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Posted on 05 November 2019

Cable Protectors

 

 

 

 

 

 

 

 

 

 

Using Cable Protectors

Cable protectors are special purpose limiters which are used to protect service entrance and distribution cable runs. The National Electrical Code (NEC) does not require using cable protectors.

When unprotected cables are paralleled, a singe conductor faulting to ground can result in damage to and eventual loss of all parallel conductors. The resultant cost of cable replacement, loss of service, and down time can be significant. This cost can be minimized by the use of cable protectors.

When each phase consists of three or more parallel conductors, cable protectors are installed at each end of each conductor. Should one cable fault, the cable protectors at each end of the faulted cable will open and isolate the faulted cable. The unfaulted cables will maintain service.

Terminations

In addition to improving system reliability, cable protectors provide a means of terminating cable, thus eliminating the need for cable lugs. Cable protectors are available with the following configurations:

Cable Protector Types

Aluminum and copper cable require different terminations. Cable protectors intended for copper cable must not be used with aluminum cable. Cable protectors intended for aluminum cable include an oxide inhibitor.

Placement of Cable Protectors

In single phase applications where a single transformer supplies the service and there are only one or two conductors per phase, a single cable protector per cable may be used. The cable protector should be located at the supply end of the cable. In all other applications, cable protectors should be placed at both ends of each cable. This allows a faulted cable to be isolated from the source end and from a back feed at its load end. Isolation of a faulted cable is only possible if there are 3 or more parallel cables per phase.

Cable Protector Ampacity

Cable protectors are not ampere rated. They are not intended to provide overload protection for the cable. Cable protectors are designed to open in case of a short circuit or after a cable has faulted. Thus total system reliability is maximized. For these reasons cable protectors are rated in terms of the cable material (aluminum or copper) and the cable size (250kcmil, 500kcmil, etc.)

Selecting a Cable Protector

The following questions must be answered to choose the correct cable protector:

  • Is the cable copper or aluminum?
  • What is the cable size?
  • What termination type is desired?
  • Is the cable protector to be insulated or protected with a heat-shrink sleeve or a rubber boot?

 

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