power quality & harmonics -...
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Power Quality & Harmonics
SM
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Mario Teti
Schneider Electric
Business Development Manager
Mario Teti is a Business Development Manager with the Schneider
Electric in the Power Solutions Group. He has worked for the
company for sixteen years and has twenty-three years experience in
Power Quality, including Power Factor Correction, Sag Mitigation
and AccuSine Active Filters. Mario has an Electrical Engineering
degree from Ryerson University in Toronto, Ontario.
Your Moderator
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6
LEARNING
OBJECTIVES
Define how harmonics are created on systems
Identify how harmonics affect electrical systems
Identify how IEEE 519 defines harmonics
Identify conventional harmonic mitigation methods
Upon completion of this
presentation, you should be
able to:
›
Hany Boulos
Harmonics Mitigation Expert
Hany Boulos, Business Development Manager,
Global Power Quality Correction Group, based
out of Toronto, Canada. Hany has over 33 years
in this industry. Hany studied Electrical
Engineering at Concordia University in Montreal
and worked for Westinghouse, Siemens, and
ABB before joining Schneider Electric North
America. Hany has presented and taught Power
Quality around the world in places such as
Australia, Europe, South Africa, Egypt, South
America and Saudi Arabia.
.
Your
Presenter
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Phase unbalancedSags/swells overvoltage
Notches Spikes
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Power factor
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Typical power quality issues in today’s electrical network
Flicker
Harmonics
Fundamental
3rd Harmonic
5th Harmonic
7th Harmonic
3rd
5
7th
Active Power (kW): Produces Useful Work
Reactive Power (kVAR)
Sets up Magnetic Fields
Total Power (kVA)
What you Pay For!
• Similarly, motors require REACTIVE power to set up the magnetic field while the ACTIVE
power produces the useful work (shaft horsepower). Total Power is the vector sum of
the two & represents what you pay for:
The Power Triangle:
Power Factor:The Beer Analogy
Mug Capacity = Apparent Power (KVA)
Foam = Reactive Power (KVAR)
Beer = Real Power (kW)
Power Factor = Beer (kW)
Mug Capacity (KVA)
Capacitors provide the Foam (KVAR),
freeing up Mug Capacity so you don’t have
to buy a bigger mug and/or so you can pay
less for your beer !
kVARReactive
Power
kWActive
Power
kVAApparent
Power
Should we be concerned about harmonics ?
• “ We don’t have harmonics in our facility ”
• “ Our devices don’t cause harmonics “
• “ Harmonics have never been a problem before…”
Distortion: what is it ?
• A linear waveform is a sinusoidal and
periodic waveform (current or voltage)
• A non-linear (or distorted) waveform is any
periodic waveform (current or voltage)
which is non-sinusoidal
Distortion and Harmonics
• A distorted waveform can be represented
as the sum of its Harmonics
Fundamental
3rd
Harmonic
5t1h
Harmonic
7th
Harmonic
3rd
5
7th
Fundamental
3rd
Harmonic
5t1h
Harmonic
7th
Harmonic
Fundamental
3rd Harmonic
Harmonic basics
What are harmonics?
A harmonic is a component of a periodic
wave having a frequency that is an integer
multiple of the fundamental power line frequency
Characteristic harmonics are the
predominate harmonics seen by the
power distribution system
Predicted by the following equation:
Hc = characteristic harmonics to be expected
n = an integer from 1,2,3,4,5, etc.
p = number of pulses or rectifiers in circuit
Harmonic Frequency
1 60 Hz
2 120 Hz
3 180 Hz
4 240 Hz
5 300 Hz
6 360 Hz
7 420 Hz
: :
19 1140 Hz
5th Harmonic
7th Harmonic
Resultant
Waveform
1 npHc
Multipulse
converters
Hc = np +/- 1
Hc = characteristic harmonic
order present
n = an integer
p = number of pulses
Hn
1 phase
4-pulse
2 phase
4-pulse
3 phase
6-pulse
3 phase
12-pulse
3 phase
18-pulse
3 x x
5 x x x
7 x x x
9 x x
11 x x x x
13 x x x x
15 x x
17 x x x x
19 x x x x
21 x x
23 x x x x
25 x x x x
27 x x
29 x x x
31 x x x
33 x x
35 x x x x x
37 x x x x x
39 x x
41 x x x
43 x x x
45 x x
47 x x x x
49 x x x x
Harmonics present by rectifier design
Type of rectifier
Skin Effect
The cables resistance may
increase due to skin effect. Skin
effect is a case where unequal
flux linkages across the cross
section of the cable causes the
AC current to flow on the outer
periphery of the conductor.
What are Harmonics?
Harmonic basicsWhy a concern?
