Download Becoming familiar with QPS systems in the LHC

Becoming familiar with QPS systems in the LHC (incl. EE)
Presentation 02 Sept. 2008
PART 1 of 3.
Part 1: General layouts and principles
Presentation of equipment
Knud
Part 2: Presentation of typical QPS signals and their
interpretation.
Bob
Part 3: Operational aspects
Possible events and first diagnostics / treatment by
1st-line team -incl. summary of failures experienced
during Hardware Commissioning. Support by
QPS specialists
Reiner / Knud
Challenge 1: Adiabatic Temperature Rise
At 13 KA it takes only 200 mS to destroy a dipole magnet.
31 Miits
(for TeV 7 Miits)
•
970
Km/Hr
• 11
GJ
Challenge 2:
Stored Energy
10.6 GJ
•84,000 Tons
•60 Km/Hr
•11 GJ
Protection features in the LHC
• Four basic protection principles:
–
–
–
–
Detection of resistive build-up
Spread of the quenching area by firing of heaters
By-passing the quenching magnet by cold diode
Extraction of the stored energy
Not all circuits require all four protection measures.
LHC What to power?
• The beams are controlled by:
-1232 SC main dipoles
-392 SC main quadrupoles
-124 SC quads/ dipole insertion magnets
-6340 SC corrector magnets
-112 warm magnets
Total current in the 8000 magnets: 1.72 MA
(1718 distinct circuits)
Comparison of the stored energy (10.6 GJ) with
Hera: 0.5 GJ
Tevatron: 0.3 GJ RHIC: 0.2 GJ
Reference for viewing circuit topologies and parameters:
http://at-mel-pm.web.cern.ch/at-mel-pm/
Also available in CCC in paper form (the QPS Reference File)
Main elements of QPS and EE
• 16’000 quench heaters
• More than 2’000 specially doped diodes for 13 kA commutation at
1.9 K
• 40’000 instrumentation wires
• 6’200 quench heater power supplies (DQHDS)
• 3’400 multi-channel detectors
• 2’650 data acquisition and monitoring controllers (AMC, AMS, AMG,
(AMR in future))
• 32 energy extraction facilities for 13 kA, comprising
- 256, 4.5 kA electro-mechanical switches
- 64 breaker control modules (DJPC)
- 32 current-equalizing busways
- 48 / 16 dipole- / quadrupole extraction resistors
• 202 energy extraction systems for 600 A.
Quench Detection in the LHC
• Type of detectors:
-DQQDL ‘local’ quench detector, one per arc dipole and quadrupole
(in total 1232 + 392 (51 x 4 + 47 x 4) = 1624 racks).
Dipoles: Aperture to aperture comparison
Quadrupoles: Half-coil to half-coil comparison in the same
aperture (F or D)
Mainly analogue electronics (because of location in the tunnel).
Balanced Wheatstone bridges used for comparison. Two channels
per card and two redundant cards.
Operating principle: Double 1 oo 2 (one out of two)
Featuring: Missed-quench probability is negligible (for asymmetric
quenches!)
Less than 10 false quench detections per year in worst modeled
scenario.
Possibility to detect broken voltage tap wires
Controller: AMC
Quench Detection in the LHC
• Type of detectors:
-DQQGPU: Digital quench detectors:
Installed outside radiation areas exclusively
TYPE A: For global protection of corrector circuits.
As no voltage taps were provided (an unforgivable mistake !) the
detection principle is based on compensation for inductive voltage,
using pre-loaded inductance tables, which have been fine-tuned
during the Hardware Commissioning.
TYPE B: ADC-based digital comparators – on Individually Powered
Dipoles and Quadrupoles (voltage taps available).
Controller: AMG
Quench Detection in the LHC
• Type of detectors:
-Main Busbar Quench Detector:
A ‘local’ detection for the main magnets implies to have a
‘global’ detection for the associated busbars
The instrumentation wires on the busbars have been minimized
The topology of the detector requires two reference magnets
and measurements of the circuit voltage at the current leads (for the
dipole circuit in either end of the sector).
The resistive voltage is calculated as the sum of the two
measured voltages minus the average of the measured reference
magnet voltages multiplied by the number of magnets in the circuit.
The ‘global’ detector also protect the associated current leads
with combined feature of HTS quenching and resistive heating
Quench Detection in the LHC
• The Quench Loop:
– Role: Passing remotely the information about quench detection
to other systems such as the energy extraction facilities and the
Power Interlock Controller.
– Solution: Two hard-wired current loops (50 mA) across each
sector, one for the main dipole circuit and one for the QF/QD
circuits combined (with simultaneous activation in both circuits).
– Every quench detector can open the current loop, the energy
extraction facilities can open the loop (in case of internal faults)
as well as react on a rupture of the loop by opening the
extraction switches.
– Information about the rupture of the quench loop will be
transmitted to the PIC for further action (shutting down of power
converter, ejection of the beams).
– NOTE: The fire-preselected-heaters loop has been deactivated.
Compression
Rings
Heat
Sinks
13 KA
Diodes
Why Energy Extraction in the LHC ?
•
•
For the LHC 13 kA circuits of the arc dipole and main quadrupole
chains the EE system is activated in the following cases:
– In case of a quench in a magnet coil: A rapid current decay is
required after transfer of the current to the cold diode of the
quenching magnet in order to preserve the by-pass diode and
its associated busbars.
– In case of a quench in a superconducting busbar or in a current
lead or in case of risk of overheating of a component of the warm
part of the power circuit (water-cooled cables or crowbar): A rapid
