1. Product Overview In recent years, HVDC transmission has been applied in China's long-distance transmission because of its high efficiency and economy. More and more DC transmission lines are put into operation. When the DC power transmission unit is operated greatly, part of the earth's pole current flows into the neutral grounding circuit of the system transformer, which has different degrees of influence on the AC power transmission system. In particular, the earth's polar current flows into the neutral point of the transformer, causing the magnetic neutrality of the transformer's neutral point to be superimposed on the DC component, causing magnetic saturation, causing harmonics, vibration, and noise of the transformer, affecting the safe and stable operation of the transformer and the AC system.

1. Product Overview The transformer neutral point resistance current limiting device (hereinafter referred to as the device) is composed of a high-power resistor and a graphite discharge gap in parallel, and is installed between the neutral point of the transformer of 110KV and above and the ground. The device mainly aims to suppress the DC bias of the transformer by increasing the loop resistance and limiting the DC current flowing through the transformer winding. When the AC grounding fault occurs in the AC system, once the neutral point voltage of the transformer exceeds the threshold value of the discharge gap, the discharge gap is instantaneously broken down to ensure reliable grounding of the neutral point of the transformer and protect the current limiting resistor. The device can be widely used to solve the single-maximal return line operation of the HVDC transmission system, and the DC bias problem caused by the urban rail transit stray current and other main AC main transformers, and ensure the safe operation of the power grid.