GE C70, Инструкция по эксплуатации

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GE Multilin C70 Capacitor Bank Protection and Control System 5-171
5 SETTINGS 5.6 GROUPED ELEMENTS
5
where: ,
,
ECA = element characteristic angle and IG = ground current
When
NEUTRAL DIR OC1 POL VOLT
is set to “Measured VX”, one-third of this voltage is used in place of V_0. The following
figure explains the usage of the voltage polarized directional unit of the element.
The figure below shows the voltage-polarized phase angle comparator characteristics for a phase A to ground fault, with:
• ECA = 90° (element characteristic angle = centerline of operating characteristic)
• FWD LA = 80° (forward limit angle = the ± angular limit with the ECA for operation)
• REV LA = 80° (reverse limit angle = the ± angular limit with the ECA for operation)
The above bias should be taken into account when using the neutral directional overcurrent element to directionalize other
protection elements.
Figure 5–67: NEUTRAL DIRECTIONAL VOLTAGE-POLARIZED CHARACTERISTICS
• NEUTRAL DIR OC1 POLARIZING: This setting selects the polarizing mode for the directional unit.
– If “Voltage” polarizing is selected, the element uses the zero-sequence voltage angle for polarization. The user
can use either the zero-sequence voltage V_0 calculated from the phase voltages, or the zero-sequence voltage
supplied externally as the auxiliary voltage V_X, both from the
NEUTRAL DIR OC1 SOURCE
.
Table 5–28: QUANTITIES FOR "MEASURED IG" CONFIGURATION
DIRECTIONAL UNIT
OVERCURRENT UNIT
POLARIZING MODE DIRECTION COMPARED PHASORS
Voltage
Forward –V_0 + Z_offset
×
IG/3 IG
×
1
∠
ECA
I
op
= |IG|
Reverse –V_0 + Z_offset × IG/3 –IG × 1 ∠ ECA
V_0
1
3
---
VAG VBG VCG
+ +
( )
zero sequence voltage
= =
I_0
1
3
---
IN
1
3
---
IA IB IC
+ +
( )
zero sequence current
= = =
827805A1.CDR
VAG
(reference)
VBG
VCG
–3I_0 line
3I_0 line
ECA line
–ECA line
LA
LA
LA
LA
ECA
FWD LA
line
FWD Operating
Region
REV Operating
Region
FWD LA
line
REV LA
line
REV LA
line
–3V_0 line
3V_0 line