GE D90 Plus Instruction Manual page 644

Plus
THE D90 DISTANCE ELEMENTS
Zero-sequence directional characteristic
Table 15-9: Zero-sequence directional characteristic angle calculation parameters
Element
A ground element
B ground element
C ground element
Overcurrent supervision
Table 15-10: Overcurrent supervision parameters
Element
AB phase element
BC phase element
CA phase element
A, B, and C ground elements
Distance element characteristic summary
Table 15-11: Directional mho phase distance functions
Characteristic
Variable mho
Reactance
Directional
Table 15-12: Directional mho ground distance functions
Characteristic
Variable mho
Reactance
Directional
Fault type
634
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.
The extra zero-sequence characteristic is achieved by checking the angle between the two
values for the elements shown in the table below. This characteristic applies to ground
distance zones 2 and 3 only.
Value 1
I_0 × Z
D
I_0 × Z
D
I_0 × Z
D
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.
The overcurrent supervision function responds to the following currents.
The following tables summarize the characteristics of the distance elements.
Comparator inputs
Input 1 Input 2
I × Z – V V_1M
I × Z – V I × Z
I × Z V_1M
D
Comparator inputs
Input 1 Input 2
I × Z – V V_1M
I × Z – V I × Z
I_0 × Z V_1M
D
I_2 × Z V_1M
D
I_0 I_2
Value 2
–V_0
–V_0
–V_0
Current
(I – I ) / √3
A B
(I – I ) / √3
B C
(I – I ) / √3
C A
3 × I_0
Limit angle
Comparator limit
Comparator limit
Directional comparator limit
Limit angle
Comparator limit
Comparator limit
Directional comparator limit
Directional comparator limit (removed when
3I_0 > overcurrent supervision and I_2 < cutoff)
50° (removed during open pole conditions or
when 3I_0 > overcurrent supervision and
I_2 < cutoff)
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 15: THEORY OF OPERATION