Generally the contacts used for interlocks should be direct or high speed contacts. We faced a problem in Main AC distribution panel.
Auto transfer scheme ( ATS)
As per ATS scheme consider incomer CB trip due fault then Bus tie should not close in both Automatically or manually.
Same condition if Bus tie trips incomers should not close in both Auto/Manual condition.
Problem faced Site:
1. Both Incomers are closed and Healthy. Incomer -1 tripped by jumper and tie was automatically not closed. But trip was given by actual current injection and bus tie closed.
2. Now Incomer -1 and bus tie is closed and Bus tie tripped by jumper and Incomer -2 was automatically not closed. But trip was given by actual current injection Incomer -2 closed.
Same happen for Incomer -2 and Bus tie combination.
The breaker trip Aux. contact is in serious of other Breaker closing path. This contact should immediately open and block the other CB closing.
But in our circuit tripping Aux contact will pick up a auxiliary relay and this relay contact open the other CB closing path. But pickup time of this relay is little bet high . During this pick up time adjesend CB was closed.
So found that problem and replace high speed Aux relay.
Auto transfer scheme ( ATS)
As per ATS scheme consider incomer CB trip due fault then Bus tie should not close in both Automatically or manually.
Same condition if Bus tie trips incomers should not close in both Auto/Manual condition.
Problem faced Site:
1. Both Incomers are closed and Healthy. Incomer -1 tripped by jumper and tie was automatically not closed. But trip was given by actual current injection and bus tie closed.
2. Now Incomer -1 and bus tie is closed and Bus tie tripped by jumper and Incomer -2 was automatically not closed. But trip was given by actual current injection Incomer -2 closed.
Same happen for Incomer -2 and Bus tie combination.
The breaker trip Aux. contact is in serious of other Breaker closing path. This contact should immediately open and block the other CB closing.
But in our circuit tripping Aux contact will pick up a auxiliary relay and this relay contact open the other CB closing path. But pickup time of this relay is little bet high . During this pick up time adjesend CB was closed.
So found that problem and replace high speed Aux relay.
