This article is used to explain the most popular styles of copper medium voltage (MV) power cables and their usage. The standard range for medium voltage cables is between 5kV – 35KV. Medium voltage cables are used in main feeder, distribution and branch circuits in commercial, industrial and electric utility installations.
The most prevalent insulating compounds used in medium voltage cables are ethylene propylene rubber (EPR) and cross linked polyethylene (XLP). In terms of jacketing compounds, you will find polyvinyl chloride (PVC), chlorinated polyethylene (CPE) and Hypalon (CSPE). Hypalon is a chlorosulfonated polyethylene and a trademark of DuPont. The most common combination of these insulation and jacketing compounds in medium voltage cables is an EPR insulation with a PVC jacket.
In terms of shielding, there are a few different options. The most common is a copper tape shield. A 5 mil (.0005 inch think) copper tape shield helically applied over the insulation of the cable. Another shield is a wire shield. This wire shield is found on XLP insulated items. It is good to note that 15KV and higher voltage rated medium voltage products require a shield of some type. Some 5KV products do not have a shield or a jacket. An example of this would be L-824C airport lighting cable which uses a simple pass of XLP insulation over a stranded bare copper construction.
Medium voltages cables typically have a 105C rating but that can vary depending on constructions. It is always good to check your application to make sure the medium voltage cable you are installing meets the temperature rating required.
There are two types of insulation levels with medium voltage cable. These are 100% and 133%. You choose a cables insulation level based on the fault clearing time of the system which it is used. If fault is cleared in one minute or less, you can use 100% insulation level medium voltage cable. If fault clearing time is from one minute to one hour, you should use 133% insulation level cable. Higher insulation levels on a cable generally means it has a thicker insulation. However, the only exception to 100% vs. 133% is the 5KV cables. In this case, most North American standards specify the same for both insulation levels. The 133% level is much more widely manufactured and installed over the 100% insulated construction.
Type MV cables are suitable in wet and dry locations for installation in conduit, ducts, troughs, aerial and direct buried. 1/0 and larger sizes are cable tray (CT) rated on most constructions as well.