Environmental AspectsEMC, radiation, UPS… Etienne CARLIER AB/BT/EC
Outline • Electrical Distribution • Architecture • Protections • EMC • Emission • Immunity • Shielding • Radiation
Electrical DistributionArchitecture • The LBDS kicker electrical distribution is based on a combination of • Normal supply for power components (power supplies…), and • Uninterruptible supplyfor control components (SCSS, BETS and TSDS). • High voltage and low voltage power suppliesare conform with the CE regulations. Normal power distribution system instabilities will not disturboperation • Apulse to pulse reproducibility of +/- 0.1% is guaranteed for a +/-10% mains variation, a 2% asymmetry between phases and a 3% variation of the mains frequency. • Surveillance of the electrical distribution system is included in the SCSS
Normal / Uninterruptible Supply FailureBETS BETSReference KickerPower Supplies BETSInterlock DumpRequest UPS Normal supply UPS Active fail-safe redundant logic • Normal supply failure • BETS reaction time is deterministic • Extraction trajectories are guaranteed within operational limits through the beam dump energy tracking interlock • Detection delay depends of the sensitivity of the BETS interlock windows, generator impedance, HV power supply hold-up time, machine mode and energy… • Uninterruptible supply (UPS) failure • BETS reaction time is not deterministic • Detection delay depends of impedance of electronics circuits, failure sequence of micro-controller, low voltage power supply hold-up time…. • BETS will fail due to the absence of power and issue a dump request (fail-safe logic) • A detection of the UPS failure faster than 80ms is achieved through a continuous surveillance of the UPS voltage
Normal / Uninterruptible Supply FailureTSDS Dump RequestReceiver Abort GapSynchronization TriggerFan out PowerTrigger HVGenerator UPS Active fail safe logic Passive fault tolerant redundant logic • Dump request distribution uses the “domino effect” • Energy required to distribute thedump requestup to the kicker HV generatoris • Pre-stored within capacitor at each stage of the triggering chain, • Used to trigger the next stage, and • Checked before a beam permit signal is issued • Normal Supply Failure • Uninterruptible supplies guarantee the correct propagation of the dump request up to the HV generator. • Uninterruptible Supply Failure (UPS) • Detected at the fail safe logic stages (“Client Interface”) • Propagation of the dump request to the HV generator relies on the ability of each passive stage of the triggering chain to maintain their output power capabilitiesin a correct operational windowsduring at least the 100 s following the detection delay, • An additional asynchronous beam dump will be triggered through a RTD unit 100 s after the detectiondelay.
Electro-Magnetic CompatibilityGeneral • Ready state : 99,99999….% of the time (Pulse Period) • Immunity to external electromagnetic perturbations • Pulse state : 0.00001… % of the time (Pulse Duration) • Emission of electromagnetic perturbations Kicker = Fast Pulsed Magnet Fast Transient [s] High Current [kA] Pulse Period + Duration Low Impedance[H & m or ]
Layout Magnet Electronic High Voltage Generator Coaxial Transmission Line
Assumptions • EMC perturbations issued by kicker systems are mainly in the High Frequency domain and are generated only during the “Pulse State”. • Components used in kicker systems and connected to the power distribution systems (mainly high voltage and low voltage power supplies) are conforming with the CE regulations and with the IEC norms for EMC emission & immunity and for Safety: • IEC 61000-3 / EN 50081-1 for EMC emission, • IEC 61000-6 / EN 50082-2 for EMC immunity, and with • EN 61010 for safety. • No specific measures implemented for immunity and emission through the connections to the mains networks (Normal and Uninterruptible). • No sensitivity to Low Frequency EMC perturbations is expected.
Operational Parameters *Value rated per system Extraction Kickers[MKD] Dilution Kickers[MKBH & V] Operational Range 450 GeV 7TeV 450 GeV 7TeV Number of generators / system 15 4 [H]6 [V] Current Pulse Rise Time 2.8 s 17.6 s [H]33.7 s [V] Current Pulse Duration >100 s(1.8 ms) >100 s(0.5 ms) Max. Switched Power * 16 kJ 10 kJ [H]18 kJ [V] Max. Peak Current * 270 kA 100 kA [H]150 kA [V] Max. dI/dt * 96 kA/s 5.5 kA/s [H]4.7 kA/s [V] Signal Spectrum 10 kHz 300 kHz 13.8 kHz [H]12.5kHz [V] Cable Return Resistance * 0.05 m 0.3 m [H]0.2 m [V]
Interconnections • Electrical distribution • Computer network • Machine timing system • Machine protection system • Access system • Beam instrumentation • Radio-frequency • Power converter • Vacuum system • Cooling • … A lot of possibilities for EMC coupling !!!
