The photo shows the busbar tails to anABB PR221DS tripping unit rated at 1000A and set to that. You can see thermal damage to the tri-rated 2x120mm2 tails. The outgoing conductors are 2x400mm2 and there is obvious thermal damage to the CTs on that side. The associate Diris meter was showing 895A normal peaking to 985A for sustained periods. The associated switching device is only 800A. This is a brand new installation!
I will forward a technical query to ABB but from a design perspective, given the load was specified at circa 900A fairly constant, would you not have opted for a larger tripping unit or are these electronic units able to run at close to In without de-rating. I also think the tail as are undersized by some margin. Given that the switching device is only 800A, it probably not suitable but I wonder if it is contributing to the considerable buildup of heat. The Flir showed 135C on the supply side.
The photo shows the busbar tails to anABB PR221DS tripping unit rated at 1000A and set to that. You can see thermal damage to the tri-rated 2x120mm2 tails. The outgoing conductors are 2x400mm2 and there is obvious thermal damage to the CTs on that side. The associate Diris meter was showing 895A normal peaking to 985A for sustained periods. The associated switching device is only 800A. This is a brand new installation!
I will forward a technical query to ABB but from a design perspective, given the load was specified at circa 900A fairly constant, would you not have opted for a larger tripping unit or are these electronic units able to run at close to In without de-rating. I also think the tail as are undersized by some margin. Given that the switching device is only 800A, it probably not suitable but I wonder if it is contributing to the considerable buildup of heat. The Flir showed 135C on the supply side.
