Chamonix Workshop XIV
D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
Session 4 – Other Issues affecting Beam Commissioning 1
Electrical Quality Assurance (ELQA)
Tuesday, 18th January 2005
Davide Bozzini, AT-MEL-EM
Thanks to S. Russeschuck, F.Rodriguez Mateos, T. Zichler & the HCWG members
1
Outline
 Introduction to the LHC Electrical Quality Assurance (ELQA)
 The ELQA activities and LHC operation with beam
D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
 Detection of electrical faults
 Classification of electrical faults
 Diagnostic methods for detection
 Examples of electrical faults diagnostic
 Acceptance and qualification criteria
 Accessibility to the electrical circuits
 Sequence and duration of diagnostic activities
 Staff experience and familiarity with the LHC machine, resources
 The experience of String 2
 Conclusion
2
The ELQA activities
Definition
 A series of actions to ensure the correct functioning of the electrical circuits of the LHC
machine
D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
Aim
 Define a quality assurance plan to apply to the machine during installation, hardware
commissioning and operation
 Provide the procedures, tools and resources to perform the necessary checks and tests
during ELQA activities
 Grant the traceability of checks and tests performed at the different stages
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The ELQA activities
D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
Time
When
Manufacturing of components
DFBX, Line N cable,…
Machine
assembly
Hardware
commissioning
Operation, Shutdown, repair
- Continuity
- Polarity
- Electrical insulation
-
Continuity
Polarity
Electrical insulation
Global resistance, inductance
Global insulation
... ...
- Insulation prior/during/after
cool-down
- Transfer function
- ... ...
- diagnostic
- re-qualification
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The ELQA plan
LHC Reference
database
D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
Electrical conformity
report
current leads
13 KA
7.5 KA
600 A
60 A
120 A
DFB
DFBX
DFBM
DFBA
magnets
dipoles
arc sss
IR sss
separation dipoles
inner triplet
bus bars
6 KA
600 A (line N cable)
Qualification and preparation before introduction into the tunnel
- Surface (cold) tests
- generation of non conformity lists
- qualification of individual electrical component
Electrical
interconnection
Layouts
ELQA activities during sub-sector assembly
Existing
electrical
non-conformities
ELQA activities of sub-sector circuits
during hardware commissioning
Generated
electrical
non-conformities
Traceability of
ELQA
documentation
generated during
assembly and
commissioning
Specification of
Components
(Electrical
parameters)
ES
type of circuits
instrumentation
Specification for
electrical
interconnections
M1 & M2
Line N BB
inner triplet
Technical
support
Beam commissioning
&
Operation
- Tools for
assembly
-Tools for
electrical
verifications
- Tools for
diagnostic
Tunnel environment
5
ELQA and LHC operation with beam
Motivation
 Though considered unlikely, it’s almost sure that due to the complexity of the LHC
machine we will face faults and problems related to the superconducting (SC) electrical
D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
circuits during the operation with the beam
 A fault affecting a SC electrical circuit can be unpredictably provoked by different
sources and, in most cases, it cannot be detected on-line or anticipated
 Most of the electrical faults will have a direct impact on the machine availability and/or on
the beam quality
 Beam Based measurements may require in-situ verification of the magnets polarities
(Chamonix X, J-P Koutchouck, Finding a faulty element of the machine)
Therefore
 Efficient postmortem ELQA diagnostic methods to be applied during commissioning and
operation with beam must be established
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Detection of electrical faults
Sources for electrical faults detection
 The beam (1)
– Via the BPM’s and after investigation
 The power converters (2)
D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
– Over voltage
– Detection of an earth fault
Events that may
launch an ELQA
diagnostic
intervention
– Monitoring of leakage current
 The quench protection system (3)
– Loss of instrumentation (Voltage taps)
– Detection of an open circuit
– Consecutive quenches in a given half/cell
 During the ELQA activities (4)
– Measured electrical characteristics after a shut down period or re-commissioning out
of specified parameters
Except for (1), practical experience acquired during hardware commissioning will be available
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Classification of the electrical faults (some examples)
D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
The notorious one’s
Fault
Consequence
Detection
Diagnostic method
Inverted polarity of a
magnet within a series
(ex: MCS)
Beam quality
- BPM’s
- Beam observations
- Polarity check
Open circuit of a main
circuit
Beam abort
- QPS
- Power converter
- Continuity check
- Transfer function
Short to ground of a main
circuit
Beam abort
- Power converter
- High voltage test
- Transfer function
Loss of instrumentation
used for magnet
protection
Beam abort
- QPS
- Continuity check
- TDR
……………..
