Transformer Winding, Solidly Earthed; Transformer Winding, Earthed Through Zig-Zag Earthing Transformer - ABB RELION 650 Series Applications Manual

Section 6
Differential protection
Due to its features, REFPDIF is often used as a main protection of the transformer winding for
all faults involving earth.
6.1.2.1

Transformer winding, solidly earthed

The most common application is on a solidly earthed transformer winding. The connection is
shown in figure 27.
REFPDIF
IdN/I
IEC09000109-4-EN V2 EN-US
Figure 27: Connection of the low impedance Restricted earth-fault function REFPDIF for
6.1.2.2

Transformer winding, earthed through zig-zag earthing transformer

A common application is for low reactance earthed transformer where the earthing is through
separate zig-zag earthing transformers. The fault current is then limited to typical 800 to 2000
A for each transformer. The connection for this application is shown in figure 28.
68
I3PW1CT1
I3P
a directly (solidly) earthed transformer winding
1MRK 505 363-UEN A
M13048-3 v9
Protected
winding
IEC09000109-4-EN.vsd
M13048-8 v11
Application manual