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Regular Maintenance And Inspection
- Sep 01, 2017 -

Common Faults and Treatment of Transformers

(A) transformer insulation resistance decreased

1, the reasons for the analysis. Pouring dry-type transformers are mostly cast by the resin, the conductor material sealed in it, so the decline in the insulation resistance is mostly by the surface of the cohesion of water vapor, the accumulation of dust or part of the insulation caused by moisture.

2, treatment methods. Clean the surface of the winding, the surface of water vapor condensation with a dry cloth to wipe, natural air can be restored. Can be used incandescent, heaters and other drying and installation of fan ventilation and other methods. Can disconnect the three-phase connection of the dry-type transformer neutral line (zero row), with a megger to determine the problem in which phase, and then carefully look for processing.

Transformer core multi-point grounding

1, the reasons for the analysis.

External factors: iron core insulation iron core, core piercing insulation tube and other insulating materials, due to condensation or moisture greatly reduce the insulation performance of the core lead to low resistance multi-point grounding; transformer in the operation of the core of the magnetic leakage to the nearby space to produce weak magnetic , To attract the surrounding metal powder and dust, if there is no maintenance of long-term cleaning will cause the core to occur more ground; due to improper operation and maintenance, long-term overload, high temperature operation so that silicon steel sheet insulation between the core, Destruction caused by multi-point grounding.

Internal factors: the quality of the choice of silicon steel sheet problems, such as silicon steel surface rough and not smooth, serious corrosion, insulating paint coating adhesion and fall off, will cause short-circuit between the film, the formation of multi-point grounding; silicon steel processing process is unreasonable, Such as the glitch exceeded, the shear caused by short-circuit between; silicon steel sheet stacked stacked when the pressure is too large, damage between the film insulation and so on.

Approach. From the maintenance aspects can be divided into two steps: (1) according to the scene transformer status analysis, to determine the external factors affect the handling of multi-point ground fault. Dry-type transformers for long-term use or no sealed, dust, moisture or condensation, the core surface can be cleaned after the use of multiple sun light on the iron yoke baking, or in conditions permitting, can be used To carry out baking. To do a good job of security work, the transformer high-side open circuit, low-voltage side of the rated voltage, the time required is shorter. If the insulation resistance is excluded, if the insulation resistance is still zero, the core can be pressurized by the AC test device. When the fault grounding point is not strong, the discharge point will appear during the step-up process. According to the corresponding discharge point For processing.

Using the step-by-step investigation method to deal with the internal factors caused by the core grounding fault. Usually use the DC, AC method to find the point of the multi-point grounding fault, check should start from the iron yoke, remove the screw after the test core to the insulation resistance. If the fault is not in the heart of the screw will need to remove the iron yoke fastening screw, so that the iron yoke and the core after the separation of the core to continue to test the insulation resistance to determine the point of failure. As the dry-type transformers three-phase high and low voltage coil is supported by the iron yoke, if you want to remove the iron yoke test its insulation resistance is very difficult, and large-capacity dry-type transformers demolition of iron yoke on-site maintenance conditions are not available. In order to try not to return to the factory, this failure can be used capacitor discharge impact method, AC arc method, high current impact method (using welding machine).

Transformer trip fault

1, transformer power trip. The original transformer high voltage secondary cabinet current protection device set the setting value is too small, because the transformer in the no-load state closing, instantaneous induced current up to the rated current of 6 to 8 times, or even higher, zero sequence current value High, the delay setting value is relatively small, if the high voltage switchgear transformer integrated protection device set value is too small, you need to re-set according to relay protection procedures.

Transformer abnormal noise

Transformer normal operation, will issue a continuous uniform "buzzing" sound, if the operation is not uniform or other special sound, that is running is not normal, according to the different sounds to find out the reasons for timely processing.

Cause Analysis.

Voltage problem. Power grid single-phase ground or electromagnetic resonance voltage increases, will make the transformer over-excitation, the sound increases and sharp, directly affect the transformer noise.

Fan, shell, other parts of the resonance problem. Fan, shell, other parts of the resonance will produce noise, the general will be mistaken for the transformer noise.

Installation problem. Poor installation of the base will aggravate the transformer vibration, amplify the transformer noise.

Suspension potential problem. Dry-type transformers of the iron yoke channel, nail bolts, pull plates and other parts in the leakage magnetic field under the action of the suspension between the various parts of the discharge sound emitted, often mistaken for the transformer high voltage or low voltage winding in the discharge.