GFN Operation
GFN is asserted for a network ground/EF when each of the following criteria are met:
-
Zero Sequence Voltage (V0) magnitude is greater than or equal to a user defined GFN threshold setting.
-
Phase-Earth voltages on two phases are above a user defined GFN uplifted phase voltage threshold setting.
-
Phase-Earth voltage on one phase is less than a user defined GFN faulted phase voltage threshold setting.
The following functions of the ACR are disabled when GFN is asserted:
-
EF protection
-
SEF protection
-
Automatic Reclose
On clearance of a ground/EF and when GFN resets, the following ACR functions are in immediate effect:
-
EF protection
-
SEF protection
-
Start of user configured Auto Reclose block time
-
Inhibit of Auto Reclose function until the user configured block time expires
A recurrence of a ground/EF that causes GFN to be asserted before the expiry of the Auto Reclose Block time will result in:
-
EF protection disabled
-
SEF protection disabled
-
Auto Reclose functionality disabled and the Auto Reclose Block timer reset to the user configured value
A recurrence of a ground/EF that causes GFN to be asserted after the expiry of the Auto Reclose Block time will result in:
-
EF protection disabled
-
SEF protection disabled
-
Auto Reclose functionality disabled
Table 46 GFN Settings/Specifications
|
GFN Settings/Specifications |
||
|---|---|---|
|
Setting |
Minimum Value |
Maximum Value |
|
V0 Pickup Threshold |
V0 Reset Threshold setting + 0.02 pu |
2.00 pu |
|
V0 Reset Threshold |
0.00 pu |
V0 Pickup Threshold – 0.02 pu |
|
Auto Reclose Block Time |
0 s |
3600 s |
|
Uplifted Phase Pickup Threshold |
Uplifted Phase Reset Threshold setting + 0.02 pu |
2.00 pu |
|
Uplifted Phase Reset Threshold |
0.00 pu |
Uplifted Phase Pickup Threshold – 0.02 pu |
|
Faulted Phase Pickup Threshold |
0.00 pu |
Faulted Phase Reset Threshold setting – 0.02 pu |
|
Faulted Phase Reset Threshold |
Faulted Phase Pickup Threshold setting + 0.02 pu |
2.00 pu |