In this paper, a new type of portable horizontal grid earth electrode has been designed for mobile equipments. With the impulse ground measurement system, the responses to double exponential pulse current of five earth electrodes in two arrangements have been tested on soil, grassplot and cement floor respectively. After filtering and calculating, the curve of transient grounding resistance (TGR) in time domain can be gotten. And in the end, some conclusions have been drawn. The analysis of discharging capacity of horizontal grid earth electrodes in time domain has great significance in the design of mobile equipments’ earth devices.

A new derivation of Transient Grounding Resistance (TGR) has been proposed in this paper. Take grounding system as naked antenna in lossy medium, and then get the input resistance of naked antenna in a given frequency based on Helen current integral equations. With inverse Fourier transform, the resistance calculation equations can be translated from frequency domain to time domain. The result can be applied to design a new grounding system and to calculate its TGR .

The portable grounding system plays an important role in the lightning protection system of mobile equipments. But the traditional earth electrodes composed of vertical rods wouldn’t work well or would take a long time to set up in some conditions such as frozen soil, hard clay and so on. In this paper, a new type of portable grounding system which can be quickly spread and folded has been designed. To analyze the TGR’s (Transient Grounding Resistance) time-domain characteristics, the grounding systems have been modeled and simulated with FDTD (Finite Difference Time Domain). The influence rule of electrodes’ number and down-lead’s position to TGR has been studied with numerical analysis and validated with experiments. The results show that the new grounding system works well even on cement floor.

Based on current situation of mobile equipments earth devices, a new type of portable horizontal grid earth electrode has been designed. With the impulse ground measurement system, different number of earth electrodes responses to double exponential pulse current have been tested on cement grounds. Impulse waves of voltage and current have been gotten by experiments, and the curve of Transient Grounding Resistance (TGR) can be calculated. The analysis of discharging capacity of horizontal grid earth electrodes in time domain has great significance in the design of mobile equipments earth devices.