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How to deal with common faults in distribution transformers

ⅠThree-phase load imbalance or seasonal overload
Three-phase load imbalance of dry distribution transformers is a common cause. Especially in rural areas, most of the electric load is single-phase load, and the load changes greatly. Therefore, there are many unbalanced load distributions of the three-phase distribution transformer, so that the three phases cannot operate symmetrically and generate zero-sequence current. . This aspect increases the loss of the transformer and on the other hand reduces the effective capacity of the transformer. The above two conditions will lead to overheating of the transformer and aging of the insulating oil, which will reduce the insulation level of the winding and eventually cause damage to the transformer. The following measures can be taken:
1 Investigate the load of the distribution transformer, including the load of 24 hours a day and the load of 4 seasons a year, to clarify the general situation of the load, and adjust the three-phase load as close as possible to make it operate close to symmetry;
2 Adjust the peak-to-valley time of power consumption to reduce the overload condition; at the same time, it is necessary to increase the capacity of the transformer in time to avoid long-term overload operation of the transformer.
distribution transformers,dry distribution transformer,oil-immersed distribution transformer
Ⅱ Poor grounding
The lightning protection work of the lightning-damage distribution transformer is generally done, but there are still two problems: 1 the lightning arrester is poorly grounded; 2 only pay attention to the high-voltage side installed lightning arrester, and neglecting the low-voltage side also needs to install the lightning arrester (especially Doree area). If the arrester is poorly grounded, when the overvoltage occurs, the arrester can not discharge the current well, which will damage the insulation of the transformer. If the arrester is not installed on the low voltage side, when the high voltage side arrester discharges a large lightning current to the ground, A voltage drop is generated at the grounding position, which acts on the neutral point of the low-voltage side winding while passing through the transformer casing, while the low-voltage side winding is grounded through the wave impedance of the low-voltage line.
The following measures can be taken:
1 Check the grounding faults related to the arrester and re-adjust as required. Note that the grounding wire of the arrester should be directly connected to the outer casing of the transformer and the neutral point of the low voltage side, and then the grounding device should be shared. The grounding resistance does not exceed 4Ω; 2 for the multi-mine area, a low-voltage arrester should be added to the low-voltage side.
Ⅲ Oil leakage
There are also many leakage phenomena of transformer oil in oil-immersed distribution transformers. Due to leakage, the amount of oil in the transformer is reduced, the oil level is lowered, and the infiltration of air and water vapor is caused, the oxidation of the oil is accelerated to deteriorate, the viscosity of the oil is increased, the convection speed is lowered, and the heat dissipation of the transformer is affected. The higher temperature rise, which further accelerates the deterioration of the oil. At the same time, the acidity of the oil after deterioration is enhanced, resulting in a decrease in the insulation resistance of the winding, and even a destructive effect on the insulation. In the long run, the transformer is inevitably damaged. The following measures can be taken: 1 Check the place where the oil leaks and make a good treatment; 2 Check whether the transformer oil deteriorates and deteriorate, and analyze the oil simply. If the transformer oil gradually turns from orange to brown, brown, and the viscosity of the oil is large, the transformer oil has deteriorated and must be cleaned or replaced. 3 When the transformer oil has not deteriorated, check whether the oil level is Too low. If it is too low, refuel to the mark on the transformer oil conservator; 4 check the insulation resistance of the winding.

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