Maintenance analysis of the hottest relay protecti

Maintenance analysis of relay protection

(1) with the popularization of microcomputer relay protection application, it has become a consensus to improve the safe operation level of equipment. Relay protection constitutes a system, not just the device itself, such as AC, DC, control circuits, etc. because some circuits have no monitoring means, it is impossible to conduct real-time technical analysis and judgment on the equipment status. For example, since the operation circuit has always been realized by hardware, except that a small amount of hardware signals can be uploaded through telecontrol or integrated equipment, the circuit has no monitoring means, forming a blank point in the protection monitoring circuit. Therefore, in terms of the application status of relay protection devices, strictly speaking, most protections do not have the conditions for condition based maintenance

(2) in fact, condition based maintenance is not simply about reducing the number of maintenance. Instead, it is necessary to carry out targeted maintenance according to the actual state of the equipment, considering its use environment and conditions, and not blindly apply "condition maintenance" to all the primary and secondary equipment of the power system. The author believes that the key of "condition based maintenance" is the operators' grasp of the "state" of power equipment, but it is difficult to grasp the "state" of power equipment in real time in practical work

(3) in the power system, the relay protection device plays a role in cutting off the power system fault in time and reflecting the abnormal working condition of the power system equipment, while minimizing the impact of the fault on the power system. Therefore, the correct action of relay protection devices plays an extremely important role in the safe and stable operation of power system

2. Relay in power system

(1) the definition and calculation of reliability index of relay protection device in power system protection are closely related to the calculation of reliability index of power system, the evaluation, use, improvement and development of relay protection device. The current statistical method in China is to use the statistical method of "correct action rate" of the former Soviet Union. This method is defined by the total action times of relay protection devices counted within a certain period (such as one year) and the correct action times among them: correct action rate = (correct action times/total action times) × 100%。 When the fault frequency of the protected object is very low, or there is no internal fault in this statistical period, which opens a new period of high-level and long-term cooperation between the two countries, the correct action rate will be very low, or even zero

(2) relay protection condition maintenance is to scientifically arrange the maintenance interval and maintenance items based on the condition monitoring of electrical secondary equipment and the results of monitoring, analysis and diagnosis. It includes three meanings: equipment condition monitoring; Equipment status diagnosis; Equipment maintenance decision. Equipment condition monitoring is the basis of implementing condition based maintenance; Equipment status diagnosis is based on equipment status monitoring, integrates the historical information of equipment, and uses neural network, expert diagnosis system and other technologies to judge the health status of relay protection equipment. The goal of relay maintenance is to reduce the power failure time of equipment, extend the service life of equipment, improve the utilization rate and safety reliability of equipment, improve the operation performance of equipment, reduce the cost of equipment operation and maintenance, and improve economic benefits

3. Grasp the "state" of relay protection device

(1) relay protection device has a unique position and role in the power system. Once the power system fails, it can quickly and accurately isolate the fault, prevent the accident from further expansion, and ensure the normal operation of power equipment other than the accident. The basic idea of "state inspection" of relay protection device is to arrange maintenance and test according to the "state" of relay protection device, and the benchmark is the "state" of relay protection device. The author has been engaged in the inspection of relay protection devices for a long time, and has participated in the inspection of relay protection devices and the handling of failure and misoperation events of relay protection devices for many times. He has accumulated some experience, but in the process of handling these accidents, some necessary tests are still needed to verify. Therefore, there are great difficulties in the actual operation process, which requires long-term experience accumulation to accurately judge the "state" of power equipment

(2) relay protection devices are usually static in the power system. Only when the power system is faulty or abnormal, they will start according to the detected system fault or abnormal electrical parameters, and then identify them through their own logic circuit to quickly remove the fault sensitively, reliably and selectively or give corresponding warnings. This action time is often only a few milliseconds to a few seconds. The operator's understanding of the state of the relay protection device is generally the understanding of its static state. If the power system has no fault and the protection device does not act, it is impossible to understand its action characteristics. In the power system, what we need to know happens to be whether the relay protection device can act quickly and accurately in case of power system failure, that is, we need to grasp the dynamic "state" of the relay protection device, and the dynamic characteristics of the relay protection device can only be shown in the following three cases: equipment fault protection action; Maloperation of protective device; Relay protection device test and transmission

4. Relay protection maintenance

4.1 according to the requirements of the regulations on the inspection of relay protection and electrical safety automatic devices, at present, the verification of relay protection devices in China is mainly divided into the following three categories:

(1) acceptance and maintenance of newly installed devices

(2) regular inspection of devices in operation

(3) supplementary inspection of devices in operation

among them, the relay protection device shall be comprehensively verified once a year after the equipment is put into operation, and then every six years, and part of the inspection shall be carried out every one to two years

4.2 at present, conventional electromagnetic protection devices have been comprehensively replaced by microcomputer relay protection devices. Compared with traditional relay protection and microcomputer protection, microcomputer protection has the following advantages:

(1) all protection data sampling and logic functions of microcomputer protection are made use of CP new materials, which also attracts the landing U of UAV industry enterprises, mold companies and new material B2B projects, and adopts standardized hardware, The outlet relays adopt advanced fully sealed relays, which greatly reduces the complexity of the secondary circuit, improves the reliability, and reduces the possibility of incorrect action of the protection device due to relay contact problems and poor contact of the secondary circuit

(2) when an abnormality or fault is detected in the device, the microcomputer protection can send a signal in time and lock the relevant protection through the advanced self-test function

(3) software programming can be standardized, modular, high sensitivity and good interchangeability; With reliable communication connection, the surface of the experimental device should be clean and dust-free, and access to the microcomputer of the plant station can enable centralized display and printing after information analysis and processing

4.3 in view of the reliability and performance of microcomputer protection relay device, compared with electromagnetic protection, the cleaning of electromechanical equipment is greatly improved in all aspects. Therefore, it is not necessary to carry out regular maintenance of secondary equipment according to the traditional regular inspection cycle. The traditional periodic maintenance (planned maintenance) only inspects the equipment at a fixed time interval, regardless of the actual situation of the equipment. Therefore, this maintenance method is very mandatory and blind

4.4 compared with regular maintenance, condition based maintenance improves electrical safety, reduces line loss, and improves power supply reliability, because condition based maintenance is more targeted; It can make the maintenance effective and solve problems in time; The maintenance workload is reduced, the overhaul cost is reduced, the economic benefit is improved, and the enterprise operation cost is saved; The switching operation is reduced, and the personal and equipment safety is improved. The implementation of condition based maintenance reduces a large number of outage maintenance and live maintenance workload, and reduces the probability of accidents; Improve the safety of equipment and prolong the service life of equipment, which is because improper maintenance, unnecessary maintenance and maintenance that does not solve fundamental problems are effectively avoided

4.5 the maintenance of equipment is closely related to the reliability of equipment. The low reliability of equipment will inevitably lead to the reduction of availability and frequent maintenance. In fact, the maintenance work can only make the equipment maintain or close to the inherent reliability determined by design and manufacturing, and the condition based maintenance is to maintain or restore the inherent reliability level of the system and equipment at the minimum cost through inspection, maintenance, repair and even update on the premise of understanding the health status of the equipment

5. Conclusion

condition based maintenance is not simply about reducing the number of maintenance. Instead, targeted maintenance should be carried out according to the actual state of the equipment. Starting from the starting point of practical guiding significance for relay protection condition based maintenance, combined with the current situation of relay protection condition based maintenance, and using the experience accumulated in the long-term on-site maintenance management, this paper deeply discusses the practical problems of relay protection condition based maintenance, hoping to have reference significance for future related work