Hybrid Gas Insulated Switchgear (HGIS) 145kV
1. General Description
145kV Hybrid Gas Insulated Switchgear (HGIS) is an extra-high-voltage switching system that combines the advantages of Gas Insulated Switchgear (GIS) and Air Insulated Switchgear (AIS). It integrates the main switching and protection components into compact gas-insulated modules while allowing external connections through conventional air-insulated equipment.
The 145kV HGIS class is widely used in 132kV/138kV transmission networks, providing a compact, reliable, and cost-effective solution for substations where full GIS installation is not required.
2. Typical Technical Specifications
·Equipment Type: Hybrid Gas Insulated Switchgear (HGIS)
·Rated Voltage: 145 kV
·System Voltage Class: 132 / 138 kV
·Rated Frequency: 50 / 60 Hz
·Rated Current: 2000 / 3150 / 4000 A
·Short-Time Withstand Current: 31.5 / 40 / 50 kA (3 s)
·Short-Circuit Breaking Current: 31.5–50 kA
·Peak Withstand Current: 80–125 kAp
·Power Frequency Withstand Voltage: Approx. 275 kV
·Lightning Impulse Withstand Voltage (BIL): 650 kVp
·Insulation Medium: SF6 / alternative insulating gas
·Circuit Breaker Type: SF6 or Vacuum Interrupter
·Installation: Outdoor / Indoor GIS hall
·Enclosure Type: Metal-enclosed gas compartments
3. Main Components
1.) Gas Insulated Circuit Breaker
·The circuit breaker is installed inside a sealed gas compartment.
Functions:
·Interrupts short-circuit faults
·Controls transmission line switching
·Protects transformers and generators
Typical features:
·High interrupting capability
·Fast operation
·Long mechanical life
·Low maintenance
Available technologies:
·SF6 circuit breaker
·Vacuum interrupter circuit breaker
2.) Gas Insulated Disconnectors
Functions:
·Provide electrical isolation
·Enable safe maintenance
·Support bus transfer operations
Advantages:
·Compact design
·Reliable operation
·Reduced environmental influence
3.) Earthing Switches
Types:
·Maintenance earthing switch
·High-speed earthing switch
Functions:
·Ground isolated sections
·Discharge trapped charges
·Improve maintenance safety
4.) Current Transformers (CT)
Integrated CTs provide:
·Protection signals
·Metering accuracy
·Fault detection
Applications:
·Distance protection
·Differential protection
·Overcurrent protection
·Energy measurement
5.) Voltage Transformers (VT/CVT)
Provide voltage measurement for:
·Protection relays
·Metering systems
·Synchronization
·Control systems
6.) Air-Insulated Connection Section
HGIS maintains AIS interfaces for:
·Overhead transmission lines
·Power transformers
·Cable terminations
·External busbars
This hybrid configuration simplifies expansion and retrofit work.
4. Advantages of 145kV HGIS
* Compact Layout
·Requires less land than conventional AIS
·Suitable for space-limited substations
* High Reliability
Gas-insulated parts are protected from:
·Dust
·Moisture
·Pollution
·Salt contamination
* Cost Effective
Compared with full GIS:
·Lower equipment cost
·Reduced gas volume
·Easier installation
* Suitable for Retrofit
·Can replace or upgrade AIS bays while keeping existing infrastructure.
* Reduced Maintenance
·Sealed primary components
·Stable insulation performance
·Less cleaning and inspection
5. Typical Applications
145kV HGIS is commonly installed in:
·132kV transmission substations
·Power generation plants
·Hydropower stations
·Wind and solar energy substations
·Industrial electrical networks
·Urban grid reinforcement projects
·Railway power supply systems
·Existing AIS substation upgrades
6. Typical Configuration Schemes
Single Busbar
·Simple and economical
·Suitable for small substations
Double Busbar
·Provides operational flexibility
·Enables maintenance without full shutdown
Ring Bus
·Improves system reliability
Breaker-and-a-Half
·Used for critical transmission substations
7. Applicable Standards
·IEC 62271-1 — High-voltage switchgear common requirements
·IEC 62271-100 — High-voltage AC circuit breakers
·IEC 62271-102 — Disconnectors and earthing switches
·IEC 62271-203 — Gas-insulated metal-enclosed switchgear above 52kV
·IEEE C37 series — High-voltage switchgear standards
Summary
145kV Hybrid Gas Insulated Switchgear (HGIS) is a 132kV-class extra-high-voltage switching solution combining GIS compactness with AIS flexibility. It typically supports 2000–4000A rated current and 31.5–50kA short-circuit breaking capacity, making it suitable for transmission substations, renewable energy projects, and modernization of existing substations requiring high reliability with optimized cost and footprint.