Importance of Bonding Adequacy Study
Problem Statement
220kV double circuit transmission line feeds a 220/132kV Grid Substation (GSS). The GSS further feeds 132/2x25kV Traction Substation (TSS) through UG Cable.
A Bonding Adequacy Study was carried out to assess the bonding voltage tolerance of UG cables between GSS and TSS
CONSEQUENCES
HV underground cables play an important role in electrical transmission system. Cable armour and sheath Grounding of HV cables is essential for its safe and reliable performance. Improper cable grounding generates induced voltage in the cable sheath causing overheat and decrease in cable ampacity. This study provides vital inferences to address bonding issues before installation.
aPPROACH
Insulation coordination study was performed to determine the effect of induced voltage on the UG cables during switching and lightning. The transient simulations performed inferred that the stress of UG cables components were within the safe limits during lightning and switching transients, but unsafe during temporary over voltage condition. Based on the simulation results a specific sheath voltage limiter was recommended to address this unsafe condition.
Benefits
Such study of HV UG cable bonding helps to ensure safe and reliable operation of electrical assets during over voltage conditions in underground transmission cables. It prevents the risk of incidents, fatal accidents and high value asset damage and enhance operational efficiency.
