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Power Quality
Karsten KAHLE Electric Power Converter Group (TE-EPC)
High Power Converter Section
Review of CERN’s Electrical Power Network24.-26. 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
0 50 100 150 200 250 300
-1.5
-1
-0.5
0
0.5
1
1.5
Time [ms]
Vol
tage
[per
Uni
t]
Undisturbed Power System
4 of 45
Main Types of Network Disturbances
0 50 100 150 200 250 300
-1.5
-1
-0.5
0
0.5
1
1.5
Time [ms]
Vol
tage
[per
Uni
t]
Mains Failure
0 50 100 150 200 250 300
-1.5
-1
-0.5
0
0.5
1
1.5
Time [ms]
Vol
tage
[per
Uni
t]
Voltage Dip due to Short Circuit
0 10 20 30 40 50 60 70 80 90 100
-1.5
-1
-0.5
0
0.5
1
1.5
Time [ms]
Vol
tage
[per
Uni
t]
Harmonic Distortion
0 50 100 150 200 250 300 350 400 450 500
-1.5
-1
-0.5
0
0.5
1
1.5
Time [ms]
Vol
tage
[per
Uni
t]
Voltage Fluctuations due to Load Variations
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
0 50 100 150 200 250 300
-1.5
-1
-0.5
0
0.5
1
1.5
Time [ms]
Vol
tage
[per
Uni
t]
Mains Failure
0 50 100 150 200 250 300
-1.5
-1
-0.5
0
0.5
1
1.5
Time [ms]
Vol
tage
[per
Uni
t]
Voltage Dip due to Short Circuit
0 10 20 30 40 50 60 70 80 90 100
-1.5
-1
-0.5
0
0.5
1
1.5
Time [ms]
Vol
tage
[per
Uni
t]
Harmonic Distortion
0 50 100 150 200 250 300 350 400 450 500
-1.5
-1
-0.5
0
0.5
1
1.5
Time [ms]
Vol
tage
[per
Uni
t]
Voltage Fluctuations due to Load Variations
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
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LHC Engineering SpecificationMain Parameters of the LHC 400/230 V Distribution System
(EDMS 113154, Sept. 2000)
Nominal voltage 400 / 230 VMax. voltage variations ± 10 %Typical voltage variations ± 5 %Max. voltage phase unbalance 2 %Nominal frequency 50 ± 0.5 HzTransients (spikes) 1200 V for 0.2 msVoltage swells + 50 % of Un, 10 msVoltage dips - 50 % of Un, 100 msMax. 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
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Machine networks for power converters, RF, cryo, experiments
General Services networks (stable networks) for lighting, cooling, a/c
Two Types of Loads at CERN
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Machine networks for power converters, RF, cryo, experiments
General Services networks (stable networks) for lighting, cooling, a/c
6kA
150 MW25 kV
18 kV
+15°
-15°
+15°
-15°
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.
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SPS Machine Network
EHT2400/18kV 90MVA
EHT3
European Grid 400 kV
EHT1400/18kV 90MVA
400/18kV 90MVA
50% SPS
400 kV
18 kV
EHT1 EHT2 EHT3
BEQ3 BEQ2 BEQ1
Harmonic filters -130 MvarTCR 150 Mvar
Harmon.filters -92MvarSat.Reactor 120 Mvar
(Spare SVC)
50% SPS
Harmonic filters -130 MvarTCR 150 Mvar
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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
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F2 F3 F5TCR F7 F11 F13 HF1 HF2Pulsating
TransformerEHT2
EMD2/BE 18 kV
Load
reactive power
50% SPS
TCR150 Mvar
Harmonic filters -130 Mvar
a) Reactive Power Compensation
18 of 45
activ
e po
wer
Reactive power taken from EDF is almost zero!
Reactive power consumed by SPS Mains
Reactive power generated by SVC
reac
tive
pow
er
(SPS)
1919 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
F2 F3 F5TCR F7 F11 F13 HF1 HF2Pulsating
TransformerEHT2
EMD2/BE 18 kV
Load
Harmonic currents
50% SPS
b) Harmonic Filtering
2121 of 45
Impedance diagram of the harmonic filters
LCf res 2
1
b) Harmonic Filtering(SPS)
22 of 45
activ
e po
wer
b) Harmonic FilteringTH
D(U
)
(SPS)
THD(U) on 18 kV busbar, EMD2/BE: 0.75 %
max. THD(U) for 20-60 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
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load
(act
ive
pow
er)
c) Voltage Stabilisation18
kV
bus
vol
tage
(SPS)
ΔU (18 kV busbar) = ± 1.8 % (transient)ΔU (18 kV busbar) = ± 0.5 %
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SVC’s and Harmonic Filters at CERN:
- Total of SVC’s / filter inst.: 12- Rated voltage: 18 kV- Total surface: 14’000 m2
- Total value (prices 2007): 45 MCHF
- Total capacitive power: 520 Mvar (=17 kA @ 18 kV)
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BEQ2 (2002)
BEQ3 (2008)
SVC’s for SPS
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BEQ3 (2008)
Thyristor Controlled Reactors (TCR) for SPS
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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 compensation reactive power 70 Mvar 0…10 Mvar
harmonic filtering THD(U)(18 kV)
20 % 0.75 %
voltage stabilization 18 kV Δ U(18 kV)
14 % ± 0.5 %± 1.8 % *1)
*1) for very fast transient changes (ramp-down)
Without SVC With SVC
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SVC Meyrin for Booster
66 kV (Prevessin)
18 kV PA1
18 kV Meyrin networkStation ME9, b. 212
BoosterTCR
BoosterFilters Meyrin Meyrin
network
LHC PA1
31 of 45
activ
e po
wer
Harmonic FilteringTH
D(U
)
(Booster)
Max. THD(U) on 18 kV busbar, Meyrin ME9: 0.7 %32 of 45
load
(act
ive
pow
er)
Voltage Stabilisation18
kV
bus
vol
tage
(Booster)
ΔU (18 kV busbar) = ± 0.8 %33 of 45
66 kV (Prevessin)
18 kVSVCPA2
18 kVSVCPA8
SVCPA6
SVCPA4
LHC machine and Experiments
CMS
ATLAS Meyrin- Booster- SVC Booster
LHC Machine Network
34 of 45
activ
e po
wer
Reactive Power Compensation
Reactive power supplied by network
Reactive power consumed by LHC in PA2
Reactive power generated by SVC
reac
tive
pow
er
(LHC PA2 with injection TI2)
3535 of 45
activ
e po
wer
Harmonic FilteringTH
D(U
)
(LHC)
Max. THD(U) on 18 kV busbar, EMD2/2E: 0.9 %
36 of 45
load
(act
ive
pow
er)
Voltage Stabilisation18
kV
bus
vol
tage
(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
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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
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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 1212714)
- 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 …
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Questions?
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