Current distortion
Added heating, reduced capacity in :
Transformers
Conductors and cables
Heating effect proportional to harmonic
order squared
Nuisance tripping of electronic circuit breakers
(thermal overload)
Blown fuses
Detrimental to capacitors
Detrimental to generators
Heating of windings
Detrimental to UPS
UPS can’t supply the current
Loads
Ih
Vh = Ih x Zh
Adding harmonics in a network…
60 Hz = 1 heating unit (amp)
5th order = 25 heating units (amps)
7th order = 49 heating units (amps)
11th order = 121 heating units (amps)
Heating Effect:
Harmonics create heat in units proportional to the square
of the harmonic order.
Harmonic basics
Voltage distortion
Interference with other electronic loads
Faulting to destruction
Creates harmonic currents in linear loads
Generator regulators can’t function
Shutdowns
Not compatible with standard PF caps
Potential resonance condition
Excessive voltage
Overheating of PF correction capacitors
Tripping of PF protection equipment
Shutdown/damage to electronic equipmentLoads
Ih
Vh = Ih x Zh
Harmonic-producing loads
Motor speed controls UPS
Servos
+ many more
HarmonicsDetecting harmonics in your network
How common is this power
quality problem?
Over $20 billion of power semiconductor products installed annually
Computers and peripherals, IT devices, VFD, UPS, and industrial power supplies
35 – 40% of all power flows through power semiconductors today
Growth to 70% in the next few years
Occasional
Frequent
Acute
Problems
Heating effects
AC motor winding and bearing destruction
Damage to loads, transformers, cables, etc.
HarmonicsDetecting harmonics in your network
Amplification of current between capacitor and transformer
Current distortion rises
Voltage distortion rises
Main transformer and/or capacitor fuses blow
Equipment damage
M M M
Utility
VFD
Harmonics and standard capacitors
• A Radio uses Resonance to Capture a Station:
AMP
Antenna
Spkr
Variable Capacitor
f1
f2
f3
How Harmonics Affect Capacitors:
Resonance:
X flL 2
Xfc
C 1
2
XL
XC
Z
Resonancefr fX
X
L
C
1
fr
( XL-Xc )
How harmonics affect capacitors:
Mixing harmonic loads with
standard capacitors
Before unfiltered capacitor installation After unfiltered capacitor installation
De-tuning a network:
“Force” the resonant point away from naturally occurring harmonics
Ih5
I<h5>
Z
f
A
f 5f 3 f 7 f 9f 1
4.2 Harmonic (252 Hz)
We control the impedance of
these two elements
Power factor correction with harmonics:
Total power factor
TPF = (DPF) x(Distortion factor)
DPF =KW
KVA f= Cos
Distortion factor =1
1 + THD(I)2
TPF = Total or true power factor
DPF = Displacement power factor
Distortion factor = Harmonic power factor
= Cos d
Variable frequency drive (PWM type)
DPF = 0.95
THD(I) = 90%
(no DC choke & no input line reactor)
Distortion factor =
TPF = 0.95 x 0.7433 = 0.7061
1
1 + 0.92
= .7433
Total power factor example
Harmonic BasicsTotal Power Factor (TPF)
●Example: Variable speed drive (6-pulse PWM type)
388.0408.095.0
408.0)21(
1
%200
95.0
2
TPF
DF
THDi
DPF
882.0928.095.0
928.0)4.1(
1
%40
95.0
2
TPF
DF
THDi
DPF
No DC choke & no input line reactor3% Z input line reactor & no DC choke
Previously:
ANSI Standard IEEE 519-1992
Issues addressed:
THD(V) delivered by utility to user (Chapter 11)
THD(V) must be < 5% [< 69 KV systems]
Defines the amount of TDD a user can cause (Chapter 10)
Based upon size of user in relation to power source
Table 10.3 for systems < 69 kV
Defines limits for voltage notches caused by SCR rectifiers – Table 10.2
Defines PCC (point of common coupling)
Recent changes:
ANSI Standard IEEE 519-2014New issues addressed:
THD(V) must be < 8% [<= 1 KV systems]
For MV and HV services the limits are the same as in the 1992 standard
LV services voltage distortion limits were 5% and without any apparent issues;
now it was raised to 8%.
The current distortion remains the same as IEEE 519-1992
Defines PCC (point of common coupling)
New with
IEEE 2014
ANSI Standard IEEE 519-2014
Where is the PCC (point of common coupling)?