Interconnections (cont.) • Electrical distribution TN-S (3PH + N + E) • Computer network ??? • Machine slow timing system Common mode • Machine protection system Fibre optics + opto-coupler • Access system Isolated Floating contact • Beam instrumentation Common mode (PU) + Isolated blocking oscillator (Trigger) • Radio-frequency/prepulse Fibre optics • Power converter Fibre optics • Vacuum system Isolated Floating contact • … Try to “isolate” as much as possible interconnections between systems
PerturbationsImmunity • Kicker systems within the UA will be sensible during the “Ready state” to electromagnetic fields (if any) generated by other equipment due to ground loops. • Ground loops in the vertical plane exist and are composed by the high voltage generator, the transmission line, the magnet and the earth common mode impedance between RA & UA. • No possibilities to “physically” reduce these loops (…integration issues) .We have to live with them and act on the electromagnetic field sources (if any). • Immunity of trigger (re-trigger) systems to external perturbations has to be guaranteed (UA63 UA67). • Use of shielded cables and differential transmission for re-trigger signals. • Use of low impedance (50 ) coaxial lines for trigger signals. • Possibility to shield cable ladders in order to increase effectiveness of the cable ladders protection against external perturbations.
Generation of common mode voltages across RA & UA grounds / earths by the coaxial transmission lines during “Pulse State”: Transmission lines are composed of a set of parallel coaxial cables (impedance reduction), During the current pulse, a voltage difference is issued between both ends of the transmission lines due to the transfer impedance of the coaxial cable screen and to the cable’s screens skin effect for the return current, This difference of voltage generates a common mode voltage between RA and UA grounds / earths. This voltage is proportional to the current in the transmission line and to the ratio of the cable transfer impedance and the earth common mode impedance. “Ground jumps”across RA & UA during “Pulse State”: During a current pulse, part of the current (typ. 0,01% of Imax) will flow through the earth circuit and generate “ground jumps” between RA and UA proportional to the earth common mode impedance PerturbationsEmission
Perturbations: Emission (cont.) Radiated Emission • The difference of current between inner and outer conductors of the coaxial transmission lines generate an electromagnetic field around the transmission line itself Cable ladders[UA & RA] Transmission Line Cable ducts [UA RA]
PerturbationsEmission (cont.) • Equipment sharing the same earths in the UA & RA will be affected by Conducted Emission perturbations during kicker “Pulse State”: • Differential measurements will / can guarantee signal integrity. • Cables crossing / passing near kicker transmission lines between UA and RA will be affected by Radiated Emission perturbations during “Pulse State”: • Good cable shielding will / can protect the signals • Levels for Conducted Emission and Radiated Emission are difficult to quantify at this stage: • Measurements from prototype installations exist but coupling effects between generators will not be negligible • Quality of the earth system in the UA, in the RA and between UA & RA has not yet been quantified. The Conducted and Radiated Emission levels depend partially on this parameter.
ProtectionGrounding and Shielding Use EUROPA crates with ALODINE 1200 surface treatment for electronic hardware Extension of the equipotential up to the front of the rack through low impedance mechanical solution Grounding through an equipotential environment in the UA Measure cables properly shielded in the cable’s ducts (parallel to the transmission lines) between UA & RA with a simple steel tube
Radiation • Electronics for the control of the LBDS kickers is located in the UA • 80% digital Most critical (single event corruption) • 20% analogue • Electronic is always located below the level of the cable ducts between UA / RA Passive shielding with concrete • No special protection implemented • No worries for electronics in the UA after the test in TCC2 in 1999/2000 before decision • For the SCSS the situation is safe a failure in one of the “SAFE” component will automatically issue a dump request. • Redundancy helps. Probability to have a simultaneous “single event” affecting redundant components is low…