This type of protection must be co-ordinated with any other overvoltage devices at other locations on the system.
Transformer
s can typically withstand a 110% overvoltage condition continuously. The withstand times for higher
overvoltages should be declared by the transformer manufacturer.
To prevent operation during earth faults, the element should operate from the phase-phase voltages. To achieve
this, you set V>1 Measur’t Mode to Phase-Phase and V>1 Operating Mode set to Three-phase. You should
typically set the overvoltage threshold V>1 Voltage Set to 100% - 120% of the nominal phase‑phase voltage. You
should also set the time delay to prevent unwanted tripping of the delayed overvoltage protection function due to
transient over voltages, which do not pose a risk to the transformer. A typical delay setting would be 1 s - 3 s, with
a longer delay being applied for lower voltage threshold settings.
The second stage can be used to provide instantaneous high-set over voltage protection. The typical threshold
setting to be applied, V>2 Voltage Set, would typically be 130 - 150% of the nominal phase‑phase voltage. For
instantaneous operation, you should set the time delay to 0 s.
If you select phase-to-neutral operation, take care to ensure that the element will grade with other protections
during earth faults, where the phase-neutral voltage can rise significantly.
This type of protection must be coordinated with any other overvoltage devices at other locations on the system.
P64x Chapter 11 - Voltage Protection Functions
P64x-TM-EN-1.3 243
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