7/30/2019 sc.cooper

1/3

Phone: 888-593-3355

www.generalcable.com

SPEC F150January, 2008

FormulaShort Circuit Current for Copper Shields

In the three conductorcables, a copper tape is applied over each extruded semi-conducting insulation shield with

a helical gap. Because the three copper tape shields are cabled in intimate contact with the bonding (grounding)

conductor, their combined total cross-sectional areas may be considered an integral shielding system for the pur-

pose of calculating short circuit capacity. It is not possible however, to determine the contact resistance between

the components, due to possible oxides or film which may form on the components or movement of the cable

core during handling. It may be advisable to consider the short circuit capacity of the individual shields indepen-

dently. Because the insulation shields are in thermal contact with the inner PVC jacket, the maximum short circuit

temperature T2 is 200C. Refer to ICEA P-45-482, Short Circuit Performance of Metallic Shields and Sheaths on

Insulated Cable, for calculations involving cables that have other operating parameters.

Under these temperature conditions the short circuit current formula is: I = amperesM . A_________

t

Meaning of Symbols: A = Effective cross-sectional area, shield or sheath

B = Tape overlap (mils) (usually 375)b = Thickness of tape (mils)dis = Diameter over semiconducting insulation shields (mils)d

m= Mean diameter of shield or sheath (mils)

ds = Diameter of wires (mils)I = Short circuit current (amperes)w = Width of tape (mils)n = Number of serving or braid wires or tapesL = Overlap of tape (percent)t = Short circuit duration (seconds)

M = 0.058 for 5-15kV cables0.060 for 25-46kV cables

FORMULA FOR

TYPE OF SHIELD OR SHEATH CALCULATING A

1. Wires applied either helically, as a braid or serving;

or longitudinally with corrugationsnds

2. Helically applied tape, not overlapped 1.27 nwb

3. Helically applied flat tape, overlapped 4 bdm x 100

2(100-L)

4. Corrugated tape, longitudinally applied 1.27[(dis+50)+B]b

5. Tubular sheath 4 bdm

2

Short Circuit Current for Copper Shields

7/30/2019 sc.cooper

2/3

Phone: 888-593-3355

www.generalcable.com

SPEC F150January, 2008

FormulaShort Circuit Currents for Copper Shields

Effective Cross-Sectional Area in kcmil

ShortC

ircuitCurrentKiloAmperes

1 Cycles

16 Cycles

2 Cycles

30 Cycles

4 Cycles

60 Cycles

8 Cycles

100 Cycles

Allowable Copper Shield Short Circuit Currents for 515 kV

1 10 100

0.01

0.1

100

10

1

0.058 .AI = _______ t

A= Effective cross-sectional area (circular mils)

t= Short circuit duration (seconds)

I= Short circuit current (amperes)

Temperature excursion range 100C200C

7/30/2019 sc.cooper

3/3

Phone: 888-593-3355

www.generalcable.com

SPEC F150January, 2008

FormulaShort Circuit Currents for Copper Shields

ShortCircuitCurrentKiloAmperes

1 10 100

1 Cycles

16 Cycles

2 Cycles

30 Cycles

4 Cycles

60 Cycles

8 Cycles

100 Cycles

0.01

0.1

100

10

1

Allowable Copper Shield Short Circuit Currents for 2546 kV

Effective Cross-Sectional Area in kcmil

A= Effective cross-sectional area (circular mils)

t= Short circuit duration (seconds)

I= Short circuit current (amperes)

Temperature excursion range 95C200C

0.060 .AI = _______

t