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MV Cable Shield Induced Voltage Calculator electrical
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MV Cable Shield Induced Voltage Calculator

Calculate standing sheath induced voltages, touch safety thresholds, and shield circulating currents in single-conductor power cables per IEEE Std 575 and IEC 60287.

Cable Installation & Geometry

Shield Bonding Method

Induced Shield Voltage & Losses

Standing Sheath Voltage at Open End
-- V
-- IEEE 575 limit
Induced Gradient
-- V/1000ft
-- V/km
Shield Circulating Current
-- A
--% of core current
Shield Mutual Reactance Xm: -- Ω / 1000 ft
3-Phase Shield I²R Losses: -- kW
Ampacity Derating Factor: --
IEEE 575 recommends keeping standing shield voltages below 25 V for exposed human contact (or 65 V if insulated sheath voltage limiters SVLs are used).

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Frequently Asked Questions

Why do single-conductor medium-voltage cables induce voltage on their shields?

When alternating current flows through a single-core conductor, it creates an intense concentric time-varying magnetic field. Per Faraday’s law of induction, this magnetic field cuts through the surrounding copper tape or wire shield, inducing a longitudinal voltage along the length of the cable.

What is the trade-off between single-point bonding and solid bonding?

Single-point bonding grounds the shield at only one end, preventing any closed circuit loop. This completely eliminates shield circulating currents and thermal losses, but allows standing voltage to accumulate at the ungrounded end. Solid bonding grounds both ends, clamping standing voltage to zero but causing high continuous circulating currents that heat the cable and derate its ampacity.

What is cable cross-bonding in high-voltage transmission circuits?

In long transmission circuits, cross-bonding divides the cable route into three equal sections and transposes the shields among the three phases (Phase A shield connects to Phase B, then Phase C). Because the three phase currents are 120° apart, the induced voltages cancel out to near zero at each major bond, virtually eliminating circulating current while keeping standing voltage below safety limits.