Ways to ensure reliable operation of relay protection

With the sustained development of China's economy, various types of electrical equipment have increased dramatically, and the normal operating current and short-circuit current in the power system have also increased. Relay protection technology has developed in this context. At present, relay protection in many areas in China cannot be operated reliably, and failures in protection actions and large-scale power outages occur from time to time, which seriously affect the smooth progress of people's production and life. Therefore, it is undoubtedly important to improve the reliability of relay protection operation.

First, ensure reliable operation of relay protection

1. Ensure that the acceptance and daily operation of relay protection can be carried out reasonably.

( 1 ) Accept inspection and acceptance of relay protection. After the completion of the installation of relay protection devices, it is necessary to carry out debugging and strict self-inspection to eliminate potential safety hazards in the bud. The factory may organize the maintenance department, operation department, and production department to carry out tests such as whole sets, switches, and jumps of the whole device, and run the effective time under the command of the production personnel of the relay protection equipment. They can be put into use only after acceptance.

( 2 ) Scientific operation and regular inspection. When there is a change in the situation concerning the relay protection device, the person in charge will make a detailed record of the change including the specific content and time of the change, and check it with the precautions. Check the operation of the device during the shift. If conditions allow, one or two comprehensive and systematic inspections should be arranged in the morning and evening classes. The contents of the inspection mainly include: whether the switch and the position of the pressure plate are correct; whether the connection of each circuit is normal; whether the relay contact is in good condition, whether the temperature of the coil and the additional resistance is appropriate, whether it is damaged by high temperature; whether the protection pressure plate starts to be used; Whether the monitor lamp indicator is accurate or not; whether the light plate, alarm bell, or accident sound is faulty.

( 3 ) Strengthen business training for operators. In addition to requiring operators to have a wealth of theoretical knowledge, they should also be given appropriate pre-job training so that they can understand the principles of relay protection. Before routine inspection of the device, the operator should familiarize himself with and understand the secondary circuit terminals, relays, signal drop and platen, etc., so that the operation can be divided according to the scope of the equipment scheduling. When writing the instruction manual for the equipment, it should be detailed, accurate, and standardized so that the on-duty personnel can better understand the contents of the manual and avoid misoperation due to lack of understanding.

In addition, companies should pay attention to the special circumstances that may arise when training employees to avoid unnecessary accidents. For example, in a 110kV substation, a 110kV female PT voltage loss occurs , the equipment is self-powered, the main supply jumps open, and the supply is not available, resulting in power loss at the entire station. After analyzing the cause of the accident, it was found that the secondary voltage line A630 Fenghuang terminal block reversed, resulting in PT pressure loss, jump the main line for the switch in the hand jump loop, hand jump will be prepared from the investment block, so that the supply is not closed Total station power loss. The phoenix terminal block can not be observed by the naked eye. The fixed value is issued by the staff responsible for the fixed value management. The actual load current of the site is only known to the protection personnel. The operation of the relay protection device is sometimes not stable. It should explain and attach importance to possible situations. Therefore, the accident was mainly due to the lack of attention paid by the staff to the operation of the relay protection device and the lack of accurate operation of the relay.

2. Transform the idea of â€‹â€‹relay protection accident handling

After the inspection and acceptance of relay protection equipment and daily inspection work are completed and the operation can be accurately performed, the probability of relay protection accidents will be significantly reduced. However, if an accident occurs during the operation of the relay protection, it is effectively treated, and the cause of the accident is thoroughly understood. Lessons learned are learned and the problems existing in the relay protection device and its operation process can be discovered in time. It carries out timely processing and rectification to ensure the reliable operation of the equipment.

( 1 ) Strengthen the use of relevant data. Generally, there is work continuity and concealment in the operation of the relay protection device, that is, the device may continue to work for a period of time after the end of the protection operation, so that it is easy to cause certain damage to the power equipment. At the same time, the operation of the relay protection device still has a certain degree of concealment, which is not easy to detect in daily operations and will be discovered when a failure occurs. The use of fault recording, time recording, computer event recording, device light display signal and other information to restore the relevant conditions of the device when the fault occurs, you can effectively find the cause of the accident, eliminating the disadvantages of continuity and concealment influences.

