summary
In an article published in the 8th issue of "Electrical Technology" magazine in 2018, Shen Wenwei and Lu Yao, researchers from State Grid Jinan Power Supply Company and State Grid Shandong Electric Power Company Maintenance Company, pointed out that the anti-misoperation interlocking system of intelligent substations is very different from the basic architecture of conventional substations. At present, the power operation departments still lack experience in the understanding, acceptance, operation and management of anti-misoperation interlocking systems of intelligent substations.
Based on my experience participating in the acceptance testing of the first fully operational smart substation in Jinan with a three-layer interlocking system, this paper provides an in-depth analysis of the three-layer architecture of the smart substation anti-misoperation interlocking system. It focuses on the implementation principle, characteristics, and main advantages of the bay-layer anti-misoperation interlocking system, proposes a "six-step method" for the acceptance testing of the smart substation anti-misoperation interlocking system, and finally summarizes the key points of operation and maintenance of the smart substation anti-misoperation interlocking system, hoping to provide a useful reference for peers.
In order to prevent electrical misoperation accidents, electrical equipment should be equipped with an anti-misoperation interlocking device (system), referred to as "anti-misoperation device (system)", and the anti-misoperation device (system) should be designed, constructed and put into operation at the same time as the main equipment ("three simultaneous" system) [1]. The anti-misoperation device (system) mainly prevents five types of accidents [2-3]: preventing accidental opening and closing of circuit breakers, preventing opening and closing of disconnecting switches under load, preventing the connection (closing) of grounding wires (grounding disconnecting switches) while energized, preventing the closing of circuit breakers (disconnecting switches) with grounding wires (grounding disconnecting switches) connected, and preventing accidental entry into energized compartments. Therefore, the anti-misoperation interlocking system is also called the "five-prevention system".
Currently, smart substations are widely used in power systems. Compared to conventional substations, the anti-malfunction systems of smart substations differ significantly. Conventional substations have two main types of anti-malfunction systems: independent anti-malfunction systems and integrated monitoring and control anti-malfunction systems.
An independent anti-misoperation system refers to a system with a separate anti-misoperation host that communicates with the monitoring system to achieve device status alignment and remote control command transmission. An integrated monitoring and control anti-misoperation system refers to a system with embedded anti-misoperation software, where both share a device database to achieve remote control operation anti-misoperation verification. Conventional anti-misoperation devices include electrical interlocks, mechanical interlocks, electromagnetic locks, mechanical coded locks, and electrical coded locks, etc., to achieve specific device interlocking.
The intelligent substation anti-misoperation system includes three layers of anti-misoperation: station control layer, bay layer, and process layer. Among them, the station control layer anti-misoperation adopts an integrated monitoring and control anti-misoperation system, while the process layer anti-misoperation is basically the same as that of a conventional substation. The bay layer anti-misoperation is based on the measurement and control device and has anti-misoperation soft interlocking and hard interlocking functions, which can provide anti-misoperation verification support for sequential control [4-5].
At present, there is still a lack of understanding, acceptance and operation and maintenance experience of the anti-misoperation system of intelligent substation. Most operation and maintenance units adopt traditional thinking to carry out anti-misoperation management. They usually directly take the bay layer anti-misoperation out of operation and only retain the station control layer and process layer anti-misoperation. This not only wastes equipment resources, but also poses a threat to the safe operation of intelligent substation [6].
This article, based on the acceptance practice of the first fully deployed three-layer anti-misoperation system in Jinan, provides an in-depth analysis of the three-layer anti-misoperation architecture of intelligent substations. It focuses on the implementation principle, technical characteristics, and main advantages of bay-layer anti-misoperation, proposes a "six-step method" for the acceptance of intelligent substation anti-misoperation systems, and finally summarizes the key points of operation and maintenance of intelligent substation anti-misoperation systems, hoping to provide a reference for the operation and maintenance management of intelligent substation anti-misoperation systems.
1. Three-layer architecture of the anti-misoperation interlocking system
The basic architecture of a smart substation is divided into three layers: the station control layer, the bay layer, and the process layer. The station control layer includes automated station-level monitoring and control systems, station area control, communication systems, and time synchronization systems, enabling monitoring, control, alarm, and information exchange for all equipment in the station. The bay layer includes relay protection devices, fault recorders, measurement and control devices, and metering devices. The process layer includes primary equipment, intelligent terminals, and merging units. Based on the equipment level at which the anti-malfunction system resides, the smart substation's anti-malfunction system is divided into three layers: station control layer anti-malfunction, bay layer anti-malfunction, and process layer anti-malfunction.
