GE D90 Plus - Page 644

634 D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
DISTANCE ELEMENTS CHAPTER 15: THEORY OF OPERATION
The limit angle of the comparator is not adjustable and equals 50°. The fault type
characteristic is intended to block ground distance elements during double-line-to-ground
faults.
Zero-sequence directional characteristic
The extra zero-sequence characteristic is achieved by checking the angle between the two
values for the elements shown in the table. This characteristic applies to ground distance
zones 2 and 3 only.
Table 15-9: Zero-sequence directional characteristic angle calculation parameters
The limit angle of the comparator is not adjustable and equals 90°. The zero-sequence
directional characteristic improves directional integrity for time-delayed operations after
the memory expires.
Overcurrent supervision
The overcurrent supervision function responds to the following currents.
Table 15-10: Overcurrent supervision parameters
Distance element characteristic summary
The following tables summarize the characteristics of the distance elements.
Table 15-11: Directional mho phase distance functions
Table 15-12: Directional mho ground distance functions
Element Value 1 Value 2
A ground element I_0 × Z
D
–V_0
B ground element I_0 × Z
D
–V_0
C ground element I_0 × Z
D
–V_0
Element Current
AB phase element (I
A
– I
B
) / √3
BC phase element (I
B
– I
C
) / √3
CA phase element (I
C
– I
A
) / √3
A, B, and C ground elements 3 × I_0
Characteristic Comparator inputs Limit angle
Input 1 Input 2
Variable mho I × Z – VV_1M Comparator limit
Reactance I × Z – VI × Z Comparator limit
Directional I × Z
D
V_1M Directional comparator limit
Characteristic Comparator inputs Limit angle
Input 1 Input 2
Variable mho I × Z – VV_1M Comparator limit
Reactance I × Z – VI × Z Comparator limit
Directional I_0 × Z
D
V_1M Directional comparator limit
I_2 × Z
D
V_1M Directional comparator limit (removed when
3I_0 > overcurrent supervision and I_2 < cutoff)
Fault type I_0 I_2 50° (removed during open pole conditions or
when 3I_0 > overcurrent supervision and
I_2<cutoff)