GE D30 User Manual

CHAPTER 9: THEORY OF OPERATION DISTANCE ELEMENTS
D30 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL 9-9
9
Mutual zero-sequence compensation can raise concerns regarding directional integrity on reverse faults in the situation
when the relay gets "overcompensated." This problem does not affect the D30 because its ground distance elements use
zero-sequence and negative-sequence currents in extra directional comparators. Both the currents are from the protected
line and are not affected by any compensation as the latter applies only to the reach defining comparators: the mho,
reactance, and blinder characteristics.
9.1.6 Distance elements analysis
9.1.6.1 Description
This subsection shows how to analyze the operation of the distance elements in steady states using the results of short
circuit studies. All quantities are secondary ohms, volts, and amperes. Ground phase A and phase AB distance elements
are analyzed.
Assume that the following settings have been entered:
Phase Rotation: ABC
Right Blinder Reach: 10 Ω
Nominal Secondary Voltage: 69.28 V
Right Blinder RCA: 88°
Distance Reach: 14 Ω
Left Blinder Reach: 5 Ω
Distance RCA: 88°
Left Blinder RCA: 88°
Polarizing Current: Zero-sequence
Non-Homogeneity Correction Angle: 3°
Directional RCA: 88°
Z0/Z1 Magnitude: 4.55
Overcurrent supervision: 3 A
Z0/Z1 Angle: –12°
Distance Comparator limit angle: 75°
Z0M/Z1 Magnitude: 0
Directional Comparator limit angle: 75°
Assume that the following signals are injected to the relay:
V
A
= 64.71 V ∠0.0° (pre-fault)
V
A
= 25.43 V ∠–19.9°
V
B
= 80.22 V ∠–133.5°
V
C
= 77.33 V ∠135.7°
I
A
= 4.47 A ∠–107.8°
I
B
= 2.92 A ∠68.9°
I
C
= 2.93 A ∠–51.1°
Based on the entered setting the relay calculates:
K0 = 3.58 ∠–15.2°
K0M = 0
Z = 14.00 Ω ∠88°
Z
D
= 1 Ω ∠88°
Z
R
= 9.99 Ω ∠−2°
Z
L
= 4.99 Ω ∠178°
For the assumed steady-state injection the relay calculates:
VA_1 = 58.83 V ∠–2.1°
VA_1M = 64.71 V ∠0.0°

GE D30 Specifications

General

Brand	GE
Model	D30
Category	Relays
Language	English