Quench Detection and Protection

1. Quench Detection and Protection Outline • Quench detection • Voltage tap and signal arrangement • QDS block diagram • QDS calibration • Quench protection • Protection circuit • Quench analysis modeling • Summary results for PS, TS1, TS2, TS3 (no cable), Ds • Detailed results for PS Quench Detection and Protection--Brad Smith

2. External lead + External lead - Internal joint .... Cryostat boundary Voltage Taps and Connections • Each coil AND each joint have one pair of voltage tap wires. • Each voltage tap wire is isolated by a resistor (not shown) Quench Detection and Protection--Brad Smith

3. Cryostat feed through Voltage divider Current limiting resistor Transient voltage suppressor Isolation amplifiers Anti-aliasing low pass filters Data acquisition system (DAS) Computer - DAS configuration & Data storage PS . . . . . . TS1 . . . Master controller w/ digital quench detector (DQD) Computer - DQDconfiguration TS2 TS3 Optional backup analog quench detector (AQD) . . . TS4 DC power supply w/ quench protection for PS coil system TS5 Power supply controller . . . DS Cryostat boundary QDS Block Diagram DC power supply w/ quench protection for DS coil system Quench Detection and Protection--Brad Smith

4. QDS Setup • QDS will be placed on a UPS to ensure protection is maintained during loss of power. • Digital QDS is backed up by an analog QDS providing redundancy. • QDS will require calibration at installation • Only the resistive component of voltage is desired from each voltage tap pair • Inductive components of voltage are produced at each voltage tap pair when any one of 6 coil circuit currents are changing (charge, discharge, quench). • Current in each power supply is sampled. • Computer also calculates dI/dt for each circuit • During installation, each coil voltage tap signal is trimmed to zero using trial ramps of each coil circuit at low current. Quench Detection and Protection--Brad Smith

5. Quench Protection • The large stored energy of each coil system must be removed externally while simultaneously maintaining coil temperatures, stresses and voltages below acceptable limits. Quench Detection and Protection--Brad Smith

6. Quench Analysis Results—All Coils Quench Detection and Protection--Brad Smith

7. PS Quench Analysis Results 1 PS Current Normal zone voltage PS1 hot spot temperature Normal zone resistance Total resistive voltage Quench Detection and Protection--Brad Smith

8. PS Quench Analysis Results 2 Al shell currents Al shell temperatures Quench Detection and Protection--Brad Smith

9. PS Quench Analysis Results 3 • Element temperature data at each time step is fed into an ANSYS structural model • ANSYS models are run with the Al shells but without thermal or mechanical preload to determine desired pre-compression from shell on coil • PS1 axial stress after 38 s, showing 45.5 MPa tension relative to the cold state with no Lorentz load • Tensile stress must be overcome by Al shell differential thermal contraction and bolting preload PS1 maximum axial compression at 2 s is 10.2 MPa Quench Detection and Protection--Brad Smith

10. Other Quench Conclusions • TSu and TSd coils should be fast discharged if quench is detected in either PS or DS to prevent over-current. • First DS coil was split in half axially to eliminate excessive, local r-z plane bending and attendant shear stress. Results after split: DS1 Shear Stress (0.67 MPa Max) DS1 Axial Stress (6.5 MPa Max Tension) DS1 Hot Spot Temperature - End of Quench Event (Peak Temp 123 K) Quench Detection and Protection--Brad Smith