Underground distribution - cross-bonding, multi-point grounding

[mafle]

Hello,

We are working on a wind farm project. The collector system is underground. We use TRXLPE 1/3CN 34.5kV cable with LLDPE jacket that are placed in a flat configuration without spacing. We do install a bare copper conductor in the trench along the cable.

The post

http://www.eng-tips.com/viewthread.cfm?qid=160969&page=1

adress the cross bonding subject.

My question is : Do we need multi-point grounding along the conductor for the concentric neutral knowing that IEEE 575 have been withdraw? If so, is cross bonding preferable and what are the benefit of such an installation.

The IEEE 575 «Guide for the application of sheath-bonding methods for single-conductor cables and the calculation of induced voltages and currents in cable sheaths» have been withdraw by IEEE. Is there another standard that we can rely on that cover that point?

Thanks
Maxime Fleury

 

[apowerengr]

Depending on where the project is located it could be local code requirements; the NEC and/or reference to NESC part 3 and Section 9 would apply in the US. Although you stated the use of 1/3 CN 34.5kV rated cable you did not state the system voltage in use. 34.5/19.9kV 4 wire grd wye, or 34.5kV 3 wire ungrounded-wye or delta or.............?

The installation of a bare copper grounding conductor raises other questions - is it intended to provide structure grounding for lightning protection or is it intended to be a part of the power circuit?

 

[mafle]

The project is installed in Canada and there is no regulation adressing that point.
It's a 34.5 kV 3 wire delta, the bare copper is effectively installed to provide structure grounding connecting every wind turbine grid.

 

[racobb]

Appears that you have the concentric neutral of the cable jacketed. If so, seems a multiple grounded neutal would render that the money spent on the jacket wasted. 34.5 kV is usually a utility voltage, but appears that it may be customer equipment for this application. If this is the case, I expect that you need to observe the local codes that might apply to the installation regarding the multiple neutral grounds and separate ground wire.

Alan

Democracy is two wolves and a sheep deciding what to have for dinner. Liberty is a well armed sheep!
Ben Franklin