Transformer Winding, Solidly Earthed - ABB RER670 Applications Manual

Section 6
Differential protection
6.1.2.1
76
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 29.
REFPDIF
I2P
IdN/I
ISI
IEC16000117 V1 EN-US
Figure 29: Connection of the low impedance Restricted earth fault function
REFPDIF for a directly (solidly) earthed transformer winding
1MRK 506 375-UEN A
Protected
winding
IEC16000117-1-en.vsdx
Railway application RER670 2.2 IEC
Application manual
M13048-3 v10