Transformer Winding, Solidly Earthed - ABB REG670 Applications Manual

Section 7
Differential protection
7.4.2.1
176
The restricted earth fault protection is not affected, as a differential protection, with
the following power transformer related phenomena:
• magnetizing inrush currents
• overexcitation magnetizing currents
• load tap changer
• external and internal phase faults which do not involve earth
• symmetrical overload conditions
Due to its features, REFPDIF is often used as a main protection of the transformer
winding for all faults involving earth.

Transformer winding, solidly earthed

The most common application is on a solidly earthed transformer winding. The
connection is shown in Figure 72.
REFPDIF
I3PW1CT1
IdN/I
I3P
IEC09000109-4-EN V2 EN
Figure 72: Connection of the low impedance Restricted earth fault function
REFPDIF for a directly (solidly) earthed transformer winding
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
1MRK 502 071-UEN -
Protected
winding
IEC09000109-4-EN.vsd
Application manual