Hybrid Gas Insulated Switchgear (HGIS) 170kV
1. General Description
170kV Hybrid Gas Insulated Switchgear (HGIS) is an extra-high-voltage switching system that combines the compact design of Gas Insulated Switchgear (GIS) with the flexibility and lower cost of Air Insulated Switchgear (AIS).
The primary switching equipment—such as the circuit breaker, disconnectors, earthing switches, current transformers (CT), and voltage transformers (VT)—is installed in sealed gas-insulated compartments, while external connections such as busbars and line interfaces can remain air-insulated.
The 170kV HGIS class is mainly used for 154kV/161kV transmission systems and high-reliability substations requiring reduced footprint and enhanced environmental protection.
2. Typical Technical Specifications
·Equipment Type: Hybrid Gas Insulated Switchgear (HGIS)
·Rated Voltage: 170 kV
·System Voltage Class: 154 / 161 kV
·Rated Frequency: 50 / 60 Hz
·Rated Current: 2000 / 3150 / 4000 A
·Short-Time Withstand Current: 40 / 50 / 63 kA (3 s)
·Short-Circuit Breaking Current: 40–63 kA
·Peak Withstand Current: 100–160 kAp
·Power Frequency Withstand Voltage: Approx. 325 kV
·Lightning Impulse Withstand Voltage (BIL): 750 kVp
·Insulation Medium: SF6 / alternative insulating gas
·Circuit Breaker Type: SF6 or Vacuum Interrupter
·Installation: Outdoor / Indoor GIS building
·Enclosure Type: Metal enclosed gas compartments
3. Main Components
1.) High Voltage Circuit Breaker
·The circuit breaker is installed inside a pressurized gas compartment.
Functions:
·Interrupts fault currents
·Performs switching operations
·Protects transmission equipment
Typical features:
·High breaking capacity
·Fast operating speed
·High mechanical endurance
·Low maintenance requirement
Available technologies:
·SF6 interrupter
·Vacuum interrupter (advanced designs)
2.) Gas Insulated Disconnectors
Functions:
·Electrical isolation
·Maintenance safety
·Bus switching operations
Features:
·Compact construction
·High insulation reliability
·Long service life
3.) Earthing Switches
Types:
·Standard maintenance earthing switch
·High-speed earthing switch
Functions:
·Grounds isolated equipment
·Removes residual voltage
·Ensures safe maintenance
4.) Current Transformers (CT)
Integrated CTs provide:
·Protection measurement
·Metering signals
·Fault detection
Typical applications:
·Differential protection
·Distance protection
·Overcurrent protection
·Energy metering
5.) Voltage Transformers (VT/CVT)
Used for:
·Voltage measurement
·Relay protection
·Synchronization
·Control systems
6.) AIS Connection Interface
The hybrid design allows connection with:
·Air-insulated busbars
·Overhead lines
·Power transformers
·Underground cables
This provides excellent compatibility for substation expansion and retrofit projects.
4. Advantages of 170kV HGIS
* Compact Footprint
·Requires less land compared with AIS
·Suitable for urban and industrial substations
* High Environmental Resistance
Gas-insulated modules protect equipment from:
·Pollution
·Dust
·Humidity
·Salt contamination
* Reduced Investment Compared with GIS
·Less gas-insulated equipment
·Lower installation cost
·Easier construction
* Excellent Retrofit Capability
Suitable for:
·AIS replacement
·Substation expansion
·Capacity upgrades
* High Operational Reliability
·Sealed primary components
·Stable insulation performance
·Reduced maintenance frequency
5. Typical Applications
170kV HGIS is commonly used in:
·154kV transmission substations
·161kV utility networks
·Hydroelectric power plants
·Renewable energy transmission systems
·Industrial power facilities
·Coastal substations
·Urban grid reinforcement projects
·Existing AIS modernization projects
6. Typical Configuration Schemes
Single Busbar
·Simple design
·Lower cost
·Used for standard substations
Double Busbar
·Improves operational flexibility
·Allows maintenance during operation
Ring Bus
·Provides higher supply reliability
Breaker-and-a-Half
·Used for critical transmission networks
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
170kV Hybrid Gas Insulated Switchgear (HGIS) is a 154/161kV-class extra-high-voltage switching solution combining GIS reliability with AIS flexibility. It typically supports 2000–4000A continuous current ratings and 40–63kA short-circuit interruption capability, providing a compact, reliable, and economical solution for modern transmission substations, renewable energy projects, and substation upgrade applications.