Figure 1 shows a typical "three-layer, two-network" framework structure of a smart substation, namely the station control layer, bay layer, and process layer, as well as the station control layer network and the process layer network. The monitoring unit sends remote control commands to the intelligent terminals of the primary equipment through the measurement and control devices to achieve remote control operation. This process requires three layers of error prevention verification. Each layer will be analyzed in detail below:
Figure 1. Three-layer anti-misoperation architecture of intelligent substation
1) Station control layer error prevention: The integrated monitoring and error prevention system adopts an integrated design of monitoring and error prevention software. The monitoring screen and the error prevention screen can be switched, and data interaction between the two is automatic. Each bay is equipped with a "Station control layer error prevention enabled/disabled" indicator, which can be independently enabled/disabled for the station control layer error prevention of this bay.
2) Interval layer anti-misoperation is implemented through monitoring and control devices and intelligent terminals. The anti-misoperation interlocking logic is stored in the monitoring and control device. After the monitoring and control device collects the position status information of relevant primary equipment in real time (directly or via network sharing), it determines in real time whether the operation command conforms to the anti-misoperation logic and sends the result to the intelligent terminal. If correct, the electrical operation circuit of the intelligent terminal is opened; otherwise, the operation circuit is locked. The interval layer anti-misoperation is activated or deactivated by "unlocking the soft pressure plate" or "unlocking the hard pressure plate" of the monitoring and control device or "unlocking the handle" of the intelligent control cabinet. Activating any one of these three methods deactivates the interval layer anti-misoperation mechanism.
3) Process-level anti-misoperation refers to traditional anti-misoperation devices installed on process-level equipment, including electrical interlocking circuits, mechanical interlocks, electromagnetic locks, mechanical coded locks, and electrical coded locks. The type of anti-misoperation used at the process level varies depending on the type of primary electrical equipment. For example, GIS equipment typically uses electrical interlocks or electrical coded locks, while switchgear equipment generally uses mechanical interlocks, coded locks, or electromagnetic locks. Mechanical and electrical coded locks are generally managed using computer keys. Maintenance personnel can exit the process-level anti-misoperation measures for this bay using the "electrical unlock handle" on the control cabinet.
2. Implementation principle and main advantages of anti-misoperation interlocking in the interlocking layer
This article takes the bay-level anti-misoperation implementation method of a 110kV substation as an example to illustrate the bay-level anti-misoperation principle. Figure 2 shows a partial primary wiring diagram of the 110kV substation. The 110kV system of this substation adopts internal bridge wiring. The following analysis focuses on the interlocking of related equipment on the 110kV I busbar.
Figure 2. Partial electrical wiring diagram of a 110kV substation.
The lateral interlocking logic of the P11-D1 grounding isolating switch on the PT busbar side of the 110kV I bus is quite complex, spanning four bays and related to the PTP11 bay of the 110kV I bus, the 101 bay of the 110kV Dangling line, the 103 bay of the 110kV incoming line of the No. 1 main transformer, and the 104 bay of the 110kV I and II inner bridges. If conventional electrical interlocking is used, its electrical interlocking circuit requires the auxiliary contacts of the P11, 101-1, 103-1, and 104-1 isolating switches to be connected in series across bays, resulting in complex wiring and significant difficulties in troubleshooting contact faults. This article takes the interlocking of the P11-D1 grounding isolating switch on the PT busbar side of the 110kV I bus as an example to illustrate how to achieve effective interlocking through bay-level anti-misoperation measures.
The permissive logic of the P11-D1 grounding disconnector is shown in Figure 3. The permissible operating conditions for the P11-D1 grounding disconnector are: P11 disconnector, 101-1 disconnector, 103-1 disconnector, and 104-1 disconnector. That is, the P11-D1 grounding disconnector is allowed to operate when all disconnectors connected to the 110kV I busbar are in the open position. If any condition is not met, for example, if 101-1 is closed (Figure 4), the operation of the P11-D1 grounding disconnector is blocked.
The engineering commissioning personnel downloaded the aforementioned interlocking logic program into the monitoring and control device of the 110kV I bus PT. This monitoring and control device then uses real-time remote signaling information from relevant equipment (P11, 101-1, 103-1, 104-1) to...
Figure 3P11-D1 Grounding Disconnect Switch Permissive Operation Logic
Figure 4 shows the blocking operation logic of the P11-D1 grounding disconnector.
The position of the isolating switch is monitored in real time to determine whether the operating conditions of the P11-D1 grounding isolating switch are met, as shown in Figure 4. Misoperation prevention at the bay level is achieved through a hard interlocking contact K1 connected in series in the equipment operating circuit, which forces the electrical equipment to be interlocked. This hard interlocking contact K1 is located in the intelligent terminal. If the operating conditions are met, the monitoring and control device outputs an operation permission signal to the intelligent terminal of that bay, controlling the hard interlocking contact K1 in the P11-D1 electrical operating circuit to close, thereby opening the electrical control circuit of P11-D1; otherwise, the hard interlocking contact K1 remains open, cutting off the P11-D1 electrical operating circuit, and simultaneously interlocking remote control and local operation.
