Transcript HVWL-FRMx

Felix Rodriguez Mateos TE/MPE-EE
High Voltage Withstand Levels
F. Rodriguez Mateos, TE/MPE-EE
on behalf of the HVWL Working Group
MQXF Workshop – Electrical QA
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Outline
• Introduction
• HL-LHC HVWL Working Group
Felix Rodriguez Mateos TE/MPE-EE
• General Strategy
• MQXF case study
• Discussion
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The HVWL WG
• Regular meetings, bi-weekly in average
• Members
Hugo Bajas TE-MSC, Secretary
Marta Bajko TE-MSC
Amalia Ballarino TE-MSC
Mateusz Jakub Bednarek TE-MPE
Jean-Paul Burnet TE-EPC
Giorgio D'Angelo TE-MPE
Paolo Ferracin TE-MSC
Christian Giloux TE-MSC
Juan Carlos Pérez TE-MSC
Jose Vicente Lorenzo Gomez TE-MSC
Félix Rodríguez Mateos TE-MPE, Chair
Frédéric Savary TE-MSC
Ezio Todesco TE-MSC
• Based on experience from LHC, the aim is to engineer a common strategy
for HL-LHC circuit components
Felix Rodriguez Mateos TE/MPE-EE
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On design of insulation and voltage withstand levels for main components
and ancillaries
On electrical measurements : dielectric, transfer functions, instrumentation,
etc
Common understanding and application of ElQA programme from
manufacturing to operation through testing and commissioning
Adequacy of test infrastructure in agreement to the agreed strategies
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The way through . . .
• Reference documents:
1. “Voltage withstand levels for electrical insulation tests …” EDMS 90327
2. “ELQA Qualification of the superconducting circuits during hardware
commissioning” EDMS 788197
3. “Guidelines for the insulation design and electrical tests …” EDMS 1264529
Felix Rodriguez Mateos TE/MPE-EE
• The LHC strategy
• Some basic questions
• The HL-LHC strategy
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General strategy
Definition of worst case voltages
from quench modeling
Definition of conditions under which
worst case voltages will show up:
ambient conditions (gas, liquid), pressure
and temperature
Scaling factor ƒ
Felix Rodriguez Mateos TE/MPE-EE
Definition of test conditions
Definition of strategy:
i) Validation that the worst case voltages will be endured with
no degradation
ii) Looking for insulation defaults
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Strategy i)
Felix Rodriguez Mateos TE/MPE-EE
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Calculate worst case quench voltage Uq
Apply safety margins to it U=2*Uq+ 500 [V]
Give worst case voltage conditions C
Define test conditions C’
In order to be in “equivalent” ambient
dielectric conditions, apply scaling factor ƒ and
get new voltage levels U’
• Apply the new calculated values U’ under test
conditions C’
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Strategy ii)
Felix Rodriguez Mateos TE/MPE-EE
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Calculate worst case quench voltage Uq
Give worst case voltage conditions C
Define test conditions C’
Define minimum distance between electrodes (active
part and ground): assume missing insulation failure
at a certain stop which creates a certain creep path
length l
• Get dielectric strength for environment under
conditions C [E in kV/mm]
• Find factor ƒ to get voltage to be applied under test
conditions C’
• U’= E × l × ƒ will be the voltage to be applied under C’
test conditions
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Main ElQA test steps
Step: –n to –1 : In fabrication process
Step 1 in SM18
From modelling, the
worst case in
operation is obtained:
Vq
Vee
Vpa
E.g. Vmax r =
Vq+Vee+Vpa
Felix Rodriguez Mateos TE/MPE-EE
75 K, 1 bar , He (gas)
Rated level
V rated= f1 * Vmaxr +
X
f1 and X are safety
factor and margin
1st test level at
arrival to test bench
V test air = f2 *
Vrated
(for LHC : f1= 2 and X= 500
V)
f2 is an equivalence
between 75 K He
and 300 K air
75 K, 1 bar , He (gas)
300 K, 1 bar , AIR
This are not easily
reproducible
conditions, therefore
values haveto be
scaled to test in
air, LHe, GHe
Step 2 in SM18
1st test level at cold in
the test bench
V test LHe = f3 *
Vrated
f3 is an equivalence
between 75 K and
4.2 K in He
4.2 K, 1 bar, He
(liquid)
Test station is limited to 3000 V
Step 3 in SM18
1st test level after
cold test in air but
possible with He gas
V test LHe = f4
Vrated
f4 is an equivalence
between 75 K and
300 K in He
300 K, 1 bar , He (gas)
This test is not
revealing the default
as we are in air
applying gas
conditions . This can
be corrected by
pressurised He.
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Dielectric strength for 0.5 mm gap
VAir, 275 K, 1 b
VLHe, 4.2 K, 1 b
2500
7000
VGHe, 275 K, 5 b
700
VGHe, 75K, 1 b
600
VGHe, 275 K, 1 b
280
Felix Rodriguez Mateos TE/MPE-EE
C.R. Huffer
f2= 2500/600 = 4.2
f3= 7000/600 = 11.7
f4= 280/600 = 0.47
VLHe, 4.2 K, 1 b = 140 kV/cm
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Case: worst case voltage QXF
• Worst case voltages as presented by
Emmanuele/Gianluca:
o Coil to ground = 620 V
o Heater to coil =
Felix Rodriguez Mateos TE/MPE-EE
• Applying the previous rules to these numbers:
o Test in dry air: 2604 V
o Test in liquid helium: 7254 V
o Test after warm up: 291 V
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Discussion
• Should we consider that in fully potted coils
bubbles can appear
Felix Rodriguez Mateos TE/MPE-EE
o What will be the p/T conditions in those
cracks/fissures?
• By testing at the levels indicated, still one could
detect absence of insulation as levels are above
the dielectric given by air/helium for the defined
distance
• Limits given by the hardware (test benches): 3 kV
to ground in SM18
• Work on overall plan (including manufacturing)
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