Product: Power Factor & Harmonics: StacoSine: MGE filter presentation
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Transcript of Product: Power Factor & Harmonics: StacoSine: MGE filter presentation
1
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
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LVE PQc - J.Macdonald - 24/9/00
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Why is Power Quality Important? Increasingly Sensitive Loads
Increasing use of power electronics in equipment
Increasing emphasis on power system efficiency and maximum utilisation
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LVE PQc - J.Macdonald - 24/9/00
Division - Name - Date - Language 3
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
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LVE PQc - J.Macdonald - 24/9/00
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Types of Power Quality Problems Harmonics Impulses Transients Excessive Neutral Currents Wiring and Earthing Problems Interruptions Sags/Surges
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LVE PQc - J.Macdonald - 24/9/00
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Where do we fit in? Our specialities include:
• Harmonic Reduction• Neutral Current Reduction• Sag Reduction
These all contribute to an increase in Reliability
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LVE PQc - J.Macdonald - 24/9/00
Division - Name - Date - Language 6
What will we discuss? This presentation will deal specifically with:
• Harmonics– 3rd (150Hz)– Others
• Neutral Currents
• Drives Harmonics
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LVE PQc - J.Macdonald - 24/9/00
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Ready?
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LVE PQc - J.Macdonald - 24/9/00
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v i
Until recently, most electrical equipment drew current in a “linear” fashion:
• Current (i) is periodic, but not “sinusoidal”
vi
• Current (i) & Voltage (v) are both “Sinusoidal”
Today, many electrical loads draw current in a “non-linear” fashion:
Why are Harmonics Seen Today?
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LVE PQc - J.Macdonald - 24/9/00
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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:
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LVE PQc - J.Macdonald - 24/9/00
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What produces “Non-linear” Current?
• Computers
• Fax Machines
• Copiers
M • Variable Speed Drives
• Electronic Ballasts
• Almost anything electronic
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LVE PQc - J.Macdonald - 24/9/00
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The source of harmonic currents:
L1
ZCL2
L3
e1
e2
e3
iIIs
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, …
Ph
N
FL
Is
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LVE PQc - J.Macdonald - 24/9/00
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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 !
v
L
RC
U
r
D
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LVE PQc - J.Macdonald - 24/9/00
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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”:
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LVE PQc - J.Macdonald - 24/9/00
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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
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LVE PQc - J.Macdonald - 24/9/00
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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.
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LVE PQc - J.Macdonald - 24/9/00
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Harmonic problems can be traced to two phenomena:
Current Distortion Voltage distortion
• Note: current distortion causes voltage distortion
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LVE PQc - J.Macdonald - 24/9/00
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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 I II
I
ITHD
hh2
23
24
2
1
2
2
1100% 100%
Total Harmonic Distortion: Current
Causes additional heating in conductors and transformers, and leads to Voltage Distortion
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LVE PQc - J.Macdonald - 24/9/00
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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:
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LVE PQc - J.Macdonald - 24/9/00
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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
Ih
Vh
V I Zh h h
+-
Voltage Distortion:
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LVE PQc - J.Macdonald - 24/9/00
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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
V
V
VTHD
hh2
232
42
1
2
2
1100 100 % %
Total Harmonic Distortion: Voltage
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LVE PQc - J.Macdonald - 24/9/00
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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:
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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
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LVE PQc - J.Macdonald - 24/9/00
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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
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LVE PQc - J.Macdonald - 24/9/00
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Standard DY11 transformer
c
c
c
Phase A- 50 A
Phase B- 52 A
Neutral- 81 A
Phase C- 51 A
I1+ Ih
I1+ Ih
I1+ Ih
I3
200% Rated Neutral Issues
Note!
Note!Note!
Note!
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LVE PQc - J.Macdonald - 24/9/00
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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!
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LVE PQc - J.Macdonald - 24/9/00
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Transformer De-rating for NL Loads% Transformer Capacity vs % Non-linear load
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
% Non-linear Load
% T
rans
form
er C
apac
ity
% 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
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LVE PQc - J.Macdonald - 24/9/00
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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)
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LVE PQc - J.Macdonald - 24/9/00
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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
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LVE PQc - J.Macdonald - 24/9/00
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Motor de-rating curve
0 2 4 6 8 10 12
0.7
0.75
0.8
0.85
0.9
0.95
1.0
Harmonic Voltage Factor % (HVF)
De-
ratin
g Fa
ctor
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LVE PQc - J.Macdonald - 24/9/00
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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:
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LVE PQc - J.Macdonald - 24/9/00
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So how do we rid a network of harmonic currents and voltages?
