Alstom SHPM 101 - Section 19. CURRENT TRANSFORMER REQUIREMENTS; 19.7 Ground fault compensation settings

SERVICE MANUAL R5888B
QUADRAMHO Chapter 1
Page 16 of 27
=
1.28 x 5
= 4.57
1.4
Zone 3 forward multiplier = (K31 + K32) K33
Select K31 = 4
K32 = 0.6
K33 = 1
Actual Zone 3 forward reach = (K31 + K32) K33 x Z
Ph
= 4.6 x 1 x
1.4
= 1.29 ohms
5
Required Zone 3 reverse reach = 25% zone 1 reach
Zone 1 reach = 0.219 ohms secondary
Required Zone 3 reverse reach = 0.25 x 0.291 = 0.073 ohms secondary
Required Zone 3 reverse reach multiplier
=
required Zone 3 reverse reach
|Z
Ph
|
=
0.073 x 5
= 0.26
1.4
Zone 3 reverse reach multiplier = (K35 + K36) K33 x K37
Select K35 = 1
K36 = 0.0
K37 = 0.25
Actual Zone 3 reverse reach = (K35 + K36) K33 x K37 x Z
Ph
= 1.0 x 1 x 0.25 x
1.4
= 0.07
/70° ohms
5
19.7 Ground fault compensation settings
Ground loop impedance of line Z
LE
= (1 + K
N
) Z
L1
where K
N
=
Z
L0
– Z
L1
3Z
L1
Neutral impedance coarse setting Z
N
= K
N
= Z
Ph
(0.749 + j1.85)
Z
LO
– Z
L1
= (0.171 + j0.47) = 1.5 /67.3°
(0.578 + j1.38)
K
N
=
1.5
/67.3 °
= 1.0
/–2.7° (100% compensation)
3 x 0.5
/70°
Compensation setting = K
N
x Z
Ph
= 1.0 /–27° x 1.4 /70° = 0.28 /67.3°
5
Select (
K4 + K5 +K6) = 0.28
5
(K4 + K5 +K6) = 1.4