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Matti Lehtonen

Harmonics in power systems of ships with electrical propulsion drives

Part 1. Effects on the equipment

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VTTTECHNICAL RESEARCH CENTRE OF FINLAND

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VTT TIEDOTTEITA - MEDDELANDEN - RESEARCH NOTES 1722

Hannonics in power systems of ships with electrical propulsion drives

Part 1. Effects on the equipment

Matti Lehtonen

VTT Energy

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TECHNICAL RESEARCH CENTRE OF FINLAND

ISBN 951-38-4877-9 ISSN 1235-0605Copyright © Valtion teknillinen tutkimuskeskus (VTT) 1996

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Cover figure: ABB Marine.

VTT OFFSETPAINO, ESPOO 1996

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Portions of this document may be illegible in electronic image products. Images are produced from the best available original document

Lehtonen, Matti. Harmonics in power systems of ships with electrical propulsion drives. Part 1. Effects on the equipment. Espoo 1996, Technical Research Centre of Finland, VTT Tiedotteita - Med- delanden - Research Notes 1722. 24 p.

UDC 621.431.74:629.1.066:62-83Keywords power equipment, ships, propulsion, drives, electric drives, electric propulsion, equipment,

marine propulsion, electric power generation

ABSTRACT

In this report the effect of harmonics on the power system equipment and loads, with special attention given to the circumstances in ships, is discussed. Some guidelines are given for the computation of additional harmonic losses in power cables and transformers. It is also shown, that if the system is rich in harmonics, these losses must be taken into account when sizing the equipment.

The effect of harmonics on electrical machines is also discussed. The influence on induction machines is usually small However, in large synchronous machines a significant degree of harmonic losses may be expected. Especially in the high voltage system the harmonics must be taken into account when selecting the machine ratings.

Also the harmonic resonances, which may arise when using reactive power compensation capacitors, are discussed. Due to the risk of harmonic resonances, the use of capacitors is not recommended in marine power systems.

Also the immunity of different load devices to harmonic distortion is discussed. The equipment considered are resistive loads, discharge lamps, universal machines and electronic equipment. Finally a brief survey is given on the standards and recommendations for the maximum distortion levels allowed.

3

PREFACE

This report is the first in the series of two reports concerning the harmonic effects and problems in marine electrical power systems, with special attention given to the electrical propulsion drives.

The first report concentrates on the harmonics related issues in general, discusses the possible measures by which the problems due to the voltage or current distortion can be mitigated or avoided and outlines the maximum permissible harmonic levels in the low voltage part of the marine power systems.

The second report in turn focuses on the effect of different types of converters on the voltage distortion. The aim is to give an objective and independent comparison between different converter techniques nowadays common in propulsion drives.

The reports have been prepared at the request of ABB Industry Oy, Marine Division. The contact person at ABB has been Mr. Juha Koukkari, who submitted material on measurements made during sea trials of several newly built vessels.

A contribution was also given by Mr. Mikko Koskela of ABB who performed some simulations in order to produce raw material for the harmonic analysis. Many thanks also go to Mr. Oscar Martelin, now with ABB Industry Oy, who worked at VTT Energy collecting material for the analysis.

The author has been responsible for all the analyses of harmonic effects presented in the two reports. The computer software used for the harmonic analyses in the model power system was built at VTT Energy. The author alone is also responsible for all the analyses of the computations.

The author hopes, that these two reports will be of valuable guidance when engineering reliable marine power systems with no harmonic related disturbances and when selecting and planning electrical propulsion drives for new ships.

In Espoo, 5. October, 1995

Matti Lehtonen

4

THE AUTHOR

Matti Lehtonen (1959) received his degrees of Master of Science and Licenciate of Technology, both in electrical engineering, from the Helsinki University of Technology, Espoo, Finland, in 1984 and 1989 respectively, and the degree of Doctor of Technology from the Tampere University of Technology, Tampere, Finland, in 1992.

From 1984 to 1987 he was with the Consulting Company Ekono, planning industrial power systems and developing computer-aided design systems. Since 1987 he has been with the Technical Research Centre of Finland (VTT), the present position being Head of the Research Group for Power Distribution Systems.

His main areas of interest are harmonics, reactive power compensation, earth-fault related problems and automation in electrical distribution networks. Mr. Lehtonen has published several international papers on harmonics related issues.

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5

VTT, Technical Research Centre of Finland

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7

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In the field of energy systems VTT Energy concentrates on four focal areas. In energy economy it develops models and methods to be applied to the planning and optimization of energy production systems including energy supply and production in power utilities and in the process industry. It also analyses options available for the operation in more open electricity markets and investigates district heating systems and energy storage alternatives.

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8

CONTENTS

ABSTRACT.............................................................................................................................3

PREFACE................................................................................................................................4

THE AUTHOR....................................................................................................................... 5

VTT.......................................................................................................................................... 7

CONTENTS.............................................................................................................................9

SYMBOLS AND DEFINITIONS....................................................................................... 10

1 INTRODUCTION....................................................................................................12

2 EFFECTS OF HARMONICS ON POWER EQUIPMENT................................ 12

2.1 Power cables.............................................................................................................. 122.2 Power transformers...................................................................................................162.3 Induction motors....................................................................................................... 172.4 Synchronous machines..........:................................... ..............................................172.5 Meters and protective relays..................................................................................... 182.6 Power capacitors.......................................................................................................18

3 EFFECTS OF HARMONICS ON ELECTRICAL LOADS................................20

3.1 Resistive loads............................................................................................................ 203.2 Discharge lamps.........................................................................................................213.3 Other load equipment............................................................................................... 21

4 DISTORTION LIMITS BY STANDARDS......................................................... 22

5 CONCLUSIONS......................................................................................................23

REFERENCES...................................................................................................................... 24

9

SYMBOLS AND DEFINITIONS

SYMBOLS

C capacitance

Cz oversizing factor due to harmonic losses (p.u.)

f frequency

fr resonant frequency

Ieq equivalent fundamental frequency load current, current that imposes losses equal to the distorted reference current

Ii fundamental frequency component of the load current

In harmonic current of order n

Ir rated sinusoidal current

L power system short circuit inductance,relative lamp life

LCI load commutated inverter

n harmonic order

Pi overall power losses by load current

Pit, power losses due to harmonics

PWM pulse width modulated converter

R„ resistance at nth harmonic component

Ro DC resistance

S rated power

u rms voltage

v harmonic order

10

a frequency dependence parameter of transformer resistance

(3 frequency dependence parameter of transformer resistance

DERNmONS

THD = H Jf^ (%)

u1 V n=2

THD, total harmonic distortion:

where Ui is the fundamental frequency voltage and U%... U50 are the voltages of the 2...50 voltage harmonic components. In this case THD is defined in %. A Similar definition can be given for the load current.

Udev = 100 * max [ u(t) - ui(t) ] ; t = 0...T

Voltage deviation:

where u(t) is the instantaneous value of the total voltage waveform and Ui(t) is the instantaneous value of the fundamental frequency voltage component. T is the time of one fundamental frequency cycle period. The above equation is given in per cent.

11

1 INTRODUCTION

Electrical solutions have become more and more popular in the propulsion systems of marine vessels. This is mainly due to their superior operational characteristics and due to the flexibility they offer for the lay-out planning of the ship's machine room.

Electrical propulsion drives set new requirements for the planning and dimensioning of marine power systems, however. The most important issue is the increased harmonic distortion, which has to be taken into consideration when selecting the power system components and when planning the power distribution systems of the vessels.

In this report, the effects of harmonics on the equipment and loads of the electrical networks of ships are discussed. With regard to the power system components, the effect of harmonics to transformers, cables, machines and capacitors is analyzed. Guidelines are given for the selection of power system components in the systems with a high degree of harmonics. The possible problems with meters and relays also are discussed. In the case of electrical loads, especially the effect of harmonics on the illumination and electronic devices is studied. The standards and regulations, concerning the accepted distortion levels are reviewed.

2 EFFECTS OF HARMONICS ON POWER EQUIPMENT

Harmonics can cause problems to power equipment because of additional losses with a corresponding heating and deterioration of the load carrying capacity. In some cases excessive voltage stresses may also occur. These can be expected especially during harmonic resonances, which may arise when capacitors are used for reactive power compensation.

2.1 POWER CABLES

In the conductors of power cables, additional losses Pih are caused by the harmonic currents as follows:

P/A = 3 Yjln Rn

n=2(1)

12

where In is the n:th order harmonic current and Rn is the resistance of the cable conductor at the corresponding frequency. The resistance increases with frequency due to skin and proximity effect [1]. The conductor resistance in the frequency range of harmonic components can roughly be approximated as follows [1]:

Rn = Ro (1 + yj (2)

where ysx4

192 + 0.8 x4; 0<x<2.8

ys - -0.136 -0.0177 x + 0.0563 x2 ; 2.8<x<3.8

ys-----0.733 + 0.354 x ; x>3.8

and where Ro is the dc resistance (ohm/cm), f is the frequency and the parameter x can be calculated as x2=(87d)/(109 Ro)- The above equations only take into account the skin effect. The reported accuracy of Equation (2) is 1% [1].

0 .500 1000 1500 2000 Hz

Fig. 1. Phase resistance frequency dependence of a belt type, 10 kV power cable with 120 mm2 Cu conductors. Solid line: skin effect and proximity effect included. Broken line: only skin effect included.

13

Table 1. Typical maximum harmonic components in the load current of pulse width modulated (PWM) and load commutated converters (LCI). Values as a per cent of the fundamental frequency current.

Harmonic order PWM La

5. 30 207. 12 14

11. 6 913. 5 717. 2.5 419. 1.5 3

Table 2 . The additional losses in the power cables with cylindrical Cu conductors due to the harmonics in the load currents of PWM and LCf converters. Pm is the increase in losses (%), I is the equivalent 50 Hz load current (%). A is the conductor cross-section (mm2).

A: 70 120 150 185

PWM-load:

11.6

105.6

12.4

106.0

12.9

106.3

13.7

106.6

La-load:

P* 8.0

103.9

8.75

104.3

9.23

104.5

9.89

104.8

14

The effect of load current distortion on the losses in power cable conductors with some selected cross-sections is illustrated in Table 2. The examples given are calculated assuming that the load is composed of converters solely, and using the harmonics spectra shown in Table 1. In Table 2, the equivalent fundamental frequency load current Ieq directly equals the required oversizing of the cable, due to the additional harmonic losses. If only a fraction of the total load is converters, the additional losses Pm decrease with the square of the converter load. For instance, if 50% of the load is converters, the harmonic losses are only 25% of those given in Table 2. This leads to a corresponding decrease in the oversizing required. In the case of a 185 mm2 cable, the value of Ieq would be 101.7% and 101.2% for PWM and LCI loads respectively.

The values in Table 2 were calculated using Equation (2) for the conductor resistance frequency dependence. The figures given only consider the resistance increase due to the skin effect. They give good enough results for power cables with cylindrical conductors. In the case of belt type cables with sector shaped conductor cross sections, the proximity effect must also be taken into account. Due to the proximity effect, the resistances are slightly increased, as illustrated in Figure 1.

The losses in power cables also greatly depend on the way the sheaths are bonded. If these are connected to each other at both ends of the cable connection, circulating harmonic currents arise. These can increase the losses significantly. In the case of cables with larger cross-sections, the harmonic sheath losses can be almost equal to the harmonic conductor losses. Some guidelines for the computation of the harmonic sheath losses are given in Reference [2],

Table 3. Typical values of the frequency dependence parameters a and (3 of some 20/0.4 kV three phase power transformers.

S/kVA 200 500 1000 1600 2000

a 0.02 0.04 0.10 0.16 0.20

P 1.6 1.6 1.6 1.6 1.6

15

2.2 POWER TRANSFORMERS

Among the power system components, the derating due to harmonics is highest in transformers. The load losses of transformers Pi can be estimated as follows:

(3)

where 1% is the fundamental frequency load current, R@ is the direct current resistance of the transformer per phase, i„ is the per unit value of the n:th harmonic current and a and (3 are the parameters governing the frequency dependence of the transformer phase resistance. The values of these are most conveniently obtained through measurements. Typical values for MV and LV transformers are a = 0.02 - 0.2 and (3 = 1.6 - 2.0 [2]. It should be noted, that these parameters not only take into consideration the winding losses, but also those caused by stray fluxes in the metallic parts of the device, as in the transformer tank. However, the majority of these losses are due to the winding losses. Some examples of the values of parameters a and p are given in Table 3 for the MVZLV transformers of a European manufacturer.

