During the operation of production equipment, unexpected accidents sometimes occur. At this time, it is necessary to accurately judge the causes of accidents so as to take corresponding countermeasures as soon as possible. However, experience shows that for electrical faults, some simple faults sometimes unexpectedly return to normal automatically during the investigation and diagnosis, while the cause of the fault is still unclear. It is very important to accurately judge the fault state, because the judgment results will have a great impact on the fault handling. However, at the scene of the accident, the time allowed for handling the accident is often very limited, and only simple measuring instruments can be used for detection. These situations are likely to lead to errors in fault judgment. Therefore, we must have sufficient knowledge of the faults of electrical equipment. This paper mainly analyzes the faults of electrical equipment and conducts management research.
1、 Faults caused by substation equipment
In recent years, the power receiving and transformation equipment has been basically maintenance free, and the attention to the power receiving and transformation equipment is getting lower and lower. However, once the power receiving and transforming equipment and machines fail, it will directly lead to the shutdown of all plants and other major accidents.
The insulation performance of the transformer decreases and the gas pressure increases. When the insulating oil of oil immersed transformer contacts with the air, its performance will deteriorate due to moisture absorption, oxidation and other effects, which will deteriorate the insulation performance of the transformer coil, thus reducing the insulation performance of the entire transformer. In order to prevent the above situations, nitrogen can be sealed inside the large capacity transformer to prevent the oxidation of insulating oil. The temperature inside the transformer will rise due to the local overheating and partial discharge of the coil, as well as the abnormality of the iron core and other reasons. The rise of temperature will cause thermal decomposition and oxidation of insulating oil, which will produce abnormal gas and dissolve or remain in insulating oil. When the above conditions are relatively light, the gas pressure will display abnormal; If abnormal heating or short circuit occurs, the gas pressure will rise sharply, which may cause the impulse pressure relay to act. In order to protect the above faults from the transformer, a double float relay is required.
The transformer and generator coils are short circuited or grounded. When the coil of transformer or generator is short circuited or grounded, its power supply circuit will be cut off, but such accidents rarely occur. First of all, for this type of accident, it is impossible to make emergency treatment on site, which is a major accident that must be returned to the manufacturer for repair. In case of coil short circuit or grounding accident of oil immersed transformer, there is a serious risk that the burning of the short circuit part will develop into transformer fire. Therefore, it is stipulated in the technical standards for electrical equipment that transformers with a rated capacity of more than 5MVA must be equipped with internal fault protection devices to quickly cut off the power supply circuit in case of a fault. In order to achieve the above purpose, ratio differential relay is recommended. Power failure operation error. As equipment maintenance is required, generally speaking, the substation shall be powered off once or twice a year. Since there are few opportunities to directly contact with the substation equipment at ordinary times, maintenance needs to be carried out with great care. Even so, unexpected errors may occur sometimes. Pay special attention to the following situations: Don't forget to check whether the grounding wire of the equipment is reliably connected after maintenance; Whether there are maintenance tools left in the control cabinet; wait. In fact, the above errors are often caused by the carelessness of maintenance personnel. In order to prevent the occurrence of these accidents, it is extremely important to resume confirmation after maintenance operations.
2、 Accidents caused by power supply lines
Short circuit to ground and short circuit between lines due to line relationship will also cause system power failure, but it is not easy to understand the cause and location of short circuit. In the initial design of the line, the switchgear and conductor capacity suitable for the equipment should be selected, and the construction should be carried out in strict accordance with the requirements of the technical standards for electrical equipment. Under the condition of normal environmental use, the maintenance and management of line insulation have been strengthened, and protection coordination measures have been taken in the selection and setting of protective devices used, which makes the action of protective devices more reasonable and also eliminates the possibility of accidents affecting other systems. The theory of AC three-phase circuit and AC single-phase circuit can be easily combined with the factory distribution line, so it has been widely used.
