power quality & harmonics -...

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Power Quality & Harmonics

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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)



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


Six 125 HP VT VFD w/3% LR


(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

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


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


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

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