ANSI05000177 V1 EN
Figure 44: Application of HZPDIF (87) function as a restricted earth fault IED for
an YNd transformer
Setting example
It is strongly recommended to use the highest tap of the CT whenever
high impedance protection is used. This helps in utilizing maximum CT
capability, minimize the current, thereby reducing the stability voltage
limit. Another factor is that during internal faults, the voltage developed
across the selected tap is limited by the non-linear resistor but in the
unused taps, owing to auto-transformer action, voltages much higher
than design limits might be induced.
Section 3 1MRK504116-UUS C
IED application
156
Application manual
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