Distribution Transformer - Distribution Transformer Fault Analysis

1, three-phase unbalanced load or seasonal overload
Distribution transformer three-phase load imbalance results from the survey substantial presence, especially in rural areas, most of the power load single-phase load, and the load changes, therefore, there are many three-phase unbalanced load distribution transformers, so can not symmetrical three-phase operation, resulting in zero-sequence current. In this regard so that the transformer losses increase, on the other hand reduces the effective capacity of the transformer. These two cases will lead to overheating of transformers, insulating oil aging, reduce the level of the winding insulation, and ultimately will lead to  Electric energy meter  damage. May take the following measures:
① survey distribution transformer load, including load 24 hours a day year four seasons with the load, the load to ascertain the general situation, and try to adjust the three-phase load, so close to the symmetry operation;
② Adjust electricity peak time, reduce the overload condition; while a timely manner to the transformer capacity increase, to avoid overloading the transformer long run.
2, poor grounding
Lightning lightning protection of distribution transformers work is generally done, but there are still two problems: ① arrester poorly grounded; ② only attach importance to high-pressure side of the installation of surge arresters, while ignoring the low side also need to install arresters problem (especially Dore area). If the arrester is poorly grounded, the occurrence of overvoltage arrester leakage current is not well, it will cause damage to the insulation transformer; arrester is not installed if the low side, when the high pressure side of the arrester discharge to the earth a great lightning current, the voltage drop on the ground position, the voltage at the same time by the transformer  circuit breakers  acts on the low voltage side winding the neutral point, and low voltage side coil by low pressure line impedance to ground. May take the following measures:
① identify with the poor grounding at the arrester, as required re-grafting. Note that first put the arrester and the transformer ground wire directly to the outer shell of low-pressure side of the neutral point is connected together and then shared grounding device. The grounding resistance is not also exceeded 4 Ω; ② For more minefields, the low  power transformers  side it necessary to add a set of low-voltage arrester.
3, permeability oil spill
Distribution transformers transformer oil leakage is greater. Since leakage, reduce the amount of oil inside the transformer, the oil level decreases the infiltration of air and water vapor, to accelerate the oxidation of the oil to deteriorate, the viscosity of the oil becomes large, convection speed decreases, the cooling of the transformer, the higher temperature, which further accelerate the degradation of the oil. Meanwhile deteriorated after oleic acid increased, resulting winding insulation resistance is lowered, or even play a destructive effect on the insulation, over time, will inevitably lead to transformer damage. May take the following measures: ① identify where oil leakage, and make treatment; ② Check whether the deterioration of transformer oil deterioration, a simple analysis of the oils. If the transformer oil gradually from the initial yellow to orange, brown, and the viscosity of the oil, transformer oil has deteriorated described, it must be purified or replaced; ③ is not deteriorated when the deterioration of the transformer oil, the oil level check low. If too low, the fuel to the transformer conservator at the standard scale; ④ Check the winding insulation resistance.