ABB RET670 Applications Manual page 134

Section 3
IED application
128
ANSI05000211 V3 EN
Figure 31: Connection of the low impedance Restricted earth-fault function
REFPDIF for a zig-zag grounding transformer
Autotransformer winding, solidly grounded
Autotransformers can be protected with the low impedance restricted ground fault
protection function REFPDIF. The complete transformer will then be protected
including the HV side, the neutral connection and the LV side. The connection of
REFPDIF (87N) for this application is shown in figure 32.
1MRK504116-UUS C
ANSI05000211_3_en.vsd
Application manual