ABB RET670 Applications Manual page 136

Section 3
IED application
130
ANSI05000213 V3 EN
Figure 33: Connection of restricted earth-fault, low impedance function REFPDIF
(87N) for a solidly grounded reactor
Multi-breaker applications
Multi-breaker arrangements including ring, one breaker-and-a-half, double breaker
and mesh corner arrangements have two sets of current transformers on the phase side.
The restricted earth-fault protection, low impedance function REFPDIF (87N) has
inputs to allow two current inputs from each side of the transformer. The second
winding set is basically only applicable for autotransformers.
A typical connection for a star-delta transformer is shown in figure 34.
1MRK504116-UUS C
ANSI05000213_3_en.vsd
Application manual