GE D30 Instruction Manual page 332
Line distance protection system, ur series
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Also See for D30:
- Instruction manual (686 pages) ,
- Communications manual (532 pages) ,
- Communications manual (526 pages)
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5.6 GROUPED ELEMENTS
The positive-sequence restraint must be considered when testing for pick-up accuracy and response time (multiple of
pickup). The positive-sequence restraint is removed for low currents. If the positive-sequence current is less than 0.8 pu,
then the restraint is removed by changing the constant K to zero. This results in better response to high-resistance faults
when the unbalance is very small and there is no danger of excessive CT errors, since the current is low.
The operating quantity depends on the way the test currents are injected into the D30. For single phase injection:
= ⅓ × (1 – K) × I
•
I
op
= (1 – K) × I
•
I
op
injected
The directional unit uses the negative-sequence current (I_2) and negative-sequence voltage (V_2).
The following tables define the negative-sequence directional overcurrent element.
Table 5–28: NEGATIVE-SEQUENCE DIRECTIONAL OVERCURRENT UNIT
MODE
Negative-sequence
Zero-sequence
Table 5–29: NEGATIVE-SEQUENCE DIRECTIONAL UNIT
DIRECTION
Forward
Reverse
Z_offset is the offset impedance, for which magnitude is the OFFSET setting and angle is the FWD ECA.
5
The negative-sequence voltage must be greater than 0.02 pu to be validated for use as a polarizing signal. Additionally,
when offset impedance is applied and negative-sequence current is above 0.2 pu, compensated negative-sequence volt-
age -V_2 + Z_offset x I_2 has to be above 0.02 pu in order to discriminate fault direction; otherwise when negative-
sequence current is less than 0.2 pu, -V_2 is then used as the polarizing signal. If the polarizing signal is not validated nei-
ther forward nor reverse indication is given. The following figure explains the usage of the voltage polarized directional unit
of the element.
The following figure shows the phase angle comparator characteristics for a phase A to ground fault, with settings of:
ECA
= 75° (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)
5-196
for I_2 mode.
injected
for I_0 mode if I_1 > 0.8 pu.
OPERATING CURRENT
I
= |I_2| – K × I_1|
op
I
= 3 × (|I_0| – K × |I_1|) if |I_1| > 0.8 pu
op
I
= 3 × |I_0| if |I_1| ≤ 0.8 pu
op
COMPARED PHASORS
–V_2 + Z_offset × I_2
–V_2 + Z_offset × I_2
D30 Line Distance Protection System
I_2 × 1∠ECA
–(I_2 × 1∠ECA)
5 SETTINGS
GE Multilin
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