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LVE PQc - J.Macdonald - 24/9/00
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Available Options:• A) Bracing • B) Blocking• C) Filtering • D) Phase shifting
Theory of Harmonic Mitigation:
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LVE PQc - J.Macdonald - 24/9/00
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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
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LVE PQc - J.Macdonald - 24/9/00
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B) BlockingExamples include: Line Reactors Isolation Transformers Employ magnetics to trap or
Impede the flow of harmonic currents
DIAGRAM (with reactors)
Ce1
e2
e3
MiIIs
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LVE PQc - J.Macdonald - 24/9/00
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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
M
Reducing the amount of harmonic current that flows through the transformer reduces the voltage distortion
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LVE PQc - J.Macdonald - 24/9/00
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Destructive interference of specific frequencies
Composite
+ 180o Phase Shifted harmonics
=Fundamental
1 3 5 7 9 11 13 15 17 19
1 3 5 7 9 11 13 15 17 19
D) Phase Shifting:
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LVE PQc - J.Macdonald - 24/9/00
Division - Name - Date - Language 37
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
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LVE PQc - J.Macdonald - 24/9/00
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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
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LVE PQc - J.Macdonald - 24/9/00
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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
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LVE PQc - J.Macdonald - 24/9/00
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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)
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LVE PQc - J.Macdonald - 24/9/00
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??End of Part 2
Questions&
Comments?
Coffee break!
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LVE PQc - J.Macdonald - 24/9/00
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The Product
Introducing the reason why we’re here…..
SineWave Active Harmonic Conditioner
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LVE PQc - J.Macdonald - 24/9/00
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LVE PQc - J.Macdonald - 24/9/00
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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.
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LVE PQc - J.Macdonald - 24/9/00
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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)
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LVE PQc - J.Macdonald - 24/9/00
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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
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LVE PQc - J.Macdonald - 24/9/00
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What’s inside? - Power Circuit
PWMINVERTER
(IGBT)
DC ENERGYSTORAGE
PWM REACTORS
OUTPUT FILTER
LINE REACTOR
+-
LN
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LVE PQc - J.Macdonald - 24/9/00
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What’s inside? - Signal Processor
Supply
Load
Sinewave
P N
Extraction of Harmonics
Regulation & Monitoring
Control Signal
Generation
Ct1
Control Electronics
Ct2
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LVE PQc - J.Macdonald - 24/9/00
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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
M M M
Final distributionenclosure
feeder 1 feeder 2 feeder 3
Secondarysw itchboard
Main LVSw itchboard (MLVS)
feeder 1 feeder 2 feeder ...n
LV
Active Filter
Active Filter
Active Filter
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LVE PQc - J.Macdonald - 24/9/00
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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.
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LVE PQc - J.Macdonald - 24/9/00
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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
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LVE PQc - J.Macdonald - 24/9/00
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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:
53
LVE PQc - J.Macdonald - 24/9/00
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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
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LVE PQc - J.Macdonald - 24/9/00
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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
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LVE PQc - J.Macdonald - 24/9/00
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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
56
LVE PQc - J.Macdonald - 24/9/00
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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
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LVE PQc - J.Macdonald - 24/9/00
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Hybrid Filter Benefits
ReliabilityCost
Capability
Passive
Hybrid
Active
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
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LVE PQc - J.Macdonald - 24/9/00
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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
M
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LVE PQc - J.Macdonald - 24/9/00
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CT Positioning
A BWhich position is correct, A or B ?
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LVE PQc - J.Macdonald - 24/9/00
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CT Positioning Cont...
SinewaveCT’s
AF Breaker
Main ACB
Bus Bars
MCCB
MCCB
MCCB
MCCB
MCCB MCCB
MCCB
MCCB
MCCB
MCCB
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LVE PQc - J.Macdonald - 24/9/00
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CT Positioning Cont...
Bus Bars SinewaveCT’s
AF Breaker
Main ACBMCCB
MCCB
MCCB
MCCB
MCCB
MCCB
MCCB
MCCB
MCCB
MCCB
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LVE PQc - J.Macdonald - 24/9/00
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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!!
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LVE PQc - J.Macdonald - 24/9/00
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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!
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LVE PQc - J.Macdonald - 24/9/00
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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.
65
LVE PQc - J.Macdonald - 24/9/00
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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 !
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LVE PQc - J.Macdonald - 24/9/00
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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.
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LVE PQc - J.Macdonald - 24/9/00
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Thank You!(Any Questions?)