Voltage Ratings?

[cblmdm]

Thanks for any help.

I have two shielded, two conductor cables. One is rated for 600 V rms and the other 750 V rms. What is voltage rating? I believe the 600 V is built very similar to the 750V, if not exactly. I could find no specs or standards to test to. It seemed to be a more qualitative aspect of the cable. A 750V cable should be able to operate indefinetly at 750V without damage.

Does anyone know of standards to test to? Or is this built into the design of the cable and if it is, what determines the voltage rating?

Thanks again

 

[peebee]

Search this site for "insulation resistance test", this has been discussed extensively.

The voltage rating is determined by the type and thickness of the insulation.

750 is a strange rating, 600 is very common, at least here in the US.

 

[buzzp]

I agree with peebee.
I have not heard of a 750 rating either.

 

[cblmdm]

Thanks for the responses. I agree too, it is an oddball rating, but nevertheless, is called out to be used.

The follow on question is, if the voltage rating is a function of the type and thickness of the insulation, what standard tells you what type and thickness of the insulation is for what voltage rating?

To say it another way, I don't believe there is a standard that says, "to have a voltage rating of 600 V you need to pass these tests (ie. HiPot, IR, etc.) at these voltages."

peebee, I did do a search, and it came up with some good info, but nothing seemed to directly answer my question.

Thanks again

 

[buzzp]

The 750V is called out in an engineering spec? If so, is it possibly a typo?
The insulation rating is determined by CSA/UL/ or others. The tests they do determines the rating. I believe the cable mfg's are accustomed to what type of materials and thickness correspond to a particular voltage rating. Although, they still need to have them tested by UL or similar. I do not believe there is a clear cut method in determining this as there are many 'additives' to cable for such things as improved flammability or improved UV characteristics. When one of these additives is mixed with the insulation material the properties change requiring retesting. Again a cable mfg probably has a good handle on what combinations give a certain rating.

I do believe there is a standard that says you must pass these tests to obtain this rating. It probably does not identify materials necessarily though. Try to go to UL sight or glabalengineering documents and search and you will likely find a standard that the wire gurus use to determine what tests will be done.

 

[DCElectrical]

In Australia .6/1kV is generally adopted to be used to indicate the voltage rating of a cable. The first number indicates the voltage rating of the insulation to ground and the second number indicates the voltage rating from one insulated conductor to another insulated conductor.

Generally if a cable is only referred to by one voltage, the second number is used. for example 450/750V cable is refered to as 750V cable.

450/750V cable (new standard) is a PVC/PVC or ‘flat TPS’ cables that form the basis of 240V wiring systems in most domestic, commercial and industrial premises. It is expected that 450/750V will be used for the majority of wiring up to 25 mm².

The advantages are reduced insulation and sheath thicknesses, results in a much smaller and lighter cable, but maintains appropriate safety standards.The insulation and sheath materials have higher temperature service performance characteristics to cope with the various installation conditions including the use of thermal insulation.

 

[peebee]

What exactly is your concern? Most shielded 2/c cables are run at 120 volts or less, so a 300-volt insulation would be acceptable. Higher insulation ratings are frequently specified, but that's basically to give them greater mechanical protection rather than any concern with the electrical resistance.

It's not quite clear to me if you're looking for manufacturer's specifications (and associated tests) or acceptance tests for cables once it's been installed. Here's some of each:

Manufacturer's Standards:

Cable construction Spec: NEMA WC 53-2000, "Standard Test Methods for Extruded Dielectric Power, Control, Instrumentation, and Portable Cables for Test". See also other NEMA wire specifications, (NEMA WC Series) listed and available for purchase at ttp://

http://www.nema.org/help/docno.html

You might check out some of the UL standards, available at

http://www.comm-2000.com/category.a...andards&CategoryID=UL+Standards(ULStandards2)

Some relevant UL standards might include UL 13, 44, 83, 1424, 1425, 1581, 1666, 2196, 2250


Acceptance Testing Specifications:

The International Electrcial Testing Association (NETA) (

http://www.netaworld.org

)Acceptance Testing Specification includes the following for Low Voltage, 600 Volt Maximum Cables:
"Perform insulation-resistance test on each conductor with respect to ground and adjacent conductors. Applied potential shall be 500 volts dc for 300 volt rated cable and 1000 volts dc for 600 volt rated cable. Test duration shall be one minute." . . . "Minimum insulation-resistance values should not be less than 50 megohms."

IEEE also publishes testing guidelines.

Beware that oftentimes with shielded 2/c cables, the insulation rating is the least of your worries. Areas of greater concern can include:

attenuation
nominal cable impedance
cable capacitance
conductor resistance
shield resistance
bend radius
conductor material
temperature rating
water resistance
sunlight resistance
plenum rating
pulling tension

Hope this helps.

 

[peebee]

See also
thread248-60200
thread248-65365
thread248-11253

 

[Midos]

750 volts is fairly common in the uk for DC use.