The tester introduces a brand new detection method in principle - waveform analysis method, whose main characteristics and advantages are high detection sensitivity, high check system distributed capacitance capacity, uninterrupted power supply search, no effect on the normal operation of the system, high anti-interference capacity, safe and reliable, etc. Waveform analysis method is to analyze and calculate the phase and phase difference of fundamental wave and harmonic of current signal by adding a certain periodic voltage signal between the DC bus and ground and detecting the current of each branch circuit with the caliber-type probe and then judge the existence of ground fault and the ground fault point. The tester measures the capacitative current and resistive current and eliminates the influence of the capacitance.

The DC system of power plant and converting station provides power supply for control, protection, signal and automatic devices and the safe and continuous operation of DC system is of great importance to guarantee power supply. Since the DC system is an non-grounded system of floating mode, the occurrence of grounding of two points may cause unwanted operation and refuse operation of the above devices so as to result in major accidents. So when one point grounding occurs, the grounding point shall be detected accurately and quickly to eliminate the ground fault while the normal power supply of DC system is guaranteed so as to avoid the damage that may be caused by two point grounding.

1. Ground point search with uninterrupted power supply of the system and no effect on the normal operation of the system.

2. High test sensitivity.

3. High anti-interference capacity, which help overcome the influence of system distributed capacitance and filter capacitance.

4. High degree of intelligence; friendly man-machine interface.

5. Safe and reliable; simple operation; easy to carry.