Why should the no load voltage regulating transformer be regulated only after it is opened?

The contact of the unloaded tap-changer is generally made by linear contact, which ensures that it is electrically conductive. If the power is not interrupted, the voltage is directly regulated, which will cause the dynamic and static contacts to indicate electrical burns, and can cause the decomposition of transformer oil under the action of a strong arc, resulting in combustible gas; At the same time, due to the electrical burn, the contact surface of the contact will be more bad, affecting the flow effect, resulting in local high temperature resulting in transformer oil aging and thermal decomposition, which will precipitate combustible gas, which may lead to the transformer in the long term.

In addition, the national standard stipulates that in order to ensure that the contact is good after switching, the transformer with no load voltage regulation must be verified by DC resistance test.

No-load pressure regulation, also known as no-load pressure regulation. The voltage regulation must be disconnected from the high-voltage side and the low-voltage side before the voltage can be adjusted, and the voltage regulating switch is generally at the top of the transformer, which is manually adjusted, and you can't go up without power. After the voltage is regulated, the three-phase DC resistance before and after the adjustment should be measured with a bridge, and the three-phase resistance should be balanced after adjustment.

For the plant-free voltage regulating transformer, if you jump the voltage with electricity, it is equivalent to a loaded broach switch, that is. There will be an arc in the voltage regulating tap, and this arc will cause internal faults in the transformer, and even the transformer**.

An electric arc is generated inside, which causes the oil to deteriorate rapidly and causes the gas relay to act.

The transformer does not have the ability to extinguish the arc inside, which will lead to oil breakdown and gas gas, and in severe cases, it will lead to transformer oil injection or **. (There is a sliding or rolling transmission pass inside the on-load voltage regulating transformer).

1) When the transformer is overloaded (except for special circumstances); 2) When the light gas action of the on-load pressure regulating device is alarmed; 3) When the oil pressure resistance of the on-load pressure regulating device is unqualified or there is no oil in the oil standard; 4) When the number of pressure regulation exceeds the specified number; 5) When there is an abnormality in the pressure regulating device. It is not allowed to adjust the on-load voltage regulating switch of the transformer.

When carrying out on-load voltage regulation, attention should be paid to whether the indication of the voltmeter is within the range of voltage regulation, whether the position indicator and counter correspond correctly, and check whether the gas relay and oil level and oil color are normal, and make a record. When the load is greater than 80% of the rated value, it is forbidden to operate the on-load voltage regulating switch.

The tap of the on-load voltage regulating transformer is equipped with a switch that can extinguish the arc, so the transformer ratio and output voltage can be adjusted without the transformer being powered off. However, there is no switch in the tap of the no-load voltage regulating transformer, so the transformer must be powered off before the tap position can be adjusted. Specifically:

The transformer is out of operation, disconnect the high-voltage side switch or other disconnected components, so that the transformer has no connection with the power supply, adjust the tap to the required position, energize and the transformer operates. If there may be power on the low-voltage side of the transformer, the outlet switch on the low-voltage side should also be disconnected.

As the name suggests, on-load voltage regulation refers to voltage conversion with load, while no-load voltage regulation refers to voltage regulation without load.

On-load voltage regulation is mostly used in places with relatively high voltage quality requirements, such as the primary substation of power supply companies, while no-load voltage regulation is mostly used in general small electricity enterprises.

The on-load voltage regulation method is relatively flexible and changeable, which is suitable for a wider range of occasions, so as to ensure the voltage quality; The no-load voltage regulation must carry out the corresponding electrical test when switching, so as to ensure that the no-load switch is in good contact, and the test can be put into operation only after passing the test, which is more troublesome, and the power must be cut off during operation, and the procedure is more troublesome.

For the lower transformer, when the input voltage is unchanged, when the voltage is adjusted from 1 to n, the secondary side voltage increases, otherwise it decreases; For step-up transformers, when the input voltage is constant, the voltage on the secondary side decreases when the input voltage is adjusted from 1 to n, otherwise it increases.