Relay Coordination for a Distribution System.
A medium-voltage utility network with rising faults and outages: revised relay settings for selective, faster fault isolation.
The Situation.
A utility supplying a residential area through several substations and feeders saw faults, outages and equipment damage increase. Protection was not isolating faults selectively.
What We Did.
- Collected single-line diagrams, existing relay settings, coordination curves and fault history for three substations and three feeders
- Built a model of the network and ran load flow and short circuit studies (fault levels from 3.2 kA to 12.0 kA)
- Reviewed existing settings, then revised them and plotted time-current curves for each relay
- Tested the settings against load variation and future expansion, and verified selective operation for a range of fault scenarios
The Result.
- Revised relay settings implemented for selective coordination and faster fault isolation
- Shorter outages and less equipment damage, with only the faulted section disconnected
- Coordination confirmed to hold under different load and expansion scenarios
Facing Something Similar?
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