IEEE PES T&D Conference & Exposition 2022 - 135

insulator. The lower dielectric strength of clean air as an
insulator must be considered in the product design. Dielectric
strength is the maximum that a material can resist before
the electrical current breaks through the insulation medium
and the medium is no longer an insulator. This is offset with
design and adjustments of electrical clearances.
Subsequently, when considering switching capabilities, the
main function of a circuit breaker, vacuum technology figure
4, right side has significant advantages. The vacuum interrupter
has a strong switching performance with a higher number
of short circuits and rated current interruptions. This is
given by low arcing energy during current breaking, causing
lower contact erosion and requiring less drive energy. When
combining clean air as an insulation medium with a vacuum
interrupter, a breaker can operate reliably in low temperatures
down to -60° C. The breaker also offers five times higher
switching capability when it comes to the number of full fault
interruptions over the life of the breaker. Due to the hermetical
sealed design, the interrupter requires no maintenance.
Based on the requirements and feedback from grid owners
and operators, vacuum switching with clean air insulation
technology is the clear substitute for SF6. No alternative
gas combines performance and reliability with that of
Technical
Performance
1
Low Health
Impact
0.5
Low Environmental
Impact
SF6
N2, Air
Fluoronitrile
Safety and
Reliability
Low Temp.
Application
health, safety, and environmental benefits while also meeting
current and future mandates.
Development and Real-World Testing
Intensive research and development, and more than 10 years
of vacuum clean air breaker field experience, shows that
developing a dead tank breaker was a challenge due to stringent
IEEE requirements. According to IEEE standard C37.042018,
a breaker must be tested for chopped wave and withstand
a dielectric type test. Therefore, following the research,
development, and simple physics, several testing interations
and design adjustments allowed by the standard were made
before finalizing the prototype dead tank breaker design for
formal type testing.
A product development process including, but not limited
to, development specifications, conceptual testing, development
testing, finalization of breaker design, production, and
final type testing is shown in Table 2.
The overall physical configuration of the world's first
clean air vacuum dead tank breaker 123kV/40kA/3000A is
identical to an SF6 dead tank breaker, including bushing current
transformers (CT), bushing orientation, control circuits/
cabinet, and customer interface.
Switching
Performance
1
0.5
Drive Energy
Long Term Stability
CO2
Fluoroketone
Stability
SF6
Vacuum
Fluoronitrile
figure 4. Evaluation of SF6 and alternatives regarding insulating and switching performance.
table 2: 123kV/40kA/3000A dead tank circuit breaker with vacuum interrupting
and clean air insulation technology, type-tested down to -60° C.
Power Tests
✔ T10
✔ T30
✔ T60
✔ T100s (a+b)
✔ T100a
✔ OP2
✔ L75
✔ L90
✔ STC/PWC
✔ Verification test
✔ Line and Cable
Charging (LC/CC)
✔ TLF 1
✔ TLF 2
Dielectric Tests
✔ Power freq. voltage
withstand
✔ Lightning impulse voltage
✔ Chopped wave (Tc ≥ 2 ns)
✔ Visible corona and RIV
✔ X-ray test
✔ Partial discharge
Mechanical Tests
✔ Mechanical endurance
incl. CC & IC
✔ Temperature rise
✔ Seismic calculation for
IEEE high (1g)
✔ Static terminal load
✔ Low and high temperature
test in acc. to IEEE C37.04 +
C37.06 + C37.09 DT -60°C
GIS -50°C
✔ Sound pressure level
April 2022 Show Issue
ieee power & energy magazine
135
Confirmations
✔ Dielectric test
of auxiliary and
control circuits
✔ EMC
No. Ik and In
Interruption
CO2
Fluoroketone

IEEE PES T&D Conference & Exposition 2022

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