action, so that the probability of refusing action of two sets of protection is extremely low. If the 220kV line protection fails, a high-voltage side circuit breaker of a main transformer G is tripped, a line A trips a side circuit breaker, and primary equipment influenced by the fault comprises the line A, a bus E and a main transformer G. The real-time reliability data of the main wiring at this time is shown in table 6.
Real-time reliability of main wiring under table 62220 kV line protection refusal action
| Availability Ps | Degree of unavailability Qs | Frequency of failure fs | Failure rate λs | Mean time between failure MTBFs(year) |
| 0.985698 | 0.014302 | 1.113182 | 1.129334 | 0.898326 |
3) Line A has a fault, and the 220kV incoming line breaker fails
The intelligent terminal receives a tripping command sent by the protection device, and if the circuit breaker of the 220kV line fails, the intelligent terminal failsAnd (4) protection action, namely tripping on the bus tie switch and all circuit breakers adjacent to the bus, operating the high-voltage side single bus at the moment, and stopping the operation of the primary equipment A, E. Let the failure probability of the breaker be PrejThen the probability of occurrence of the event is:
P＝A×Prej＝0.999932×0.000025＝0.0000245；
the real-time reliability data of the main wiring at this time is the same as scenario 2).
The real-time availability of the main connection of the transformer substation is reduced by 1.41%, the fault frequency of the main connection is increased from 0.126920 to 1.113182, and the increase ratio is large.
4) The protection normally works, and the breaker normally trips.
The probability of this event occurring is:
P＝A×(1-Prej)＝0.999932×(1-0.000025)＝0.99986761；
when the line A breaks down, the intelligent terminal receives a tripping signal from the protection device and then trips the breaker, the fault line A is normally cut off, and the real-time reliability of the main wiring is the same as that of the scenario 1).
Summarizing the four failure scenarios to obtain the occurrence probability of the 220kV line protection failure scenario and the affected primary equipment, as shown in table 9. Affected equipment refers to primary equipment that is removed or affected after a protection system fails. The occurrence probability of the failure scenario 1 is the false operation rate 0.00003397 of a single set of 220kV line protection system. The failure scenario 3 is that the circuit breaker fails to operate, and the influence of the circuit breaker failure at different positions is greatly different, and needs to be analyzed specifically, and is not detailed in any more detail.
The influence of the main transformer protection system and the 220kV bus protection system failure situation is shown in tables 7 and 8.
TABLE 7 influence table for failure situation of main transformer protection system
| Event sequence number | Probability of occurrence of event | Fault influencing device |
| 1 | 0.00016767 | G |
| 2 | 0.00000001 | A、B、E、G、I、L |
| 3a | 0.00002499 | A、B、E、G |
| 3b | 0.00002499 | G、I |
| 3c | 0.00002499 | G、L |
| 4 | 0.99975734 | G |
Note: 3a is the high-voltage side breaker failure, 3b is the medium-voltage side breaker failure, and 3c is the low-voltage side breaker failure
Influence table for failure situation of table 8220 kV bus protection system
| Event sequence number | Probability of occurrence of event | Fault influencing device |
| 1 | 0.00014520 | E |
| 2 | 0.000000009 | A、B、E、G |
| 3a | 0.00004999 | A、B、E、G |
| 3b | 0.00002499 | Total station power loss |
| 3c | 0.00002499 | A、B、E、G |
| 4 | 0.999755 | E |
Note: 3a is power line circuit breaker refusal, 3b is bus-bar circuit breaker refusal, and 3c is high-voltage side circuit breaker refusal
Affected primary equipment under condition of failure of watch 9220 kV line protection system
| Failure scenario | Probability of occurrence of event | Affected equipment |
| 1 | 0.00003397 | A |
| 2 | 1.6×10-9 | A、E、G |
| 3 | 0.0000245 | A、E |
| 4 | 0.999932 | A |
The specific calculation process is as follows:
take the line protection a of the power inlet in the 220kV substation electrical structure of fig. 5 as an example. The load loss under different fault conditions is obtained by simulation experiments.
(1) Abnormal failure risk calculation of 220kV line protection system
1) And the risk of protection misoperation when no fault exists.
For 220kV line protection glitches, p1Is the steady state false rate, S1Is the corresponding loss of load, D1Is the ratio of the failure frequency of the main connection after protection against malfunction to the failure frequency before malfunction, D1Each data is taken to formula (1) 0.12748017/0.12691938-1.00442, resulting in a risk of 220kV line protection malfunction:
R1＝0.00003397*20.4*1.00442＝0.000686；
2) double protection simultaneous refusal
Refusing action risk R of 220kV line protection2，p2Is its steady state rejection rate, S2Is the corresponding loss of load, D2Is a double-set protection refusing action
And (3) taking each data into (1) according to the ratio of the fault frequency of the rear electric main wiring to the fault frequency when the protection acts correctly, and obtaining the action refusing risk of the line protection:
R2＝1.6*10-9*809.7*(1.11318176/0.12748017)＝0.000011；
if the line has a fault, the protection system and the circuit breaker cooperate to remove the fault, which is not regarded as the operation risk of protection. The risk R of a 220kV line protection system is the sum of the risks of the two failure scenarios, i.e.
