LQ Quench Protection – G. Ambrosio 1 LQ DS video Mtg – May. 23, 2007 BNL - FNAL - LBNL - SLAC...

BNL - FNAL - LBNL - SLAC

Long Quadrupole Quench Protection Giorgio Ambrosio

LQ DS Video-Meeting May. 23, 2007

OUTLINE:

• LQ Quench protection• Spikes recorded during TQS01c test• Comparison with real quench signals• Plan

LQ Quench Protection – G. Ambrosio 2LQ DS video Mtg – May. 23, 2007

TQ/LQ conductor parameters

Parameter Unit Value

N of strands - 27

Strand diameter mm 0.700

Bare width mm 10.050

Bare inner edge thickness mm 1.172

Bare outer edge thickness mm 1.348

Keystoning angle deg. 1.000

Radial insulation thickness mm 0.125

Azimuthal insulation thickness mm 0.125

Copper to non-copper ratio - 0.89

Copper RRR - 100


Magnet parametersParameter Unit LQ

N of layers - 2

N of turns - 136

Coil area (Cu + nonCu) cm2 29.33

Length m 3.6

Jc(12 T, 4.2 K) = 2400 A/mm2

4.2 K temperature

Quench gradient T/m 223.49

Quench current kA 13.47

Peak field in the coil at quench T 11.59

Inductance at quench mH/m 4.1

Stored energy at quench kJ/m 372

1.9 K temperature

Quench gradient T/m 240.57

Quench current kA 14.57

Peak field in the coil at quench T 12.48

Stored energy at quench kJ/m 435


LQ Quench Protection

• QuenchPro Input– Magnet parameters: TQC01 x 3.6 m coils

• Conductor: TQ cable (Jc 2400 A/mm2)

• Total energy: 1.3 MJ @ 4.4K

• Code and input validation– Geometry, inductance, mat. prop (QLASA/Opera/ROXIE/TQC01): Done

– Effect of changes to quench propagation routine: Very small

• Comparison with TQs data – TQ tests set MIITs limit: in progress

• Quench protection parameters (aggressive)– Detection time: 5 - 10 ms based on TQs

– Heater delay time: 10 - 15 ms based on TQs


Protection heater delay + detection time

0

10

20

30

40

50

60

70

80

90

0 2000 4000 6000 8000 10000

Current (A)

Tim

e (m

s)

200 V

300 V

400 V

TQs Heater Delay & Detection Time

• Heater delay time: t ~ 10 ms close to quench plateau; t < 15 ms at I = 62% Issl

• Detection time: 3 - 11 ms during TQS01c training– Flux jumps up to 600 mV with MJR cable

TQC01

TQC01 protection heater studies by using spot heaters to initiate the quench.

mse

c

TQS01c


MIITs Limit

• During TQC01 test, one QI vs. T measurementI: 5000 A , QI: 9.05 MIITs, Peak Temp: 340 K

• Impact on quench performance of high-MIITs quenches (TQS01c)

• + 4% after 8 MIITs• - 2.9% after 8.1 MIITs• - 7.4% after 8.7 MIITs• - 18.4 after 9.5 MIITs• Small bumps at 7.5 MIITs


100% coverage 75% coverage 50% coverage

4.4 K

Hot Spot

7.6MIITs

Heaters

4.6MIITs

7.9MIITs

4.9MIITs

8.3MIITs

5.3MIITs

Turn-turn

55 VGround

446 V 65 V 459 V 84 V 536 V

1.9 K

8.4MIITs

4.9MIITs

8.7MIITs

5.2MIITs

9.2MIITs

5.7MIITs

72 V 489 V 85 V 520 V 109 V 615 V

MIITs and Voltage at quench currentDump = 60 m

Detection time = 5 msHeater delay time = 12 ms

High MIITs at 1.9K

Voltages OK


How to get margin for safe LQ test?

– 100% heater coverage with 4 independent circuits per coil • to be ~safe in case of failure (easier heater manufacturing, see LR)

– Shorter detection time and/or heater delay time?• Heater design, and QP system upgrade

– Larger dump resistance?• Hard at 1.9K: with 60 mohm we have ~ 1 kV at the leads• Possible at 4.5 K: could go up to 75 mohm

– Lower RRR in order to have shorter detection time?• …risky…

– Improve/upgrade VMTF Quench Detection System: • Low threshold * small time: in order to avoid trips induced by spikes• Capability of changing QDS threshold easily during tests

Y

Y

?

N

Y

LQ quench protection with TQ-like coils is

challenging but doable at 4.5K


Needs for LQ QP

• Four independent circuits for protection heaters• Change dump resistance at 1.9K?• Design LQ protection heaters• Easily changeable detection threshold• Develop smart quench detection to avoid spikes

with low threshold?– Time

– Voltage slope

– Spike recognition

– Current depending threshold


Last trip by flux jump

Threshold was 600 mV


Half coil


• 4 coils


Quad 2 = Coil 8 segments


VSDS

Quench

NO quench

NO quench


Quenches

Quench 51 - I = 9600 A, T = 4.5 K, Rate = 20 A/s

Time for decision should be less than 2 ms


New QDS … in progress

FPGA-based system: • It is firmware running in a PXI board, and it does not depend on an

operating system such as VxWorks, Linux, or Windows. • Note that you already depend on this approach for VMTF quench

detection and protection: in the current VMTF system, the Quench Logic Module (QLM) logic is programmed in firmware, and you depend on this module to perform properly to protect a magnet.

• This can really simplify the complexity of the system, as we have seen with the Stand 3 example. It can also make it easier to implement the type of adaptive logic we discussed during the meeting.

• Of course we need to discuss what level of redundancy or analog backups we need for risk mitigation.


Appendix


Quench Pro I

• Analytical code

• Adiabatic approximation

• Temperature computed from Quench Integral– Field is constant (average); different values for hot spot and bulk

– Epoxy included in QI

– Strand non_Cu = 76% Nb3Sn, 33% bronze (by Arup)

• Longitudinal propagation by QP velocity

• Quench starts under heaters – after detection time + heater delay time

• Temperature is uniform (given by QI) in normal zone of each cable – Different between Hot-spot and bulk


Quench Pro II

• Current decay– Magnet can be switched to a dump resistance (after

detection) or leads are short-circuited – Current decay is computed based on the instantaneous

time constant (computed from the growing resistance and the inductance)

– Inductance is computed based on position of each turn (inductance matrix)

• Voltages– Computed based on current, resistance, dI/dt,

inductance matrix, (at dI/dt max)– Turn to ground– Turn to turn


Sensitivity to Quench Prop. simulation

• New quench propagation routine in QuenchPro to better fit LQ magnet features

Very small effect!

Temperature vs. MIITs tuned on TQC01Dump = 60 m

Detection time = 8 msHeater delay time = 15 ms

100% coverage 75% coverage 50% coverage

1.9 K

412 KHot spot

108 KHeaters

449 K 121 K 504 K 143 K

412 K 108 K 441 K 118 K 490 K 138 K

OLDroutine

NEWroutine

LQ Quench Protection – G. Ambrosio 1 LQ DS video Mtg – May. 23, 2007 BNL - FNAL - LBNL - SLAC...

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