Product: Power Factor & Harmonics: StacoSine: MGE filter presentation

transcript

LVE PQc - J.Macdonald - 24/9/00

Division - Name - Date - Language 1

Now the learning...

Introduction to the topic of harmonics Why is Power quality Important? Causes of Harmonics Effects of Harmonics Standards Governing Harmonics

Why is Power Quality Important? Increasingly Sensitive Loads

Increasing use of power electronics in equipment

Increasing emphasis on power system efficiency and maximum utilisation

Definition of a Power Quality Problem A power quality problem is:-

“Any occurrence that manifests itself in voltage, current or frequency deviations that results in failure or miss-operation of

end-user equipment”

… a very broad problem

Types of Power Quality Problems Harmonics Impulses Transients Excessive Neutral Currents Wiring and Earthing Problems Interruptions Sags/Surges

Where do we fit in? Our specialities include:

• Harmonic Reduction• Neutral Current Reduction• Sag Reduction

These all contribute to an increase in Reliability

What will we discuss? This presentation will deal specifically with:

• Harmonics– 3rd (150Hz)– Others

• Neutral Currents

• Drives Harmonics

Ready?

Until recently, most electrical equipment drew current in a “linear” fashion:

• Current (i) is periodic, but not “sinusoidal”

• Current (i) & Voltage (v) are both “Sinusoidal”

Today, many electrical loads draw current in a “non-linear” fashion:

Why are Harmonics Seen Today?

Fundamental & all harmonics

The “Choppy”, non-linear current drawn by electronic loads is actually a “fundamental” (50hz) component plus many integer multiples of that fundamental frequency:

These “integer multiples of the fundamental frequency” are just higher frequency currents & they cause the problem

The Cause of Harmonic Currents:

What produces “Non-linear” Current?

• Computers

• Fax Machines

• Copiers

M • Variable Speed Drives

• Electronic Ballasts

• Almost anything electronic

The source of harmonic currents:

Single Phase Loads: Phase to Neutral Switch Mode Power Supplies

•PC’s, Electronic Lighting, Fax’s, Copiers, etc generate high 3rd harmonic primarily responsible for ‘Neutral Currents’

3-phase loads: Rectifiers / Chargers controlled Graetz bridges

•Drives, UPS generate high harmonic currents of orders 5, 7, 11, 13, …

The source of harmonic currents:

Single Phase Loads: Phase to PhaseEg. Welders, HID lighting generate high 3rd harmonic

• Those 3rd harmonics flow only in the phase conductors

lasts between 20 and 50 cycles !

Each type of load draws current in a unique way which produces a “signature” which determines the frequency of the harmonics present:

Typical 1 Phase Load

1 3 5 7 9 11 13

Typical 3 Phase Load

1 3 5 7 9 11 13

Harmonic “Signatures”:

Typical single load spectra’sPredominant harmonic spectrums for common loads

LoadLoad Type 3rd 5th 7th 9th 11th 13th

Distorted Composite Waveform

Personal Computer Single Phase

Office equipment Single Phase

Electronic Lighting Single Phase

High-bay Lighting Single Phase

Main frame computer

Three Phase

UPS Three Phase

6-pulse VFD Three Phase

12-pulse VFD Three Phase

Note: loads shown above produce smaller amounts of harmonics not specifically highlighted

Harmonic “Signatures”:

What this means is• We can predict which type of harmonic will be dominant

dependant upon the load profile• Knowing that, we know what the likely problems will be• Knowing that, we know what the likely solutions will be.

Harmonic problems can be traced to two phenomena:

Current Distortion Voltage distortion

• Note: current distortion causes voltage distortion

A measure of the amount by which a composite current waveform deviates from an ideal sine wave

Caused by the manner in which electronic loads draw current for only a part of a complete sine wave

Measured as THD:

I I II

1100% 100%

Total Harmonic Distortion: Current

Causes additional heating in conductors and transformers, and leads to Voltage Distortion

Overheating of conductors and insulation degradation Neutral overload * Increased transformer losses (need to over-size) Nuisance tripping of circuit breakers Neutral-earth potential * Significant voltage distortion on networks with generators Overheating and possible resonance with capacitors Lighting ballast failures PC monitor stroboscopic effect * Improper operation of microprocessor-based equipment * Re-injection of harmonic currents into the utility network.* Caused by third or triple-n (triplen) harmonics

Effects of current Distortion:

As those harmonic currents flow across the network impedance, they create a voltage drop at the same frequency as the harmonic current. This cause voltage distortion.

