GE D30 Instruction Manual page 451

8 THEORY OF OPERATION
= 80.22 V ∠–133.5°
V
B
= 77.33 V ∠135.7°
V
C
= 4.47 A ∠–107.8°
I
A
= 2.92 A ∠68.9°
I
B
= 2.93 A ∠–51.1°
I
C
Based on the entered setting the relay calculates:
K0 = 3.58 ∠–15.2°
K0M= 0
Z = 14.00 Ω ∠88°
Z = 1 Ω ∠88°
D
Z = 9.99 Ω ∠−2°
R
Z = 4.99 Ω ∠178°
L
For the assumed steady-state injection the relay calculates:
= 58.83 V ∠–2.1°
V _1
A
= 64.71 V ∠0.0°
V _1M
A
= 1.37 A ∠–68.2°
I_0
= 1.37 A ∠–68.1°
I _2
A
= 29.18 V ∠8.4°
–V_0
= 93.35 V ∠32.0°
(V –V )_1
A B
= 112.08 V ∠30.0°
(V –V )_1M
A B
= 7.39 A ∠–109.1°
I –I
A B
b) MHO PHASE A TO GROUND ELEMENT (BEFORE MEMORY EXPIRES)
× Z + I_0 × K0 × Z + I
I
A A
V _1M
A
I _2 × Z
A D
I_0 × Z
I_0 × Z
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.
The MHO phase A ground element will operate for this fault.
c) 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 will use the actual voltage for polarization.
× Z + I_0 × K0 × Z + I
I
A G
V _1
A
_2 × Z
I
A D
I_0 × Z
I_0 × Z
D
GE Multilin
× K0M × Z – V = 103.33 V ∠–3.9°
A
= 64.71 V ∠0.0°
= 1.37 V ∠19.8°
= 19.11 V ∠19.8°
= 1.37 V ∠19.8°
× K0M × Z – V = 103.33 V ∠–3.9°
A
= 58.83 V ∠–2.1°
= 1.37 V ∠19.8°
= 19.11 V ∠19.8°
= 1.37 V ∠19.8°
D30 Line Distance Protection System
8.1 DISTANCE ELEMENTS
8-9
8