What Is the Reason for Water Ingress and Moisture in the Transformer?

When we use transformers, we need to pay attention to avoid accidents, such as water ingress and moisture in transformers, which is a problem that can cause transformer accidents and burnout. Many transformers continue to operate after water ingress, which poses a threat to the safety of the power system. Generally speaking, transformers will be water-ingressed and damp, basically for the following reasons:

1. Poor sealing of the bushing top connection cap

When the connection cap is not sealed well, moisture enters the winding insulation along the lead wire, causing a breakdown accident. The main reasons for poor sealing at the end of the bushing are unreasonable structure and incorrect installation of the rubber pad, which can be paid attention to during maintenance.

2. Dampness during maintenance

When the transformer cover is hung for maintenance, the body will be exposed to the atmosphere. At this time, if the relative humidity of the air is high, it will absorb moisture in the air. This process starts with surface insulation. The higher the relative humidity and the longer the time, the deeper the moisture penetration.

3. Cooler brass tube rupture

According to regulations, the cooler should be tested for leakage before installation in order to detect the rupture defects of the cooler, otherwise it may cause insulation breakdown accidents. For example: a 150MVA, 110kV power transformer, during operation, the light and heavy gas protection tripped, and the explosion-proof shell sprayed oil. After inspection under the hanging cover, a total of 24 segments were burned in the lower part of the A-phase high-voltage winding, 4 short circuits, and two holes of 100mm were accidentally melted. The reason was that the cooler copper tube ruptured and water entered the transformer.

The main distribution device was dampened by water, which greatly damaged the electrical and physical and chemical functions of the insulating medium. The presence of moisture will damage the insulation strength of the oil and also corrode metals such as copper and iron. Therefore, when water enters the transformer, it must be dealt with in time.

Therefore, we must pay attention when using the transformer.