UK Eddy currents??

[LouDog]

After a bit of advice. Have a 630A MCCB feeding a DB, it's fed with 4 x 300mm single core, non armoured HO7 cables and a 185mm earth. The DB is GRP and plastic compression glands have been used. The main panel has an aluminium gland plate and brass A2 glands have been used, however, the lock nuts are steel. Will this cause issues, do the lock rings need to be changed to brass also?

 

[LouDog]

Good shout with the slot in the lock ring, might give it a test and see how it holds up

 

[LouDog]

Thanks for the input over the weekend. Back out today, tested the slot method, good quality locknuts and they tightened nicely. Still slightly unsure about the whole thing and whether it's necessary, is the only concern the locknuts getting warm?

 

[westward10]

Yes there is a possibility of heat being generated.

 

[pc1966]

Overheating is really the #1 concern.

It can slightly increase the loop impedance, but that would be taken in to account when measured. Also for very high fault currents the ferromagnetic material is going to saturate anyway, so any inductance would drop to more-or-less the free space values.

Incidentally that is one big PV install if you have a 630A 3-phase connection!

 

[LouDog]

Around the 400kW mark.

 

[LouDog]

I was talking to the lads terminating 12 x 400mm singles (3 per phase and neutral) from the LV side of a transformer to the 2500A main ACB of another panel onsite today. They were using the exact same glands as mentioned before, brass A2 glands with a steel locknut into an aluminium plate. Said they had done hundreds and hundreds of these type of installs, using AWA and HO7's and always used steel locknuts, never had any problems or heard of any. Interesting.

 

[pc1966]

I guess the locknuts are just not big enough to cause enough heat for trouble. Useful to know!

 

[stevethesparks]

Sigh of relief