ABB Relion 670 Series Technical Reference Manual page 514

Section 8
Voltage protection
Voltage
VA
VB
VC
ANSI05000016 V2 EN
Figure 257: Voltage used for the inverse time characteristic integration
508
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B C 0
100
EQUATION1435 V1 EN
The highest phase (or phase-to-phase) voltage is always used for the inverse time delay
integration, see figure 257. The details of the different inverse time characteristics are
shown in section "Inverse characteristics"
Trip signal issuing requires that the overvoltage condition continues for at least the
user set time delay. This time delay is set by the parameter t1 and t2 for definite time
mode (DT) and by selected voltage level dependent time curves for the inverse time
mode (TOV). If the PICKUP condition, with respect to the measured voltage ceases
during the delay time, and is not fulfilled again within a user defined reset time
(tReset1 and tReset2 for the definite time and tIReset1 and tIReset2 for the inverse
time) the corresponding PICKUP output is reset, after that the defined reset time has
elapsed. Here it should be noted that after leaving the hysteresis area, the PICKUP
condition must be fulfilled again and it is not sufficient for the signal to only return
back to the hysteresis area. The hysteresis value for each step is settable (HystAbs2) to
allow an high and accurate reset of the function. It should be noted that for Two step
overvoltage protection OV2PTOV (59) the TOV reset time is constant and does not
depend on the voltage fluctuations during the drop-off period. However, there are three
1MRK505222-UUS C
(Equation 129)
IDMT Voltage
Time
ANSI05000016-2-en.vsd
Technical reference manual