Specifically, to prevent the risk of interlocking caused by reversed remote signaling of the busbar-side disconnector position or incomplete auxiliary contact positioning, the monitoring and control device determines the equipment status by collecting "dual-position remote signaling" information, that is, simultaneously collecting the positions of the normally open and normally closed auxiliary contacts. When the normally open contact value = 1 and the normally closed contact value = 0, the disconnector is determined to be in the closed position; when the normally open contact value = 0 and the normally closed contact value = 1, the disconnector is determined to be in the open position; when both position values are 1, or both values are 0, the disconnector position is determined to be invalid, and the equipment operation circuit is interlocked to ensure effective interlocking.
Misoperation prevention in the control and measurement device bay layer generally includes two parts: soft interlocking (misoperation prevention logic judgment) and hard interlocking (controlling the opening or closing of the interlocking contacts of the intelligent terminal). Taking the closing process of the remote control P11-D1 grounding isolating switch as an example, the functions of soft interlocking and hard interlocking are analyzed, as shown in Figure 5.
Figure 6. Flowchart of remote control closing of P11-D1 grounding disconnect switch
The specific process is as follows: remotely select "remotely close P11-D1 grounding isolating switch" → the anti-misoperation logic (soft interlocking) is true → the hardware selection object is correct → the selection is successful → open the hard interlocking contact (hard interlocking) → remotely execute → the hardware execution object is correct → the execution is successful → wait for the switch to actually operate or fail to time out → retract and disconnect the hard interlocking contact.
Compared with traditional error prevention, spacer layer error prevention has the following advantages:
1) Comprehensive coverage
It fully covers all equipment nodes in the station. As long as the remote signaling signal of any switch, disconnector, or other equipment in the substation is connected to the monitoring and control device, it can participate in the bay layer anti-misoperation interlocking[7]. Relying on the intelligent substation GOOSE networking, the remote signaling information of the monitoring and control device is shared, saving a lot of communication wiring and making implementation convenient.
2) Real-time interlocking
By acquiring remote signaling signals of all station equipment in real time, and judging the electrical operation circuits of equipment to automatically lock or open based on the anti-misoperation logic, intelligent locking is truly realized, and the phenomenon of "empty trip" in traditional microcomputer anti-misoperation is eliminated[8].
3) Forced locking
Electrical interlocking uses multiple interlocking contacts connected in series, and the auxiliary contacts have a higher probability of failure. The bay layer anti-misoperation system uses only one hard interlocking contact, resulting in a lower probability of hard circuit failure. Although errors in equipment remote signaling can also cause interlocking failure, as mentioned earlier, this risk can be effectively reduced through dual-position remote signaling. Therefore, overall, the bay layer anti-misoperation failure probability is relatively low. On the other hand, when the monitoring and control device malfunctions, or only the monitoring and control device is under maintenance, or when communication with related equipment is interrupted, the bay layer interlocking contact remains normally open, automatically locking the equipment operation circuit [9-10]. Note: When the intelligent terminal and the monitoring and control device are under maintenance simultaneously (i.e., simultaneously activated), the interlocking contact closes, thus opening the equipment operation circuit.
4) Highly expandable
The bay-level anti-misoperation mechanism obtains the real-time location of the equipment through data acquisition or network sharing, offering strong scalability. When the equipment is modified or expanded, there is no need to change the hard circuit of the equipment's electrical operation, which can save a lot of cable laying work; however, it should be noted that the "soft circuit" of the bay-level anti-misoperation mechanism (the telemetry and control device subscribing to the remote signaling quantity SCD and the interlocking logic) still needs to be modified and downloaded and tested before the bay-level anti-misoperation expansion can be completed.
It should be specifically noted that bay-level anti-misoperation and traditional electrical anti-misoperation are two different interlocking methods. According to existing regulations, they are not interchangeable but complementary. The DL/T1404—2015 standard also recommends using both interlocking methods simultaneously to increase the reliability of the anti-misoperation system.
3. Acceptance Method
The three-layer interlocking relationship of the intelligent substation anti-malfunction system includes two aspects: ① The three layers are logically ANDed, meaning that the electrical equipment control circuit can only be opened when all three operation permitting conditions are met simultaneously; ② The three layers are independent of each other, meaning that if any layer of anti-malfunction fails, that layer of anti-malfunction system can be independently deactivated without affecting the other two layers. To ensure the correctness of each layer of anti-malfunction system, each layer should be accepted separately.
