GE L90 Instruction Manual page 708

DISTANCE ELEMENTS
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
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.
10.3.6.4 Mho AB phase element
) × Z – (V
(I – I – V
A B A
)_1M = 112.08 V ∠30.0°
(V – V
A B
(I – I ) × Z = 103.50 V ∠–21.2°
A B
(I – I ) × Z = 7.39 V ∠–21.2°
A B D
• Overcurrent supervision: | (I
• Mho difference angle = | –78.7° – 30.0° | = 108.7° > 75°
• Reactance difference angle = | –78.7° – (–21.2°) | = 57.5° < 75°
• Directional difference angle = | –21.2° – 30.0° | = 51.2° < 75°
The mho comparator is not satisfied, so the MHO AB phase element does not operate for this fault.
Repeating this analysis, one concludes that out of the six distance elements only the ground element in phase A operates
for this fault.
10.3.6.5 Quad phase A to ground element (before memory expires)
I × Z + I_0 × K0 × Z + I
A
V _1M = 64.71 V ∠0.0°
A
j3
j × I_0 × e = 1.37 A ∠24.8°
I _2 × Z = 1.37 V ∠19.8°
A D
I_0 × Z = 1.37 V ∠19.8°
D
I × Z + I_0 × K0 × Z
A R
× Z + I_0 × K0 × Z
I
A R
× Z + I_0 × K0 × Z
I
A L
× Z + I_0 × K0 × Z
I
A L
• Overcurrent supervision: | 3 × I_0 | = 4.09 A > 3 A
• Reactance difference angle = | –3.9° – 24.8° | = 28.7° < 75°
10
• Zero-sequence difference angle = | –19.8° – 0.0° | = 19.8° < 75°
• Negative-sequence directional difference angle = | –19.8° – 0.0° | = 19.8° < 75°
10-30
× K0M × Z – V = 103.33 V ∠–3.9°
G A
) = 88.65 V ∠–78.7°
B
– I ) / | = 4.27 A > 3 A
A B
× K0M × Z – V = 103.33 V ∠–3.9°
G A
+ I × K0M × Z – V = 87.6 V ∠–109.2°
R G R A
= 91.5 V ∠–93.0°
R
× K0M × Z = 57.0 V ∠108.7°
+ I – V
L G L A
= 45.8 V ∠82.9°
L
CHAPTER 10: THEORY OF OPERATION
L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL