1.ac harmonic filters

7/30/2019 1.AC Harmonic Filters

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Ac harmonic filters



FILTER

FILTER

HVDC Main Components

T8396



AC Harmonic Filters



Idealised harmonic currents

Practical harmonic currents Characteristic harmonics

Theoretically cancelled harmonics

Non-characteristic harmonics

Types of Harmonic

T8395

Filter Design Objectives

Limit voltage distortion

Minimise reactive power imbalance

Minimise losses

Improve system performance



Idealised harmonic currents

Practical harmonic currentsCharacteristic harmonics

Theoretically cancelled harmonics

Non-characteristic harmonics

Types of Harmonic

T8395



Idealised Current Waveforms….

T8397



Combined Waveform…..

T8399



12 Pulse

Practical Harmonic Currents….

T8402



λ λ

π ω ω ω ω ω

λ

π ω ω ω ω ω

/

(cos cos cos cos cos ...

/

(cos cos cos cos cos ...

I I D

t t t t t

I I D

t t t t t

= − + − +

= + − + −

2 3 1

55

1

77

1

1111

1

1313

2 3 1

55

1

77

1

1111

1

1313

∆

Fourier Analysis

T8398



I I D t t t

t t

= − +

− +

4 3 1

1 1 1 1

1

1 3 1 3

1

2 32 3

1

2 52 5

π ω ω ω

ω ω

( c o s c o s c o s

c o s c o s . . .

Fourier Analysis

T8400



9

8

7

6

5

4

3

2

1

10 3020 40

Overlap angle (degrees)

I11

I1

11th Harmonic as a Percentage of Fundamental

T8404



0.2 0.4 0.6 0.8 1.0

1

2

3

4

5

H

a r m o n i c l i n e c u r r e n t % o

f

r a t e d f u n d a m

e n t a l

Transmitted power (PU)

11th

13th

Characteristic Harmonic Generation

T8405



0.5

0.4

0.3

0.2

0.1

0.2 0.4 0.6 0.8 1.0

5th

7th

Transmitted Power(PU)

H a r m o n i c l i n e c u r r e n t % o

f

r a t e d f u n d a m e n t a l

Theoretically Cancelled Harmonic Generation

T8407



100

10

1.0

0.1

0.01

0.00110 20 30 40 50

Harmonic Number

In

I1%

Typical Spectrum…

T8409



Orders n = 1, 2, 3, 4 etc.

AC system unbalance (NPS)

Transformer reactance phase unbalance

Pre-existing distortion

firing angle jitter

Non - Characteristic Harmonics

T8408



Filter

Zfn

System

ZSnIcn

Ifn

VSn

ISn

T8378



Rmin

X ( O h m s )

R(Ohms)

400kV System Harmonic Impedance

T8381

Rmax

2



Sasaram Filters

T8379

400kV

Double Damped

Filter

400kV

Double Tuned Filter



AC Filter Layouts…

Components mounted on the ground

Insulation and magnetic clearances

Two types of harmonic filter

Double damped filter

Double tuned filter

Key Interlocking System for safety - to permit access onlywhen filter is de-energised and earthed.



AC Filter Layouts Double Damped Filter



Admittance vs frequency for 400kV 112Mvar 3/13 double frequency filter

0.0000

0.0050

0.0100

0.0150

0.0200

0.0250

0.0300

0.0350

0 2 4 6 8 10 1 2 14 1 6 18 2 0 22 24 26 28 3 0 32 34 3 6 38 40 42 4 4 46 48 50 5 2 54

Harm onic

A d m i t a n c e

3/13th Double-Frequency Filter



Admittance vs frequency for 400kV 112Mvar 11/25 double frequency filter

0.0000

0.0050

0.0100

0.0150

0.0200

0.0250

0.0300

0.0350

0.0400

0.0450

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54

Harm onic

A d m i t a n c e

11/25th Double-Frequency Filter



Single frequencytuned filter

2nd Orderbroadband

damped filter

3rd Orderbroadband

damped filter

‘C’ Typebroadband

damped filter

Types of Filter

T8412



Advantages

Maximum attenuation at single harmonic

Low loss

Disadvantages

May be de-tuned

Off-circuit adjustment

Single Tuned

T8413



f1 f0 f2 Frequency

High Q

Low Q

Y

Effect of De-tuning

T8414



Advantages

Attenuation over a spectrum of harmonics

Less sensitive to de-tuning Disadvantages

Needs higher Mvar to achieve same performance as singletuned

Additional losses in resistor

2nd Order Damped

T8416



Tuned / Damped Filters

f1 f0 f2 Frequency

Damped filter

Tuned filter

Filter admittance

T8417



Single frequency

tuned filter

2nd Order

broadband

damped filter

3rd Order

broadband

damped filter

‘C’ Type

broadband

damped filter

Types of Filter

T8418



Advantages

Lower losses in resistor

Disadvantages Poorer performance than 2nd order

Additional cost of capacitor

3rd Order Damped

T8419



Advantages

lower losses in resistor

Better performance than 3rd order Disadvantages

Poorer performance than 2nd order

Additional cost of capacitor

May require off-circuit adjustment

C - Type

T8421



Advantages

Only one HV capacitor bank

Only one reactor subject to HV tests

Reduced number of filter arms

No minimum size

Improved redundancy

Low fundamental losses (double tuned)

Multiple Tuned Filters

T8422



Double Tuned Double Tuned

Double Tuned Filters

T8423



0.03

0.02

0.01

0

-0.01

0 10 20 30 40 50

Harmonic

A d m i t t a n c e ( m h o s )

G

B

Admittance Characteristic

(G= conductance, B= susceptance)

T1774



Main Capacitor

Corona Rings

Base Insulators

Horizontal MountedCans

LV Terminal

HV Terminal



Auxiliary Capacitor

Base Insulators

Steel Frames

HV terminal

LV terminal



Reactors

Spiders

Terminal

Coil

Base

Insulators

Pedestals



Resistors

Roof

Base

Insulators

Bushings



Thank You

1.ac harmonic filters

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