Transformer fault cause and treatment

Fault Analysis and Handling of Transformers: When the transformer is in normal operation, it will emit a continuous and uniform “click” sound. If the generated sound is uneven or there are other special sounds, it should be regarded as abnormal operation of the transformer, and the fault can be found according to the sound and processed in time. There are mainly the following aspects of failure: 1. Overvoltage occurs in the power grid. When single-phase grounding or electromagnetic resonance occurs in the grid, the transformer sound is sharper than usual. When this happens, a comprehensive judgment can be made in conjunction with the indication of the voltmeter. 2. The transformer is overloaded. The load changes greatly, and due to the harmonic action, the intermittent sound of “wow” or “giggle” occurs instantaneously in the transformer, and the pointer of the measuring instrument is oscillated, and the pitch is high and the volume is large. 3. The transformer clamp or screw is loose. The sound is louder than usual and has obvious noise. However, when there is no obvious abnormality in current and voltage, the internal clamp or the screw of the pressing core may be loose, resulting in increased vibration of the silicon steel sheet.
Partial discharge of the transformer. If the transformer's drop fuse or tap changer is in poor contact, there is a "beep" discharge sound; 4. If the transformer's transformer sleeve is dirty, the surface enamel is detached or cracked, you can hear "嘶嘶"Sound; if the internal discharge or electrical connection of the transformer is poor, a "吱吱" or "噼啪" sound will be emitted, and the sound will change with the distance from the fault. At this time, the transformer should be deactivated immediately. 5. The transformer winding is short-circuited. The sound is mixed with water, and the temperature changes abruptly. If the oil level rises, it should be judged that the transformer winding has a short-circuit fault. In severe cases, there will be a huge roar, and then it may catch fire. At this time, the transformer should be deactivated immediately for inspection. 6, the transformer shell flashover discharge. This sound occurs when the high voltage of the transformer winding causes the outgoing lines to flash with each other or when they are flashed to the outer casing. At this time, the transformer should be deactivated. (1) smell, color abnormality:
Explosion-proof tube explosion-proof membrane rupture: explosion-proof tube explosion-proof membrane rupture will cause water and moisture to enter the transformer, resulting in insulation oil emulsification and transformer insulation strength reduction.
Casing flashover discharge, casing flashover discharge will cause heat to cause aging, insulation damage and even this explosion.
The lead wire (wiring head) and the wire card are overheated to cause abnormality; the fastening part of the bushing terminal is loose or the nose of the lead wire is slippery, etc., the contact surface is severely oxidized, the contact is overheated, the color is darkened and the gloss is lost, and the surface coating is also Damaged.
Casing fouling causes abnormality; casing fouling produces corona, flashing will produce ozone odor, cooling fan, oil pump burning will give off charring smell.
In addition, excessive moisture absorption, damage to the gasket, and too much water entering the oil chamber may cause discoloration of the moisture absorbent.
(2) Abnormal oil temperature: It is found that under normal conditions, the oil temperature is higher than 10 degrees Celsius or the load is constant and the temperature is rising continuously (in the case of normal operation of the cooling device), it can be judged that there is an abnormality inside the transformer. Mainly:
An internal fault caused an abnormal temperature. Internal faults, such as winding turns or inter-layer shorts, coils to the screen discharge, internal lead joints, iron core multi-point grounding, eddy currents increase overheating, zero-sequence unbalanced current and other magnetic leakage through the iron tank to form a loop and heat Other factors cause the transformer temperature to be abnormal. When these conditions occur, they will also be accompanied by gas or differential protection actions. In the event of a serious fault, it is also possible to inject the oil from the explosion-proof tube or the pressure relief valve. In this case, the transformer should be deactivated immediately.
Temperature anomaly caused by abnormal operation of the cooler. The cooler is not operating properly or malfunctioning, such as the submersible pump is out of service, the fan is damaged, the radiator pipe is fouled, the cooling effect is not good, the radiator valve is not open, the thermometer indicates failure, and many other factors cause the temperature to rise. Perform maintenance and rinsing to increase its cooling effect. (3) Abnormal oil level: The oil level abnormality and oil leakage phenomenon are common in the operation of the transformer. It is necessary to conduct inspections and inspections from time to time. The main performances are as follows.
1. False oil level: the oil standard pipe is blocked; the oil pillow pipette is blocked; the air hole of the explosion-proof pipe is blocked. 2, the oil surface is low: the transformer is seriously oily; the staff is unable to replenish in time due to the need to drain the oil; the temperature is too low and the oil quantity is insufficient, or the oil pillow capacity is too small to meet the operational requirements.