Sensitive ground-fault relaying

Sensitive ground-fault protection refers to the concept of detecting low levels of ground-fault current that might cause electrocution of any human that becomes part of the ground-current path and providing warnings. The concepts behind sensitive ground-fault relaying for use on AC and DC low-voltage utilization systems are covered. The background for these relaying types is presented, and it is shown that the critical component in sensitive ground-fault relay design is the current sensor. Zero-sequence devices for three-phase industrial utilization systems and a saturable-transformer device for DC utilization are discussed. Relaying schemes for both AC and DC systems are presented. This study is aimed at mine power systems but could be applicable to any portable low-voltage portion of industrial power systems that involve handling by personnel