Insulation Shield – Volume Resistivity Test ( WC 5, ICEA S-61-402 )

This procedure determines the volume resistivity of the insulation shield layer in power cables.

Test Setup:
- Four silver-painted annular-ring electrodes are applied to the insulation shield surface.
- Two potential electrodes are placed at least 2 inches (50.8 mm) apart.
- A current electrode is placed at least 1 inch (25.4 mm) beyond each potential electrode.
- If high accuracy is not necessary, the test may use only two electrodes spaced at least 2 inches apart.
- Test circuit power must not exceed 100 milliwatts.
- The test shall be conducted at the specified temperature using either AC or DC voltage.

Volume Resistivity Formula:
ρ = (2R × (D² - d²)) / (100 × L)

Where:
ρ = Volume resistivity in ohm-meters
R = Measured resistance in ohms
D = Outer diameter over the insulation shield (in inches)
d = Diameter over the insulation (in inches)
L = Distance between potential electrodes (in inches)

Important Notes:
- The factor 2R accounts for current flow through a cylindrical shield layer.
- This test validates whether the semiconducting insulation shield maintains proper resistivity values for effective electric stress control.