Network Z

V I Zh h h

Voltage Distortion:

A measure of the amount by which a composite voltage waveform deviates from an ideal sine wave

Caused by harmonic currents flowing across system impedance's

Causes erratic behaviour or failure of equipment sensitive to voltage waveform

Measured as THD:

V V V V

1100 100 % %

Total Harmonic Distortion: Voltage

Causes linear devices to draw non-linear current (resulting in current distortion effects)

Torque pulsation in motors Capacitor dielectric failure Insulation breakdown PC monitor and power supply failure Electronic lighting failure.

Effects of Voltage Distortion:

Sequence Components Any complex sinusoidal can be described by a series of positive, negative or zero sequence components. The fundamental plus all harmonics have a sequence (rotation) associated with them.

• Positive sequence voltages cause rotation in the positive direction• Negative sequence voltages cause rotation in the negative direction• Zero sequence voltages result in no rotation

• Note that all even harmonics cancel (due to symmetry)• Note that 5th & 11th (etc) harmonics cause a negative rotation (this causes torque pulsation in motors).• Note zero sequence components won’t cancel & don’t rotate

Sequence Components:Harmonic: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21Rotation: + - 0 + - 0 + - 0 + - 0 + - 0 + - 0 + - 0

3rd Harmonic Issue Third (triple-n) harmonics in the phase conductors add in

the neutral Neutral current can be up to 172% of phase currents

Third harmonics circulate in the delta winding, causing overheating of the Tx

Neutral conductors must be oversizedEddy current losses cause excessive heating in the

transformer: De-rating requiredStandard transformers DO NOT cancel harmonics

Standard DY11 transformer

Phase A- 50 A

Phase B- 52 A

Neutral- 81 A

Phase C- 51 A

I1+ Ih

200% Rated Neutral Issues

Note!Note!

Transformer De-rating Standard transformers experience excessive heating from harmonics:

• Increased Eddy current losses• Increased I2R losses• If the neutral conductors are 200% rated, so must the transformer have a 200%

rated neutral internally. Problem: no such “standard” transformer exists! In order to get 200% rated neutrals inside the transformer, you must

specify K-Rated transformers.OR

Standard transformers should be de-rated • if over-sized standard transformers are used, circuit protection must be suitably

under rated- this may cause nuisance tripping from transformer inrush.

Either option is expensive!

Transformer De-rating for NL Loads% Transformer Capacity vs % Non-linear load

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

% Non-linear Load

% Tx Capacity

A Transformer carrying 2/3 non-linear load needs to be doubled in size

Sources: (1) BSRIA (2) ANSI/IEEE Std C57.110

3rd Harmonic phenomenon - BreakersNuisance tripping can occur for several reasons:Residual current circuit breakers are electromechanical devices. They do not sum high frequency components and therefore can trip spuriouslyThe current flowing in the circuit will be higher than expected due to the presence of harmonic currents. The trip settings may therefore be incorrect.Peak sensing breakers may trip needlessly since the crest factor of distorted waveform may be high (Crest Factor = Peak/RMS)

Breakers with 200% rated neutrals Many specifier’s are calling for 200% rated switched-neutral

breakers• THEY DON’T EXIST

This forces manufacturers to supply double sized breakers (e.g. 200A for 80A phase current) In order to protect neutrals

When large incoming breakers are involved, it may require PARALLEL breakers to meet the specification.

• You cannot adequately co-ordinate parallel breakers. One will ALWAYS beat the other under a fault condition.

• This in turn causes problems of co-ordination with downstream breakers

Motor de-rating curve

0 2 4 6 8 10 12

Harmonic Voltage Factor % (HVF)

G5/3 is considered the standard across the UK for acceptable levels of THD

Stage 2 for Current Limits Stage 3 for Voltage limits

• Maximum 5% THD in voltage for LV systems• Maximum 4% THD for 11kV systems

HARMONIC 3 5 7 11 13 17 19 thdG5/3 LEVEL STAGE 2 (A)

34 56 40 19 16 6 6 -

G5/3 LEVEL STAGE 3 (%V)

4 4 4 4 4 4 4 5

U.K. Limits for THD:

So how do we rid a network of harmonic currents and voltages?

