Alstom MiCOM P546 - 3.2.2 System data; 3.2.3 Relay settings; 3.2.4 Line impedance; 3.2.5 Residual compensation for ground fault elements

P54x/EN AP/La4 Application Notes
(AP) 6-56 MiCOM P543, P544, P545 & P546
AP
3.2.2 System data
Line length: 100 km
Line impedances: Z
1
= 0.089 + j0.476 = 0.484 79.4 /km
Z
0
= 0.426 + j1.576 = 1.632 74.8 /km
Z
0
/Z
1
= 3.372 -4.6
CT ratio: 1 200/5
VT ratio: 230 000/115
3.2.3 Relay settings
It is assume
d that Zone 1 Extension is not used and that only three forward zones are
required. Settings on the relay can be performed in primary or secondary quantities and
impedances can be expressed as either polar or rectangular quantities (menu selectable).
For the purposes of this example, secondary quantities are used.
3.2.4 Line impedance
Ratio of se
condary to primary impedance =
1200 / 5
230000 / 115
= 0.12
Line impedance secondary = ratio CT/VT x line impedance primary.
Line Impedance = 100 x 0.484 79.4 (primary) x 0.124
= 5.81 79.4  secondary.
Select Line Angle = 80 for convenience.
Therefore set Line Impedance and Line Angle: = 5.81 80  secondary.
3.2.5 Residual compensation for ground fault elements
The
residual compensation factor can be applied independently to certain zones if required.
This feature is useful where line impedance characteristics change between sections or
where hybrid circuits are used. In this example, the line impedance characteristics do not
change and as such a common KZN factor can be applied to each zone. This is set as a
ratio “kZN Res. Comp”, and an angle “kZN Angle”:
kZN Res. Comp, kZN = (Z0 - Z1) / 3Z1 i.e.: As a ratio
kZN Angle, kZN =  (Z0 - Z1) / 3Z1 Set in degrees
ZL0 - ZL1 = (0.426 + j1.576) - (0.089 + j0.476)
= 0.337 + j1.1
= 1.15 72.9
kZN =





4.79484.03
9.7215.1
= 0.79 –6.5°
Therefore, select:
kZN Res. Comp = 0.7
kZN Angle = - 6.5°