The PCC is usually the point in the power system closest to the user where the
system owner or operator could offer service to another user (mainly the HV side)
IEEE 519
Defines current distortion as TDD
Total demand distortion
Largest amplitude of harmonic current occurs at maximum load of nonlineardevice – if electrical system can handle this it can handle all loweramplitudes
Always referenced to full load current
Effective meaning of current distortion
Defines voltage distortion as THD
Total harmonic voltage distortion
Does not use THD(I)
Total harmonic current distortion
Instrument measurement (instantaneous values)
Uses measured load current to calculate THD(I)
• Total Harmonic Distortion: Current
• 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:
Causes additional heating in conductors and transformers, and leads to Voltage Distortion
• Expressed as a %, THD is of little value
• Total Demand Distortion is becoming accepted
I
I I I
I
I
ITHD
h
h22
32
42
1
2
2
1
100 100L
% %
Evaluating Severity of Harmonics
IEEE 519
TDD and THD(I) are not the same except at 100% load
As load decreases, TDD decreases while THD(I) increases
Example:
Harmonic standards
Most harmonic problems are not at the PCC with utility.
Typically harmonic problem occur:
Within a facility
With generator & UPS operation
Where nonlinear loads are concentrated
Need to protect the user from self by moving the harmonic mitigation requirements to where harmonic loads are located
Typically applied per device
Line reactors/DC bus chokes/isolation transformers
5th harmonic filters (trap filters)
Broadband filters
Multipulse transformers/converters
System solution
Active harmonic filter
Conventional harmonic
mitigation methods
The system solution
The system solution:
Single point of responsibility for the “total” harmonics
One specification for harmonic definitions
One validation responsibility and guarantee
Standard nonlinear products
3% input line reactors on most non-linear devices, 3% DC bus choke okay for PWM VFD
Limits rms current at load for diode rectifiers
Avoids interaction with snubber circuit for SCR rectifier
Best cost and performance
Compatible with all nonlinear products
Compliance with harmonic specifications
Controls harmonic levels with facility
Active harmonic filter
AHF Load
L
CT
Source
Is
Ia
I l
~
AHF
Parallel connected
Is + Ia = Il
Ia includes 2nd to 25/50th harmonic current
Is <5% TDD
Application of AccuSine
Sourcenon linear
load
active
conditioner
I.s I.h
I.ac
I. source I. Harmonics
-2-1,5-1
-0,50
0,51
2
1,5
=+-2
-1,5-1
-0,50
0,51
1,52
-2-1,5-1
-0,50
0,5
1
2
1,5
-2-1,5-1
-0,50
0,51
1,52
I. Active Conditioner I. resultant
Typical system solution example
A 125 HP variable torque 6-pulse VFD with 3% LR
Required AHF filtering capability = 47.5 amperes
Two 125 HP VT 6-pulse VFD w/3% LR
Required AHF size = 84.4 amps
Three 125 HP VT 6-pulse VFD w/3% LR
Required AHF size = 113.5 amps
Six 125 HP VT VFD w/3% LR
Required AHF size = 157.6 amps
(not 6 x 47.5 = 285 amps)
AS off AS onOrder % I fund % I fundFund 100.000% 100.000%3 0.038% 0.478%5 31.660% 0.674%7 11.480% 0.679%9 0.435% 0.297%11 7.068% 0.710%13 4.267% 0.521%15 0.367% 0.052%17 3.438% 0.464%19 2.904% 0.639%21 0.284% 0.263%23 2.042% 0.409%25 2.177% 0.489%27 0.293% 0.170%29 1.238% 0.397%31 1.740% 0.243%33 0.261% 0.325%35 0.800% 0.279%37 1.420% 0.815%39 0.282% 0.240%41 0.588% 0.120%43 1.281% 0.337%45 0.259% 0.347%47 0.427% 0.769%49 1.348% 0.590%TDD 35.28% 2.67%
Example of active
filter performance
Active filter injection
Source current
At VFD terminals
45
●Main Goal
● Comply with harmonic standards and reach a TDD level
below 5%
●2 solutions
Active Harmonic Filters for multiple standard VFD
● Active Harmonic Filter (AccuSine PCS+ 60,120,200 or 300A) :
● For groups of multiple ATV600 & ATV900, up to 630kw each
● Achieve a TDDbelow 5%
● AC or DC chokes are needed at VFDs level (3-5% Z) to
meet 5% TDD
● Can also be used to compensate for harmonics from non-
VFD loads on the same bus as well as to provide PFC for
line connected motors
‘Low Harmonic’ drives up to 630kW “ATV680 & ATV980”
● One enclosure with ATV680 & ATV980, complete with AFE module
● 380 to 480 V, 50/60Hz, IP23 & IP54, THDi < 5%
●Can achieve a PF of 100%
ATV
M
AFE
2 ways to achieve ‘Low Harmonic’ system
2
End-User
< 5% TDD
46
AFE VSD Harmonic
Solution
AFE VSD main building blocks
A
C
S
o
u
r
c
eLCL
Filter
Converte
r
Inverte
r
DC
Bus
AC
Motor
IGBT IGBT
AFE Drive advantages 1. It’s normally more cost effective for
application with one large drive in
comparison to AHF.
2. It has a foot print advantage over the
AHF for installation of one or two
drives.
