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

2
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)

3
QDS Block Diagram
DC power supply w/ quench protection for DS coil
system
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.

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.

6
Quench Analysis ResultsAll Coils
7
PS Quench Analysis Results 1
PS Current
Normal zone voltage
PS1 hot spot temperature
Normal zone resistance
Total resistive voltage
8
PS Quench Analysis Results 2
Al shell currents
Al shell temperatures
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
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)