Time/Voltage Characteristics - ABB REU 523 Technical Reference Manual

1MRS 750942-MUM
4.1.4.5.
Combined Overvoltage and Undervoltage Relay
Technical Reference Manual
The positive-phase-sequence protection function requires that the relay is in
three-phase and not in single-phase use.

Time/voltage characteristics

Each of the over and undervoltage stages can be given either a definite-time or an
inverse definite minimum time (IDMT) characteristic. The settings of switches
SGF4/1 and SGF4/2 determine the operation mode of stage U>, those of switches
SGF4/3 and SGF4/4 that of stage U>>, those of switch SGF4/5 that of stage U< and
those of switch SGF4/6 that of stage U<<. Refer to section Settings for further
information.
At IDMT characteristic, the operate time of the stage is dependent on the voltage
value: the greater the deviation from the setting value, the shorter the operate time.
Three time/voltage curve groups are available: A, B and C.
The recording of the operate time does not start until the deviation between the
measured voltage and the setting value exceeds six percent. The operate time
accuracy stated in the technical data applies when the deviation is ten percent or
higher.
Characteristics of the overvoltage stages
The IDMT characteristic curve groups A and B are designed for overvoltage stages
U> and U>>. Stages U> and U>> can be configured to use different characteristics.
The relationship between time and voltage at IDMT characteristic can be expressed
as follows:
×
k a
t s [ ]
= ------------------------------------------------- -

U U> –
×
b ----------------- - 0.5 –

U>
where
t = operate time
k = time multiplier k> or k>>
U = measured voltage
U> = set start value for U> or U>>
a = constant 480
b = constant 32
c = constant 0.035
p = constant (see table 4.1.4.5-1)
The A- and B-type characteristics are illustrated in Fig. 4.1.4.5.-1 and Fig. 4.1.4.5.-2.
+ c
p


REU 523
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