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BEPCII superconducting IR magnets commissioning and quench protection system

BEPCII superconducting IR magnets commissioning and quench protection system. CHEN, Fusan September 17, 2008. Outline. Commissioning of the Superconducting IR Magnet (SIM) The first commissioning revealed many problems. (Reported in IMAC report, May 11, 2007)

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BEPCII superconducting IR magnets commissioning and quench protection system

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  1. BEPCII superconducting IR magnets commissioning and quench protection system CHEN, Fusan September 17, 2008

  2. Outline • Commissioning of the Superconducting IR Magnet (SIM) • The first commissioning revealed many problems. (Reported in IMAC report, May 11, 2007) • The second commissioning is successful. SIM and SSM are powered to operating currents at the same time. (May 2007~ June 2007) • Field measurement at offline position. (June 2007 ~ July 2007) • Field measurement at online position. (September 2007) • SIM running status • Running without SSM. (October 2007 ~ March 2008) • Running with SSM. (June 2008 ~ now) • About 90 times of protection actions are triggered from the time of the second commissioning. • Improvement in the future

  3. The second commissioning • Insufficient cooling of the GCL cool end • Adjust the cooling parameters

  4. The second commissioning • Power all coils to 110% operating current • ASW: 2 training, ASE: 3 trainings • 5 ramping cycles from 0 to 110% current.

  5. SIM field measurement • YU, Chenghui will give a detailed report about SIM field measurement

  6. Running status • 90 times of protection actions are triggered • 52 times caused by ps or ps control system problems. • Ps fault: 8 • Current pulse at turn main circuit on: 10 • Ps control system bug: 34 • 20 times of ground faults • 6 times of mis-operation: over current • 5 times of quench training • 4 times of insufficient cooling • 3 times of chain action.

  7. Protection action analysis • Ps faults • A capacitor failure in ASW ps results in the current oscillation. • The DCCT signal sent to quench detector is unstable • Current pulse • A huge current pulse while turning on the main circuit

  8. Protection action analysis • Ps control system bugs. • Ramping too fast. • Ramping un-smoothly. • For conventional magnet: 10A/s = 5A/step × 2step/s • For superconducting magnet: 10A/s = 0.5A/step × 10step/s • ……

  9. Protection action analysis • Ground faults • All coils and the powering circuits should float to ground. • Hipot test shows the insulation of the circuits can not meet the requirement. (20Mohm) • Water on top of the valve box makes the insulation worse. • Ground faults seldom occur afteradjusting the cooling parameters.

  10. Protection action analysis • Chain action • The two SIMs are completely independent at the beginning. • Troubles appear after running with SSM. • If one SIM quenches, different voltages are induced in the 3 SSM sections for about 1.8 seconds. SSM quench protection system considers that SSM quenches after 1.2 seconds of voltage imbalance. When SSM implements its protection actions, the cold mass is exhausted. The non-quenched SIM quenches too because SIMs and SSM use the same cryogenic dewar to provide Helium. • The troubles: • It take several hours to recover the cryogenics system. • The SSM’s quench switch (mechanical) gets damage after each high-load (about 3360A) opening. • Possible Solution: • One SIM quenches, Protection actions are triggered at both sides. • Increase the dump resistor of SIM to finish the protection process in 1.2 seconds. • Improve the quench detector of SSM.

  11. Protection action analysis • Discover PS faults from quench data • SCQ dump resistor damaged. • SCB IGBT failed to shut off.

  12. Improvement in the future • The quench protection system is reliable. • The power supplies for SCQ, SCB and correctors will be rebuilt. • The ground faults will be treated as a secondary fault in new power supplies. • The ground currents will be monitored and logged with new system. • ……

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