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The common fault manifestations of high-voltage switchgear are mainly the sudden trip of the running equipment and the electric manual cannot be closed. The common fault types of high voltage switchgear can be divided into electrical faults and mechanical faults. Electrical faults can be divided into electric energy storage, electric failure, and electric failure.
I. Judgment and treatment of sudden trip failure of high voltage switchgear during operation
1) Fault phenomenon: The cause of this fault is the protection action. The high voltage cabinet is equipped with overcurrent, quick disconnect, gas and temperature protection. When a line or transformer fails, the protective relay acts to trip the switch. After the trip, the green light of the switch cabinet flashes (if no flash bus does not flash), the switch handle is vertically up after the switch. There is an audible and visual alarm signal in the high voltage cabinet or in the central signal system, and the relay is off. The computer monitoring system has alarm information of “protection action†and “switch displacement changeâ€.
2) Judgment method: Judging the cause of the fault can be judged according to the situation of the relay falling off, the remote information, and the like. After the gas and temperature protection actions in the high voltage cabinet, there is a corresponding signal relay drop indication. Overcurrent and quick break cannot be distinguished when the overcurrent relay (GL type) operates. The overcurrent and quick-break in the definite time protection circuit are respectively protected by two (JL type) current relays. When the relay is activated, the red LED is on, and the cause of the action can be clearly determined.
3) Processing method: The overcurrent relay action causes the switch to trip because the line is overloaded. Before the power transmission, the user should negotiate with the user to reduce the load and prevent the power from being tripped again. Busbars, transformers, and lines should be checked during quick trips. Find the short-circuit fault point and remove the fault before sending power. The overcurrent and quick-break protection actions allow the relay to be reset after the switch trips, and this feature can be distinguished from temperature and gas protection. Gas and temperature protection actions when the transformer is internally faulty or overloaded. If the internal fault of the transformer causes heavy gas to move, the transformer must be overhauled. If the newly moved, refueling transformer has a light gas action, the internal gas can be released and continue to be put into operation. The temperature protection action is because the transformer temperature exceeds the set value. If the setting is correct, you must try to reduce the temperature of the transformer. It can be ventilated to reduce the ambient temperature, or it can reduce the load and reduce the temperature rise of the transformer. If the setting is too small, you can increase the setting. Through the above several methods, the temperature contact is opened, and the switch can be powered.
Second, the high-voltage switchgear storage energy failure judgment and treatment in the pressure cabinet, before the closing must be pre-storage energy can be closed. The energy storage mechanism is driven by a motor to drive the gear mechanism to lengthen the spring. There are two methods of operation: electric and manual. Failure to store energy manually should be a mechanical failure of the mechanism. Manual energy storage, but electric energy storage is an electrical fault. The mechanical wear of the mechanism that is used for a short period of time is generally small and there is generally no mechanical failure. The following mainly analyzes electrical faults.
1. Incorrect adjustment of the stroke switch: The stroke switch is a limit switch that controls the energy storage position of the motor. The motor power is cut off when the motor is in storage. If the limit is too high, the energy storage of the mechanism is full. The fault phenomenon is: the motor does not stop during idle rotation, and the energy storage indicator does not light. The motor can only be stopped if the control switch (HK) is turned on. When the limit adjustment is too low, the motor energy storage is not full before the machine stops. Since the energy storage is not in place, the switch cannot be closed. The way to adjust the limit is to manually store the energy to find the correct position and tighten it.
2, motor failure: If the motor windings burn out, there will be odor, smoke, fuses and other phenomena. If there is voltage across the motor, the motor does not turn. It may be a malfunction such as a carbon brush falling off or a serious wear. The method of determining whether the motor is faulty is to measure the voltage across the motor, the resistance, or replace it with another good motor.
3. Control switch failure or open circuit: When the control switch is damaged, the circuit can not be closed and the control circuit is broken, causing the open circuit. The fault manifests that the motor does not rotate and there is no voltage at both ends of the motor. The search method is to measure the voltage or resistance with a multimeter. The measuring voltage method is that when the control circuit is energized, the multimeter is adjusted to the voltage level. If there is voltage (except the step-down element), there is an open point between the two points measured. The measurement resistance method should pay attention to the on/off of the bypass. If there is a bypass parallel circuit, the end of the line to be tested should be disconnected.
Third, the high-voltage switchgear closing fault judgment and handling Closing fault can be divided into electrical faults and mechanical faults. There are two types of closing methods: manual and electric. Manual failure to close is generally a mechanical failure. Manually can be closed, electric can not be closed is an electrical fault.
1. Protection action: The protection action has been analyzed in the front to make the switch trip. Before the switch is powered, the line has a fault protection circuit to make the anti-skip relay function. The switch immediately trips after closing. Even if the transfer switch is still in the closed position, the switch will not close again and continuously jump.
2. Protection fault: Now the five-proof function is set in the high-voltage cabinet. It is required that the switch is not in the running position or the test position cannot be closed. That is, the position switch is not closed, and the electric motor cannot be closed. This type of failure is often encountered during the closing process. At this time, the running position light or the test position light does not light. Move the switch cart slightly to close the limit switch to send power. If the limit switch offset distance is too large, it should be adjusted. In the JYN type high voltage cabinet, the position switch can not be moved outwards, and a V-shaped piece can be added to ensure the limit switch is reliably closed.
