EPR

Awareness of step and touch potential, caused by a rise of earth potential. Is essential for anyone working on high-voltage power transmission and distribution systems above 1 kV.

A rise of earth potential

A rise of earth potential is caused by electrical faults that occur at electrical substations. Power plants, or high-voltage transmission lines. Therefore, short-circuit current flows through the plant structure. And equipment and into the earthing electrode.  Since the Soil Resistivity is not zero. Therefore, any current injected into the earth at the earth electrode produces a ‘Rise of Earth Potential’. This earth potential rise (EPR) is concerning an infinitely distant reference point. The resulting rise of earth potential can cause hazardous voltage. And, many hundreds of metres away from the actual fault location. Thus, many factors determine the level of hazard. Including available fault current. And, soil type, soil moisture, temperature, underlying rock layers. Also, clearing time to interrupt the fault.