Alstom SHPM 101 - 19.16 Selecting Zone 2 reach

SERVICE MANUAL R5888B
QUADRAMHO Chapter 1
Page 22 of 27
The relay coarse reach (Z
Ph
) should be set to the nearest value below the required
Zone 1 reach. It is important to set Z
Ph
as high as possible since the relay current
level detector sensitivities are inversely proportional to |Z
Ph
| and it is best to have
the most sensitive settings possible.
Z
Ph
=
K1 + K2
I
n
; θ
Ph
in this case rated current = 1A
Select θ
Ph
= 70°
K1 + K2 = 8.8
Select K1 = 4
K2 = 0.8
Actual Z
Ph
= 4.8 /70°
With K1 + K2 = 4.8 (max value) current level detector sensitivities are at their
base values.
Required Zone 1 multiplier setting
=
required Zone 1 reach
|Z
Ph
|
=
8.8 = 1.83
4.8
Select K11 = 1
K12 = 0.8
K13 = 0.02
K14 = 1
Actual Zone 1 setting = (K11 + K12 + K13) K14 x Z
Ph
= 1.82 x 1 x 4.8 /70°
= 8.74
/70° ohms secondary
19.16 Selecting Zone 2 reach
Required Zone 2 reach =
FEB – MARCH line impedance + 50% (MARCH – AUG line impedance)
Required Zone 2 reach
= 60 x 0.44
/69° + 0.5 x 40 x 0.44 /69°
= 35.2
/69° ohms primary
= 14.68
/69° ohms secondary
Required Zone 2 multiplier setting =
required Zone 2 reach
|Z
Ph
|
=
14.68 = 3.06
4.8
Select K21 = 3
K22 = 0.1
Actual Zone 2 reach = (K21 + K22) Z
Ph
= 3.1 x 4.8 /70° = 14.88 /70° ohms secondary