In the 6 ~ 35kV neutral point ungrounded power grid, when the bus is no load or there are few outgoing lines, the voltage transformer will be over saturated due to the excitation of closing charging or grounding fault elimination during operation, which may lead to ferromagnetic resonance overvoltage. Abnormal phenomena such as unstable phase to ground voltage, misoperation of grounding indication, and fusing of high-voltage fuse of voltage transformer may lead to burnout of voltage transformer and other accidents. In this case, it is necessary to install a microcomputer harmonic elimination device.

The common fault of microcomputer harmonic elimination device in voltage transformer cabinet is single-phase grounding or internal fault of voltage transformer cabinet. This protection can be realized by using a very simple fuse. It is not necessary to install special protection device for voltage transformer. In general, the voltage transformer parallel device is installed on the voltage transformer for voltage switching. For the voltage transformer over-voltage alarm or voltage transformer disconnection, there is generally a small current grounding line selection device protection.

Generally, the intelligent microcomputer harmonic elimination device needs to be installed as long as there is nonlinear load. Now the load is increasing rapidly, so it is generally necessary to install a microcomputer harmonic elimination device.