Overvoltage Protection; Overvoltage Protection Theory - NR Electric PCS-9611 Instruction Manual

3.13 Overvoltage Protection

3.13.1 Overvoltage Protection Theory

This relay provides a two-stage overvoltage protection with definite time delay characteristics. The
two stages have same protection logics. Each stage can be used for tripping or alarming through
the PCS-Explorer and the default is for tripping.
This protection can support all kinds of VT connection: three phase voltage (Ua, Ub, Uc), three
phase-to-phase voltages (Uab, Ubc, Uca), two phase-to-phase voltages (Uab, Ubc), anyone of
three phase voltages or anyone of three phase-to-phase voltages.
Two methods are used to check the overvoltage condition by the setting [59P.Opt_1P/3P]. If
setting [59P.Opt_1P/3P] is set as "0", and all of the three voltage values are greater than the
voltage setting, the overvoltage protection will operates after the appointed time delay; and if the
setting [59P.Opt_1P/3P] is set as "1", and anyone of the three voltage values is greater than the
voltage setting, the overvoltage protection will operates after the appointed time delay.
The setting [59P.Opt_Up/Upp] is used to decide the voltage input mode. If it is set as "1", the input
voltage is phase-to-phase voltage; and if it is set as "0", the input voltage is phase voltage. So the
voltage setting must be set in accordance with the setting [59P.Opt_Up/Upp]; i.e. if the setting
[59P.Opt_Up/Upp] is set as "1", the voltage setting is set according to phase-to-phase voltage;
and if the setting [59P.Opt_Up/Upp] is set as "0", the voltage setting is set according to phase
voltage.
The following figure shows the logic diagram of the stage 1 overvoltage protection.
Uab > [59P1.U_Set]
Ubc > [59P1.U_Set]
Uca > [59P1.U_Set]
Uab > [59P1.U_Set]
Ubc > [59P1.U_Set]
Uca > [59P1.U_Set]
[59P.Opt_1P/3P]
[59P.Opt_Up/Upp]
Ua > [59P1.U_Set]
Ub > [59P1.U_Set]
Uc > [59P1.U_Set]
Ua > [59P1.U_Set]
Ub > [59P1.U_Set]
Uc > [59P1.U_Set]
[59P1.En]
[59P1.En1]
[59P1.Blk]
Figure 3.13-1 Logic diagram of the stage 1 overvoltage protection
Where:
[59P1.U_Set] is the voltage setting of the stage 1 overvoltage protection;
"t " is the setting [59P1.t_Op], the time setting of the stage 1 overvoltage protection;
OV1
PCS-9611 Feeder Relay
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Date: 2014-04-08
t 0
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OV1
3 Operation Theory
[59P1.St]
[59P1.Op]
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