GE D30 Instruction Manual page 598
Line distance protection system
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DISTANCE ELEMENTS
I_0 = 1.37 A ∠–68.2°
IA_2 = 1.37 A ∠–68.1°
–V_0 = 29.18 V ∠8.4°
(V
–V
)_1 = 93.35 V ∠32.0°
A
B
(V
–V
)_1M = 112.08 V ∠30.0°
A
B
I
–I
= 7.39 A ∠–109.1°
A
B
9.1.6.2 Mho phase A to ground element (before memory expires)
× Z + I_0 × K0 × Z + I
I
A
_1M = 64.71 V ∠0.0°
V
A
_2 × Z
= 1.37 V ∠19.8°
I
A
D
I_0 × Z = 19.11 V ∠19.8°
I_0 × Z
= 1.37 V ∠19.8°
D
•
Overcurrent supervision: | 3 × I_0 | = 4.09 A > 3 A
•
Mho difference angle = | –3.9° – 0° | = 3.9° < 75°
•
Reactance difference angle = | –3.9° – 19.8° | = 23.7° < 75°
•
Zero-sequence directional difference angle = | 19.8° – 0.0° | = 19.8° < 75°
•
Negative-sequence directional difference angle = | 19.8° – 0.0° | = 19.8° < 75°
•
Fault-type comparator difference angle = | 19.8° – 19.8° | = 0.0° < 50°
All four comparators and the overcurrent supervision are satisfied, so the MHO phase A ground element operates for this
fault.
9.1.6.3 Mho phase A to ground element (after memory expires)
After the memory expires, the relay checks the actual positive-sequence voltage and compares it with 10% of the nominal
voltage:
| V
_1 | = 58.83 V > 0.1 × 69.28 V
A
After the memory expires the relay uses the actual voltage for polarization.
I
× Z + I_0 × K0 × Z + I
A
V
_1 = 58.83 V ∠–2.1°
A
I
_2 × Z
= 1.37 V ∠19.8°
A
D
I_0 × Z = 19.11 V ∠19.8°
I_0 × Z
= 1.37 V ∠19.8°
D
•
Overcurrent supervision = | 3 × I_0 | = 4.09 A > 3 A
•
Mho difference angle = | –3.9° – (–2.1°) | = 1.8° < 75°
•
Reactance difference angle = | –3.9° – 19.8° | = 23.7° < 75°
•
Zero-sequence directional difference angle = | 19.8° – (–2.1°) | = 21.9° < 75°
•
Negative-sequence directional difference angle = | 19.8° – (–2.1°) | = 21.9° < 75°
•
Fault-type comparator difference angle = | 19.8° – 19.8° | = 0.0° < 50°
All four comparators and the overcurrent supervision are satisfied, so the Zone 1 MHO phase A ground element operates
9
for this fault.
•
Zero-sequence directional difference angle for zones 2 and higher (phase A) = | 19.8° – 8.4° | = 11.4° < 90°
Zones 2 and higher phase A ground elements pick-up, time-out, and operate.
9.1.6.4 Mho AB phase element
(I
– I
) × Z – (V
– V
A
B
A
9-10
× K0M × Z – V
= 103.33 V ∠–3.9°
A
A
× K0M × Z – V
= 103.33 V ∠–3.9°
G
A
) = 88.65 V ∠–78.7°
B
CHAPTER 9: THEORY OF OPERATION
D30 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
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