R＝R1+R2＝0.001393+0.000011＝0.001404；
Similarly, the risk of abnormal failure for each of the other protection systems is calculated, as shown in table 10.
TABLE 10 abnormal failure Risk tables for different protection systems
| Protection system | Risk of malfunction | Risk of refusal to move | Value of risk |
| 220kV line protection | 0.000686 | 0.000011 | 0.000697 |
| 220kV bus protection | 0.025981 | 0.000001 | 0.025981 |
| Main transformer protection | 0.029912 | 0.000001 | 0.029913 |
| 110kV bus protection | 0.001496 | 1.210094 | 1.225057 |
(2)220kV line protection system outage failure risk calculation
For the protection system of the 220kV line A, the shutdown failure risk R' of one protection system is that of the other protection system after one protection system is shut down and quits
Maloperation risk R'1And refusal to move Risk R'2And (4) summing. Calculated from equation (1):
R′1＝0.00003397*20.4*(0.12748017/0.12691938)＝0.000696。
R′2＝0.00003945*809.7*(1.11318176/0.12748017)＝0.278930。
R′＝R′1+R′2＝0.279626；
similarly, the shutdown failure risk of other duplicate protection systems is calculated, and the calculation result is shown in table 11.
TABLE 11 shutdown failure Risk tables for different protection systems
| Protection system | Risk of malfunction | Risk of refusal to move | Risk of outage failure |
| 220kV line protection | 0.000696 | 0.278930 | 0.279626 |
| 220kV bus protection | 0.012990 | 0.515600 | 0.528589 |
| Main transformer protection | 0.013343 | 0.781188 | 0.794531 |
(3) Comprehensive risk calculation of total-station protection system under outage failure risk of 220kV line protection system
For the protection systems of the 220kV line, when the other protection system can generate the misoperation and the refusal of protection after one protection system exits, the shutdown failure risk R 'is obtained'L220＝0.279626。
The risk of abnormal failure of other protections is calculated at this time, and is respectively:
abnormal failure risk R of certain 220kV line protection systemL220＝0.000697。
Abnormal failure risk R of certain 220kV bus protection systemB220＝0.025981。
Abnormal failure risk R of certain main transformer protection systemT＝0.029913。
Abnormal failure risk R of certain 110kV bus protection systemB110＝1.225057。
The comprehensive operation risk R of the total station protection system under the condition that a single set of 220kV line protection system stops operation and the other set of line protection system fails is as follows:
R＝R’L220+3*RL220+2*RB220+2*RT+2*RB110；
＝0.279626+3*0.000697+2*0.025981+2*0.029913+2*1.225057＝2.843619；
220kV line shutdown failure risk R'L220Ratio of integrated risk R at total station protection system β:
β＝R’L220/R＝0.279626/2.843619＝9.83％；
similarly, the comprehensive risk and the proportion of the comprehensive risk of the intelligent substation total station protection system under the outage failure risk effect of other duplex protection systems are calculated, as shown in table 12.
Through the calculation, risk values caused under different failure situations (abnormal protection actions or one set of failure and the other set of failure) of different protections of the intelligent substation can be obtained quantitatively, the proportion of failure risks of a certain protection system in the comprehensive risks of the total-station protection system can be obtained, and the influence degree of each protection failure can be obtained. TABLE 12 comprehensive risks and their occupation ratios of the protection systems of the intelligent substation under the effect of outage failure risks of the different protection systems
| Protection system | Risk of outage failure | Total station integrated risk | Outage failure percentage β (%) |
| 220kV line protection | 0.279626 | 2.843619 | 9.83 |
| 220kV bus protection | 0.528589 | 3.070126 | 17.22 |
| Main transformer protection | 0.794531 | 3.332136 | 23.84 |
The invention provides a comprehensive risk assessment method for an intelligent substation secondary system considering protection failure. The steady-state probability of each secondary device is calculated by using a Markov process, and a foundation is laid for risk calculation for protecting the distributed functions. And (3) calculating the steady-state fault action rate, the steady-state rejection rate and the steady-state availability of each protection system by adopting a reliability frame graph method according to the decomposition of each function in the IEC61850 aiming at the intelligent substation. The method is characterized in that three factors of the occurrence probability, the load loss amount and the main wiring fault frequency relative value of a certain protection system under each failure situation are comprehensively considered, the abnormal failure risk of the certain protection system is constructed, and the outage failure risk of the duplicate protection system is considered.
The method comprises the steps of calculating the reliability index of a main wiring under the failure situation aiming at various failure situations of various protection systems in a specific intelligent substation, and obtaining the abnormal failure risk, the outage failure risk and the proportion of the comprehensive risk of the protection systems in the total substation, so that the influence of the failure of the protection systems on the operation risk of the total substation is quantitatively reflected, and a certain reference is provided for the operation and maintenance of the intelligent substation.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.
