7SG16 Ohmega 402 60 Commissioning
©2010 Siemens Protection Devices Limited
Chapter 9 Page 19 of 19
A.2
Fault Loop Compensation For Phase Faults
The relay is set in terms of positive sequence impedance. To calculate the actual fault loop impedance follow the
steps below.
Calculate voltage from the formulae:
V = 2IZ
1
Where Z1 is the positive sequence impedance (i.e. the relay setting)
Zone 1
Phase Effective
Impedance
Total Loop
Impedance
Current
Injected
Phase
Angle
Voltage
Injected
Phase
Angle
A
B
C
Zone 2
Phase Effective
Impedance
Total Loop
Impedance
Current
Injected
Phase
Angle
Voltage
Injected
Phase
Angle
A
B
C
Zone 3 (Fwd)
Phase Effective
Impedance
Total Loop
Impedance
Current
Injected
Phase
Angle
Voltage
Injected
Phase
Angle
A
B
C
Zone 3 (Rev)
Phase Effective
Impedance
Total Loop
Impedance
Current
Injected
Phase
Angle
Voltage
Injected
Phase
Angle
A
B
C