Each HV cable sheath bonding method has its advantages and applications. Solid bonding is simple but leads to sheath losses, single-point bonding eliminates circulating currents but requires voltage control, and cross-bonding is the most efficient for long cables, minimizing losses. The choice depends on system requirements, cable length, and operational efficiency.
1️⃣ Solid Bonding:
✅ In this method, the metallic sheath of the cable is bonded at both ends and connected to the earth.
✅ This results in continuous current flow in the sheath due to the induced voltage.
✅ Advantages: Simple to install.
✅ Disadvantages: High circulating currents in the sheath lead to power losses and increased heating.
✅ Best suited for: Short cable routes where sheath current losses are minimal.
2️⃣ Single-Point Bonding:
✅ The sheath is bonded to the earth at only one end, with the other end left open and insulated.
✅ An earth continuity conductor is used to maintain equipotential grounding.
✅ This method eliminates circulating currents but results in induced sheath voltages, which can be high. To control this, sheath voltage limiters (SVL) are used.
✅ Advantages: Reduces power losses as no sheath currents circulate.
✅ Disadvantages: Requires careful management of sheath voltages.
✅ Best suited for: Medium-length cable systems.
3️⃣ Cross-Bonding:
✅ The cable length is divided into three equal sections (minor sections) within a major section.
✅ At each section junction, the sheaths are cross-bonded using link boxes to balance out induced voltages.
✅ This technique cancels out circulating currents, reducing sheath losses significantly.
✅ Advantages: The most efficient method, significantly reducing losses.
✅ Disadvantages: Complex installation and maintenance.
✅ Best suited for: Long-distance high-voltage cable routes.
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