Training LHC Powering R. Denz Quench Protection System R. Denz AT-MEL.

Training LHC Powering R. Denz

Quench Protection System

R. Denz AT-MEL

2Training LHC Powering R. Denz

LHC Quench Protection and Energy Extraction Systems

• Protection system for the superconducting elements of LHC– Magnets, busbars (including superconducting links), HTS current leads

– Circuits with INOM > 120 A (+ RCO.77)

– Commonly named QPS & EE or magnet protection– QPS / EE elements

• Quench detection systems• Quench heater discharge power supplies• Energy extraction systems (circuit breakers and dump resistors)• Data acquisition systems

– Supervision of QPS / EE equipment and superconducting elements

– Protection elements not within the scope of QPS• Cold by-pass diodes (used for main magnet protection)• Internal extraction resistors (corrector magnets)

– By the way … QPS• is not protecting quenches• has more than 7500 ways to stop LHC • Google hits:

– Quench = 6100000, Quench Protection = 60300, Quench Protection System = 26100


Protection Elements - Overview

• Quench Detector– Characterized by detection threshold and discrimination time

– In case of trigger creates always a FAST POWER ABORT of the associated circuit

– If applicable triggers as well heater and Energy Extraction Systems

• Energy Extraction System– Extracts energy from the superconducting circuits by switching dump

resistor(s) into the warm part of the concerned circuit

• Quench Heater Discharge Power Supply– Discharges energy stored in its capacitor bank into quench heater strips inside

the cold mass of a magnet

– By heating the magnet slightly the quench is distributed over the total magnet thus avoiding a local burnout of the coil

• Cold bypass diodes– By-pass the current of a main circuit around a quenching magnet


Protection Elements I – Main circuits

• Main circuits RB, RQD and RQF– Analog quench detectors

• One detector per MB, two detectors by MQ

• One detector = 2 redundant devices (as for all other detector types)

• Integrated into Local Protection Unit together with data acquisition system

• UThreshold = 100 mV tDiscrimination = 10 ms

– Quench heater discharge power supplies• Four power supplies per MB, two per MQ, 710/714 units per sector

– Acquisition and monitoring controllers• Supervision of magnet, detectors and quench heater discharge power supplies

• Communication with QPS supervision via fieldbus network (WorldFip)

– Protection units and quench heater power supplies and controllers installed in protection racks located underneath MB (as well MQ protection)

• 154 racks for MB, 47/51 for MQ

– Cold bypass diodes (installed inside cold mass, not managed by QPS)


Main Circuits Continued

• Protection of the main busbars– Dedicated detector using several voltage probes distributed over the sector

– Master device in the even points, slaves in the alcoves and the odd point

– Operates an independent fieldbus network in order to guarantee deterministic real time data exchange between master and slaves

– UThreshold = 1 V tDiscrimination = 1 s

• Protection of the High Temperature Superconductor current leads– High precision protection system for HTS and resistive part of the lead

– Analog input stage + microcontroller with integrated 24 Bit ADC

– UThreshold = 3 mV tDiscrimination = 100 ms (HTS part)

– UThreshold = 100 mV tDiscrimination = 100 ms (resistive part)


Main Circuits Continued II

• Energy Extraction Systems– In case of a quench the elements of the superconducting circuit can support the current

only for a limited time

– Natural time constant of the main circuits is far to long (e.g. 15095 s for RB)

to be reduced by switching dump resistors into the warm part of the circuit • RDump = 2 x 75 m for RB

• RDump = 7.7 m for RQD/RQF with 51 x MQ, RDump = 6.6 m for RQD/RQF with 47 x MQ

– Energy stored in the non-quenching magnets will be dumped into these resistors• Two 13 kA Energy Extraction Systems for the RB circuit

• One 13 kA Energy Extraction System (per circuit) in the even point for RQF and RQD

– In case a 13 kA Energy Extraction system fails a selected amount of magnets will be deliberately quenched (emergency measure to save the circuit)

• QPS internal interlock loop– Hardwired current loop linking all QPS and EE systems of the main circuits

– Interfaces to the PIC via the Quench Loop Controller• Interfaces in the even and odd point (type A interlock)

• Current source in the even point

– Links as well the PIC of the even with that of the odd point

– Transmits as well the Selected Heater Firing signal


Protection Elements I – Main Magnet Quench Scenario


Protection Elements II – Corrector Circuits

• Corrector magnet circuits with 120 A < Inom <= 600 A (+ RCO.77)

– Global Protection of magnets and busbar by special detection system• Numerical DSP based quench detector

– Analog input stages, ADC, digital signal processing

• Dedicated current sensing device for determination of dI/dt

• Reduced detection thresholds requested for bad splice detection / protection

– UThreshold = 20 mV tDiscrimination = 10 ms

– Individual protection of the HTS current leads• High precision protection system for HTS and resistive part of the lead

