Transient grounding impedance and transient resistivity measurements using a very short current lead

• An improved technique for measurements of the transient impedance is presented.
• The innovation is the use of a physically short current reaction lead.
• The methodology is discussed and validated in field studies using a vertical rod.
• A comparison with calculated values is also presented.
• The influence of the length of the potential lead is investigated.

This work describes a system for measurements of the transient impedance of grounding electrodes using a portable impulse generator and a new arrangement of test leads. The major innovation is the use of a physically short current reaction lead, using a transmission line with very low propagation velocity (2% of the velocity of light). The methodology for obtaining the transient impedance from the measurements is discussed and validated in field studies using a 2.4 m long vertical rod. A comparison with calculated values is also presented. Additionally, the influence of the length of the potential lead is investigated using the very short current lead and the transient soil resistivity is also calculated.