Dry-type transformer is a simple and efficient transformer with stable performance and easy maintenance.

Due to its simple structure, even if a fault occurs, troubleshooting and maintenance are relatively convenient. Here, we will summarize the common faults and maintenance methods of dry-type transformers to facilitate quick troubleshooting.

Leilang Electric's main business: transformers, reactors, voltage regulators, and voltage stabilizers

1. Decrease in insulation resistance

The windings of dry-type transformers are mostly made of resin, and the conductor material is sealed in them. Therefore, the decrease in insulation resistance is mostly caused by the condensation of water vapor on the winding surface, the accumulation of dust, or the moisture in part of the insulating material. It can be divided into the following categories:

(1) High and low voltage windings are all made of cast epoxy resin. If the insulation resistance decreases, it is generally caused by water vapor condensation, dust and other debris on the winding surface.

(2) If the high-voltage winding is cast with epoxy resin but the low-voltage winding is not, the epoxy plate used to fasten the low-voltage winding can easily cause insulation degradation due to moisture absorption. When installing the transformer in place, there is a gap between the inside of the low-voltage winding and the core column. Occasionally falling debris can also easily cause the overall insulation to degrade. When measuring the insulation between the core and the ground with a megohmmeter, insulation degradation often occurs.

At this time, it is necessary to cut off the power supply, clean the winding surface, and use natural air drying or drying to process it.

2. Multi-point grounding of the transformer core

The causes of multi-point ground faults in the core of dry-type transformers can be divided into external and internal factors:

(1) External factors include: negligence during on-site construction and installation, inadvertently leaving metal foreign objects, such as nuts, iron filings, etc., causing the core to be grounded at multiple points; the simple insulating materials used in the core are subject to moisture and condensation, which greatly reduces Multi-point grounding caused by insulation performance; long-term lack of cleaning attracts surrounding metal powder and dust; long-term overload and high-temperature operation cause the insulation between silicon steel sheets to age, and the insulation between the sheets is destroyed, causing multi-point grounding.

(2) The internal reason is: defects in the internal insulation materials of the transformer or improper product design and installation process, resulting in multi-point grounding in the transformer core.

The processing of multi-point grounding of the transformer is more complicated. If it is an external factor, the transformer needs to be cleaned and dried. If necessary, the no-load method can be used for baking. If it is an internal factor, it needs to be dealt with using the step-by-step troubleshooting method. This requires using the DC and AC methods to find the multi-point ground fault points of the core. If the cause is not found, it is recommended to return the product to the factory for processing.

3. Transformer tripping fault

There are two types of transformer tripping faults: tripping during power transmission and tripping due to transformer protection action during operation.

The reason for tripping during power transmission may be that the setting value of the current protection device of the high-voltage secondary cabinet is too small, and it needs to be re-set according to the relay protection regulations.

If the transformer protection action trips during operation, you need to check whether there are obvious abnormalities in the appearance of the dry-type transformer, whether there are problems with the temperature control fan device, whether the three-phase temperature probes are damaged, and check the contact conditions of the door lock device contacts. Check the action record of the comprehensive protection device of the dry-type transformer, and whether the protection and DC secondary circuits are normal. Check whether the input and output side power supplies, switch control cabinets and other equipment are faulty, and conduct necessary electrical tests.

4. Abnormal noise

When the transformer is operating normally, it will emit a continuous and uniform "buzzing" sound. If the operating sound is uneven or there are other special sounds, it means it is not operating normally. Find out the cause based on the difference in sound and deal with it in time. We have introduced this in detail in previous articles.

5. Winding overheating

The overheating of the winding during operation is related to the ambient temperature and the condition of the transformer itself. The condition can be analyzed by referring to the intrinsic factors of multi-point grounding of the transformer. The external environment is also an important factor. It is necessary to check the ventilation conditions and whether the cooling system is normal.
Of course, due to different actual working environments and working conditions, the reasons for failure are also complex and diverse. This article only starts from some basic principles to popularize science. If a transformer failure occurs in real life, you must find professional maintenance personnel to handle it.