Power Quality Karsten KAHLE Electric Power Converter Group (TE-EPC) High Power Converter Section Review of CERN’s Electrical Power Network October 2012

1. Definition of Power Quality 2. The Characteristics of the Load 3. Static Var Compensators – How do they work? 4. Performances of our SVC’s 5. SVC’s – Limitations 6. Consolidation and Upgrades Contents: 2 of 45

1. Definition of Power Quality 2. The Characteristics of the Load 3. Static Var Compensators – How do they work? 4. Performances of our SVC’s 5. SVC’s – Limitations 6. Consolidation and Upgrades Contents: 3 of 45

Power Quality = Quality of electrical energy supplied 4 of 45

Main Types of Network Disturbances Mains failure Voltage fluctuations due to pulsating active and reactive power Voltage dips due to short-circuit outside or inside CERN Harmonic voltage distortion due to non-linear load 5 of 45

Main Types of Network Disturbances Mains failure Voltage fluctuations due to pulsating active and reactive power Voltage dips due to short-circuit outside or inside CERN Harmonic voltage distortion due to non-linear load SVC 6 of 45

LHC Engineering Specification Main Parameters of the LHC 400/230 V Distribution System (EDMS , Sept. 2000) Nominal voltage400 / 230 V Max. voltage variations± 10 % Typical voltage variations± 5 % Max. voltage phase unbalance2 % Nominal frequency 50 ± 0.5 Hz Transients (spikes)1200 V for 0.2 ms Voltage swells+ 50 % of Un, 10 ms Voltage dips- 50 % of Un, 100 ms Max. total harmonic distortion (THD)5 % Typical total harmonic distortion (THD)2 % The following tolerance levels for user’s equipment are defined: 7 of 45

1. Definition of Power Quality 2. The Characteristics of the Load 3. Static Var Compensators – How do they work? 4. Performances of our SVC’s 5. SVC’s – Limitations 6. Consolidation and Upgrades 8 of 45

Two Types of Loads at CERN 9 of 45 Machine networks for power converters, RF, cryo, experiments General Services networks (stable networks) for lighting, cooling, a/c

Two Types of Loads at CERN 10 of 45 Machine networks for power converters, RF, cryo, experiments General Services networks (stable networks) for lighting, cooling, a/c

SPS Main Dipole Converters 12 stations in operation: SMD1 to SMD12 (+2 spares). Each station can be considered as a 12-pulse power converter. The potential of the DC system is floating with respect to earth of 45

SPS Machine Network 50% SPS 400 kV 18 kV EHT1 EHT2 EHT3 BEQ3 BEQ2 BEQ1 Harmonic filters -130 Mvar TCR 150 Mvar Harmon.filters -92Mvar Sat.Reactor 120 Mvar (Spare SVC) 50% SPS Harmonic filters -130 Mvar TCR 150 Mvar 12 of 45

Typical SPS supercycle in 2012 (with 1x North Experimental Area, 4x CNGS, 1x LHC pulses) Peak power = 150 MW, 2 Mio power pulses per year! SPS Main Dipole Converters 13 of 45

CERN Total Load 400 kV active power reactive power (Measurement taken in 1999) 14 of 45

1. Definition of Power Quality 2. The Characteristics of the Load 3. Static Var Compensators – How do they work? 4. Performances of our SVC’s 5. SVC’s – Limitations 6. Consolidation and Upgrades 15 of 45

Static Var Compensators (SVC’s) What are their functions? How do they work? a)Reactive Power Compensation b)Harmonic Filtering c)Voltage Stabilisation 16 of 45

Static Var Compensators (SVC’s) What are their functions? How do they work? a)Reactive Power Compensation b)Harmonic Filtering c)Voltage Stabilisation 17 of 45

reactive power 50% SPS TCR 150 Mvar Harmonic filters -130 Mvar a)Reactive Power Compensation 18 of 45

active power Reactive power taken from EDF is almost zero! Reactive power consumed by SPS Mains Reactive power generated by SVC reactive power (SPS) of 45 a)Reactive Power Compensation

Static Var Compensators (SVC’s) What are their functions? How do they work? a)Reactive Power Compensation b) Harmonic Filtering c)Voltage Stabilisation 20 of 45

Harmonic currents 50% SPS b) Harmonic Filtering of 45

Impedance diagram of the harmonic filters b) Harmonic Filtering (SPS) 22 of 45

active power b) Harmonic Filtering THD(U) (SPS) THD(U) on 18 kV busbar, EMD2/BE: 0.75 % max. THD(U) for ms: 2.3 % 23 of 45

Static Var Compensators (SVC’s) What are their functions? How do they work? a)Reactive Power Compensation b) Harmonic Filtering c)Voltage Stabilisation 24 of 45

load (active power) c) Voltage Stabilisation 18 kV bus voltage (SPS) ΔU (18 kV busbar) = ± 1.8 % (transient) ΔU (18 kV busbar) = ± 0.5 % 25 of 45

SVC’s and Harmonic Filters at CERN: -Total of SVC’s / filter inst.: 12 -Rated voltage:18 kV -Total surface:14’000 m 2 -Total value (prices 2007): 45 MCHF -Total capacitive power: 520 Mvar (=17 18 kV) 26 of 45