Available Options:• A) Bracing • B) Blocking• C) Filtering • D) Phase shifting

Theory of Harmonic Mitigation:

Examples include: Oversized neutrals Conductor spacing/ sizing Specifying maximum harmonic levels for equipment Isolation of harmonic loads Grouping Non-Linear (NL) transformers Non-Linear (NL) panelboards

Good practice anyway

A) Bracing

B) BlockingExamples include: Line Reactors Isolation Transformers Employ magnetics to trap or

Impede the flow of harmonic currents

DIAGRAM (with reactors)

Passive Filters Capacitor/Reactor combinations can be tuned to provide a low

impedance path to specific frequencies• Harmonic currents normally flow from source to utility. Filtering provides a

low impedance path for the harmonics so that they don’t flow to the utility.

C) Filtering

Reducing the amount of harmonic current that flows through the transformer reduces the voltage distortion

Destructive interference of specific frequencies

Composite

+ 180o Phase Shifted harmonics

=Fundamental

1 3 5 7 9 11 13 15 17 19

D) Phase Shifting:

Available Equipment:

A) K-Rated Txs; NL Panels

B) Line reactors, Isolation Transformers

C) De-tuned Capacitor/Reactor Systems

D) Active filter technology, Harmonic reducing transformers Phase Shifting

Blocking

Bracing

Filtering

Harmonic Mitigation

Designed to handle harmonic currents without overheating, or de-rating Relatively low cost Little chance of misapplication

Disadvantages of K-Rated Equipment Assumes neutral conductors also oversized Does not reduce or eliminate harmonics

• other equipment will still be affected May still introduce voltage distortion Over sizing may worsen harmonics

Advantages of K-Rated transformers

Very effective at reducing specific harmonics Very cost effective at 415V Power Factor Correction (demand reduction)

Disadvantages of Tuned L/C Filters Requires detailed network study for proper design Must not add additional capacitors without study: significant changes/

additions to network may change tuning point, lead to resonance Only suitable for removing a single offending harmonic

Advantages of Tuned L/C Filters

Advantages of line reactors Line reactors are relatively inexpensive when only a few drives are

in question, or if there is relatively little (<30%) drive load and the goal is to minimise harmonic problems

Disadvantages of line reactors & Isolation Tx’s Blocking reactors are not effective enough to reduce the harmonic

currents below the level of causing problems when large number of drives are present

Expensive when added to a large number of drives Isolation transformers DO NOT remove 5th, 7th, 11th, 13th, etc

harmonics, the primary output of the drives they are applied to!• They will only block Triple-n harmonics (3rd, 9th, 15th)

??End of Part 2

Questions&

Comments?

Coffee break!

The Product

Introducing the reason why we’re here…..

SineWave Active Harmonic Conditioner

The Product Sinewave was developed by MGE when they were wholly owned

by Schneider It is currently on its 2nd generation, having been in the market

since 1994 Employs digital electronics and IGBT

switches (Drive Technology) to measure and create and equal amount of harmonic current which it injects anti-phase into the network, thus cancelling the harmonics

It negates the need for 200% rated neutrals, K-rated transformers, etc.

The Product

Is a ‘plug n play’ black-box technology which is relatively easy to apply

Available in sizes from 20A RMSto 480 A RMS (60A to 1440A Neutral current)

Connects in parallel as any otherload

Require three xxx:1 CT’s(placement is critical)

Active Filter Technology:

N o n -lin e a r lo a d s

L in e a r lo a d sA c t iv e

F ilte r

What’s inside? - Power Circuit

PWMINVERTER

(IGBT)

DC ENERGYSTORAGE

PWM REACTORS

OUTPUT FILTER

LINE REACTOR

What’s inside? - Signal Processor

Supply

Sinewave

Extraction of Harmonics

Regulation & Monitoring

Control Signal

Generation

Control Electronics

Active Filter Topology:

Although Active Filters can be located in a variety of places, it’s best to locate as close to harmonic source as possible

Final distributionenclosure

feeder 1 feeder 2 feeder 3

Secondarysw itchboard

Main LVSw itchboard (MLVS)

feeder 1 feeder 2 feeder ...n

Active Filter

Active Filtration With the increase in variable speed drives and non

linear loads, harmonic filtration is becoming essential.

Power Factor of such loads is improving with a VSD typically 0.93 power factor.

IT loads increasing the amount of 3rd harmonic on the system

Neutral filtration becoming the norm. Conventional passive filtration

methods becoming limited. Mixing passive and active filters to

get most cost effective solution for high power applications.

Sinewave Active Filters Sinewave Active Filters are the best on the market for small/ medium

installations. Neutral filtration is an almost unique feature as others have no

neutral connection. The devices are plug and play and require little or no modelling

Sinewave is rated for filtration in the phase conductors, so is able to filter up to 3 times the phase output. For example a 20 amp active filter can filter up to 60 amps of 3rd harmonic in the neutral.

