Grounding system impedance measurement using shifted frequency method

The measurement of grounding system impedance may be affected by power system frequency interference and its harmonics. The Shifted Frequency Method (SFM) is potentially insensitive to the electromagnetic interference. In this paper, we evaluate this method in the hydroelectric power plant for two different load conditions of the connected overhead power lines. Presented field tests results further validate and justify the SFM method.

I. Introduction

The primary function of grounding system is to provide a continuous path for currents that may otherwise present hazard to the personnel and equipment. The grounding system impedance is an important factor which ensures efficiency and safety of the grounding system. Consequently, the grounding system impedance of power facility should be measured. The main problem concerning the measurements is related to the test conditions. Due to economic reasons and system operational constraints, the measurement should be performed with the system under normal operating conditions. In that case, the power frequency interference and its harmonics may affect the measurement of the grounding system impedance.