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Chapter 7) 7SR23 DAD Applications Guide
©2013 Siemens Protection Devices Limited
Chapter 7 Page 34 of 42
6.3
Restricted Earth Fault Protection
The approach to the calculation is the same as for the three phase differential protection.
REF
Relay Circuit
REF
Relay Circuit
Transformer
Figure 6-5
Balanced/Restricted Earth Fault Protection Applied to a Delta/Star Transformer
6.3.1
Primary Operate Current (Fault Setting)
To achieve correct sensitivity to in-zone faults, the protection scheme must typically operate for a primary current
of 10-25% of the protected winding rated current.
6.3.2
Stability Level
Typically the through fault current is taken as 16 times the rated current of the protected winding or as otherwise
agreed.
Summary of Contents for 7SR23 DAD
Page 1: ...Answers for energy 7SR23 DAD High Impedance Protection Relay Reyrolle Protection Devices ...
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