3. It will be compliant to IEEE 519 when
operating as Low Harmonic Drive
when transmitting full load power.
4. It has a high power factor, going as
high as 99% lagging, for most
application it will have a lower kVA
demand than AHF combined with 6-
pulse VSD.
5. It’s capable of re-injecting power into
the grid during dynamic breaking,
therefore yielding some operation
expenses saving during these
instances.
AHF PCS+ advantages
when
Combined with standard
6-pulse VSD
+
1. When the AHF is sized appropriately,
compliance to IEEE 519-2014 is attained
regardless of the VSD loading.
2. One AHF can correct for multiple 6-pulse
VSD unlike an AFE VSD where you need
one for each drive product, making AHF
more cost effective for multiple drive
application, especially when redundant
pumps are present.
3. AHF have less losses compared to AFE
Drive, therefore it reduces the installation
operating cost over time.
4. AHF introduces less switching ripple than
AFE because it uses a higher commuting
frequency, therefore reducing the risk of
interaction with other loads present in the
network.
5. AHF can simultaneously correct PF and do
load balancing while mitigating harmonic,
therefore improving the overall power
quality of the installation.
AHF PCS+ advantages
when
Combined with standard
6-pulse VSD
+
6. The AHF parallel installation makes it easy
to retrofit an installation and it also
increases the continuity of service,
basically the drive can still operate even
though the AHF is off line.
7. The AHF can easily be integrated in MCC
or in switch gear which can optimize the
installation footprint and reduce
construction costs.
8. Generally speaking, 6-pulse VSD are
more robust and less complex than AFE
VSD, therefore reducing maintenance
frequency and complexity when they are
combined with AHF.
9. AFE VSD offer begins at 110 KW and
increases with KW rating. AHF advantage
is that it be applied to all KW ratings (from
0.75 KW to 900 KW).
Harmonics Generated by LED Lighting (15W)
Flicker producing loads
Rock crushers
Automobile shredder
Arc welder
Large motor
Var injection
High speed VAR injection
Combination of passive & active technologies
+
• Use fix caps for inrush support
• Always on line
• Instant response
• Use AccuSine for fine tuning
• Injects leading or lagging VARs
• Cancels fix caps leading VARs at
no load
• Adds leading VARs as loads
increase
• One half cycle response
Hybrid Approach
HVC Performance
HVC
-1000
-500
0
500
1000
1500
2000
0 2 4 6 8 10 12 14 16 18
Time in cycles
Vars
Lead
ing
/Lag
gin
g
Fixed Kvar
Load
Accusine
Result Kvar
Voltage problems – basics
Chronic voltage problems
Voltage outside ±10% for > 60 seconds
Voltage sag
Voltage < 90% for ½ cycle to 1 minute
Interruption
Voltage < 10% for >3 cycles
95% of voltage quality problems
Chronic voltage problems
Brownout – intentional reduction in grid voltage
External: line drops & brownouts
Sure-Volt ™ - Voltage regulator
• The standard Sure-Volt™:
• Microprocessor controlled tap-switching
• Input voltage range: +10 to -25% (528V to 360V)
• Output regulation: ±3%
• Response time: 1 cycle typical
• Overload capacity: 1000% for 1 second
• No load or power factor limitations
• Independently regulated, shielded, isolated output
• Fan-free and maintenance-free
• Single or three phase
• 5 to 3,000 kVA
• 50 or 60 Hz
• Any input or output voltages up to 600v
Voltage problems – basics
Chronic voltage problems
Voltage outside ±10% for > 60 seconds
Voltage sag
Voltage < 90% for ½ cycle to 1 minute
Interruption
Voltage < 10% for >3 cycles
A sub-cycle problem
Voltage sags
Source: EPRI DPQII
Not much going on here
Many more sags than interruptions
Sag Fighter™
Protection from:• Deep voltage sags
- Down to 30% Nominal 1 or 2 phase sag
(down to 144V on 480V)
- Down to 60% Nominal 3 phase sag
(down to 288V on 480V)
• Voltage imbalance
• Phase shifting
• Waveform distortion
Without energy storage
Lowest Cost & Eco-Friendly Sag Protection
Sag Fighter™ - UPS Comparison
UPS Sag Fighter
First cost, typical installation $210K $210K
Annual service contract $7K N/A
Annualized wear parts (batteries)* $13K N/A
Annual energy losses** $43K $4K
Total annual operation & maintenance cost $63K $4K
10 year total owning cost (First + 10x annual O&M) $840K $250K
*24 to 30 month replacement cycle **UPS: 90% efficiency - $0.10/kw-hr
Typical 500 kVA, 480V – 5 minute battery capacity UPS
30% of UPS Cost and No Battery Disposal
Page 63Confidential Property of Schneider Electric |
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