MV cable AC testing (Hi-Pot) - calculation of required kVA 1

[JuanBC]

Hello,

I would like your guidance calculating the required kVA a source should have to test a MV cable doing an AC Hipot test.

The test described in IEC 60502-2 consist on applying phase-to-phase voltage for 15 minutes at a frecuency of 20 to 300 Hz between the conductor and the metal screen/sheath.

We are willing to test the following cable: 2 AWG 3/C CU 15KV 220 NL-EPR 133% TS ARMOR-X PVC MV-105

Based on datasheet (attached) the reactance Xc@60Hz is 0.053 Mohm/Mft. Is this reactance value between conductors? Or is from one conductor to ground (screen)?

If I am not wrong, the required power should be kVA.required = U^2/Xc = U^2/(1/wC) where U should be test voltage, 15 kV and C the capacitance from one conductor to ground, in F

Thank you in advance


JBC
.......
"The more I read, the more I acquire, the more certain I am that I know nothing"

 

[7anoter4]

The capacitance of a single insulated core between conductor and shield :
Cs=eps.r/18/ln(D/d) microF/km where [for 2 awg 3/c cable]:
D=insulated core diameter [included semiconducting shield] =0.76+2=0.78 inches
d=conductor diameter=0.283 inches.
eps.r=3 for EPR insulation dielectric constant [relative]
Cs=3/18/ln(0.78/0.283)=0.16439 microF/km or 0.3048*0.16439= 0.0501/10^6 F/1000 ft.
Xc=1/ωCs ω=2*π*60=377 Xc=52945 Ω/1000 ft=0.052945MΩ/1000 FT.

 

[7anoter4]

Correction: 0.76+0.02=0.78"

 

[JuanBC]

Hello 7anoter4

Thank you very much for your answer! It is very clear and explanatory.

Do you agree with me that the required power for a Hi-Pot AC test will be kVA.required = U^2/Xc or am I thinking something wrong?

Best regards.






JBC
.......
"The more I read, the more I acquire, the more certain I am that I know nothing"

 

[7anoter4]

If the cable length is L[km] then C=0.16439*L[F/10^6] and XcL=10^6/377/(0.16439*L) [ohm]
Q=U[kV]^2/XcL [MVAr]

 

[JuanBC]

Thank you!

JBC
.......
"The more I read, the more I acquire, the more certain I am that I know nothing"

 

[VLFit]

It may be easier to calculate the kVA needed by calculating the current required to apply your test voltage. If you know the capacitance per unit length of the cable, then calculate the current required by A = 2pifCV. C = capacitance in Farads and V = test voltage in rms volts. Once A is know for any given frequency and test voltage, kVA is known.