Distribution transformer, referred to as "distribution", refers to a kind of static electric appliance that transmits AC energy according to the electromagnetic induction law to convert AC voltage and current. In some areas, power transformers with voltage levels below 35 kV (mostly 10KV and below) are called “distribution transformers”, referred to as “distribution transformers”. The place and place where the “distribution” is installed is both a substation. The distribution transformer should be installed on the column or on the open floor. The installation method, installation precautions, supply and distribution methods, capacity selection, operation and maintenance, etc. are described in detail.

What are the main points of operation and maintenance of distribution transformers?

1. Overloading of distribution transformers

The overload operation of the transformer means that the load current exceeds the rated current of the transformer. Under normal circumstances, when the transformer is running under small load, its insulation material can not fully play its role. In the continuous overload operation, the transformer will generate high temperature, so that the insulation part of the winding is burnt and hard off, forming a turn-to-turn short circuit; The sludge accumulates on the fuel tank plate, the windings and the iron core, causing poor heat dissipation of the transformer oil. This vicious circle not only seriously affects the life of the transformer, but also causes high-voltage breakdown and transformer burnout. Therefore, it is necessary to observe the three-phase load current frequently. The three-phase load current is consistent, and if there is a deviation, it should not exceed 10%.

2. Abnormal sound of the distribution transformer

When the AC power passes through the transformer winding, a normal and uniform “click” sound is generated due to the self-vibration of the iron core. If an abnormal sound occurs, you need to find the reason and report it to the relevant department in time. The sound is different when the transformer is under no load and after loading. According to the characteristics of the abnormal sound, it can be put into operation after the cause is found.

3. Inspection of distribution transformer temperature

The operating temperature of a transformer has a lot to do with its life. The transformer operates at a normal temperature of 95 °C and has a service life of 20 a; if it is operated to 110 °C, the life is shortened to 7 a; if the temperature rises to 130 °C, its life is shortened to 2 a; the transformer is at 170 °C. Continuous operation at temperature, d will be scrapped. 10 The temperature exceeds the allowable value of the transformer. To find out the cause, take timely measures.

4. Is the distribution transformer oil level normal, with or without seepage, oil leakage or oil color abnormality?

There are many reasons for the drop in oil level. Due to poor welding quality and poor sealing, the heat pipe, valve, box edge and the like are easily bleed and oil leakage. When the oil level drops below the upper cover of the transformer, the contact surface of the oil and air increases, and it is easy to oxidize and deteriorate and absorb the moisture in the air, so that the compressive strength of the oil is lowered, thereby destroying the insulation performance of the winding. When the oil shortage is serious, the insulation between the conductive parts of the transformer and the ground is reduced, causing phase-to-phase or ground-to-ground breakdown discharge. At this time, if it continues to be used, the transformer oil will not be able to circulate normally, causing the transformer oil temperature to rise, shortening the life and even burning [1].

5. Distribution transformer insulation bushings for damage, cracking and discharge marks

The insulating sleeve is not cleaned for a long time, or there are damage cracks and discharge marks. In rainy or foggy weather, the leakage current of the insulating sleeve increases due to the humidity of the air, and the insulation drops, and flashing to the ground occurs. In addition, the insulating casing is heavily fouled, and large fragments and cracks on the insulating casing can cause flashover or explosion accidents. To solve this phenomenon, besides observing the insulating sleeve itself, it is also necessary to pay attention to the fouling law of the casing, such as the wind direction and the surrounding environment, so that the cleaning work can be done well.

6. Regular cleaning of distribution transformers

It is necessary to regularly clean the dirt on the distribution transformer, check whether the casing has flashover discharge, whether the grounding is good, whether there is disconnection, desoldering or breaking. The grounding resistance should be measured periodically, and its resistance is not more than 4 Ω (capacity). 100 kV·A and above) or 10 Ω (capacity less than 100 kV·A), or take anti-fouling measures and install the anti-fouling cap of the casing. When connecting and removing the power distribution transformer lead line, it is necessary to strictly follow the process operation to avoid internal breakage of the lead wire.

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