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HIGH RESISTANCE PULSE GROUNDING
Low-Voltage High-Resistance Grounding Where continuity of service is a high priority, high-resistance grounding can add the safety of a grounded system while minimizing the risk of service interruptions due to grounds. The concept is a simple one: provide a path for ground current via a resistance that limits the current magnitude, and monitor to determine when an abnormal condition exists. This provides for maximum continuity of service, since no tripping occurs for the resistance limited ground fault. The ground current path is provided at the point where the service begins, by placing resistance in the connection from system neutral to ground. Control equipment continuously measures ground current; a relay detects when the current exceeds a predetermined level. An alarm alerts building personnel that a ground exists. The system has built-in fault tracing means to assist in finding the source of the ground. An integral transformer provides control power from the primary source. 600/347V (Maximum) WYE Systems To add high-resistance grounding to a Wye-connected system, resistors are placed in series with the neutral-to-ground connection of the power source. The resistors are chosen to limit the current to a maximum value of 5 Amperes. 600V (Maximum) Delta Systems To add high-resistance grounding to an ungrounded delta-connected system, a neutral point must be created. Three single-phase transformers can be interconnected in a zig-zag or Wye-broken delta configuration to provide such a neutral point. The transformers and grounding resistors are chosen to limit the ground current to a maximum value of 5 Amperes. |
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POWER QUALITY
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