Filtration removes the cause of the problem not the effect.

The device is connected in parallel and as such does not add a potential point of failure as with a series connected device.

Active Filter TechnologySinewave active filters have significant benefits for filtering triple-N (3rd) harmonic current:

Active Filter Technology - 200% neutrals:By introducing Sinewave active filters at source, 200% neutral can be avoided

This has significant benefits:No need for costly 200% rated neutral bus-bars (standard ratings

can be used)No need for costly 200% rated switchboards (standard ratings

canbe used)No need for transformer de-rating (standard ratings can be used)

Standard product means reduced prices

and standard delivery

SineWave installed base:

Royal Opera House Chelsea building Society (Office) Sainsbury’s Homebase South West Water Land Registry (Office) Mersey Tunnel Manchester Airport East of Scotland Water North Devon Hospital

Buchanan House (Office) Seven Trent Water Axis Resources (Office) MOD Carlton Television Alsthom ...

Sinewave has been proven in the field with customers

Advantages of Active Filters: Removes almost 100% of harmonic current, Including

neutral currents! Highly effective Can not be misapplied: plug & play Simple operation No danger of resonance Can not be over-loaded Can filter 3rd harmonic (phase - neutral)

Disadvantages of Active Filters Expensive for large power applications Specialist maintenance

For hi power applications, we have the hybrid filter

Hybrid Filter Benefits

Cost-effective high power filtering of one specific harmonic via the passive elements means a smaller, thus lower cost, active element

Broadband filtering of all other harmonics via the active element 3rd harmonic filtration via the active element Low cost power factor correction via the passive element Greater reliability than either element alone

Hybrid filters combine the best attributes of both Active and Passive filters. By combining those two elements within one enclosure, they provide benefits over either element alone:

Non-linear loads

Linear loadsPassive

Filter

Hybrid Filter Benefits

ReliabilityCost

Capability

Passive

Hybrid

Active

Points of Connection

As with PFC, dependant on where the problem is

Main Incomer Sub board feeder Individual motors/

equipment

Golden Rule: The Golden Rule: The Sinewave CT Sinewave CT must must notnot see the AF output see the AF output

CT Positioning

A BWhich position is correct, A or B ?

CT Positioning Cont...

SinewaveCT’s

AF Breaker

Main ACB

Bus Bars

MCCB MCCB

CT Positioning Cont...

Bus Bars SinewaveCT’s

AF Breaker

Main ACBMCCB

Alternative Connection-up to 6 loads

Each Ct sized for total load(I.e. total = 1000amp each ct should be 1000/1)All CT’s in same directionP1P2 etcS1s connected togetherS2s connected together•Not Summated!!

Sizing Sinewave Determine if the goal is to meet G5/3 (G5/4) or to reduce the

requirement for 200% rated neutrals• The former is generally more expensive

For existing installations, take measurements• Contact PQc to arrange a harmonic survey

For new installations, supply a schedule of loads• Include primary transformer rating, % Impedance• Include a diversity factor

Rule of thumbs for budget purposes:• £200/Amp • 120A per 1000kVA Transformer (50% non-linear load)

Remember, it can always be expanded!

Use the survey form!

The Market Sinewave is sold via:

• MGE direct (generally into the UPS market), • through =SE=, • though J&P (Delta)

MGE prefer not to promote the product themselves, but rather leave it to us (it’s a tiny portion of the UPS business and too specialised for their general sales force)

Delta are not effective; having only one person to market and promote MGE are receptive to giving us exclusive channel rights in the UK.

The Competition: ABB offer an active filter that does not inject third harmonic and

therefore does not reduce or remove neutral currents. As such it will not overlap with our push into the commercial building markets.

ABB do offer a separate THF (third harmonic filter) but it is ineffective and causes many problems. It is not accepted in the marketplace.

Seimens offers an active filter but only as a front end to their 6 pulse drives

Claude Lyons offers an active filter but it is more costly and less effective than Sinewave

WE HAVE A DECIDED ADVANTAGE !

How do we move forward? Mention or ask about the 200% rated issue and sell our solution to

consultants and end users To leave behind a brochure that explains the issues and the

solution To arrange seminars to gain awareness

The key to success is awareness. It’s a relentless track that will get results.

Thank You!(Any Questions?)

Product: Power Factor & Harmonics: StacoSine: MGE filter presentation

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