• Identical hard and firmware as for 13 kA and 6 kA leads

– Protection systems integrated into Global Protection Unit type A• One unit protects up to 4 different circuits

– Supervised by one physical acquisition and monitoring controller

• Interlock type B1

– 600 A Energy Extraction System (where applicable)• 2 redundant circuit breakers + additional back-up (named A, B, and Z)

• Circuit breaker and extraction resistor integrated in one system


Protection Elements III – Insertion Region Magnets

• Insertion region magnets– Concerns individually powered Q10 through Q4, superconducting separation

dipoles D1 and D2 and inner triplets

– Global Protection of magnets and busbar• Similar to corrector magnets but detector operating in bridge configuration

• As well reduced detection thresholds requested for bad splice detection / protection

– UThreshold = 20 mV tDiscrimination = 10 ms

– Quench heater power supplies

– Individual protection of the HTS current leads

– Integrated into Global Protection Units type B• One unit protects up to 2 different circuits

– Supervised by one physical acquisition and monitoring controller

• Interlock type B2

• Any trigger of the associated detectors will fire the quench heaters and stop both power converters


QPS Installations I

3 Racks3 Racks

2 Racks2 Racks 3 Racks

3 Racks

3 Racks

9 Racks

3 Racks

3 Racks

8 Racks

9 Racks

8 Racks

8 Racks

8 Racks

2 Racks

1 Rack

2 Racks

1 Rack

3 Racks3 Racks

2 Racks2 Racks 3 Racks

3 Racks

3 Racks

9 Racks

3 Racks

3 Racks

8 Racks

9 Racks

8 Racks

8 Racks

8 Racks

2 Racks

1 Rack

2 Racks

1 Rack

– 90 standard racks in the LHC underground areas and alcoves

– 1670 special protection racks in the LHC tunnel

– 240 Energy Extraction Systems 600 A

– 32 Energy Extraction Systems 13 kA


QPS Installations II

MB protection rack Protection unit Q4.L8 & D2.L8

Quench heater connection Q5.L8Quench heater power supplies Q4.L8


QPS Installations III

13 kA EE systems

13 kA EE extraction resistors RB

13 kA extraction resistors RQD/RQF

600 A EE systems


QPS Supervision

DQGTW(1 per point, 2 segments)

TIM

ING

FU

LL

FIP

ET

HE

RN

ET

DQAMC DQAMC

DQ

QD

L

DQ

HD

S

DQ

HD

S

DQAMG

DQ

QD

C

DQ

RB

DQ

SB

MQ protection 13kA energyextraction

MB protection

DQ

HD

S

DQ

HD

S

DQ

HD

S

DQ

HD

S

DQ

QD

L

DQ

QD

L

DQ

EM

C

DQ

QD

G

DQ

QD

C

DQAMS

600A energyextraction

Global protectiontype A - correctorcircuits (up to 4circuits)

DQAMSDQAMG

DQ

QD

C

DQ

QD

I

DQ

QD

C

Global protection type B- insertion regionmagnets (up to 2circuits)

DQ

QD

I

DQ

QD

C

DQAMGD

QQ

DC

DQ

QD

C

Global protection type C- inner triplets

DQ

QD

T

DQ

QD

C

DQ

QD

C

DQAMG

DQ

QD

C

DQ

QD

C

DQ

QD

B

DQ

QD

C

DQ

QD

C

DQ

QD

B

DQ

QD

B

DQ

QD

C

DQ

QD

C

DQ

QL

C

DQAMG

Global protection type D- main busbars

Quench LoopController

DQGTW(2 per sector, 2 segments)

TIM

ING

FU

LLF

IP

ET

HE

RN

ET

FU

LLF

IP

FU

LL

FIP

QPS SupervisionLHC Logging

LHC Post MortemLHC Alarms

PIC (POWER_PERMIT)QPS Expert Application

AB-CO

AT-MEL

LHC Slow Timing LHC Slow Timing


QPS / EE Acquisition & Monitoring Controllers

• Fieldbus (WorldFip) controlled data acquisition system– Supervision of QPS and Energy Extraction Systems (~2100 devices in LHC)

– Synchronized to accelerator time (1 ms precision)

– Up to 8 analog inputs and to 80 digital I/O channels

– Local bus for communication with associated equipment

• Basic types– DQAMC

• Main magnets, one device per magnet

– DQAMG• Corrector circuits, insertion region magnets, main busbars

• One physical device associated with up to 4 circuits

• One virtual controller per circuit

– DQAMS• Energy Extraction Systems, one device per system


Acquisition & Monitoring Controllers – State Diagram

Sendinglogging data

Starting up

Sendingtemperature

Sending nameDQAMC

Test patternZerocalibration

Sendingcoefficients

Resettingslaves

Logging off

Preparingpositive test

mode

Preparingnegative test

mode

Test inprogress

Filling buffer

Buffer ready

Last block

Sending postmortem data

QUENCH

RESET(from all states possible)

Unidirectional change of stateinitiated by user command

Unidirectional automatic change ofstate

Bidirectional change of stateinitiated by user command

Grey shaded states referto expert commands notaccessible from theaccelerator control system.


