MTS incorporate the use of air-insulated and gas insulated components
and switchgear. In a substation, some or all switching bays consist of
compact Gas Insulated Substations (GIS) modules with circuit breakers,
instrument transformers, disconnectors, and grounding switches. The
busbars, bay connections and often complete switching bays originate in
conventional Air Insulated Substations (AIS) technology.
The main focus when talking about MTS is originated in compact GIS
modules with bushings and with special requirements resulting of
interaction with larger AIS substation parts. MTS can differ in their
engineering design depending on the required configuration. Three
combinations are possible:
Components & enablers
Insulation gas (commonly SF6)
Combined disconnector and earthing switch for cables and busbars
Current and voltage transformer
Advantages & field of application
First MTS modules were developed in the 1990's. They are compact
switchgear applications mainly used in the refurbishment and expansion
of substations with air-insulated outdoor and indoor switchgear.
Application of MTS allows reducing bay footprint by up to 50 percent.
Depending on the national regulation, this can result in the technology
having a lower cost of ownership compared to AIS.
Technology advancements in hybrid Insulated Substations follow the same
trends of GIS and AIS installations. MTS modules are commercially
available for all voltage levels up to 420 kV.
Technology Readiness Level
TRL depends on the gas mixture used in the GIS technology-based
2020: TRL 5 (SF6 free)
2025: TRL 7 (SF6 free)
2030: TRL 9 (SF6 free)
For SF6 based MTS, TRL is 9.
Research & Development
Current fields of research: The research on MTS focus on
requirements resulting of interface between different insulating media
and equipment stresses (e.g. switching of loop currents).
Power system technologies manufacturers focuses their effort on the
transportability of large assembled MTS modules. Key innovation is the
rotating bushing concept, which takes less than 30 second per bushing
from the in-service position to the transport position and back again at
the installation site.
Innovation priority to increase overall TRL: n/a.
Best practice performance
Maximum continuous current: 63 kA
Maximum voltage rating: 420 kV
Standard definition: IEC 62271-205
Expected lifetime: 50 years
Best practice application
A 420 kV MTS was commissioned in 2015 to help ensure the reliability of a new high voltage 2 GW power link between Sicily and the Italian mainland.
With very limited space on the island substation and the need to perform maintenance on the modules while in service, conventional solutions were ruled out. The 420 kV MTS arrived on site factory assembled and tested, ready for rapid installation and energization.
Ensuring the reliability of 2000 MW power transmission capacity between Sicily and the Italian mainland while abiding to the limited available space.
Construction of a substation for the link between two network levels in the region of Schleswig Holstein.
Two transformers connect the 380 kV level with a 110 kV network with a capacity of 300 MVA.
Onshore generated wind-electricity will be easily integrated and transmitted from the north to the south in the future.
 Cigre. Mixed Technology HV Switchgear and Substations: Optimised
Service Strategies. [Link]
 EE publishers. Mixed technology switchgear saves space and time.
 Pandit A, Sinha A. High Voltage Mixed Technology (Hybrid)
Switchgear -- Steps Up to 400kV. [Link]
 ABB. ABB hybrid switchgear PASS 420 kV supports reliable power
supply in strategic new Terna power line. [Link]
 Tennet. Umspannwerk Wilster: zwei Transformatoren erreichen einen
der wichtigsten Netzknoten Deutschlands. [Link]