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ABB’s high fault rating makes circuit protection easy
Installing power protection equipment does not always mean you need to redesign your circuit protection. ABB’s PCS100 MV UPS has a high fault current rating meaning circuit protection can operate as expected.
The truth about UPS fault current levels
Not all UPSs can provide the necessary current levels to trip protection in the case of a fault. This often means a compromise is made when installing power protection equipment, or protection devices must be replaced for more sensitive types, adding cost and increasing the risk of nuisance tripping.
Graphic: A simplified MV critical process single line diagram (SLD)
PCS100 MV UPS Operation
ABB’s PCS100 MV UPS uses robust semiconductor technology (manufactured by ABB) to connect the utility to the load. During normal operation it is this semiconductor switch that will conduct fault currents in the event of a downstream fault. Other UPSs may limit their current on the output. This current may be insufficient to trip the protection device, and isolate the fault, before the UPS must trip to protect itself. If the UPS trips, then all the loads are dropped, rather than just isolating the fault.
What happens with faults in the low voltage network?
Graphic: This graph shows the PCS100 MV UPS and circuit breaker withstand times vs. current
What happens with faults in the LV network?
If a short circuit was to happen in a downstream low voltage branch, then the peak fault current will be limited by the step-down transformer. In the example single line diagram, a fault in one of the low voltage loads will result in 1.8 kA flowing in the UPS (300 percent current). The PCS100 MV UPS can tolerate this level of current with ample time for the low voltage circuit breaker (CB-C) to clear and keep the rest of the plant running
What happens with faults in the medium voltage network?
At medium voltage the peak fault currents are limited only by the impedance of the upstream feeder. In the example single line diagram, a fault current of 10.5 kA will be flowing in the UPS if there is a fault in the MV motor or VSD. The PCS100 MV UPS can tolerate this current for up to 1 second, allowing time for circuit breakers to clear. If fuses are employed then higher fault levels can be tolerated due to the faster clearing time of fuses.
To find out more about ABB’s PCS100 MV UPS solutions, please visit: www.abb.com/pcs100-power-converters
For product information, email email@example.com