All transmission and generation equipment have limits on their useful capacity and these are expressed through what we call “facility ratings”. Facility ratings include things like the maximum voltage, current, real power, and reactive power of various types of power system equipment. The ratings of equipment are affected by things like the ambient temperature, wind (which cools equipment), solar heating, and distance from other equipment or objects. For instance, a transmission line rating takes into account the maximum temperature the metal can continually operate at and the amount of sag that results when the metal expands when heated to ensure it doesn’t come into contact with other lines, structures, or equipment underneath it.
My EE skills are quite rusty, but since your's are sharp, please calculate the comparative losses of transmission lines being undergrounded vs on huge towers, in the air. It will help me setting an argument about "why don't they just put the transmission lines underground and avoid outages". Literally, asking for a friend. Thanks in advance.
When it comes to overhead vs underground, the key difference is cost. Depending on the specifics of the project, an underground t-line can cost 10X or more than a comparable overhead alternative. In addition, depending on the length of the line, underground lines have distance limitations that require additional (expensive) equipment to extend their length.
Capacitance is higher with cables, but losses are typically lower than overhead lines for high voltage applications. Here is a good comparative analysis from Australia:
WAPA-SNR has a RAS scheme on their New Melones powerhouse that uses conductor temperature sensors to activate it. New Melones taps an existing PG&E 230kV line.
My EE skills are quite rusty, but since your's are sharp, please calculate the comparative losses of transmission lines being undergrounded vs on huge towers, in the air. It will help me setting an argument about "why don't they just put the transmission lines underground and avoid outages". Literally, asking for a friend. Thanks in advance.
When it comes to overhead vs underground, the key difference is cost. Depending on the specifics of the project, an underground t-line can cost 10X or more than a comparable overhead alternative. In addition, depending on the length of the line, underground lines have distance limitations that require additional (expensive) equipment to extend their length.
Here's a good overview from Excel Energy: https://www.transmission.xcelenergy.com/staticfiles/microsites/Transmission/Overhead%20vs%20Underground%20fact%20sheet%20-%20updated%2010-2022.pdf
Thank you, but I was primarily wondering about the losses due to the higher capacitance.
Capacitance is higher with cables, but losses are typically lower than overhead lines for high voltage applications. Here is a good comparative analysis from Australia:
https://s37430.pcdn.co/ciet/wp-content/uploads/sites/16/2023/11/04_Cost_Economics_Aspects.pdf
Per mile, for example.
WAPA-SNR has a RAS scheme on their New Melones powerhouse that uses conductor temperature sensors to activate it. New Melones taps an existing PG&E 230kV line.