IEEE Power & Energy Magazine - March/April 2020 - 51

chemical stability, which was the main property necessary
for arc quenching in circuit breakers.
GISs have been designed to have less than a predetermined percentage value of annual structural leakage [as
stated in International Electrotechnical Commission (IEC)
Standard 62271-1 for HV switch and control gear]. However,
higher leakage rates have been experienced, sometimes up
to 5%, due to aging or ultraviolet-dried joints. Finding leaks
in complex, compact GISs is challenging when there are
low gas flows and too few continuously monitoring sensors
on the equipment to provide reference data for comparison.
The French system consists of approximately 150 SF6 GIS
substations (from 63 to 400 kV) and roughly 12,800 SF6
circuit breakers.
However, alternatives to SF6 and new switching-equipment designs (such as vacuum chambers) are ready for a
system prototype test in an operational environment, at
least up to a 132-kV voltage level. They could be considered
for use at a greenfield demonstration project at a 63-kV GIS
substation (Grimaud) in Southern France that incorporates
an alternative gas mixture named g 3, which is provided
by General Electric. RTE also launched a European R&D
tender procedure, the Innovation Partnership, to develop a
pilot site to test concepts for its upcoming compact-substation generation.

The project was initiated in 2018, and energization was
completed in the second quarter of 2019. Maintenance and
operations staff are gathering information that will be examined to monitor the equipment's performance.

Next-Generation Compact Substation
The Grimaud 63-kV substation is a prototype demonstration
project for validation in an operational environment (Figures 7 and 8). However, other concepts for SF6-free 63-kV
substations have emerged, and there are comparable ideas
for 225- and 400-kV facilities. There is currently no off-theshelf solution for every voltage level employed by the TSO.
The requirements that encompass all voltage levels are
as follows:
✔✔ eco-design of the substation with no SF6 gas (or at
least a massive reduction in its use)
✔✔ reduced and compact geographic footprint

Grimaud 63-kV GIS Substation Project
Grimaud is a new 225- and 63-kV substation. All of the
225-kV components use a classic SF6 GIS design. However, a test will be conducted using the recently developed fluronitrile mixture (NOVEC 4710 + oxygen + CO 2)
instead of SF6 for all of the components (circuit breakers,
disconnectors, bus bars, and instrument transformers) in
the 63-kV substation, which is located in a separate building. An experiment will be conducted to analyze gas solutions and monitor partial discharges to collect reference
data from the time of installation throughout the life of the
components. New tools to perform equipment maintenance
will also be evaluated.
Since there are two technologies (SF6 and non-SF6) in
the same substation, special devices had to be designed or
adapted to be maintenance friendly.
✔✔ Non-SF6 compartments are painted green.
✔✔ All of the monitoring equipment and associated wires
are purple for immediate identification.
✔✔ Special filling taps and caps with different sizes, shapes,
and colors were designed to avoid gas confusion.
✔✔ Maintenance crews use CO 2 and carbon-monoxide
sensors and wear masks with air cartridges (as done
in classic SF6 GISs years ago).
✔✔ A dedicated filling tool for injecting the premixed gas
in the components was purchased.
✔✔ SF6 and non-SF6 spare parts are stored in different locations to prevent worker confusion (the non-SF6 does
not use the same pressure as the SF6).
march/april 2020

figure 7. The Grimaud substation and RTE personnel.
(Source: RTE; used with permission.)

figure 8. Since SF6 and non-SF6 technologies are used in
the same substation, the non-SF6 components are painted
green, and different sizes are chosen to prevent improper
operation by maintenance crews. (Source: General Electric;
used with permission.)
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IEEE Power & Energy Magazine - March/April 2020

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