GE ALPS Instruction Manual page 76

2.3 PROTECTION SETTINGS
109: Z1GLEVDET - Zone 1 Ground Level Detector
(Series Capacitor Model Only)
Use the total protective level
Z1GLEVDET =
110: Z1BLOCK - Supervise Zone 1 Functions By Blocking Functions
2
This setting prevents the Zone 1 functions from producing an output if the respective blocking functions have operated.
This type of operation is required when series capacitors are located behind the ALPS system as shown in Figure 2–3:
POWER SYSTEM ONE LINE DIAGRAM WITH SERIES CAPACITORS on page 2–10. For this situation, the voltage
applied to the system would reverse for a fault beyond the capacitors if gap flashing were not to occur or if the MOV protec-
tion did not conduct significantly. Z1BLOCK can be set to either YES or NO. Set Z1BLOCK to YES if there are series
capacitors located behind the ALPS system as shown in Figure 2–3: POWER SYSTEM ONE LINE DIAGRAM WITH
SERIES CAPACITORS on page 2–10.
111: Z1GCHARANG - Zone 1 Ground Characteristic Timer Angle
(Revision B models only)
Z1GCHARANG can be set from 80° to 155° in increments of 1°. This setting determines the "tilt" of the reactance portion of
the quadrilateral ground distance characteristic.
A ground distance function employing a reactance/quadrilateral characteristic provides excellent protection on a homoge-
neous system where the fault current at the relay location is essentially in phase with the total fault current for a single line
to ground fault at the remote end of the line; or if the fault current at the relay location is more lagging than the total fault
current for a single line to ground fault at the remote end of the line. On a non-homogeneous system where the fault current
at the relay location is more leading than the total fault current for a single line to ground fault at the remote end of the line,
a conventional reactance/quadrilateral characteristic will tend to overreach, especially when fault resistance is present. In
this situation, the "tent" characteristic shown below should be used.
112: Z1RGREACH - Zone 1 Resistive Ground Reach
(Revision B models only)
Z1RGREACH can be set from 0.01 to 100.00 Ω for a 5 A rated relay (0.05 to 500 Ω for a 1 A rated relay). It determines the
position of the right resistive blinder for the ground distance quadrilateral characteristic to provide coverage for resistive
ground faults. If Zone 2 is also set to Quad mode, this setting should be calculated as 0.8 or less of the Zone 2 Resistive
Ground Reach (Protection Setting 211: Z2RGREACH). If Zone 2 is not set to Quad mode, the setting should be calculated
at 0.8 (if "tent" characteristics are used) or less (0.6 to 0.7 if "tent" characteristics are not used) of the positive-sequence
resistance seen by the relay under maximum load conditions and unity power factor. Also, to maintain zone accuracy, it is
recommended that the resistive reach is not greater than 10 times the Ground Distance Reach (Protection Setting 105:
Z1GRDREACH) for this zone.
2-12
determined with the Z1PLEVDET setting to calculate Z1GLEVDET:
PL
t
2
0.15 PL
+
t
X
"TENT" CHARACTERISTIC
4
Figure 2–4: TENT CHARACTERISTIC
ALPS Advanced Line Protection System
1
3
2
2 CALCULATION OF SETTINGS
R
GE Power Management