The per unit oversizing factor of a. transformer c%, due to harmonic currents, can be computed as follows:

y.(l+anp)in(4)

where Ir is the rated current and Ii is the fundamental frequency component of the distorted load current considered. The sensitivity of the power transformers to the load current harmonics depends on the way the neutral is earthed. Since marine electricity usually is floating, i.e. the system neutral in unearthed, the harmonic components of the 3rd and its multiple orders do not penetrate through the transformer.

Examples of the oversizing factors c% of power transformers are given in Table 4. The load is assumed to be converters solely. It is seen that in the case of large transformers the oversizing required can be about 17 to 19%. For PWM converters c% is higher than for LCI converters. This is due to the much higher 5th order harmonic component. The oversizing factor varies approximately with the square of the load current distortion. For instance, if only 50% of the load were converters, the values for c% would be about 1.04 to 1.05 for a 2000 kVA transformer.

16

Table 4. Examples of oversizing factors cz computed for 20/0.4 kV three phase power transformers using the frequency dependence parameters of Table 3 and load current spectra of Table 1.

S/kVA 200 500 1000 1600 2000

PWM: 1.07 1.09 1.13 1.17 1.19LCI: 1.05 1.07 1.11 1.15 1.17

2.3 INDUCTION MOTORS

For harmonic frequencies, the slip of an induction machine is close to unity. Hence the current of the motors can be computed, if the harmonic voltages and the short circuit impedance of the machine at the frequency concerned are known. In practice, the impedance is dominated by the short circuit reactance, which varies almost linearly with frequency.

Harmonics cause additional losses in induction machines mainly as load losses in windings. In addition, some stray losses are induced in the metallic parts by magnetic fluxes. At normally accepted distortion levels, the increase in total losses due to harmonics is small. For instance, if the supply voltage distortion is 10%, the harmonic losses are 2 to 3% of the rated ones, with the corresponding derating of about 1 to 1.5% [3]. This applies to the losses of typical standard machines, which can be used in association with converter drives also. If the machine has not been designed with attention given to the supply voltage distortion, the derating can be somewhat bigger.

2.4 SYNCHRONOUS MACHINES

Synchronous generators are more sensitive to the harmonics than induction motors. In general, the relative harmonic losses are bigger for large machines with large winding cross-sections. For synchronous machines, there is a large variety of types and manufactures, however. Hence general data can not be given for their harmonic properties.

For secure operation, when selecting the rating of synchronous machines, the additional losses imposed by the harmonics produced by the propulsion drives must carefully be taken into account. However, usually the converters, generators and propulsion motors are supplied by the same manufacturer, who takes the responsibility for the compatibility of these devices.

17

2.5 METERS AND PROTECTIVE RELAYS

To the meters, the harmonics can cause excessive errors, if the measurement principle is based on the average value or peak value. For example, with a chopped sine wave signal at a firing angle of 45°, these kind of meters will indicate an rms value about 13% less than the true rms value. If the meter is designed to respond to the true rms value, however, the measurement is relatively immune to the waveform distortion [4].

Harmonics affect the protective relays in several ways leading to possible misoperations. Relays that depend on current or voltage zeroes for their operation are affected by the waveform distortion. The presence of the third order harmonics can cause the earth fault relays to false trip. However, the latter is not usually a problem in marine networks, since the system neutral is not earthed. Due to harmonics, the relays tend to operate slower and with higher pickup values. The changes are in most cases relatively small over the moderate range of distortion expected during normal operation. Harmonic levels of 10% and more require a careful selection of protective devices [5].

2.6 POWER CAPACITORS

The capacitors used for reactive power compensation are sensitive both to additional losses caused by harmonic currents and excessive stresses due to harmonic voltages. According to the standard IEC 70, the capacitors must be able to operate up to 110% of rated rms voltage and 130% of rated rms current. The maximum stresses are likely to be exceeded especially in the case of harmonic resonances. For these, two different cases can be distinguished (Figure 2). A series resonance can arise between the stray inductance of the supplying transformer and the capacitance of the compensation unit..

In distribution systems, the parallel resonance which may occur if a large part of the transformer load is nonlinear, is usually more dangerous.. The resonant frequencies can in both cases be estimated as follows:

Sr1

2k-JlC(5)

where C is the phase capacitance of the compensation unit and Lis the subtransient short circuit inductance of the network. This equation gives a rough estimate only. For detailed analysis the network components must be modeled separately for each frequency of interest, using the methods discussed in reference [6], for instance. Harmonic resonances may greatly increase the distortion. Consequently, in marine networks, which are rich in harmonics, the use of compensation capacitors is not recommended.

