Customized 145 kV HGIS for a Substation Project in Oman

Oman’s high ambient temperatures, frequent sandstorms, coastal salt spray, and occasional heavy rain present multiple challenges for outdoor high-voltage equipment. These conditions require appropriate protection against dust and moisture, durable corrosion protection, and an external insulation design suited to the installation environment. The project also required customized arrangements for equipment monitoring, cable routing, and maintenance.

• Protection against dust, corrosion and water ingress: Frequent sandstorms posed a risk of dust entering mechanism boxes and local control panel (LCP) cabinets, potentially affecting the reliability of internal components. Salt spray increased the risk of corrosion, while heavy rain could cause water to accumulate on cabinet tops.

• External insulation: The outdoor installation required an insulation design suited to local environmental conditions to help mitigate flashover risks.

• Critical component monitoring: The voltage-transformer configuration needed to support independent gas density monitoring for each phase.

• Project-specific requirements: The customer specified requirements for cable routing, document storage, maintenance earthing safety and accessory configuration.

• Enhanced enclosure and corrosion protection

  Sieyuan upgraded outdoor mechanism boxes and local control panel (LCP) cabinets from IP54 to IP65 using double-layer sealing and optimized door locks and hinges. To address coastal salt spray and industrial corrosion, steel bracket hot-dip galvanizing was increased from 80 μm to 120 μm, with dedicated anti-rust oil applied. Sloped cabinet tops were adopted to reduce rainwater accumulation.

• Optimized external insulation

  The bushing specific creepage distance was increased to 50 mm/kV through a redesigned composite-insulator structure and raised conductor rods, adapting the external insulation design to the specified environmental conditions.

• Independent voltage-transformer monitoring

  The shared three-phase gas chamber was replaced with three independent phase chambers, each equipped with its own gas density meter. This configuration enables independent monitoring of each phase’s gas density.

• Customized maintenance provisions

  Dedicated cable trough boxes were provided to accommodate site cable routing requirements, and the LCP document box was enlarged from A4 to A3 to store larger drawings. An FES fast earthing switch was specified to support maintenance safety and equipment protection.

• Environmental resistance

  IP65 enclosure rating and C5 corrosion protection design.

• External insulation
  50 mm/kV specific creepage distance.

• Voltage-transformer configuration
  Three independent voltage-transformer gas chambers with individual gas density monitoring.

• Maintenance safety
  FES fast earthing switch with millisecond-level switching and withstand capability against the system’s maximum short-circuit current.