Discussion on relay protection maintenance and fau

2022-08-09
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On relay protection maintenance and fault handling

relay protection device is a very important part of power system, and its development has also experienced the development process of electromagnetic type, transistor type, integrated circuit type and microcomputer type like power system. So far, different forms of protection still exist and play a role in the power system. Due to the special role of relay protection in power system, it is necessary to ensure the normal response of relay protection devices. Therefore, it is particularly important to maintain the relay protection device in daily life. Once a fault occurs, it should be judged and handled accurately as soon as possible

the capacity of copper foil is 27100 tons/year. 1. What are the basic requirements and functions of relay protection

as a whole, there are two kinds of disastrous accidents that must be avoided in the security of power system: one is major power equipment damage, and the other is long-term large-scale power outage. In these aspects, power system relay protection has always played a special and important role

1.1 basic requirements for relay protection

basic performance requirements for electrical relay protection, including reliability, selectivity, quickness and sensitivity. Some of these requirements complement each other and some restrict each other. They need to be coordinated separately according to different use conditions. The research and analysis of these problems is a top priority for the operation Department of electric relay protection system. (1) Selectivity. The basic meaning is that when the protection device acts, only the fault components are removed from the power system, so as to minimize the scope of power failure, so as to ensure the safe operation of the non fault part of the system. (2) Quick action. Quick action means that the relay protection device should disconnect the faulty element as quickly as possible. In this way, the damage of faulty equipment can be reduced, the working time of users under low voltage can be reduced, and the stability of power system operation can be improved. (3) Sensitivity. The reaction ability of the protection device to the fault or abnormal operation within its protection range is called sensitivity (sensitivity). Sensitivity is often measured by sensitivity coefficient. After the action value of the measuring element of the protection device is determined, it is verified according to the most unfavorable operation mode, fault type and the specified point within the protection range, and meets the relevant standards. (4) Reliability. Reliability refers to that the protection device shall act reliably (i.e. not refuse to act) when a fault that it should respond occurs within the specified protection range of the protection device. In any other case that does not belong to the protection action, it should not act (i.e. not maloperation)

when selecting the relay protection scheme, in addition to meeting the above four basic performances, attention should also be paid to its economy. That is, not only the investment and operation and maintenance costs of the protection device, but also the losses to the national economy and social life caused by the refusal or misoperation of the device due to its imperfection must be considered

1.2 relay protection tasks

relay protection device is a safety automatic device composed of relays and other auxiliary components. It can reflect the fault and abnormal operation state of electrical components, and act on the tripping of circuit breaker or send signals. (1) Fault: remove the fault element (with the help of circuit breaker); (2) Abnormal state - automatically send signals (for timely processing), which can prevent accidents and narrow the scope of impact of accidents, and ensure power quality and power supply reliability

2 maintenance of relay protection device

2.1 general examination

no matter what kind of protection, general inspection is very important, but it is also an item that is easy to be ignored on site, at least it is not done seriously. General inspection generally includes the following aspects:

(1) whether the connectors are fastened, whether the welding points are faulty, mechanical characteristics, etc. At present, there are many terminal screws in the terminal strip behind the protection screen, especially after the newly installed protection screen has been transported and handled, most of the screws have been loosened. After it is in place on site, it must be fastened carefully and one by one, otherwise it is the hidden danger of protection refusal and misoperation

(2) all plug-ins of the device should be pulled out for inspection, all chips should be pressed tightly, the screws should be tightened, and the solder joint should be checked. In the inspection, it is also necessary to tighten the screws of various components, protection panels, control panels and terminal boxes as an important work. (3) Clean the relay protection device. The cleaning work must be carried out by two people to prevent accidental contact with operating equipment, and pay attention to keeping a safe distance from live equipment to avoid personal electric shock and secondary circuit short circuit and grounding accidents. Record the current and voltage sampling values of microcomputer protection once a week, and check and print the printer of microcomputer protection regularly every month

2.2 establish a post system so that each panel and cabinet is in the charge of a person on duty

make sure that everyone has a post and each post has a person. Generally, the operators on duty are only allowed to connect or disconnect the pressing plate, change-over switch and remove the fuse during the operation of the protection device. During the working process, they should strictly report that they should abide by the safety work regulations of the electric industry. 2.3 regularly check and evaluate the maintenance of relay protection devices and equipment

(1) check whether the change-over switch, various buttons and actions are flexible without jamming and flexible. Is there enough pressure and burns in contact

(2) check whether the marks and names of each element of the secondary equipment are complete

(3) check whether the meter, relay and wiring terminal screws on each panel and cabinet are loose

(4) check whether the light plate and red and green indicator bulbs in the control room are in good condition

(5) check whether the secondary lead terminals of voltage transformer and current transformer are in good condition because the enterprise has not reduced the price due to high inventory

(6) check whether the operating mechanism of the circuit breaker operates normally

(7) whether the wiring is neat and whether the fixing clip falls off

2.4 should we understand the development trend of relay equipment technology and adopt new technology to supervise and maintain the equipment

with the high development of power industry, increasingly severe relay protection and imperfect relay protection equipment, it is necessary to strengthen the application of new technologies, so as to ensure the scientific and effective protection devices and play their due contributions in the protection of power system

3 fault handling of relay protection

relay protection is a highly technical work. If you only want to learn to debug the equipment, it is not difficult. As long as you have a period of training, you can implement it in turn according to the debugging outline. Once an abnormal phenomenon occurs, it is not easy to deal with it. It requires the staff to have a solid theoretical foundation, but also to have effective methods to solve the problem. A suitable method can help you avoid detours and improve efficiency in your work. It can be said that the technical nature of relay protection is largely reflected in the ability of fault handling. Therefore, how to use the fastest and most effective method to deal with the fault and reflect the technical level has become a common topic for the majority of relay protection workers. Here are some common troubleshooting methods:

3.1 swap method

use the same components that are good or considered normal to replace the suspected or considered faulty components to judge whether they are good or bad, which can quickly narrow the scope of fault finding. This is the most common method to deal with the internal faults of integrated automatic protection devices. When some microcomputer protection fails, or some unit relays with complex internal circuits, it can be replaced by plug-ins and relays that are nearby for standby or temporarily under maintenance. If the fault disappears, it means that the fault is in the replaced component, otherwise continue to check the fault in other places

for example, the operation indicator light of a 110 kV bypass L fp-941a microcomputer protection flickers, and no fault report is printed, so installation 1 must be done well, and it is difficult to judge why the fault is. There is a spare interval nearby. Take each plug-in and exchange it accordingly. Find out that the fault is on the CPU plug-in. With this method, it is necessary to pay special attention to whether the jumpers, programs and constant value chips in the plug-in are the same, and replace them only after confirmation, and simulate the transmission according to the situation

3.2 short circuit method

connect a section or part of the circuit with a short circuit to determine whether the fault is within the scope of the short circuit or elsewhere, so as to narrow the scope of the fault. This method is mainly used for electromagnetic lock failure, open circuit of current circuit, non action of switching relay, and judging whether the contact of control KK and other transfer switches is good. The following is an example:

electromagnetic lock failure is often encountered in substation maintenance. See the following figure for the principle. In the figure, 7d2 DS is the electromagnetic lock of the grounding knife switch at the 110 kV side of the main transformer, 8g is the auxiliary node of the bypass disconnector at the 110 kV side of the main transformer, 3G is the auxiliary node of the disconnector at the 220 kV side of the main transformer, 4G is the auxiliary node of the bypass disconnector at the 220 kV side of the main transformer, and 9g is the isolation switch at the 35 kV side of the main transformer

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