ABB REB670 Series, Руководство по применению

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I> I>
A1 B1
Feeder
Time axis
t=0 t=t
2
t=t
3
The fault
occurs
B1 trips and
A1 starts
Breaker at
B1 opens
=IEC05000205=2=en=Original.vsd
Fault
t=t
4
Protection
A1 resets
t=t
1
B1 and A1
start
IEC05000205 V2 EN-US
Figure 93: Sequence of events during fault
where:
t=0 is the fault occurs,
t=t
1
is the trip signal from the overcurrent protection at IED B1 is sent. Operation time of this protection is
t1,
t=t
2
is the circuit breaker at IED B1 opens. The circuit breaker opening time is t2 - t1 and
t=t
3
is the overcurrent protection at IED A1 resets. The protection resetting time is t3 - t2.
To ensure that the overcurrent protection at IED A1, is selective to the overcurrent protection
at IED B1, the minimum time difference must be larger that the time t3. There are uncertainties
in the values of protection operation time, breaker opening time and protection resetting
time. Therefor a safety margin has to be included. With normal values the needed time
difference can be calculated according to equation 35 .
40 100 40 40 220 t ms ms ms ms ms
D ³ + + + =
EQUATION1266 V1 EN-US
(Equation 35)
where it is considered that:
the operation time of overcurrent protection B1 is 40 ms
the breaker open time is 100 ms
the resetting time of protection A1 is 40 ms and
the additional margin is 40 ms
7.3 Directional residual overcurrent protection, four steps
EF4PTOC
IP14509-1 v8
1MRK 505 370-UEN D Section 7
Current protection
Busbar protection REB670 159
Application manual