High Voltage Distribution Network Discrimination
High Voltage Distribution Network Discrimination
(OP)
Please give me your opinion, We have an 11Kv HV network connected to the national grid. We have 4x(1200Amp) Incomers onto a Bus Bar and 800Amp Feeders feeding radial circuits. There are large 11Kv 3MVA Motors on some circuits, This particular Feeder relay over current protection is by IDMT set at 900Amp pick up. The equipment (Cable and Circuit Breakers) are rated at 800Amps. Are there situations on HV networks such as this where the over current IDMT protection can be set above the rating of the equipment, or should this never be the case and protection always to be set below the equipment rating?






RE: High Voltage Distribution Network Discrimination
Regards
Marmite
RE: High Voltage Distribution Network Discrimination
With the set up as is currently, would it be possible to have a 3 phase fault that could draw a load above the equipment rated 800amp but below the 900amp IDMT setting that could allow continuous over current flow through the 800amp breaker and cable?
RE: High Voltage Distribution Network Discrimination
Veman.
RE: High Voltage Distribution Network Discrimination
RE: High Voltage Distribution Network Discrimination
However they can be configured to operate simultaneously.
One overcurrent/earth fault relay cannot perform as a fault and an overload protection device.