ABB REF615 Applications Manual page 163

1MRS756378 D
REF615
Application Manual
A070760 V2 EN
Figure 77: Intermittent earth-fault situation in neutral compensated network
Transient earth fault in networks
Transient earth fault is a special type of fault which can be detected by using the
INTRPTEF function in transient mode. In this mode the fault direction is detected
from the first transient pulse in the residual current. The algorithm requires also the
residual voltage to exceed the set value. The function starts when the transient is
detected in the set direction and the residual voltage is over the set limit. The function
stays in the start state as long as the residual voltage limit is exceeded. When
INTRPTEF has started and the operate delay time has elapsed, the function operates
and sends a trip command to the circuit breaker. The following figure shows the
transient earth fault detection and operation of the INTRPTEF function.
Section 5
Protection functions
157