Basic Knowledge Of Dry Type Distribution Transformer
Dry type distribution transformer manufacturers believe that the transformer needs to be carefully checked before it is put into operation, and it can be energized for trial operation. During commissioning, special attention must be paid to check the following points, that there are no abnormal sounds, noises and vibrations. First of all, although dry-type transformers have strong moisture resistance, they are generally open structure and are prone to moisture, especially domestically produced dry-type transformers with low insulation level (low insulation grade). Therefore, dry-type transformers can achieve high reliability only when the relative humidity is lower than 70%. Dry-type transformers should also be out of service for a long time to avoid serious damp. When the insulation resistance value is lower than 1000V (operating voltage), it means that the transformer is seriously damped, and debugging should be stopped.
Dry type distribution transformer manufacturers believe that dry-type transformers used in step-up power stations are different from oil-immersed transformers, and open-circuit operation on the low-voltage side is prohibited to avoid insulation breakdown of dry-type transformers caused by overvoltage transmission caused by grid-side overvoltage or lightning strikes. To prevent the spread of overvoltage hazards, a set of overvoltage protection arresters should be installed on the voltage bus side of the dry-type transformer.
Dry type distribution transformer manufacturers believe that the commissioning of transformers before operation:
(1) Check the transformer ratio and connection group, measure the DC resistance of the high and low voltage windings, and compare the results with the factory test data provided by the manufacturer.
(2) Check the insulation resistance between the coils and between the coils and the ground. If the insulation resistance is significantly lower than the factory measurement data, it indicates that the transformer is damp. When the insulation resistance is lower than 1000V (working voltage), the transformer must be dry.
(3) The dry-type transformer manufacturer believes that the test voltage of the withstand voltage test should meet the regulations. When doing the low pressure withstand voltage test, the temperature sensor TP100 should be taken out. After the test, put the sensor back in place in time.
(4) When the transformer is equipped with a fan, the fan should be energized to run and ensure its normal operation.
Dry-type transformer manufacturers believe that there are three reasons for transformer phase loss:
1. The power supply lacks one phase of electricity;
2. One-phase fuse of the transformer high-voltage fuse is blown;
3. Due to careless transportation, the high-voltage lead wire is thin, causing the transformer to break due to vibration (but not grounded).
Dry-type transformer manufacturers believe that when the transformer is put into operation, if the tap changer is not in place, it will make a loud chirp sound, which will cause the high-voltage fuse to blow in severe cases; Spark discharge. Once the load increases, the tap changer contacts may burn out. In this case, it is necessary to cut off the power supply and repair it in time.
Dry type distribution transformer manufacturers believe that when the through-core screw of the transformer clamping the iron core is loose, leaving nut parts or small metal objects on the iron core and falling into the transformer, the transformer will make a ding ding ding knocking sound or a blowing sound and the like. The squeak sound of the small spacer was picked up by the magnet, but the voltage, current and temperature of the transformer were normal. This situation generally does not affect the normal operation of the transformer, and can be dealt with in a power outage.
