5 kv under ground

[frank134]

I'd like to know if there is any code in regard to making right or left turns on 5 kv cable under ground in rigid conduit beside the code on 600 volt or higher radius code.
Also also on manholes
1. is there a certain distance needed between manholes?
2. do you have to have a manhole when making a right or left turn?

I also like to know if you need to run a continuious ground wire from the main outdoor switch were the 4160 comes in and then branches off through underground conduits and goes out to feed additional outdoor switches at various buildings in a complex. These various switches feed 4160delta primary/120/208 wye secondary pad mounted outdoor transformers.
OR
Should each building just have it own separate ground.

 

[Nick]

Re: 5 kv under ground

1. No
2. No
Over 600V applications still must comply with the other sections of the code unless modified by the over 600V sections. That is a pretty general statement but that is how it works. For underground pulls you must not exceed three things.
1. More that 360 degree of bend.
2. Less than the minimum bending radius of the cable.
3. More than the maximum pulling tension and sidewall pressure recommended by the cable manufacturer.
You must have an equipment grounding conductor pulled with your 4160V feeders if your 4160V system is a grounded system.

 

[bennie]

Re: 5 kv under ground

I hope this is rigid PVC ducts. The location of manholes are determined by the difficulty of pulling the cable.

A sweeping factory 90 will facilitate making a turn. Some use GRC 90 s. for this.

The supply system secondary is 4160/2400 wye MGN system. You must run the neutral/ground to each transformer. Connect to the frame and X-O of the secondary. Each transformer should have a ground electrode connected to the X-O. Each transformer is a separate ground electrode system.

 

[bob]

Re: 5 kv under ground

The requirement is not a code requirement. You will need to make pulling caculation to decide if you will need a manhole. High voltage cable has limits on the distance it can be pulled. This is based on the size and weight of the cable.
The pulling caculations will tell you if you can make 90 degree turns. You must not exceed the mfg. requirements on cable tension and cable sidewall presure.

 

[frank134]

Re: 5 kv under ground

the system is a delta system with three wire and no neutral. so I take this to mean that I don't have to run a ground.

 

[frank134]

Re: 5 kv under ground

benni . what did you mean you hope this is pvc rigid pvc. can I use rigid galvanized . no pull is over 250' and it 4" rigid and were only pulling 3 4/0 so I think were ok their. just not to sure about the grounding.

 

[bennie]

Re: 5 kv under ground

Frank: The utility secondary to the primary of the distribution transformer should be a 4160/2400 wye. The utility companies will not run an ungrounded secondary.

GRC will not last as long. The internal friction will be greater.

 

[don_resqcapt19]

Re: 5 kv under ground

Frank,
You still need an equipment grounding conductor, even if you are feeding a transformer with a delta primary.
Don

 

[bennie]

Re: 5 kv under ground

Frank: Observing three active conductors connecting to three high voltage bushings, does not indicate the supply secondary system is a delta.

On a power pole, the single cable below the phase conductors is the MGN.

You must extend the system MGN to the secondary of each transformer to prevent 2400 volts from appearing on the service enclosure and all other conductive surfaces, in the event of a winding to winding fault.