Claims (7)
1. A risk assessment method for a secondary system of an intelligent substation based on protection failure is characterized by comprising the following steps:
s1: collecting reliability data of secondary equipment in each protection system of the intelligent substation, analyzing failure situations of each protection system, and obtaining the occurrence probability of each failure situation;
s2: calculating a real-time reliability index of the corresponding main electrical wiring according to each failure situation;
s3: calculating the abnormal failure risk or outage failure risk of the protection system according to the occurrence probability and real-time reliability index of each failure situation of the protection system;
s4: and calculating the failure risk of other protection systems to obtain the comprehensive operation risk of all the protection systems in the total station.
2. The intelligent substation secondary system risk assessment method based on protection failure according to claim 1, further comprising calculating risk assessment indexes of the intelligent substation protection system, wherein the calculation process is as follows:
risk of operation R of a certain protection system jj：
In the formula, RjRepresenting the risk of the protection system j, n being the number of failure scenarios, pjiIs the probability of occurrence of the i-th failure scenario of the protection, SjiIs the loss of load, D, brought by the i-th failure scenario of the protectionjiIs the relative value of the main wiring fault frequency under the ith failure situation of the protection;
defining a comprehensive operational risk R of a total station protection systemsAnd then, the sum of the operation risks of all protection systems of the total station is as follows:
in the formula, RLiIs a line LiR of the protection systemBjIs a bus BjR of the protection systemTkIs a main transformer TkL, m and n are the number of corresponding protection systems in the intelligent substation.
3. The intelligent substation secondary system risk assessment method based on protection failure according to claim 1, wherein the reliability data in step S1 includes reliability data of protection devices, merging units, intelligent terminals, optical fibers and switches;
and collecting the steady-state probability of each device based on the Markov process according to the data, wherein the collection process is as follows:
calculating a state transition matrix R of a certain element:
the steady-state probability of an element in each state is represented by a 3-dimensional column vector P, and the matrix R and the vector P satisfy the following equation:
in the formula, PiThe ith dimensional column vector P corresponding to the element.
4. The intelligent substation secondary system risk assessment method based on protection failure according to claim 1, wherein before collecting reliability data of secondary devices in each protection system of the intelligent substation in the step S1, the following reasonable assumptions and simplifications are further included:
1) because the failure rate of each element is very low, the condition that two or more elements simultaneously fail is not considered;
2) the failure processes of the elements are independent; the protection system relates to a merging unit, an intelligent terminal, a protection device and the like, and each element failure is an independent individual behavior;
3) assuming that the voltage/current transformers all work normally;
4) two sets of protection systems at the same interval are independent and do not influence each other;
5) if the main protection refuses to be operated, the backup protection successfully operates and removes the fault;
6) if the circuit breaker fails, the fault is removed by failure protection;
7) information delay is not considered; the communication performance of the existing transformer substation meets the most severe time delay limit.
5. The intelligent substation secondary system risk assessment method based on protection failure according to claim 1, wherein the reliability data in step S1 includes reliability data of a single protection system, and the connection relationship of the reliability data of the single protection system in the test is as follows:
the bus merging unit MU1 is connected with the line merging unit MU2 through a first optical fiber FB 1;
the line merging unit MU2 is connected with the line protection PL through a second optical fiber FB 2;
the line protection PL is connected with a line intelligent terminal IL through a third optical fiber FB 3;
the line intelligent terminal IL is connected with a spacing switch SW1 through a fourth optical fiber FB 4;
the interval switch SW1 is connected with the central switch SW2 through a fifth optical fiber FB 5;
the central switch SW2 is connected to the bus differential protection via a sixth optical fiber FB 6.
6. The intelligent substation secondary system risk assessment method based on protection failure according to claim 5, characterized in that the reliability data of a single set of protection system comprises: the steady state false action rate, the steady state rejection probability and the steady state availability; wherein,
the steady state fault rate of the single set of protection system is Pwu，Pwu＝2PMU_W+PPL_W+PIL_W；
The steady-state failure probability of the single set of protection is Pju，Pju＝2PMU_J+PPL_J+PIL_J+3PFB_J；
The steady-state availability of a single protection system is a, a is 1-Pwu-Pju。
7. The intelligent substation secondary system risk assessment method based on protection failure according to claim 1, wherein the reliability data of the secondary devices in each protection system of the intelligent substation in step S1 includes reliability analysis data of the protection failure on the main wiring, specifically including:
(1) the line has no fault, and the line protection system malfunctions;
(2) when a line fails, the two sets of protection systems refuse to operate simultaneously;
(3) when a line fails, the incoming line breaker fails;
(4) the protection system works normally, and the breaker is normally tripped.
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| CN113361856A (en) * | 2021-05-07 | 2021-09-07 | 广东电网有限责任公司电力调度控制中心 | Method and device for evaluating running risk of direct-current transmission system |
| CN113361856B (en) * | 2021-05-07 | 2022-10-28 | 广东电网有限责任公司电力调度控制中心 | Method and device for evaluating running risk of direct-current transmission system |
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