Current in High Voltage electricity transmission lines

amacca

I'm wondering if anyone here could help with a query.

I'm trying to find out exactly what sort of current or current range would typically flow in High Voltage or EHT electrical transmission lines?

I'm finding it hard to get a definitive trustworthy answer, some sites are giving 200 amps others are giving up to 40,000 amps (which seems very high to me and would surely lead to more than just the heating losses high voltage and therefore low current transmission is supposed to prevent)

Any help appreciated or a point in the direction of where it might be more appropriate to ask the question!

gctest50

The Inga-Kolwezi one is 1700kms long, 560 MW ±500 kV ( dc line though )

http://new.abb.com/systems/hvdc/references/inga-kolwezi

amacca

Thanks I appreciate it, everything helps, any ideas where might I go digging around for current ratings on high voltage AC lines - presumably it would be AC lines in this country as we have transformers on the end of them? AC needed for a transformer to operate?

Carawaystick

The ieast west interconnector is 500MW and +/-400kV so that's 625A in each wire.

na1

Lol, people who're saying 40,000 amps might have mistaken amps and volts.

Its easy to evaluate the average current by the type of the wire & the cross section.
The maximum allowed continuous current would be 1.5-2 amp per square mm for aluminium cable, and around 10-20 amp per square mm for a steel cable

amacca

na1 wrote: »

Lol, people who're saying 40,000 amps might have mistaken amps and volts.

Its easy to evaluate the average current by the type of the wire & the cross section.
The maximum allowed continuous current would be 1.5-2 amp per square mm for aluminium cable, and around 10-20 amp per square mm for a steel cable

Tks, v useful information and this tallies more with what I would expect. Are there any engineers reference sites or places where this type of info can be obtained directly....short of trawling the web and wondering about the accuracy of whats been quoted

na1

amacca wrote: »

na1 wrote: »

Lol, people who're saying 40,000 amps might have mistaken amps and volts.

Its easy to evaluate the average current by the type of the wire & the cross section.
The maximum allowed continuous current would be 1.5-2 amp per square mm for aluminium cable, and around 10-20 amp per square mm for a steel cable

Tks, v useful information and this tallies more with what I would expect. Are there any engineers reference sites or places where this type of info can be obtained directly....short of trawling the web and wondering about the accuracy of whats been quoted

There are many wire gauge charts on the web like this one for copper:
http://www.powerstream.com/Wire_Size.htm

you just need to know what [font=Optimum, Optima, Geneva, sans-serif]AWG [/font][font=Optimum, Optima, Geneva, sans-serif]is and how to convert it[/font]

Michael Collins

Carawaystick wrote: »

The ieast west interconnector is 500MW and +/-400kV so that's 625A in each wire.

This calculation implies that the wire actually dissipates 500 MW, which would be rather inefficient!

It's impossible to say without more specific information e.g. line length, line voltage, power handling capability.

Doing a rough calculation based on values here:

http://large.stanford.edu/courses/2010/ph240/harting1/

for a single-wire 100 km transmission line of 500 MW capacity, 400 kV voltage, you could expect to see up to a few kA on the line when under maximum load. However, I've no way of knowing how accurate the values at that website are, so take it as a very rough figure - which to me seems a reasonable value!