The role of the grounding transformer is to provide an artificial neutral point for the neutral point of the system is not grounded, to facilitate the use of arcing coil or small resistance grounding method, in order to reduce the size of the ground capacitance current of the distribution network occurs when the grounded short-circuit faults, and to improve the reliability of power supply of the distribution system.
Grounding transformer referred to as grounding variable, according to the filling medium, grounding variable can be divided into oil and dry; according to the number of phases, grounding variable can be divided into three-phase grounding variable and single-phase grounding variable.
The working characteristics are as follows:
(1) low zero sequence impedance to ensure the output of zero sequence current;
(2) high excitation impedance to reduce the no-load current;
(3) low no-load loss to save the energy consumption of daily operation.
Expanded Information
The current situation of grounding transformer in China:
China's grounding transformer usually adopts Z-type wiring (or zigzag wiring), in order to save the investment and the space of the substation, usually add the third winding on the grounding transformer to replace the used transformer, and supply power for the equipment used in the substation. According to China's "reactor" national standards, grounding transformer grounding can be divided into direct grounding;
Through the reactor, resistance and arcing coil grounding. Directly grounded in our country is not currently used, but the power research department has begun to explore this area.
Foreign grounding transformer is usually used or Z-type connection, used for 10kV ungrounded system, constitutes the distribution network grounding protection, when the system has a ground fault, the grounding transformer on the positive sequence, the negative sequence current presents a high impedance, on the zero-sequence current presents a low impedance, so that the grounding protection is reliable action.
Baidu Encyclopedia - Grounding Transformer