7SG16 Ohmega 402 60 Commissioning
4 MAIN PROTECTION
4.1 Distance Protection
4.1.1 Impedance Reach Test.
Set the distance scheme to the stepped time scheme and programme output relays accordingly.
4.1.1.1
Earth Fault Elements Test.
Check that the minimum impedance reach of the relay, on the line angle is as per the relay setting for Earth
Faults.
Line Angle
=
°
EF Comp Z0/Z1 Ratio
=
EF Comp Z0 Angle
=
°
Calculated Earth Fault Compensation Factor, K
N
=
⎟
⎠
⎞
⎜
⎝
⎛
−
1
Z
Z
3
1
1
0
=
If the test set incorporates automatic earth fault compensation ensure that this is configured correctly on the test
set. Alternatively, if the test set has no automatic earth fault compensation then see Appendix A for details of how
to measure the fault loop impedance. Record the impedance reach of each earth fault element in all zones in the
table below.
Element
Relay Setting (
Ω
)
Fault
Type
Measured
Impedance (
Ω
)
% Error
A-E
B-E
Zone 1
C-E
A-E
B-E
Zone 2
C-E
A-E
B-E
Zone 3
C-E
A-E
B-E
Zone 3
(Reverse)
C-E
Ensure that the error does not exceed
±
5%, or
±
0.15
Ω
, (whichever is larger)
Checked
OK
©2010 Siemens Protection Devices Limited
Chapter 9 Page 7 of 19