Siemens Reyrolle 7SR5 Manual page 284

Protection and Automation Functions
5.19 67 Directional Overcurrent/Earth Fault
Compensated Coil Earthing Netorks
In compensated networks the resonant coil (Petersen coil) is tuned to match the capacitive charging currents
such that when an earth fault occurs, negligible fault current will flow. However, resistive losses in the primary
conductors and the earthing coil will lead to resistive (wattmetric) components which can be measured by the
50/51GS elements and used to indicate fault position.
Core balance CTs are recommended for this application to achieve the necessary accuracy of residual current
measurement.
[dw_7SR5_function67SettingExample5, 1, en_US]
Figure 5-37
3 methods are commonly employed to detect the wattmetric current – 7SR5 devices can be configured to
provide each of these methods.
[dw_7SR5_function67SettingExample6, 1, en_US]
Figure 5-38
284
Earth Fault Current Distribution In Compensated Network
Earth Fault Current Direction In Compensated Netowrk
Reyrolle 7SR5, Transformer Protection Device, Device Manual
C53000-G7040-C015-1, Edition 11.2019