APC MW II User Manual
17
Symmetra MW II 1200 kW 3 x 400/230 V Installation - 990-1979E-001
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.
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.
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.
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.
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
Max. prospective RMS short-circuit current on DC terminals: 50 kA