This article proposes a "six-step method" for acceptance testing, which includes six steps: reviewing the error prevention logic table, compiling the error prevention acceptance form, independently accepting each layer of error prevention system, verifying local/remote operation interlocks separately, verifying interlock/permission conditions separately, and jointly debugging the three layers of error prevention system.
1) Review the error prevention logic table
First, verify the correctness of the error prevention logic. The error prevention logic should comply with relevant regulations and procedures, and meet the safety requirements of various operating modes and equipment operating states. Note that the logic at the station control layer, bay layer, and process layer should be consistent and free from conflict.
2) Compile an error prevention acceptance form
The anti-misoperation acceptance form should include the interlocking information of all equipment. During acceptance, each item should be checked according to the form. After each item is checked, a "√" should be marked in the corresponding position to confirm. It is forbidden to omit or skip items.
3) Independently inspect and accept the anti-misoperation systems at each level.
When accepting a certain layer of anti-misoperation system, the other two layers of anti-misoperation systems should be shut down to ensure the independence of the acceptance of that layer of anti-misoperation system; otherwise, it is impossible to determine whether the interlocking of that layer is effective.
4) Verify the local/remote control interlock separately.
During acceptance testing, both local and remote operations should be conducted to ensure the reliability of the anti-misoperation system in locking both local and remote operations.
5) Verify the locking/permission conditions separately.
During acceptance testing, both the locking and permissive conditions should be verified in both directions to ensure that each AND condition reliably locks the device and each OR condition reliably operates.
6) Joint debugging of the three-layer anti-misoperation system
After the station control layer, bay layer, and process layer anti-misoperation measures have been independently accepted, a joint debugging process should be conducted. That is, after all three layers of anti-misoperation measures are put into operation, local and remote operation tests should be performed according to the anti-misoperation acceptance checklist to ensure that the interlocking logic of the three layers of anti-misoperation measures is consistent.
4. Maintenance and Operation Precautions
1) Each layer of the error prevention system must pass acceptance testing before it can be put into use. Design drawings, acceptance records, error prevention logic, equipment spare parts lists, and other relevant documents should be properly preserved for future maintenance.
2) Data backups for each layer of error prevention logic should be performed, and updates should be made promptly when information changes, with update records maintained [11-12]. Backups must be the most recent data, and the previous backup must be deleted at the same time with each backup.
3) When the substation wiring method, equipment is changed, or the measurement and control device is upgraded, the anti-misoperation logic should be updated in a timely manner. It can only be put into operation after the equipment operation and maintenance management unit has verified that it is correct and after a comprehensive anti-misoperation transmission test is passed.
4) Each layer of anti-misoperation system should be equipped with independent and reliable anti-misoperation activation and deactivation control measures. The operation and maintenance personnel should be clear about the activation and deactivation methods of each layer of anti-misoperation system, including the station control layer anti-misoperation activation and deactivation (usually activated and deactivated by interval, and cannot be deactivated throughout the station), the interval layer measurement and control device unlocking soft pressure plate (hard pressure plate), the smart terminal unlocking key, the electrical interlocking unlocking key, and other unlocking tools. Unlocking tools (keys) or passwords should be strictly managed in accordance with relevant regulations. When unlocking or deactivating the anti-misoperation interlocking device, relevant regulations should be strictly followed [13]. No one may arbitrarily deactivate the anti-misoperation interlocking device.
5) Annual training should be conducted for substation operation and maintenance personnel to ensure they are proficient in anti-malfunction devices and achieve "four understandings and three skills" (understanding the principles, performance, structure, and operating procedures of anti-malfunction devices; being able to operate them proficiently; being able to troubleshoot problems; and being able to maintain them) [3,14]. Newly hired operators must undergo training on anti-malfunction devices and pass the examination.
in conclusion
This paper analyzes the architecture of the intelligent substation anti-misoperation system, the implementation principle and main advantages of the bay-level anti-misoperation system, and summarizes the acceptance and operation and maintenance methods of the three-layer anti-misoperation system for intelligent substations, drawing the following conclusions:
1) The anti-misoperation system of intelligent substation is divided into a three-layer architecture: station control layer, bay layer and process layer.
2) The anti-misoperation interlocking of the interval layer is based on the measurement and control device and the IEC61850 network, and has the advantages of comprehensive interlocking, real-time interlocking, mandatory interlocking and easy expansion.
3) A "six-step method" for the acceptance of intelligent substation anti-misoperation systems was summarized to ensure that the anti-misoperation measures at each level are correct and effective.
4) The operation and maintenance of the intelligent substation anti-misoperation system should include backing up the interlocking logic data, managing the unlocking tools or passwords for each level of interlocking, and providing personnel training.