( 2 ) Effectively distinguish the cause of the fault. There are many types of failures in the operation of relay protection, and there are many reasons. Sometimes it is difficult to define whether it is a human accident or an equipment accident. Therefore, the judgment of the cause of an accident must not be based solely on past experience, but must be based on principles. Step by step to check. For the problems existing in the equipment, operators and staff on duty should faithfully report to the technicians so that the technicians can more accurately judge the reliability of the equipment and eliminate the problems in the bud.

( 3 ) Use the correct method for handling accidents. Before dealing with the accident, ensure that the relay protection tester and phase shifter used have strong stability. The multimeter, voltmeter, and oscilloscope have high input impedance performance, and they must be ensured in accordance with the requirements of relevant parties. The power used for the test was a separate DC power supply. In addition to preparing for accident handling, inspection methods that are appropriate to the type of accident are also used. Commonly used inspection methods include: the entire group of test methods, sequential inspection method and reverse order inspection method.

The whole set of test methods mainly identify the root cause of the problem by checking whether the relay protection device's operation time and action logic are normal. The main advantage of this method is that it can reproduce the fault in a short time. The disadvantage is that it cannot find the cause of the fault effectively. After the problem is discovered through this inspection method, the reliability of the entire device can be improved after processing .

The sequential inspection method is performed in sequence according to external inspection, insulation inspection, fixed value inspection, power supply performance testing, and protection performance inspection, and the fault is found through inspection and debugging. The equipment is inspected and debugged for the unreliability of the protection of the relay in the operation of the relay protection, such as refusal to move or logical problems.

The law of the reverse order is to start from the result of the accident and search it one level at a time until it finds the root cause. For the unreliability of the relay protection device during operation, this method can be used for inspection. 3. Improve the technical level of relay protection

Improving the technical level of relay protection can make the acceptance, daily management and operation of relay protection more convenient and effective, and also reduce the occurrence of related accidents. It is also a key factor to ensure the reliable operation of relay protection. By synthesizing its development history, we can improve the technological level of relay protection from the following two aspects.

( 1 ) Improve the level of computerization and networking of relay protection operations. With the continuous development of telecommunication technology, the technological content of microcomputer protection hardware has also been greatly improved. Now , the function, speed, and storage capacity of IPCs that are similar in size to microcomputer protection devices far exceed those of minicomputers of the year. The idea of â€‹â€‹using a set of IPCs as relay protection has become technically feasible. In this way, the unreliability of the microcomputer in the operation of the relay protection can be controlled. However, how to better meet the power system requirements for microcomputers , how to further improve the reliability of relay protection, and how to achieve greater economic benefits still need to conduct in-depth research. It can be said that the computer network will go deep into various industrial fields and provide communication means for the power system, completely changing the operating mode and status of relay protection.

Judging from the actual situation at this stage , except for differential protection and pilot protection , all relay protection devices can only reflect the amount of electrical protection at the installation location. The role of relay protection devices can only be to remove faulty components . Reduce the impact of the accident. The purpose of installation and use of relay protection devices is not only to reduce the scope of the accident, but also hope that it can ensure the safe and stable operation of the power system. This requires that each protection unit can share system-wide operation and failure information data , and each protection unit and reclosing device coordinate actions based on the analysis of these information and data, thereby further improving the timeliness and accuracy of protection. The prerequisite for realizing this idea is to connect the protection devices of the main equipments of the entire power system through the computer network and realize the networking of the micro-computer protection devices. The technical level in this area needs urgent improvement.

( 2 ) Improve the intelligent level of relay protection operation. Intelligence is an important technological innovation to improve the operational reliability of relay protection. At present, the term â€œartificial intelligence technologyâ€ has emerged in many fields of society, such as neural networks, evolutionary planning, genetic algorithms, fuzzy logic and other technologies in the power system. It has been applied , and research in the field of relay protection is also ongoing and deepening. The introduction of artificial intelligence technology will greatly increase the stability of relay protection devices, and the unreliability of its work continuity and concealment will be effectively controlled and improved.

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