ZFP8N – Out-of-step protection relay
ection relay ZFP8N belongs to SIGMA-N digital protection fine and it performs the function of out-of-step protection far generators.
| FUNCTIONS | ANSI |
| Out-of-step protection relay |
78 |
The operation of the ZFP8N protection relay is based on the impedance measurement method.
The impedance vector is computed from the positive sequence components of the measured voltages and currents; the protection relay verifies the absence of negative sequence components of the currents.
The evolution of the measured impedance vector is checked on the X-R diagram with the polygonal out-of-step characteristic to identify power swing occurrences.
When an out-of-step condition occurs, a timer is started and a counter is increased; during the programmed time delay the protection relay will verify the number of out-of-step occurrences and will increase the counter if any.
The protection relay will trip if the counter reaches the programmed maximum number of allowed out-of-step occurrences in the lime delay.