3. Electrical cascading failure: In the high-voltage system, some electrical interlocks are set for the reliable operation of the system. For example, in a single bus segmentation system with two power supply lines, it is required that the two switches of the two incoming line cabinets and the female joint cabinet can only be combined. If all three are closed, there is a danger of reverse power transmission. And the short-circuit parameter changes, and the short-circuit current increases in parallel. The form of the chain circuit is shown in Figure 4. The incoming line cabinet chain circuit is connected to the normally closed contact of the female joint cabinet, and the incoming cabinet of the female joint cabinet is required to be closed. The interlocking circuit of the mother cabinet is connected by a normally open and a normally closed series of two incoming line cabinets. In this way, it can be ensured that the mother cabinet can only be powered when one of the two incoming cabinets is closed and the other is opened. When the high voltage cabinet cannot be electrically closed, first of all, it should be considered whether there is electrical interlocking, and manual closing cannot be used blindly. Electrical interlocking faults are generally improperly operated and cannot meet the closing requirements. For example, the joint busbar is one-in-one, but the handcart in the bayonet cabinet is pulled out and the plug is not plugged in. If the interlock circuit fails, you can use a multimeter to check the fault location.
It is simple and convenient to judge the auxiliary switch fault by using red and green lights, but it is not reliable. Can be determined with a multimeter check. The method of repairing the auxiliary switch is to adjust the angle of the fixed flange, adjust the length of the auxiliary switch link, and the like.
4. Open circuit fault of control circuit: In the control loop, the control switch is damaged, the line is disconnected, etc., so that the closing coil can not be powered. At this time, the closing coil has no sound. There is no voltage across the measuring coil. The method of inspection is to check the open circuit point with a multimeter.
5, closing coil failure: closing coil burning is a short circuit fault. At this time, there are phenomena such as odor, smoke, and insurance melting. The closing coil is designed for short-time operation and the power-on time cannot be too long. After the failure of the closing, the cause should be found in time, and the composite brake should not be repeated multiple times. In particular, the closing coil of the CD type electromagnetic operating mechanism is easily burned out due to a large number of closing currents.
The test power transmission method is often used when troubleshooting a high voltage cabinet that cannot be closed. This method can eliminate line faults (except transformer temperature, gas faults), electrical interlock faults, and limit switch faults. The fault location can basically be determined inside the handcart. Therefore, in the emergency treatment, the test position can be used to send power, and the standby hand truck can be replaced for power transmission. This can do more with less and reduce power down time.
Fourth, the high-voltage switchgear opening fault judgment and handling of the opening fault can also be divided into mechanical faults and electrical faults. Electrical faults mainly include open circuit of control circuit, coil fault, and auxiliary switch fault.
1. Fault phenomenon: When the red light is not on, the electric motor cannot be opened and the auxiliary switch is faulty. When the opening coil is burnt out, there are obvious phenomena such as smoke, odor, and fuse melting. The open circuit fault of the control circuit means that the transfer switch and other parts are disconnected, and the trip coil cannot be powered.
2. When checking the coil fault, you can use a multimeter to measure the resistance at both ends of the coil. When the resistance is too small or zero, the internal turns are short-circuited, and when the resistance is infinite, the internal circuit is open. The way to find an open circuit fault is to use a multimeter to measure voltage and resistance. There is voltage at the open circuit point and the resistance is infinite.
V. Judgment and Handling of Mechanical Faults in High Voltage Switchgear The common mechanical failures of high voltage cabinets are: mechanical cascading failures, operating mechanism failures, etc. The fault parts are mostly loose parts, worn parts, improper adjustment of the limit.
1. Mechanical cascading failure: In order to ensure the correct operation of the switch, some mechanical interlocks are set in the switch cabinet. For example, when the handcart enters and exits the cabinet, the switch must be opened. The disconnector cannot be operated when the switch is closed. These types of faults come in many forms and should be searched along the mechanical transmission path. The general protection mechanism is relatively simple, rarely intersects with other organizations, and the search is convenient. In the JYN-type high-voltage cabinet of station No. 2, there was such a fault: because the fixing nut of the pedal and the connecting rod fell off, the mechanism would release the scorpion and the scorpion could not be closed.
2. Operation mechanism failure: The most faulty part of the operating mechanism is the limit point offset. For example, in the CT8 type mechanism, the amount of engagement between the sector wheel and the trip axle is the key to mechanism adjustment. The amount of meshing is large, the tripping resistance is large, and it is easy to get stuck. The amount of meshing is small, it is easy to jump, and it cannot be closed. The method of adjustment is to change the length of the limit bolt and the length of the opening link.
Although the fault modes of the high-voltage cabinet are various, as long as several common electrical or mechanical faults of the high-voltage switchgear can be judged under the condition that the accident trips and the electric manual cannot be closed, the fault location is determined according to the fault phenomenon and the inspection result. Can troubleshoot quickly.
Common faults of high voltage switchgear and their treatment
High-voltage switchgear is widely used in power distribution systems to control and protect circuits. In the event of a failure of the high-voltage switchgear, resulting in a large-scale power outage, port production will not be possible. Due to the complicated structure of the high-voltage switchgear and various types of faults, it is difficult for the operation and maintenance personnel to judge the fault. In order to facilitate the operation and maintenance personnel to accurately determine the type of fault, the cause of the fault, and timely maintenance, and shorten the power outage time, several common fault judgments and treatments of the high voltage switchgear are described below.