GE T60 Instruction Manual page 356

5.6 GROUPED ELEMENTS 5 SETTINGS
The phase directional element responds to the forward load current. In the case of a following reverse fault, the ele-
ment needs some time – in the order of 8 ms – to establish a blocking signal. Some protection elements such as
NOTE instantaneous overcurrent may respond to reverse faults before the blocking signal is established. Therefore, a
coordination time of at least 10 ms must be added to all the instantaneous protection elements under the supervi-
sion of the phase directional element. If current reversal is of a concern, a longer delay – in the order of 20 ms –
may be needed.
5
Figure 5–109: PHASE DIRECTIONAL SCHEME LOGIC
5-220 T60 Transformer Protection System GE Multilin