cable lashing?

[malachi constant]

I am the consulting engineer on this project. The issue is the calculated short circuit rating is greater than the custom switchgear (still being manufactured) will be braced for. The switchgear manufacturer is saying "no problem, just have the electrician lash the cables, that will take care of the rating discrepency."

The available fault current is 93,000, the gear is rated for 85,000 "without cable lashing". I've never heard of cable lashing before and can't find anything with a quick google. Is anyone familiar with this practice? Does it affect the short circuit calculation?

 

[jim dungar]

There are two concerns with short circuit ratings of bussing in switchgear/switchboards.

First, the problem with the cables moving during a fault condition and being pulled out of their terminations or damaging the bus bars due to their movement. This area can be mitigated by lashing the cables with rope in a manner prescribed/approved by the manufacturer.

Second, is the probelm with the bus bracing being capable of preventing the bus bars from damage during the fault. This is only controlled by the manufacturer during construction of the equipment.

Neither cable lashing nor bus bracings are factors considered during the short circuit calculations.

 

[malachi constant]

Thanks for your reply Jim.

I misunderstood the equipment manufacturer - they did NOT say that cable lashing would take care of the short circuit rating discrepancy. They said they would change their equipment so that it was braced for 100,000kAIC. Additionally, because of the higher fault current, they instruct the contractor to lash the cables.