The neutral grounding of transformer is broken. Single phase 3-wire transformer can output two kinds of voltage. When 3-wire wires of the same thickness are used, the copper consumption can be reduced by 37.5% compared with the single-phase 2-wire type. Single phase three wire transformer is widely used in lighting, electric heating load and power supply for general single phase load. The primary side of the transformer is single-phase high voltage, and the secondary side is 210V and 105V. The neutral line at the secondary side adopts Class B grounding construction. Therefore, the voltage of the transformer to the ground is less than 150V, which can also prevent the risk of voltage rise at the low-voltage side when the high-voltage side contacts with the low-voltage side. However, it is very dangerous when the grounding wire has been disconnected but the transformer still supplies power to the load. If other voltage phases are short circuited to the ground at this time, the grounding resistance value of the grounding wire will have a great impact on the distribution line, the transformer, the equipment and machines on the secondary side, etc.
Short circuit accident of underground high-voltage cable to ground. Considering the conditions of power supply lines, the protection of lines, the suitability of landscape, and the required funds, underground power supply is mostly used in the factory. Therefore, the factory power supply line does not need to undergo visual inspection and accident repair. Because of this, the temperature of the cable laying site should be stable, and the laying site should be safe from the perspective of injury protection.
The laying of underground cables can be divided into trench type, underground pipe type and direct burial type. Of course, once the short circuit to ground or between lines occurs, the underground power supply mode will bring great difficulties to the determination and repair of the fault point. Especially for large capacity cables, the arrival time needs more than one month. If there are no spare parts in stock, the factory will be forced to stop production for a long time. Therefore, the actual situation of the site is that in order not to affect the production, we must do everything possible to carry out the minimum emergency treatment for the accident point, so that power can be transmitted as soon as possible. Due to the variety of accident causes, many problems need to be solved during cable construction. Only by fully doing the prevention and maintenance work can accidents be prevented.
3、 Faults caused by control circuit and control equipment
The circuit breaker is put into operation incorrectly. Whenever the equipment is inspected, repaired or modified, it is necessary to put the circuit breaker back into power supply to confirm whether the circuit operation has returned to normal. The power circuit of production equipment consists of power circuit and control circuit. Generally speaking, the power supply of the control circuit shall be activated first, and the relay and electromagnetic switch shall not operate abnormally. The power supply can be put into operation only after confirming that there is no alarm and other abnormal conditions.
Influence of line capacitance on control relay. When PLC and DCS and other systems communicate with each other, they need to quickly process a large amount of information. In order to prevent the occurrence of the above interference accidents, it is better to adopt special communication methods such as optical cable communication that are not affected by the above induction.
The influence of poor insulation treatment of the line. The equipment in normal operation stops in an emergency without alarm. In case of an accident, most of them are short circuited or short circuited to ground. In this case, since the protective device has been activated, the cause of the accident can be clearly investigated. Generally speaking, the automation degree of the production line is very high. If one operation link fails to shut down, the entire production line will stop running. At this time, a "shutdown" alarm will be issued in the central monitoring room. The normal operation of the production line can only be resumed after the maintenance is completed and the fault is eliminated. If the shutdown accident occurs frequently, it will be difficult to investigate the cause, but it can be said that the cause is basically electrical.
Background of electromagnetic contactor burning. When the load in operation needs to be started and stopped frequently, electromagnetic contactors can be used. When selecting electromagnetic contactors, appropriate models and specifications can be selected according to the nature of the load and its operating characteristics. The electromagnetic contactor has a firm structure and a long service life. The main contact is the main part of the electromagnetic contactor to be maintained. In engineering practice, it is generally judged whether the contactor works normally according to whether the sound during operation is abnormal or by observing the appearance. It is difficult to find the abnormality of the main contact in time. Sometimes an accident occurs, but it is often too late to realize the original abnormality in retrospect. There are many reasons for the burning loss of electromagnetic contactor, such as the impact of dust in the setting place, temperature and humidity of ambient air, and the impact of fault current caused by insulation deterioration, which may cause the burning loss of main contact of electromagnetic contactor.
4、 Conclusion
The failure of electrical equipment will cause the failure of the entire operation system, so we need to put our energy into more scientific and reasonable research on the management mode of electrical equipment to continuously enhance the reliability of electrical equipment operation and improve the stability of the power system.
00000000000000