Transcript Introduction to HV cablesx

An introduction to HV cables
J. Borburgh
With valuable input from B. Balhan, L. Ducimetiere and T. Kramer.
22/6/2016
An introduction to HV cables,
TE/ABT group meeting
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Outline
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High Voltage cable types
Cable construction
Cable testing
Cable aging tests
Procurement
22/6/2016
An introduction to HV cables, TE/ABT
group meeting
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Usage of HV cables
Within TE/ABT group HV cables are commonly
used for:
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Kicker PFN + Transmission; pulsed application,
impedance very critical, low loss requirement
Electrostatic septa; DC application, high voltage
requirement, low leak current, resistance to
radiation, low capacitance
Voltage range in use:
• Pulsed: 10 - 80 kV
• DC: 150 - 300 kV
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HV DC links proposed for Europe
• Several projects have been
studied to transport energy
in Europe over large
distances.
• All rely on HV DC current
cables.
• The potential market for
this type of grid, sparked
interest of several cable
companies and HVDC
cables are being developed
for higher voltage than ever
before.
• Norms for HV cables (AC
as well as DC) are now
An example of a proposal for a 800 kV HVDC grid
getting more and more
overlaying the 400 kV AC grid presently in place
mature [2,4]
[1].
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Conventional Coaxial HV-cable
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Foam
Dielectric
Good signal
transmission
properties
However voids
in the foam will
not allow for
HV (used up
to ~15 kV)
An introduction to HV cables, TE/ABT
group meeting
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Conventional Coaxial HV-cable
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Commonly used for septa
and kickers - Our “work
horse”.
Solid PE dielectric, copper
braid.
Used in ABT up to 300 kV.
Exists in different variants
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With/without semiconducting
layer
Several impedances
An introduction to HV cables, TE/ABT
group meeting
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SF6 gas filled HV-cable (kickers)
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Dielectric: thin PE foil wrapped around inner
conductor, pressurized with SF6 gas fills all voids
Superior dielectric strength
Lower velocity factor due to PE core
No issues with surface discharge
Low attenuation/losses (no semiconducting layers)
~14 km in operation at CERN since the seventies
(no issues seen so far)
Nominal voltages up to 80 kV
Disadvantage:
• Vacuum and SF6 gas systems needed
• Special gas tight connectors ( in house production)
• No quick disconnect
• Cable relatively stiff and heavy (FAK: 1PFL =2.6 t )
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An introduction to HV cables, TE/ABT
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GIPFL – Gas Insulated Pulse Forming Line
© TE-ABT-FPS
Used for energy distribution (up to 500kV/5kA) e.g. installed below Palexpo,
extensively used in the alps for caverned hydropower stations.
Advantage:
• Simple and robust.
• Perfect for tunnel
installation (fire safety).
• Long life time (~50yrs).
• No maintenance (gas
enclosed).
• Largely self healing.
Siemens GIL
Disadvantage:
• Spacers are critical for
surface discharges.
• Not (yet) designed for
pulse transmission.
• Not flexible.
• Bigger diameter than SF6
cables.
• High velocity factor due to
gas insulation (<er).
Also a “gas” insulated coax:
Reusenleitung “cage lines” used for signal transmission to longwave radio
transmitter e.g. in Poland (left) and Austria (right, 240kW).
Low loss, high power.
Outline
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•
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•
•
High Voltage cable types
Cable construction
Cable testing
Cable aging tests
Procurement
22/6/2016
An introduction to HV cables, TE/ABT
group meeting
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HV Cable extruding facility
Extruder
heads
Vulcanisation
Cool down
Outer
conductor
winding
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Conventional HV coaxial cable construction
Max. permissible voltage: 𝑉𝑚𝑎𝑥 =
1
𝐷
𝑆.
𝑑.
𝑙𝑛
2
𝑑
1 𝜇 𝐷
Chacteristic impedance: 𝑍 =
𝑙𝑛
2𝜋 𝜀 𝑑
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S: insulation breakdown voltage [V/m]
D: outer insulation diameter [m]
d: inner insulation diameter [m]
An introduction to HV cables, TE/ABT
group meeting
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Impedance
Reflection
coeff.
=
50 − 50
=0
50 + 50
In case of inhomogeneity's the reflection coeff. will be ≠ 0
For cables with very small losses L
and C dominate hence simplified:
Material and diameters
can be selected
Attenuation / losses
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Resistive losses
skin effect, proximity effect
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Losses in the dielectric
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Radiated losses
for high frequencies only ( less
important for our applications)
Outline
•
•
•
•
•
High Voltage cable types
Cable construction
Cable testing
Cable aging tests
Procurement template
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AC cable acceptance tests
Typically 3 types of tests [2,3]:
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Type tests
Done on cable sample, or cable sample of comparable cable;
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Fire tests [5]
Bending test
Tan δ
Heating cycle test
Impulse voltage test
Partial discharge test
Routine tests
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Done on each cable length produced; non destructive electrical tests
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Partial discharge test
Voltage test
Electrical test on non-metallic sheath
Sample tests
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Done on samples of cable from same production batch;
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Measurement of material properties, thickness, resistance of conductor,…
Destructive electrical tests to determine cable limits (CERN)
Aging tests
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DC cable acceptance tests
For DC cables the 3 types of tests used for AC
cables are complemented with a 4th type [4]:
• Pre-qualification tests
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on cable and accessories (connectors)
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done at 1.45x rate voltage
Done with using varying (predefined) daily load cycles
Done in different thermal conditions (pre-defined)
Minimum duration 360 day!
