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:

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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

Contents:

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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

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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:

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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

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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

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CERN Total Load 400 kV

active power

reactive power

(Measurement taken in 1999)

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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

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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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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

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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

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F2 F3 F5TCR F7 F11 F13 HF1 HF2Pulsating

TransformerEHT2

EMD2/BE 18 kV

Load

Harmonic currents

50% SPS

b) Harmonic Filtering

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Impedance diagram of the harmonic filters

LCf res 2

1

b) Harmonic Filtering(SPS)

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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

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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

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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

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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)

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activ

e po

wer

Harmonic FilteringTH

D(U

)

(LHC)

Max. THD(U) on 18 kV busbar, EMD2/2E: 0.9 %

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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 %

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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

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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

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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

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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

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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?