cable rating

[alwaink]

This is a stupid question, but how are cable ratings established? Is it based on the thickness of insulation or cable gauge size?

Does a 4kV rated cable mean 4kV peak voltage? So can it actually take on 8kV of peak to peak voltage?

thanks

 

[dpc]

The current-carrying capacity of insulated cable is based on keeping the insulation temperature below its rated maximum. So both the insulation and the wire size are factors.

Cable voltage ratings are typically ac rms values.

 

[cuky2000]

QUESTION 1: Does a 4kV rated cable mean 4kV peak voltage? In the ANSI marketplaces, the selection of the cable insulation level to be used in a particular installation shall be made on the basis of the applicable phase to phase voltage and overvoltage duration indirectly considered in the minimum standard insulation thickness of 100%, 133% or even 173% in accordance with ICEA/NEMA, AEIC and other standards.

QUESTION 2:...So can it actually take on 8kV of peak to peak voltage?

There are cable with dual rating such as 5 kV with 133% insulation for ungrounded system and 8 kV with 100% insulation for grounded system as shown in the enclose link.

http://www.okonite.com/Product_Catalog/section2/sheet4.html.

 

[alehman]

4kV typically means the insulation is rated for 4kV RMS AC. Peak-to-peak is 2 * sqrt(2) * Vrms (for sinusoidal waveforms).

Voltages are typically given as phase-to-phase, assuming the system is solidly grounded. For system that are impedance grounded (where ground offsets occur only during faults), 133% rated insulation is usually specified. Many engineers also specify 133% for solidly grounded systems for a little safety factor. For ungrounded system, use 173%.