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Partial discharge test
Partial discharge test aims at finding
localised breakdowns of a small portion
inside the insulation.
Usually these indicate the presence of voids,
cracks or inclusions in the insulation.
Partial discharge test, done at 10% below rated
voltage, sensitivity 10 pC (routine test).
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Tests of interest to kickers and septa
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AC cable tested at ~1.4x rated voltage.
DC cable tested at 1.85x rated voltage.
Bending test:
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Bending of cable on a drum (1 turn at least), unwinding and repeat
process in reverse direction, followed by partial discharge test.
Lightning impulse test: 10 positive and 10 negative impulses
(@ 250 kV for 45 kV cable, 750 kV for a 160 kV cable!)
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An introduction to HV cables, TE/ABT
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Outline
•
•
•
•
•
High Voltage cable types
Cable construction
Cable testing
Cable aging tests
Procurement
22/6/2016
An introduction to HV cables, TE/ABT
group meeting
29
Cable aging
Cable aging can be verified artificially according to IEC 60811.
Sample is kept at 100°C for 42 days, equivalent to 10 yrs of
normal (= non radioactive environment) operation.
State of cable materials can be assessed using:
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Traction Tests (TT), where elongation at break is measured,
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Differential Scanning Tests (DSC), where the Oxygen
Induction Time (OIT) is measured.
Two contributions to aging:
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exposure to air (mainly oxygen) and UV (storage conditions)
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exposure to ionising radiation
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An introduction to HV cables, TE/ABT
group meeting
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DSC vs. TT results
Cable lifetime strongly influenced by additives to base
material (for ex. anti-oxidants, colour pigments etc. )!
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MKP RG-220 cable installed during LS1
60 cables replaced in 2013 during the LS1 [6].
Cable
CLP50
TT 118121
TT 118121
118121
Position
In operation
Storage, installed
during LS1
From 2013 (LS1)
Behind shielding
wall
From 1994 to 2013
Manufacturing year
2004
Downstream
TIDVG, installed
From 1994 to
2013
1993/94
1993/94
Behind shielding
wall
From 2000 to
2013
1997
Estimated integrated dose
0
2.5 105 GY
2.5 105GY
1.8 105 GY
Traction Test: Elongation at break
Sheath 293%
±7%
PE 478% ±3%
PE 208% ±44%
Sheath 127%
±16%
PE 509% ±55%
Sheath 140%
±30%
PE 417% ±212%
PE : 28 min
PE : 1.4 - 18 min
Traction test: Elongation at break after artificial
ageing (100°C 42 days)
DSC test: Oxygen Induction Time
DSC test: Oxygen Induction Time after artificial
ageing (100°C 42 days)
PE : 0.2 - 19
min
PE : 0 – 4.6 min
Should foresee replacement in 2023.
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An introduction to HV cables, TE/ABT
group meeting
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Outline
•
•
•
•
•
High Voltage cable types
Cable construction
Cable testing
Cable aging tests
Procurement
22/6/2016
An introduction to HV cables, TE/ABT
group meeting
33
Cable specification template
In 2014 RIAC* WG developed a cable
specification template [7], to make sure the
requirements for cable aging testing to be
included systematically.
The template can be found at the procurement
service templates webpage:
https://procurement.web.cern.ch/documents/procurement-templates
*Replacement of Irradiated and Aging Cables Working Group
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References
[1]L. Barthold et al., “ DC is where we started”, IEEE Power & Energy
society eNews Update, April 2016
[2] “Power cables with extruded insulation and their accessories for rated
voltages above 30 kV (Um = 36 kV) up to 150 kV”, IEC 60840, 2011
[3] “Power cables with extruded insulation and their accessories for rated
voltages above 150 kV (Um = 170 kV) up to 500 kV (Um = 550 kV)”, IEC
62067, 2006
[4] “Recommendations for testing DC extruded cable systems for power
transmission at a rated voltage up to 500 kV”, CIGRE WG B1.32,
Technical Brochure 496, 2012
[5] IS 23, Criteria and Standard Test Methods for the Selection of Electric
Cables and Wires with Respect to Fire Safety and Radiation Resistance,
EDMS 335745, 2012
[6] L. Ducimetiere, “SPS-TS1+ Kicker HV Cables (RG220) - History and
Tests Analysis”, EDMS 1385241
[7] D. Ricci et al., “TEMPLATE FOR TECHNICAL SPECIFICATIONS SUPPLY OF CABLES”, EDMS 1137965
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