current decay is needed to remain within the thermal limits of the
component, which has a problem
– In case of a failure in the energy extraction switches: A rapid
transfer of the current to the dump resistors is required to avoid
damage of the breaker system
In each of the above cases, the rapid current decay is obtained by
switching external resistance into the circuit. Almost the complete
stored energy is absorbed by the external dump resistors (99.5 % in
the dipole chains and 92 % in the quadrupoles).
Why Energy Extraction in the LHC (contd.)?
• For the LHC 600 A corrector magnet circuits:
– No quench heaters nor by-pass diodes are provided in the
corrector magnet chains
– Apart from the presence of parallel resistors across certain
corrector magnets, protection relies entirely on the operation of
an energy extraction system
• Particularly important: Short reaction time and small time
constant for the current decay is required due to reduced
thermal margins for the superconducting busbars (typically
60 ms reaction time is required).
– Two different energy extraction systems are foreseen:
• Medium-voltage, separate extraction facilities
• Low-voltage, converter-integrated systems
Current-equalizing Busways for distribution of
currents into the four branches of breakers.
The Dump Resistors for the LHC 13 kA Circuits
•
In spite of the large energy difference (664 MJ per diode system and
22/24 MJ per quadrupole circuit) the two extraction resistor types have
much in common. The basic design criteria for both types are:
– In order to maintain the peak voltage across the resistor at its lowest
possible level, as defined by the resistance at room temperature, a
‘zero’ inductance concept are applied and an absorber material with
low temperature coefficient have been selected.
– The resistor bodies are dimensioned for high temperature operation,
but within safe margins for long term reliability of its materials and
components. Typically, the operating temperature at the end of the
energy deposit attain 200-280 oC.
– The design assures a high short- and long term reliability.
– The resistor units are available for energy extraction without need of
any infrastructure, such as mains power and cooling water, during
the extraction period.
– The heat dissipation to the surrounding air is close to zero, due to
underground installation. Connection to LHC de-mineralized cooling
water circuit is therefore needed for evacuation of the heat.
– A design, in which the resistor body is not immersed in water, has
been favored. Direct cooling by forced air is a good choice, but
requires an air-to-water heat exchange. Such a device is
incorporated in the resistor assembly.
– The units have their own water reservoir with sufficient capacity to
assure worst-case no-boiling conditions.
– The maximum cooling period shall be maximum 2 hours
Energy Extraction
Updated on 16-Jul-06
Version 1 600A EE CERN - AT / MEL
1
600 A Extraction
Constructional Details
•
•
•
•
•
•
•
•
Separate facilities, located back-to-back or next to the associated
power converter.
Two systems share one standard rack.
The chosen topology is a Series-inserted system with two main
breakers (A & B) operated simultaneously, with a third breaker (Z) as
back-up.
The extraction switch is based on 3-pole electro-mechanical AC
breakers (RU military standard), retro-fitted with DC Arc Shutes and
Capacitive Snubber Circuits for arc suppression. The capacitor
bank, bridging the switches, will strongly reduce the contact erosion
(no arcing contacts), it will reduce the noise and it will shorten the
arcing time.
The 600 A is shared by the three poles in parallel.
Also these AC switches have two independent modes of release,
herewith providing a four-fold redundancy.
The system controls are based on the controller AMS. The Power
Abort Link is common with the associated power converter.
All cards are made as SMD and burnt-in. The control electronics is
commonly designed by CERN and BINP.
Other Basic Parameters
• Typical total opening time with pulsed release: 11 - 17 ms
• Typical total opening time with under-voltage release: less
than 20 ms
• Total opening time with motor drive / electromagnetic
driver: 65 ms!
• Maximum DC voltage across one breaker during opening:
420 V
• Required Snubber Capacitance: 320 F.
• Extraction Resistor: 0.7 . Stainless steel.
• Equalizing resistors are required for current balance
through the multi-pole breakers.
• All elements are natural-air cooled (low losses).
• Cooling time of Rdump after complete discharge with max.
energy (160 kJ): Typically 10 min.
• Local controls and the supervision electronics mounted in
a single 3U Euro-chassis.
600 A Energy Extraction Facility
600 A warm cables 400mm2
Switch
A
Fuse
32 A

Switch
B
Snubber
Capacitor
0.8 mF
Switch
Z
Equalizing Resistors

each
600 A warm cables 400mm2
Block Diagram
Extraction
Resistance
Voltage
Measurement
Extraction Resistance
Temperature
A
Interlock
Switch
Status
S3A
S3-B
Switch
Control
B
S3-Z
Z
Switch
Control
Z
Mains
Control
230V
UPS Mains
Interface
0
WorldFip
B
Snubber C
Extraction Resistance
Switch
Control
A
AMS
Interface
1
FPA
OPEN - CLOSE
Fast
Power
Abord
Power
Interlock
Controller
Final Remarks
•
All components were designed, manufactured and tested in close
collaboration with CERN
•
The 234 Energy Extraction Systems represent 296 Tons of Components
•
89 % is procured through contributions from Non-Member States (11 %
from European Industry)
•
The total cost of the systems is 18 MCHF (European Reference Price).