Substation Bay Jumpers

[Engineer1916]

Hello Everybody,
I am trying to figure out how to select the size, quantity and spacing of an ACSR Bay jumper in a substation. Also what temperature rating should be used. Any help would be highly appreciated. Thank you.

 

[Paulsey88]

1916,
Download RUS Bulletin 1724E-300, read 4.10 regarding bare conductors. That will answer the straightforward questions. IME, using the largest single conductor up to about 2500MCM is best, dictated by ampacity. Above 2500, conductors are difficult to work with and connectors are harder to source. Spacing - you need to meet minimum phase to phase and phase to grounded component spacing - do you have access to IEEE 605 & 738?

 

[Engineer1916]

Paulsy88,
Thank you very much for your response. I will keep the 2500MCM limit in mind when selecting the conductor size. I have gone through 1724E-300, 4.10 and found the temperature limit of 90C.
I am sorry I wasnt clear in my question. I am not talking about the phase to phase or phase to ground spacing. I was talking about spacing of subconductors in case I have double bundle jumpers from terminals to terminals. How to determine the spacing required between subconductors in one phase and secondly how to calculate the impact of that spacing on ampacity? Will the subconductors have impact on each other's impedance because of proximity? Will they have any thermal effect on each other?

 

[Paulsey88]

1916,
Thank you for the clarification on your question. The answer is yes, there will certainly be an effect of paralleled or bundled conductors, although probably less than you may be worried about. I would:
Search and read "ATC Substation Equipment Ampacity Ratings", document # CR-0063. Published by American Transmission Company. Section 12 covers bare conductors. Section 12.7, Table 18 for specifics to you. You'll find that unless you have large conductors spaced very tight (4" or less), the effect is negligible. For your spacing: look at manufactures like SEFCOR, will the conductor and connectors you are likely to use be that close? If so, I would then get a copy of IEEE 738 and it will walk you through calculating values. There is also software, I think SKM and ETAP have modules that will assist.

I have a document from aluminum association (somewhere) that may have a lot of the same info as IEEE 738. I will look for it.

 

[Engineer1916]

Paulsey 88,
Thank you kind sir! I really appreciate your help. the ATC document was very helpful. I will respond if I needed to calculate the value using IEEE 738.

 

[dauwerda]

Attached is a spreadsheet I put together about 10 years ago for calculating the deratings for bundled conductors per IEEE 738. You may find it helpful for checking the effects of different spacings.

 

[Engineer1916]

Dauwerda,
Thank you very much. I will check out the calcs.

 

[bacon4life]

ACSR is operated anywhere from 49C to above 125C. The links below describe some justification for various temperatures. Your utility or regional transmission organization may have similar guidance documents.

Equipment manufactures typically recommend operating no higher than 90C in part because the anti-oxidization compound may drip out of the connectors at higher temperatures. Utilities often use 100C as the ACSR conductor limit, assuming that actually getting to 100C would be a very rare event for most lines. Occasional IR scans may be used to identify high resistance joints that develop after extreme loading events. For locations that regularly experience full load (i.e GSU connections), planning for a typical operating temperature below 75C may be prudent. Unlike the slow degradation flexible connectors experience at high temperatures, rigid bus can fail catastrophically due to thermal expansion. There should be a buffer between the maximum rated operating temperature and the expansion joint capability.

https://pjm.com/~/media/planning/de...-overhead-transmission-conductor-ratings.ashx

http://www.oasis.oati.com/woa/docs/MEC/MECdocs/100_kV_Transmission_Facility_Ratings_Methodology.pdf

 

[cuky2000]

Bundled conductors helps to reduce corona discharge because the smaller inductance and electric field compare with single conductor while improve ampacity due to cooling in larger surface, reduce the skin effect, minimize losses and control interference in communication and audible noise.
Twin bundle satisfy a wide range of cases below below 500 kV. Triple, quad and larger bundle are also used in special cases.