For dry-type transformers, the so-called balance voltage of the relay is the voltage value that keeps the relay from operating. The purpose of setting the balancing voltage in advance can be achieved by setting a variable resistor in the voltage sensing circuit of the voltage relay. In this way, it is possible to preset the voltage value of the adjustable range of the resistor. Dry-type transformers usually need to maintain the remote bus voltage at a fixed level. When the line voltage drop increases due to the increase of the load, the line voltage compensation device can be used to include an adjustable resistance and a tap with a tap, and the reactor is connected to the secondary side of a current transformer once at the current transformer. The current flowing through the side is the load current. By properly adjusting the resistor and reactor parameters, depending on the line characteristics, it is possible to maintain a constant voltage at a certain point in the system without having to consider changes in the load and power factor. The connection method of the voltage relay circuit shall be such that the voltage applied to the voltage relay is subtracted from the supply voltage.
In this way, as the dry-transformer load current increases, the voltage relay’s equilibrium state will be actuated by the segment voltage adjustment device, so that the voltage at the primary side voltage supply point of the voltage relay is increased, and its value is just equal to the line impedance voltage drop, so that the voltage relay Restore balance. When the load is reduced, the situation is the opposite. The voltage relay and the compensation device are usually used in the three-phase circuit. However, since the voltage coil of the relay is single-phase, the spring is generally connected between the two phases. The only difference between the three-phase line voltage compensation devices is that when the voltage transformers and the current transformers are connected on the primary side, the corr