Alstom SHPM 101 - Section 19. CURRENT TRANSFORMER REQUIREMENTS; 19.5 Selecting Zone 2 reach; 19.6 Selecting Zone 3 reach

SERVICE MANUAL R5888B
QUADRAMHO Chapter 1
Page 15 of 27
With K1 + K2 = 1.4 current level detector sensitivities:
=
4.8
x base settings = 3.43 x base settings
1.4
Required Zone 1 multiplier setting =
required Zone 1 reach
Z
Ph
=
0.292 x I
n
=
0.292 x 5
= 1.043
(K1 + K2) 1.4
Zone 1 multiplier = (K11 + K12 + K13) K14
Select K11 = 1
K12 = 0.0
K13 = 0.04
K14 = 1
Actual Zone 1 setting = (K11 + K12 + K13) K14 x Z
Ph
= 1.04 x 1 x
1.4
= 0.291
/70° ohms
5
19.5 Selecting Zone 2 reach
Required Zone 2 reach = +50% (JUNE – JULY line impedance) MAY – JUNE
line impedance.
Required Zone 2 reach = (10 + 0.5 x 20) (0.171 + j0.47) ohms
= 10.0/70° ohms primary
= 0.73/70° ohms secondary
Required Zone 2 multiplier setting =
required Zone 2 reach
Z
Ph
=
0.73 x 5
= 2.61
1.4
Zone 2 multiplier = (K21 + K22) K24
Select K21 = 2
K22 = 0.6
Actual Zone 2 setting = (K21 + K22) K24 x Z
Ph
= 2.6 x 1 x
1.4
= 0.728
/70° ohms
5
19.6 Selecting Zone 3 reach
Required Zone 3 forward reach = +125% (JUNE – JULY line impedance) MAY –
JUNE line impedance.
Required Zone 3 forward reach = (10 + 1.25 x 20) (0.171 + j0.47)
= 17.5
/70° ohms primary
= 1.28 /70° ohms secondary
Required Zone 3 forward reach multiplier
=
required Zone 3 forward reach
|Z
Ph
|