……………….
……………………
…………………
Fault
Consequence
Detection
Diagnostic method
Quench of bus bar
segments or splices
Beam abort
- QPS
?
Transitory shorts to
ground or between
circuits
Beam abort
- Power converters
?
High ohmic resistance of
bus bar interconnect
?
- QPS
- Cryo system
…………………
The malicious one’s
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Diagnostic tests (1)
For the notorious faults
Diagnostic test
Electrical insulation
D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
Capacity
Continuity
Polarity
Applied to
Method
segment - ground
DCV supply
segment - segment
I leakage
Circuit - ground
Measurement of C
S segments
DCA supply
Circuit
Closed loop
S segments
DCA supply
Circuit
Voltage drop via V_taps
Instrumentation
Current lead V_taps
Diode polarity
MB,MQ diodes
Transfer function
DCV
DCA supply
Voltage drop via V_taps
ACV supply
Turn on voltage
Circuit
Z(f)
Circuit - ground
Z(f)
 Wide experience acquired during machine assembly and hardware commissioning
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Diagnostic tests (2)
For the malicious faults
 All tests of the previous slide are applicable but probably not enough
 Several ideas on the air, some of them already tested
D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
– Time domain Reflectometry + high voltage pulse
– High voltage partial discharge
– Specific hardware to be locally and temporarily installed during operation in order to
get detailed information about transitory faults
– Power dissipation measurements to localize ohmic resistances (require collaboration
with cryogenic specialists)
– ……………………..
 A systematic approach will be difficult to be applied
 Experience will only be acquired on field when such faults will arise
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Electrical fault diagnostic (1)
Transfer function Z(f)
 Transfer function of MQD and MQF
string circuits at cold (1.8 K)
Phase / imag
– RQF (reference)
Gain/
real
– RQD Z(1Hz)= 6309 ohm
– RQD has a high resistance
somewhere, NOT OK
Frequency [Hz]
– Coils of two MQs (blue and green),
OK
Phase / imag
 Transfer function of a portion of circuit
via the local voltage pick-up
instrumentation
Gain/
real
D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
– RQD phase(1Hz)= 0º !!
– Portion of circuit including three
dipoles (red), NOT OK
Frequency [Hz]
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Electrical fault diagnostic (2)
Detection of a high ohmic resistance in a MQF circuit
 Progressive powering (without beam) of the SC circuit
 Follow-up of temperature trend through the string of
magnets
 Localization of an increase of temperature
RQF Power dissipation test @ 1.8 K
1.E+03
1.E+03
2.0E+00
8.E+02
1.5E+00
6.E+02
Current
1.0E+00
4.E+02
U_diff
5.0E-01
2.E+02
Resistance
Time
27/06/2003
10:13:20
27/06/2003
10:11:40
27/06/2003
10:10:00
27/06/2003
10:08:20
27/06/2003
10:06:40
27/06/2003
10:05:00
27/06/2003
10:03:20
0.E+00
27/06/2003
10:01:40
0.0E+00
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Power dissipation [W]
Power dissipation
2.5E+00
27/06/2003
10:00:00
U_diff [V],
Resistance [ohm]
3.0E+00
Current [kA],
D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
 Calculation of the dissipated power by joule effect
Electrical fault diagnostic (3)
Partial discharge test of a PS dipole magnet
 Allows to determine the quality of the electrical insulation
 Is a qualitative analysis
D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
 Requires time and a high practical experience, good feeling and good luck
Courtesy T. Zickler
13
Electrical fault diagnostic (4)
Electrical insulation degradation
D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
 Example of the MB circuit of
String 2 phase 3
 Resistance to ground out of
specification but not a firm short
to ground
 Localization of fault only possible
if the circuit can by split in sub
circuits (opening of
interconnections is needed)
Description
RB [Mohm]
Reference at warm before pump down
of phase 3
(2003-03-28)
10.1
Reference at cold before pump down
of phase 3
(2003-04-28)
9.4
Reference at cold after 13 kA
circuit problems
8.7
Warm cables connected, cold masses
under gaseous helium
10
After warm cable dismantling
14
After cold mass purge and
injection of air
29.6
After MRB dismantling
30.8
Separation of Bus Bars in the MRB
ext BB
int BB
After short circuit dismantling
and BB cleaning
31.6
725
MB4-to-MB6
13100
9150
DFB-to-SSS4
31.4
16800
After
disconnection of
RB Bus bars in
between SSS4 and
MB4
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Acceptance and qualification criteria
Current leakage of a main dipoles (MB) electrical circuit
 The power converter will turn off if Ileak > 50 mA
D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
(LHC-D-ED-0001 rev 2.0)
 By specification (LHC-M-ES-0001 rev 1.1) the
maximum current leakage allowed for a MB circuit
corresponds to the number of components that
composes the circuit (434) times 20uA /
component. This gives an Imax < 8.68 mA
 Active leakage current detection level is 5 times higher that the maximum leakage
accepted in the specification
 The leakage may change depending on the machine/circuit conditions. It is essential to
store all the measurements during the time to allow analysis and understanding of the
variation
 Need to define how to deal, in particular at the beginning of the machine operation with
measured values between the two limits
 Applicable to all 1715 SC circuits
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Accessibility
Warm machine
 PS machine “warm”. Electrical circuits
are easily accessible and visible
D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
 For diagnostics almost all senses can
be used: hearing , visual, smell, touch
Cold machine
 LHC machine “cold” electrical circuits will not be
directly accessible
 This picture shows the String 2 phase 1, i.e. 54
meters without access to the circuits. Diagnostic has
been a nice exercise. LHC machine will be 2700 m!