Controls Applications & QPS / EE

• QPS supervision ( H. Milcent)– General supervision tool for QPS based on PVSS

– Three different user levels:• Monitor: restricted access

• Operator: all commands required for LHC operation are accessible

• Expert: no restrictions – user should know what he is doing …

• QPS expert application ( B. Dupuy, H. Milcent)– Expert tool to be used for diagnostics, debugging, development …

– Allows the expert to issue special commands required for LHC hardware commissioning

• In addition during commissioning and operation QPS will make heavy use of many controls applications– PMA viewer and analysis tools

– TIMBER

– LASER

– etc.


QPS Basic Signals – Power Permit

• QPS & EE Power Permit– Software signal to be issued prior to a powering

sequence or a re-start of a ramp from injection current

– Signal is calculated on circuit level by QPS supervision based on the results of the individual QPS and EE components

• Complexity depends on circuit: e.g. RB Power Permit = 163 individual elements

– On request by the PIC the signal is transmitted to the PIC via the QPS supervision (PVSS level)

– Change of state during powering will create an alarm ( LASER) on the circuit level but not provoke a FAST POWER ABORT

– In general Power Permit is false if the corresponding data acquisition systems are not ready for data recording

– Power Permit generation and transmission will be tested within PIC1 procedure


QPS Basic Signals – CIRCUIT_OK_QPS

• Signals initiating a FAST POWER ABORT– In addition energy extraction systems and quench heaters

will be activated (if applicable)– Hardwired signal with high to low transition– Hardwired interface (current loop) to PIC and power

converter per circuit– 3 type of interfaces

• A: main circuits + inner triplets (includes discharge request)• B1: corrector circuits• B2: insertion region magnets (2 power converters)

– Change of state triggers as well the generation of a PM data block

• Trigger time encoded in SDDS filename (1 ms precision)

– Signal sent to PIC and Power Converter is called CIRCUIT_OK_QPS

• Sum (hardwired serial connection) of individual QPS and EE devices of the respective circuit


QPS / EE Organisation

• QPS and EE systems are managed by the PM section of the AT-MEL group (section leader K. Dahlerup-Petersen)

• Within hardware commissioning– Four teams consisting of one crew leader plus three experts (two spare

teams)

– Four QPS coordinators

• QPS coordinators– G. Coelingh

– K. Dahlerup-Petersen

– R. Denz

– S. Le Naour

• QPS and EE systems will be fully commissioned within LHC HC– Once operational system will be highly autonomous and requiring very little

information (hopefully …)

– Its purpose is to preserve valuable equipment not to annoy operators


QPS Specific Safety Issues

• Quench heater circuits– Once switched on quench heater discharge power supplies may discharge at

any time

• QPS racks in LHC underground areas– Detection electronics is on magnet potential!

– Only to be accessed by experts• Also experts are supposed to follow the rules …

• Energy extraction systems– Don’t stand close while associated circuit is powered (unless you are a heavy

metal drummer since 20 years …)

• QPS controls - expert mode– Expert commands are required for debugging and specific hardware

commissioning procedures• Reserved for QPS experts

• Not needed and not to be used for LHC operation


References

• QPS web page: http://at-mel-pm.web.cern.ch/at-mel-pm/– Includes links to all kind of QPS and EE documentation

• QPS & EE equipment codes: https://edms.cern.ch/cedar/plsql/codes.list?cookie=6268364&initial=D&type=CODE&code=EqCode

• QPS signal names: https://edms.cern.ch/file/356568/1.2/LHC-DQ-ES-0003-10-10.pdf

• QPS individual system test: https://edms.cern.ch/file/720806/1.0/LHC-DQ-TP-0002-10-00.pdf

• EE individual system test: https://edms.cern.ch/file/717559/0.1/LHC-DQ-TP-0001-00-10.pdf


Glossary

Local Protection Unit

Global Protection Unit

Quench Detector

Detection threshold

Discrimination time

Quench Heater Discharge Power Supply

Energy Extraction System

Selected Heater Firing

Acquisition and Monitoring Controller

Virtual controller

Current Sensing Device

Quench Loop Controller

Cold By-pass Diode

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Training LHC Powering R. Denz Quench Protection System R. Denz AT-MEL.

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