ABB RET670 Applications Manual page 133

1MRK504116-UUS C
Application manual
Due to its features, REFPDIF (87N) is often used as a main protection of the
transformer winding for all faults involving ground.
Transformer winding, solidly grounded
The most common application is on a solidly grounded transformer winding. The
connection is shown in figure 30.
I3PW1CT1
REFPDIF (87N)
I3P
ANSI05000210 V3 EN
Figure 30: Connection of the low impedance Restricted earth-fault function
REFPDIF (87N) for a directly (solidly) grounded transformer winding
Transformer winding, grounded through Zig-Zag grounding transformer
A common application is for low reactance grounded transformer where the
grounding is through separate Zig-Zag grounding 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 31.
Section 3
IED application
ANSI05000210_3_en.vsd
127