ABB RET670 Applications Manual page 418

Section 3
IED application
412
Protection operation 15-60 ms
time:
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
51
t=0 t=t
1
The fault Protection
occurs B1 trips
ANSI05000205 V1 EN
Figure 187: Sequence of events during fault
where:
t=0 is when the fault occurs,
t=t is when the trip signal from the overcurrent protection at IED B1 is sent to the circuit breaker. The
1
operation time of this protection is t
t=t is when the circuit breaker at IED B1 opens. The circuit breaker opening time is t
2
t=t is when the overcurrent protection at IED A1 resets. The protection resetting time is t
3
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
B1
51
t=t t=t
2 3
Breaker at Protection
B1 opens A1 resets
,
1
1MRK504116-UUS C
Feeder
Time axis
en05000205_ansi.vsd
- t and
2 1
- t .
3 2
.
3
Application manual