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ELQA testing during and beyond LS1

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Overview• ELQA

o What? When? Why?

• Tests:o TP4, DOC, MIC, LS1 PAQ, AIV

• Sub-tests:o IRC, ICC, ORC, TFM, BBC, HVQo 48V Insulation Monitoring

• Qualification Stages• Equipment used for ELQA

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ELQA: What, When and Why?

What is ELQA?• ELQA are the Electrical Quality Assurance activities which take place during

technical stops and shutdowns of the LHC.

When is ELQA performed?• ELQA campaigns are performed predominantly before and after thermal

cycles of the LHC. They can, however, be performed after any form of testing or manipulation of electrical circuits of the LHC, in particular following the splice consolidation work.

Why is ELQA performed?• ELQA tests are there to verify the continuity, configuration and integrity of

the insulation of the LHC electrical circuits. It is an important process in finding any NC’s (Non Conformities) which are present in the LHC. Following any thermal cycles of the machine the electrical circuits must be ELQA qualified before powering can begin.

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Main ELQA Tests• TP4 – Test Procedure 4 (TP3/ TP2 & TP1 were performed during machine assembly)

o HV and LV tests of circuits powered via DFBso 743 circuits

• DOC – Dipole Orbit Corrector check o HV and LV tests of circuits powered locallyo 914 circuits

• MIC – Magnet Instrumentation Checko HV and LV tests done locally on each magnet – it includes quench heater

qualificationso 1763 magnets.

• LS1 PAQ – Partial Qualification during Long Shutdown 1 o HV and LV test following the consolidation work (SMACC)o Up to 26 x 2 conductors in each sector; test is done on a daily basis.

• AIV – Arc Interconnection Verificationo LV test done after installation or replacement of magnets composing the

continuous cryostat.

Details of these tests are described on EDMS: 788197, 1269114, 1269127

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Measurement details: IRCIRC – Instrumentation Resistance Check• To detect:

o Open V-tapso Cold solderingo Bad contacts on the cable routing

• Typically done using a 2-wire mode Ohm-meter or with a very little current (max 100mA)

• This test is done in the frame of TP4, DOC and MIC tests

PE

Cable segment

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Measurement details: ICCICC – Instrumentation Continuity Check• To detect:

o Swapped connectorso Swapped pinso Swaps in the PE (Proximity Equipment) or cable segmento Labelling problemso Cooling problems in current leads

• It is done using a 4-wire method with a precision DVM and a DC current source• Max applied current is 3 A• This test is done in the frame of TP4 and DOC tests

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Measurement details: ORCORC – Ohmic Resistance Check• To detect:

o Open circuito At warm an abnormal resistance might mean

• Short internal to the circuit• Wrong number of magnet coils• Wrongly connected bus-bars

o At cold • Resistive circuit due to internal joints or cooling problems

• Not independent - done together with the ICC test• This test is done in the frame of TP4 and DOC tests

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Measurement details: TFMTFM – Transfer Function Measurement• To detect:

o Open circuito An abnormal inductance might mean

• Short internal to the circuit or coil• Wrong number of magnet coils• Wrongly connected bus-bars

• Gain-phase analyser is used together with a reference resistance and a power amplifier

• Max 10 V AC • Max 1 A• Frequency sweep from 1 Hz to 100 kHz• This test is done in the frame of TP4 and DOC tests

Gen.

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Measurement details: BBCBBC – Bus-Bar Continuity check• To detect:

o Open or highly resistive circuito Circuit cross connected with another one

• 4 wire method is used with a current source and a precision DVM• Max 500 mA• Max 24 V• This test is done in the frame of LS1 PAQ test

M1

M2

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Measurement details: HVQHVQ – High Voltage Qualification• To detect:

o Short circuit to ground or other circuitso Insulation degradation

• DC voltage of max 2.1 kV• Output current limited by hardware to 2 mA• Leakage current measurement • Each circuit energised individually with respect to

ground• All other circuits grounded• Voltages levels defined in HVQ ELQA database• Applied voltages different depending on thermal

state• Safety precautions necessary• This test is done in the frame of TP4, DOC, MIC and LS1 PAQ tests

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LS1 PAQ example

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TP4-CDuring the warm-up and cool-down processes the insulation of main circuits is monitored

• 48 V DC• Repetitively applied one by one to each circuit for 60 s• Early warning if thermal contraction leads to a short to ground• In some cases the short might disappear but the

insulation is damaged

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Measurement details: QHRQHR– Quench Heater Resistance measurement• To detect:

o Open or abnormally resistive quench heater circuits• Semi 4-wire method• DC current 300 mA max.• Accuracy affected by contact resistances• This test is done in the frame of MIC test only

IFS

QH

QH

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Measurement details: AIVAIV – Arc Interconnection Verification• To detect:

o Wrongly connected spool and line N bus-barso Wrongly connected corrector magnetso Swapped V-taps

• DC current of 300 mA• Used extensively during assembly of the machine• Will be reactivated for magnet replacement

EE

xxx

A B

R_demux

R1_L

0

R_demux

R1_RVV

V

V

V

0

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Qualification Stages

Local dipole orbit correctorTP4-A MIC-W TP4-B TP4-C TP4-D MIC-C TP4-E DOC-W DOC-C

At warm

At warm

After flushing

During cool-down

At 80 K

At cold

At cold

At warm

At cold

ORCHVQTFMICCDPCMIC

Circuits powered via the DFB

• The ELQA-TP4 procedures are composed of 4 stages. ELQA-DOC is performed at 2 stages.

• Each stage has to be performed at a given temperature and pressure in the different cryogenic enclosures containing the superconducting circuits.

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Equipment used for ELQA• HV crate• TP4 system

For special diagnostics we have many devices that can be used in non standard configurations. Up to now these were used mainly during technical stops in the phase of operation.

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TP4 system sketch

• The resistors are used for setting the working point of the power supply and for current measurement.

• 18 Internal voltage taps are routed to the inputs of the multiplexers.

A set of 4 multiplexers allows• 4 wire resistance measurement in

any configuration• Simultaneous measurement of two

signals

Device selector

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Standard test fails, what’s next?

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Thank you for your attention!

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Backup slides

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Follow-up webpage

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Statistical analysis tools

Many tools exist already, some more still need to be developed.

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Database structure