On load tap changer (OLTC) is a type of transformer that can complete tap voltage switching during load operation. It can adjust the tap position of the transformer to maintain voltage stability and ensure power supply quality when the system voltage fluctuates or the user load changes.

The task of a power transformer is to directly supply power to the load center, with the primary side connected directly to the main voltage grid (220 kV and above) or to the regional power grid (35-110 kV). This type of transformer not only provides active power to the load, but also often simultaneously provides reactive power, and generally has a high short-circuit impedance.

Therefore, for on load tap changers that directly supply power to the power supply center, under the premise of achieving local balance of reactive power zoning, with the increase or decrease of regional load, the tap changer is adjusted in conjunction with the parallel switching of capacitors and low-voltage reactors of reactive power compensation equipment to ensure the quality of power supply voltage to users at any time.