Instantaneous Differential Relay - Why do you need it?
Instantaneous Differential Relay - Why do you need it?
(OP)
If you have a differential relay (GE Multilin 745) that has time/overcurrent elements, then why do you need the instantaneous differential element? Wouldn't the overcurrent instantaneous element perform the same function?






RE: Instantaneous Differential Relay - Why do you need it?
RE: Instantaneous Differential Relay - Why do you need it?
1)Reduced damage due to lower currents and likely less time. (Faults generally take time to develop to reach the IOC level)
2)Less bump on the system due to lower amplitude faster clearing
Point 1 is the the major justification.
RE: Instantaneous Differential Relay - Why do you need it?
RE: Instantaneous Differential Relay - Why do you need it?
Simple overcurrent functions can falsely operate for inrush and through faults. Lead time for power transformer repairs or replacement is often quite pricey, {to say nothing about consequent lost production} so differential protection can economically limit damage.
RE: Instantaneous Differential Relay - Why do you need it?
Bung
Life is non-linear...
RE: Instantaneous Differential Relay - Why do you need it?
RE: Instantaneous Differential Relay - Why do you need it?