A PC-BASED GROUND IMPEDANCE MEASUREMENT INSTRUMENT

This paper presents a PC based instrument for ground impedance measure ments. The instrument injects a transient electric current between the ground under measurement and an auxiliary ground, and it measures gro und potential differences (GPDs) around the ground under measurement. The GPD measurements are processed with software which rejects externa l noise using correlation methods. Subsequently, estimation methods ar e used to extract the ground potential rise and ground impedance. The final result is the ground impedance versus frequency in a user select ed frequency range. The instrument has been constructed and field test ed by three utilities.