18

ft

T CE

Fig. 2. Resonances in electrical distribution networks, a) series and b) parallel resonance.

19

3 EFFECTS OF HARMONICS ON ELECTRICAL LOADS

3.1 RESISTIVE LOADS

A large share of power system loads can be modeled as passive resistances. These loads include for instance incandescent lightning and electrical heating. Here, with constant fundamental frequency voltage, the per unit increase in power due to the harmonics is limited to the voltage distortion factor squared. In this group of devices, the incandescent bulb is among the most sensitive ones with regard to the increased heating effects. A relative equation for the lamp life is:

L = -\ ; u = ■J(U2, + U22+...+U2n)/Ui (6)u

where u is the per unit rms voltage, Ui is the fundamental frequency voltage and k is the parameter for bulb life voltage dependence. A representative value for k is 13 [5]. Hence large distortion factors can significantly shorten the lamp life.

500 Hz 600

Fig. 3. 50% Flicker perceptibility curve for interharmonics (36 W fluorescent lamp with an inductive ballast) [7].

20

3.2 DISCHARGE LAMPS

The effect of harmonics on the discharge lamps depends on the type of the ballast. During normal lamp operation, the ballast functions as a series current limiting and smoothing element. With inductive ballasts, the influence of voltage distortion would be roughly described by the distortion factor. With the usually modest distortion factors, there will only be small changes in the lamp operation. In the presence of large interharmonics, there will however be an increased risk of flicker. Here the lowest frequency components are the most difficult, the most sensitive band being from about 20 to 80 Hz (Figure 3).

In typical customer installations it is often customary to provide the fluorescent lamps with reactive power compensation capacitors. However, due to the increased risk of harmonic resonances, the use of compensation capacitors is not recommended in marine power systems.

3.3 OTHER LOAD EQUIPMENT

The effect of harmonics on the universal machines, used in vacuum cleaners and hair dryers for instance, have been studied in Reference [8]. According to the results, the main effect is the additional losses and consequent heating. These devices are not very sensitive to harmonics, however. A typical additional temperature rise at the 10% supply voltage distortion is only from 1 to 3% of the rated temperature.

Regarding electronic equipment, harmonics may cause instantaneous disturbances in the devices which rely on the detection of zero crossing of the supply voltage signal [9]. Also converters, which sense for zero crossing to implement firing delays, appear to be vulnerable to distortion. Electronic loads are however often affected by waveshape rather than by harmonic magnitudes alone. Hence the distortion factor often is not a suitable measure of distortion effects on these loads. The voltage deviation factor is often used instead [5].

Voltage deviation effects are complex as the deviation is affected by both the harmonic amplitude and the harmonic phase angle. The amplitudes can be summed in order to provide the upper limit. Due to the phase angle differences however, the actual deviation can be substantially lower than the magnitude factor given by the arithmetic summation.

21

10

5

>3

3 1

0.5

0.2---------------------------------------------------------------

0.1 -------------------1—I—I---- ----------------------1 3 5 7 10 15 25 100

v ------- —

Fig. 4. Limit of immunity of electrical appliances to supply voltage harmonics according to Germanischer Lloyd [10]. Uv is the harmonic voltage and vis the harmonic number.

4 DISTORTION LIMITS BY STANDARDS

The matter of acceptable distortion levels can also be approached by the aid of standards, regulations and recommendations. According to Germanischer Lloyd, the electrical appliances which operate in conjunction with power electronics facilities in marine power supply systems should have at least the immunity to harmonics as is shown in Figure 4.

For the devices to operate correctly, there also must be some margin between the immunity of the appliances and the actual distortion levels. For the maximum allowed levels of individual harmonic components in marine power systems, there are no accepted recommendations or standards yet. However, according to Det Norske Veritas [11], the total harmonic distortion (THD) in voltage shall normally not exceed 10%. If this limit is exceeded, it is to be documented that no malfunction will be caused to equipment aboard. Hence, THD over 10% is accepted in the high voltage busbar, if it is ensured by careful design that the apparatus connected to the high voltage system has been selected according to the actual harmonic conditions. For low voltage systems, where general load appliances are used, 10% must be regarded as a strict limitation.