 Diagnostic may require the local access to the circuit
(opening of interconnections).
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D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
Sequence and duration of diagnostic activities
Activity
Activity
Diagnostic phase #1
Diagnostic phase #1
Analisys and decision
Analisys and decision
Diagnostic phase #2
Diagnostic phase #2
Intervention repair
Intervention repair
Re-qualification
Re-qualification
T0
T1
T2
T3
T4
T5
Time
T0
T1
T2
T3
T4
T5
T6
T7
Time
Opening of the machine
for local diagnostics
 Time for diagnostic phases #1 and #2
- fixed, if the fault is observable
- variable, if the fault is not observable
 Time for analysis and decision
- variable, and relies on decision makers
 Time for intervention and repair
- fixed, if the intervention is known
- variable, if the intervention is new
 Time for re-qualification
- fixed, procedures known from HC
17
Staff experience and familiarity with the LHC machine,
resources
 Fundamental experience will be acquired during machine assembly and hardware
commissioning
 Beam commissioning starts in 2007 most of the knowledge will be gone
 Interventions during beam
commissioning and
operation will have to deal
with radiation
 Staff shall be familiar not
only with the ELQA
procedures but also with
safety rules and tunnel
environment
Hardware
commissioning
Assembly
18
Beam commissioning
and operation
HNINP collaboration
16
Nr. of person
D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
 Success of ELQA activities during beam commissioning need experienced and well
trained personnel
FSU
14
Tech. Students
12
Staff
10
8
6
4
2
0
Q1
2005
Q2
2005
Q3
2005
Q4
2005
Q1
2006
Q2
2006
Q3
2006
Time
Q4
2006
Q1
2007
Q2
2007
Q3
2007
Q4
2007
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The Experience of STRING 2
 Reference documents
– From String 2 to the Hardware commissioning of the first sector: A challenge?,
slides,F. Rodriguez Mateos, LHC days workshop 2003
D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
– F. Rodriguez Mateos, String 2 Report, EDMS
 Outcomes related to the ELQA activities
– Time for diagnostic and analysis was largely underestimated
– Several new methods for diagnostic where tested to determine the source of
the faults. →some of them described in this speech
– Despite all the effort put into diagnostic and analysis we could not determine
what was the fault in a bending dipole magnet
– The beam, the radiation and most of the tunnel environment constraints were
not there
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Conclusion
 Assuming a successful hardware commissioning, day 1 of commissioning with beam
might be successful, nevertheless we must be prepared for diagnostic interventions
during the following days, weeks, months
D. Bozzini, AT/MEL/EM, Chamonix Workshop XIV, January 2005
 Operation with beam will have an impact on ELQA activities. Access, safety, radiation
rules shall be respected
 The detection of faults will be done by different systems (PC, QPS, BPM’s,…).
Exchange of information, collaboration is essential
 Be ready for unpredictable faults requiring hard interventions (opening of
interconnections)
 Resources: Experience acquired during hardware commissioning is not granted for
2007 and later. A sufficient number of CERN staff specialists supported by the extension
of the HNINP collaboration (motivated now by the need of personnel during beam
commissioning and operation) shall be considered
 On call service 24/24 and 7/7 seems to be necessary. Not foreseen at the moment
 String 2 was an excellent exercise. A sector test with beam would be a must for
optimization of ELQA diagnostic activities
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