Typical Capacitance values for Control Cable?

[majesus]

I have a few ABB relays that are controlled by long distance cables. I want to determine the maximum cable length, so I am using the "Permissible single length for the control circuit conductors on contactor opening" table on sheet two of the following ABB published document:

http://www.abb-control.com/pdf/catalog/ac1000/1.77.pdf

However the table doesn't base max cable runs on the cable gauge/diameter but on the cable's line capacitance per uF/km. (Table showns mF/km, it is a typo.) I have no clue what the typical capacitance value is for 2c-#14, 2c-#12 or 2c-#12. I am using an Aluminum interlocked armored cable (TECK 90, 600V).

I understand that capacitance for cables depend on many factors: such as cable type, cable materials, capacitance between other phase lines, capacitance between ground, capacitance with other cables in proximity, etc... However, I am looking for "nominal" cables capacitance values that I can use as typical. Or a method / guideline that approximates cable capacitance. It is impossible to be precise, but a ballpark figure so I have something to work with in establishing estimated cable lenghts.

Thanks,
Majesus

 

[waross]

After a few hours of calculations, energize some cable and measure the leakage current. Leakage will be based on impedance rather than capacitive reactance and may be a safer value to use. If there is enough leakage current to cause mis-operation, the phase angle of the current is immaterial.
If you want to be safe, measure the cable yourself or use data developed from measurements on that particular run of cable.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[majesus]

That's great if it was physically installed. Still in the design phase, it's all on paper.

I may use the capacitance charts from Belden. It's for fire control/alarm cable... but it is the best I can find.

http://www.belden.com/pdfs/TechInfo/techinfo.htm

 

[resqcapt19]

This one is uses wire sizes but is based on specific Square D coils.

http://ecatalog.squared.com/techlib/docdetail.cfm?oid=0900892680079349

 

[majesus]

That's a good document, that's the paper I refer to when I have these type of issues to deal with.
However, I got these ABB relays and they referred to me to their publication for those relays. However the publish values in uF/km cable and not by cable diameter. Understandable as theoretical point of view, but realistically, how is one to know the capacitance of the control cable (2c-#12 teck) if it is in the design phase? (I can't implement Waross's suggestion.)

 

[7anoter4]

I agree with waross the capacity calculation of a control cable cannot be accurately done as it is a lot of unknown parameters as dielectric constant and the insulated core diameter and distances.
The following article may be useful. On my opinion use of DC operated contactors. It is better. See:

http://www.moeller.net/binary/ver_techpapers/ver949en.pdf