
GE Power Management
750/760 Feeder Management Relay
12-
27
12 S5 PROTECTION
12.4 GROUND OVERCURRENT
12
12.4.4 GROUND DIRECTIONAL
The ground directional feature controls the operation of all ground overcurrent elements and allows them to
discriminate between forward or reverse faults. Refer to Section 12.2: DIRECTIONAL OVERCURRENT
CHARACTERISTICS on page 12–6 for more details on directional principles. Ground directional can be either
voltage, current, or dual polarized. The ground current input is always the operating current.
When voltage polarized, the polarizing quantity is the zero sequence voltage which is calculated from the bus
input voltages. The
VT CONNECTION TYPE
must be
Wye
in this case. If the polarizing voltage drops below the
MINIMUM OPERATING VOLTAGE
setting the direction defaults to forward. The following table shows the operating
current and polarizing quantities used for ground directional control.
†
Note: On relays with bootware revision 3.00 or newer, the ground directional element may only be voltage
polarized since these relays do not have a polarizing current input. Otherwise, the polarizing current is input
via a dedicated polarizing CT input. See Section 3.2: TYPICAL WIRING on page 3–5 for more details.
When current polarized, the ‘Polarizing CT Input’ is used to determine ground current direction. The polarizing
current comes from a source CT measuring the current flowing from the ground return into the neutral of a
ground fault current source which is usually a transformer. The direction is
Forward
when the sensitive ground
current is within
±
90
°
of the polarizing current. Otherwise, the direction is
Reverse
. If the polarizing current is
less than 5% of CT nominal then the direction defaults to forward.
Dual polarization provides maximum security and reliability. If the polarizing voltage magnitude is insufficient
then the current polarizing takes control. If the polarizing current magnitude is insufficient then the voltage
polarizing takes control. If neither voltage nor current polarizing is possible then the direction defaults to for-
ward.
Table 12–10: GROUND DIRECTIONAL CONTROL CHARACTERISTICS
QUANTITY
OPERATING
CURRENT
POLARIZING VOLTAGE
(VT connection = Wye)
POLARIZING CURRENT
Ground
I
g
–
V
o
= –(
V
a
+
V
b
+
V
c
) / 3
I
pol
†
Содержание 750
Страница 2: ......
Страница 4: ......
Страница 124: ...8 14 750 760 Feeder Management Relay GE Power Management 8 12 INSTALLATION 8 S1 RELAY SETUP 8 ...
Страница 144: ...10 14 750 760 Feeder Management Relay GE Power Management 10 10 MISCELLANEOUS FUNCTIONS 10 S3 LOGIC INPUTS 10 ...
Страница 152: ...11 8 750 760 Feeder Management Relay GE Power Management 11 3 OUTPUT RELAYS 3 7 AUXILIARY 11 S4 OUTPUT RELAYS 11 ...
Страница 216: ...12 64 750 760 Feeder Management Relay GE Power Management 12 9 BREAKER FAILURE 12 S5 PROTECTION 12 ...
Страница 484: ...17 78 750 760 Feeder Management Relay GE Power Management 17 10 PLACING THE RELAY IN SERVICE 17 COMMISSIONING 17 ...
Страница 488: ...A 4 750 760 Feeder Management Relay GE Power Management A 1 FIGURES AND TABLES APPENDIXA A ...
Страница 490: ...B 2 750 760 Feeder Management Relay GE Power Management B 1 EU DECLARATION OF CONFORMITY APPENDIXB B ...
Страница 492: ...C 2 750 760 Feeder Management Relay GE Power Management C 1 WARRANTY INFORMATION APPENDIXC C ...
Страница 502: ...x 750 760 Feeder Management Relay GE Power Management INDEX ...
Страница 503: ...GE Power Management 750 760 Feeder Management Relay NOTES ...