Mar 2015
Electricity Transmission
SF6 Management and Alternative Gases
Mar 2015
Mar 2020
National Grid Electricity Transmission
Mark Waldron
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Network Innovation Allowance
Leak Detection and Refilling

The aim of this work package is to develop automatic and more accurate leak detection techniques, for both outdoor and indoor use, to more efficiently manage GIS and SF6 filled equipment. Success in this area will allow utilities to move from reactive to proactive planning of resource by applying modern monitoring techniques to order equipment where bigger benefits would be delivered. By also developing improved and automated gas handling techniques, the level of SF6 used can be significantly reduced.

Leak Sealing and Repair

The aim of this work package is to identify ways of reducing leak rates in order to achieve a significant leak reduction through development of techniques for SF6 switchgear that are sustainable and long-lasting. This work package will investigate and develop new technologies and installation methods and test them on-site to analyse their performance.

SF6 Capture and Reuse

The aim of this work package is to identify a methodology for efficient gas capture which allows for gas cleansing and quality re-use of SF6. Initial work will involve the development and laboratory testing of the technology. If successful, the technology will be trialled on-site.

SF6 Alternatives

This work package is looking at two new gases both at different stage of development, G3, a novel gas composed of 4% NOVEC and 96% CO2, and CF3I mixtures. This programme is stage-gated and divided into three phases detailed below. This project will look at the first one.

Phase 1: Use of G3 on two-life gas insulated busbar sections terminating in cable-sealing ends. By trailing this initially in passive sections, implementation will be de-risked and practical experience gained.

Phase 2: Installation of G3 in a full substation on all assets except circuit breakers.

Phase 3: Trialling of G3 on active sections.

Phase 1

G3 is a new gas matches the dielectric strength of SF6 when operated at a higher pressure and reduces the global warming potential from 23,500 to 345.

This new gas has never been installed on life equipment and to do so, modification to the GIS wall sections and flanges need to be made. From an operational perspective, new gas-handling systems and parts need to be developed and tested. For this reason, in order to trial this new gas, the following steps will be taken:

1) Modification to the GIS-to-air bushings

2) Modification to the flanges

3) Installation of the two modified GIS busbar sections

4) Development and testing of gas-handling equipment and maintenance practices

5) Monitoring of the gas performance for a period of 3 years

The scope is limited to two busbar sections on a substation.

The second gas requires further development in order to understand whether it may be of use to the industry as a 400kV insulator based on CF3I gas. In order to develop this gas further, we are supporting an iCASE studentship to look at the properties of this gas and mixtures in gas insulated busbars on a laboratory demonstrator.

Leak Detection and Refilling

This work package is aimed at delivering three key outputs:

  • A technology capable of detecting SF6 leaks at various dew points and in indoor environments.
  • A technology capable of automatically refilling leaks to maintain a constant pressure.
  • An improved SF6 trolley to improve safety of handling staff.

Leak Sealing and Repair

This work package’s objective is to investigate novel leak sealing and repair techniques capable of being used on two specific situations:

  • On large leaks which require rapid curing of epoxy compound or valve to reduce pressure
  • On porcelain/metal sections.

SF6 Capture and Reuse

This work package aims at investigating and developing a technology for capturing SF6 gas and, if necessary, filtering it to a stage where it could be re-introduced to the equipment for reused as insulating material.

SF6 Alternatives – Phase 1

G3: This new gas has never been installed before on any life equipment. The successful implementation will prove the potential of new gases to be successfully introduced into the electricity industry as alternative insulation.

CF3I: Mixtures based on this gas are still under development and its use for HV applications has not been proved. This area of work will look at key techniques for the characterisation of its insulating properties and will include preliminary investigations into the interaction of CF3I with key high voltage materials.

Leak Detection and Refilling

A successful outcome of this work package would see would see the three deliverables, described in the objectives above, successfully developed and tested.

Leak Sealing and Repair

If successful, this work package will develop a technology and/or compound capable of being used for large gases and for both porcelain and metallic interfaces.

SF6 Capture and Reuse

If successful, this work package will deliver a technology capable of capturing any leaking gas, filtering and if required, refilling the tank.

SF6 Alternatives – Phase 1

A successful project will see the modifications to the GIS equipment being performed without impacting the reliability of the whole substation as well as see the introduction of G3 into the system for a period of three years without faults. It will also see the development of a CF3I mixture capable of being used in transmission applications.