Zero-Sequence Voltage Unit - ABB REJ 527 Technical Reference Manual

ABB Substation Automation
Products and Systems
4.1.3.3.
1MRS750616-MUM
Technical Reference Manual
~ 60 ms start time when the set start current is exceeded. When the set operate time
elapses, the earth-fault unit operates.
The low-set stage of the earth-fault unit may be given a definite-time or an inverse
definite minimum time (IDMT) characteristic. When the IDMT characteristic is
chosen, six time/current curve groups are available. Four of the groups comply with
the standards IEC 60255 and BS 142, and are called "normal inverse", "very
inverse", "extremely inverse" and "long time inverse". The two additional inverse-
time curve groups are called "RI-" and "RD-curves".
The inverse-time function of stage I
In this case, the operate time is determined by stage I
If not needed, the stage I
indicated by three dashes "---" on the LCD and by "999" when the set start current
value is read via serial communication.
The set start current value I
start situation, i.e. when the object to be protected is connected to a network. Thus a
set start current value below the connection inrush current level may be selected for
the stage I >>. A start situation is defined as a situation where the phase current rises
0
from a value below 12 % x I
start situation ends when the current falls below 125 % x I

Zero-sequence voltage unit

The two current stages I
stages, making the unit a three-stage zero-sequence voltage module. All the three
stages measure the same voltage but can have separate settings both for sensitivity
and operate time. The signalling and trip relays can also be selected separately for
all the three stages.
When the zero-sequence voltage exceeds the start voltage value set for the low-set
stage U >, the voltage unit starts delivering a start signal after a preset ~ 70 ms start
0
time. When the set operate time at definite-time operation elapses, the voltage unit
operates. In the same way, the high-set stage U
delivering a start signal after a preset ~ 60 ms start time, when the set start voltage
is exceeded. When the set operate time elapses, the unit operates.
The low-set and high-set stages of the zero-sequence voltage unit operate on the
basis of the definite-time characteristic.
The high-set stage U >> may be set out of operation by means of the switch SGF2/
0
3. When the stage is out of operation, three dashes "---" on the display and "999" in
communication via the serial bus indicate that the operation value is infinite.
> can be inhibited when stage I
0
>> can be set out of operation completely. This state is
0
>>/I of stage I >> can be automatically doubled in a
0 n 0
> to a value above 150 % x I
0
> and I >> can be replaced by two additional voltage
0 0
>> of the voltage unit starts
0
REJ 527
>> is started.
0
>>.
0
> in less than 60 ms. The
0
>.
0
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