Low-Impedance/High-Impedance Earthing

Specifications

Low-Impedance/High-Impedance Earthing

The Symmetra® MW is easily integrated into either a solid grounded system, or a high-impedance grounded system.

In a solid grounded system, the neutral power source (mains, generator, or UPS) is solidly grounded. In the event of a down-stream ground fault, the fault current will have a path back to the source, and the over-current device feeding the faulted part of the installation will trip and isolate the fault.

In a high-impedance grounded system, the source is grounded with an impedance (grounding resistor). In the event of a down-stream fault, the fault current will be limited by the impedance of the grounding resistor. The value of a high-impedance system is its ability to maintain operation with a given system fault to ground, i.e. the over-current device will only trip at line-to-line faults or double ground faults.

For a high-impedance system to provide enhanced power system reliability and availability, a ground- fault monitoring/alarm system is required.

Note: Grounding electrode conductor to be supplied by the customer.

For more information refer to “Appendix” in Installation Guide.

Electrical Specifications

Warning: Supply the UPS from a dedicated, 3 × 400/230 V, L1, L2, L3, N, PE source or a high-impedance grounded system.

Caution: Ensure clockwise phase rotation (L1, L2, L3) of input voltages.

Caution: AC and DC disconnect switches and overcurent protection must be included in the installation.

Note: All wiring must comply with all applicable national and/or local electrical codes.

Note: Max. prospective RMS short-circuit current on input terminals: 200 kA

Max. prospective RMS short-circuit current on DC terminals: 50 kA

Symmetra MW II 1200 kW 3 x 400/230 V Installation - 990-1979E-001