BEQ2 (2002) BEQ3 (2008) SVC’s for SPS 27 of 45

BEQ3 (2008) Thyristor Controlled Reactors (TCR) for SPS 28 of 45

1. Definition of Power Quality 2. The Characteristics of the Load 3. Static Var Compensators – How do they work? 4. Performances of our SVC’s 5. SVC’s – Limitations 6. Consolidation and Upgrades 29 of 45

Performance of the SVC’s for SPS reactive power compensationreactive power70 Mvar0…10 Mvar harmonic filteringTHD(U) (18 kV) 20 %0.75 % voltage stabilization 18 kVΔ U (18 kV) 14 %± 0.5 % ± 1.8 % *1) *1) for very fast transient changes (ramp-down) Without SVCWith SVC 30 of 45

SVC Meyrin for Booster 66 kV (Prevessin) 18 kV PA1 18 kV Meyrin network Station ME9, b. 212 Booster TCR Booster Filters Meyrin network LHC PA1 31 of 45

active power Harmonic Filtering THD(U) (Booster) Max. THD(U) on 18 kV busbar, Meyrin ME9: 0.7 % 32 of 45

load (active power) Voltage Stabilisation 18 kV bus voltage (Booster) ΔU (18 kV busbar) = ± 0.8 % 33 of 45

66 kV (Prevessin) 18 kV SVC PA2 18 kV SVC PA8 SVC PA6 SVC PA4 LHC machine and Experiments CMS ATLAS Meyrin -Booster - SVC Booster LHC Machine Network 34 of 45

active power Reactive Power Compensation Reactive power supplied by network Reactive power consumed by LHC in PA2 Reactive power generated by SVC reactive power (LHC PA2 with injection TI2) of 45

active power Harmonic Filtering THD(U) (LHC) Max. THD(U) on 18 kV busbar, EMD2/2E: 0.9 % 36 of 45

load (active power) Voltage Stabilisation 18 kV bus voltage (LHC PA2 with injection TI2) ΔU (18 kV busbar) = ± 1.9 % (transient) ΔU (18 kV busbar) = ± 0.5 % 37 of 45

1. Definition of Power Quality 2. The Characteristics of the Load 3. Static Var Compensators – How do they work? 4. Performances of our SVC’s 5. SVC’s – Limitations 6. Consolidation and Upgrades 38 of 45

Limitations Ability to control the voltage depends on SVC rating (ΔU ≈ Qsvc / Sk”) - SVC’s for SPS are very powerful (22% of Sk”) - SVC’s for LHC are quite small (only 8% of Sk” each) Response time of TCR typically 50 ms - Unsuitable for faster transient disturbances SVC’s themselves are sensitive to network disturbances - Power output is proportional (^2) to network voltage - Trip due to under- / overvoltage - Trip due to auxiliary power disturbances SVC’s themselves cause power quality issues: - TCR is a major source of harmonics (6-pulse) - capacitor inrush current causes transient overvoltage during energization (+30% for 10 ms) 39 of 45

1. Definition of Power Quality 2. The Characteristics of the Load 3. Static Var Compensators – How do they work? 4. Performances of our SVC’s 5. SVC’s – Limitations 6. Consolidation and Upgrades 40 of 45

SVC Booster / Meyrin filters - SVC can be repaired within a few hours / days (spare components) SVC’s for SPS machine -We require two SVC’s for machine operation -In addition, we have one hot spare system (BEQ1) -Switch-over within 1 hour SVC’s for LHC machine -All harmonic filters critical for LHC 7 TeV operation -LHC operation possible with one TCR tripped (3 remain in operation) -SVC can be repaired within a few hours / days (spare components) Degraded Mode and Redundancy 41 of 45

Consolidation of our SVC’s is a permanent process. - optimise shape of pulses with respect to power quality (with CCC operators) - increase reliability and improve operation: - new digital filter protection relays (LS1) - new PLC’s (LS1) - transient recorders for post-mortem analysis (LS1) - reliable auxiliary power source (LS1) - new earthing switches (LS1) - new thyristor valves (LS2) - improve performance - new digital control system (LS2) Consolidation of existing SVC’s 42 of 45

a)Future projects: Avoid large thyristor rectifiers, use AFE and energy storage (POPS technology) - Reduction of harmonic distortion and amplitude of active power pulses, cos(phi)=1 b) Machine networks at CERN -Machine networks supply pulsating loads / non-linear loads -Voltage stabilisation required (harmonic filters and TCR) c) General Services networks (stable networks) -Stable networks supply non-pulsating loads -No voltage stabilisation required (harmonic filters without TCR) Principles for Future Projects 1/2 43 of 45

d) Standardisation of SVC’s - Very little standardisation of existing SVC’s - Future SVC’s: Develop standardised harmonic filter designs and ratings - Use identical standardised harmonic filter components for all SVC’s (same ratings) - Standardised control system - Standardised TCR ratings 44 of 45 Principles for Future Projects 2/2

Booster 2 GeV project - Upgrade of existing thyristor power supply by ‘POPS-solution’ with AFE + energy storage Project: new spare SVC BEQ1 for SPS (EDMS ) - Replace obsolete SVC (satur. reactor) with modern SVC identical to BEQ2-3 (TCR) - Standardised design, using identical components as for BEQ2-3 - Commissioning end of LS2 For new machine network Meyrin: SVC with TCR proposed - Harmonic filtering and voltage stabilisation - Space is reserved close to new 66/18kV station Harmonic filters for Meyrin stable network proposed - Only harmonic filtering, without TCR Future Projects … 45 of 45

Questions?