Robust ABB SACE PR111/P Protection Unit: Mitigate Downtime in Critical Power Circuits

Description

Application Scenarios

In the main low-voltage distribution board of a commercial office building, a critical feeder supplies a server room. A downstream fault, such as a short circuit in a rack PDU, must be cleared quickly to prevent damage to upstream cables and equipment, but the main incoming breaker must remain closed to keep power on for the rest of the building. The ABB SACE PR111/P​ protection release, installed on the feeder breaker, is configured with precise time-current curves. When the fault occurs, the PR111/P‘s short-time protection function senses the high current. It intentionally introduces a brief, programmable time delay (e.g., 200ms). This delay allows a downstream breaker (with a faster curve) to clear the fault first if it is within its zone. If the fault persists (indicating the downstream device failed), the PR111/P​ then commands its breaker to trip. This “time-grading” coordination, orchestrated by the intelligence of the PR111/P, achieves selective discrimination, isolating the fault to the server room feeder only and maintaining power to all other building loads, directly addressing the pain points of unnecessary widespread outages and equipment stress.

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