Protection operation
time:
15-60 ms
Protection resetting time: 15-60 ms
Breaker opening time: 20-120 ms
Example for time coordination
Assume two substations A and B directly connected to each other via one line, as
shown in the figure 187. Consider a fault located at another line from the station B. The
fault current to the overcurrent protection of IED B1 has a magnitude so that the
protection will have instantaneous function. The overcurrent protection of IED A1
must have a delayed function. The sequence of events during the fault can be described
using a time axis, see figure
187.
A1 B1
Feeder
Time axis
t=0 t=t
1
t=t
2
t=t
3
The fault
occurs
Protection
B1 trips
Breaker at
B1 opens
Protection
A1 resets
en05000205_ansi.vsd
51
51
ANSI05000205 V1 EN
Figure 187: Sequence of events during fault
where:
t=0 is when the fault occurs,
t=t
1
is when the trip signal from the overcurrent protection at IED B1 is sent to the circuit breaker. The
operation time of this protection is t
1
,
t=t
2
is when the circuit breaker at IED B1 opens. The circuit breaker opening time is t
2
- t
1
and
t=t
3
is when the overcurrent protection at IED A1 resets. The protection resetting time is t
3
- t
2
.
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 than the time t
3
.
Section 3 1MRK504116-UUS C
IED application
412
Application manual
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