A high impedance grounding system, recently was requested as a solution to reducing high fault levels. The fault levels are in the 100K plus range, creating issues of concern on transfer switches, downstream panels, circuitbreakers etc.
Some givens in the program - fuse combinations are not permitted, series rated circuit breakers are forbidden, distance from power source to 20 amp circuit breakers are insufficient to lower the cost. Voltage is 480, Utility Transformer is 2500KVA, multiple gen sets are in play to provide tier 2 power redundancy
A solution offered for consideration is using a high impedance ground system, increasing the impedance on the system to reduce incoming fault. Yet, to achieve this result, the neutral conductor from is disabled, code disallows line to neutral connections, resulting in a main switchboard with out a neutral.
The main switchboard contains three phase breakers to UPS equipment, and mechanical loads. A small 480 to 208/120 volt wye transformer would be attaached for general "dirty" power receptacles and lights.
Yet, while on the initial read, the concept appears to solve some problems, I am fearful that it will create other issues that I cannot at the moment discern. Beyond the somewhat obvious issues of not having a neutral within the main switchboard and someone accidentally trying to attach a single phase load.
Any ideas and thoughts are sincerely appreciated.
RobVA
Some givens in the program - fuse combinations are not permitted, series rated circuit breakers are forbidden, distance from power source to 20 amp circuit breakers are insufficient to lower the cost. Voltage is 480, Utility Transformer is 2500KVA, multiple gen sets are in play to provide tier 2 power redundancy
A solution offered for consideration is using a high impedance ground system, increasing the impedance on the system to reduce incoming fault. Yet, to achieve this result, the neutral conductor from is disabled, code disallows line to neutral connections, resulting in a main switchboard with out a neutral.
The main switchboard contains three phase breakers to UPS equipment, and mechanical loads. A small 480 to 208/120 volt wye transformer would be attaached for general "dirty" power receptacles and lights.
Yet, while on the initial read, the concept appears to solve some problems, I am fearful that it will create other issues that I cannot at the moment discern. Beyond the somewhat obvious issues of not having a neutral within the main switchboard and someone accidentally trying to attach a single phase load.
Any ideas and thoughts are sincerely appreciated.
RobVA