ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Where is Everyone?
by luckyshadow - 11/21/21 10:14 AM
It's been an interesting career
by The Watt Doctor - 11/19/21 09:56 AM
Well I am back to stay (nearly 6 years)
by The Watt Doctor - 11/19/21 09:17 AM
Motor Load Relationships Between Fans and Pumps
by The Watt Doctor - 11/18/21 09:24 AM
GFCI's pops in large numbers
by dsk - 11/05/21 06:45 AM
New in the Gallery:
240/208 to a house
240/208 to a house
by wa2ise, October 9
Now you know.
Now you know.
by Tom_Horne, September 7
Who's Online Now
0 members (), 24 guests, and 22 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Joined: Aug 2002
Posts: 8
Y
yooper Offline OP
Junior Member
Two 12470 circuits come thur customer owned swithgear, then go thur a ductbank system (pvc) to transformers in verious locations all underground. Both circuits go to each building.The building are also tied together by common phone , gas ect. QUESTION is an equipment ground wire required to run in each pve conduit with the phase conductors??What if a neutral is present,Can the grounding then be done at each location if so sizing of equipment ground wire?? also would it have to be HV shilelded as the phase conductors,if run with the phase conductors I have talked to many so called experts in this field and found a big difference in opions. Cable manf. tell me there shield is NOT a gr. wire.

2017 / 2014 NEC & Related Books and Study Guides
Joined: May 2001
Posts: 717
G
Member
Yooper,
You're not getting any response because there probably 1/2 dozen different styles of MV cables, and you're not providing sufficient info.

Most MV cables I've worked with DO have a shield that is a full ground/neutral (in some cases), but I have worked with just a shield. That shield is grounded, but is not of sufficient size to be considered a ground in the true sense.

The shield in that case is there only to displace lateral stress on the cable, and if it is not grounded, your cable will NOT last long. You normally do not pull a ground in these conduits, but some designs absolutely require it. Where are you? do you have many thunderstorm days? Wide open area like an airport? Ground wire is indicated IF the shield is not at least 50%.

That's probably all I can help (confuse?) with the info provided.

Joined: Nov 2000
Posts: 2,148
R
Member
yooper,
In my opinion, you need some type of EGC conductor between the main switchgear and the transformers. This is needed to clear any faults on the primary side of the transformer. Each of these transformers would be separately derived systems and would need a grounding electrode system. If the secondary side has a neutral, they will also need a main bonding jumper.
Where I am currently working, we use a similar set up only with 4.16kV distribution. The 5kV cables have either wire or tape shield. These shields are not suitable for use as a grounding or neutral conductor. We pull in a bare or 600 volt insulated EGC in each raceway. This is bonded to the frame of the transformers. The size is based on the rating of the primary OCPD and Table 250.122.
Don


Don(resqcapt19)
Joined: Apr 2002
Posts: 2,527
B
Moderator
To the original poster — Is NFPA 70 the prevailing document for the subject installation? What edition? Are the are the current-carrying conductors listed type MV90 or MV105 cable? Is it single or multiconductor assembly? Are there any phase-to-neutral-connected transformer windings supplied in the installation?

[Nota Bene: 15kV-class equipment and cables are termed by ANSI, IEEE, NFPA and UL to be medium voltage.]


Link Copied to Clipboard
Featured:

Tools for Electricians
Tools for Electricians
 

* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
timmp
timmp
Leo, IN, USA
Posts: 28
Joined: June 2004
Top Posters(30 Days)
Trumpy 5
dsk 3
Popular Topics(Views)
286,157 Are you busy
218,583 Re: Forum
204,800 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.5