Sheath current for a proper cross bonded cable is not zero, even in the balanced condition, how to achieve zero sheath current for a cable?

In a proper cross bonded cable, in every minor section the seath current should ideally be zero as (Va+Vb+Vc=0). In simulink using the cable model the sheath current is not coming zero, Please explain the reason or how to acieve zero seath current.

[David Goodmanson]

Hi Arittra,

what is a proper cross bonded cable, and is the sheath an additional layer over the regular cable shield?

Answer 1

[Anshuman]

Hi Arittra,

The cross-bonding arrangement connects the cable sheaths in a manner that ideally cancels out the induced voltages in each section of the cable sheath, leading to a theoretical zero sheath current in each minor section when the system is perfectly balanced ((V_a + V_b + V_c = 0)).

However, achieving zero sheath current in simulations (like in Simulink) or in real-world applications can be challenging due to several factors such as cable system imbalances, ground potential difference along the cable, model accuracy and parameter selection.

To minimize sheath current in a cross-bonded cable system, both in simulations and in practice, consider the following approaches:

• Ensure that the cable model accurately reflects the physical characteristics of the cable system. Use detailed and accurate parameters for the cables, including their mutual inductances and capacitances.
• Aim to balance the load as much as possible across the three phases. While perfect balance might not be achievable, minimizing the imbalance will help.
• Ensure that the model includes all relevant inductances and capacitances, including those between the cables and the ground.

Hope this helps!