22

According to Lloyd's [12], the general limitation for voltage TED is set at 8%. The individual harmonic components of an order of more than 25 must not exceed 1.5% of the fundamental component. In addition, for the maximum voltage deviation allowed, 10% of the crest value of the sine wave is given.

5 CONCLUSIONS

In this report the effect of harmonics on the equipment and loads, with special attention given to the circumstances in ships, was discussed. It was shown, that in general the harmonic components cause additional losses in power cables and transformers. If the system is rich in harmonics, these losses must be taken into account when sizing the equipment.

The effect of harmonics on induction machines is usually small. However, in larger synchronous machines a significant degree of harmonic losses may be expected. Especially in a high voltage system the harmonics must be taken into account when selecting the machine ratings.

Due to the risk of harmonic resonances, the use of reactive power compensation capacitors is not recommended in marine power systems. This is also the case with regard to the capacitors associated with the fluorescent lamps.

Also the immunity of different load devices was considered. In general, a safe maximum limit for supply voltage total harmonic distortion in a low voltage system is 8% to 10%. However, in the case of electronic devices, the voltage deviation factor can be a better measure than THD. The corresponding maximum value for this can be selected 10%.

In a high voltage system, the limit of 10% for THD can be exceeded, if the compatibility of the power system equipment in ensured by careful design. This means that the rating of power cables, transformers and machines, connected to the high voltage busbar, are selected with a sufficient margin that allows for harmonic effects.

23

REFERENCES

1. Graneau, P. Underground power transmission. New York: John Wiley & Sons, 1979. 515 p.

2. Lehtonen. M. The effect of harmonics on the load carrying capacity of power system components in public distribution networks. ISEDEM93 Conference, Singapore 27 - 29 October. Singapore: IEEE Singapore section, 1993. Pp. 366 - 371.

3. Lehtonen, M. Harmonic losses and the load carrying capacity of power system components in industrial networks. 11th CIRED Conference on Electricity Distribution, Liege, 22 - 26 April. Liege: AIM, 1991. Pp. 5.2.1 - 5.2.6.

4. Wagner, V. E. et al. Effects of harmonics on equipment. Report of the IEEE Task Force. IEEE Transactions on Power Delivery 1993. Vol. 8, No. 2, pp. 672 - 680.

5. Ortmeyer, T. H. et al. The effects of power system harmonics on power system equipment and loads. Report of the IEEE Task Force. IEEE Transactions on Power Apparatus and Systems 1985. Vol. PAS-104, No. 9, pp. 2555 - 2563.

6. Arrillaga, J., Bradley, D. A. & Bodger, P. Power system harmonics. New York: John Wiley & Sons, 1985.336 p.

7. Mombauer, W. Flicker caused by interharmonics. Elektrotechnische Zeitschrift, 1990. ETZ-Archiv, Bd.12, H. 12, pp. 391 - 396.

8. Fuchs, E. F., Roesler, D. J. & Kovacs, K. P. Sensitivity of electrical appliances to harmonics and fractional harmonics of the power system's voltage. Part II: Television sets, induction watthour meters and universal machines. IEEE Transactions on Power Delivery 1987. Vol. PWRD-2, No. 2, pp. 445 - 455.

9. Ranst, A van. Harmonics, causes, consequences, remedial actions. Revue E, Vol. 110, No. 1, pp. 5 -14.

10. Germanischer Lloyd: Rules for the classification and construction of seagoing steel ships. Chapter 4 - Electrical installations. 1989 Edition.

11. Det Norske Veritas Classification AS: Rules for classification of ships. Newbuildings, Machinery and Systems Main Class. Part 4, Chapter 4, Electrical Installations. Hoevik, Norway: January 1995.

12. Lloyd's Register of Shipping: Rules and regulations for the classification of ships. Part 6: Control, Electrical, Refrigeration and Fire. London: January 1995.

24

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Vuorimiehentie 5, P.O.Box 2000, FIN-02044 VTT, Finland Phone internat. + 358 0 4561 Telefax + 358 0 456 4374

Series title, number and report code of publication

VTT Tiedotteita 1722 VTT-TIED-1722

Date Project numberJanuary 1996 N5SU00022

Authors) Name of project

Lehtonen, Matti 63LATVA

Commissioned by

Title

Harmonics in power systems of ships with electrical propulsion drivesPart 1. Effects on the equipment

Abstract

In this report the effect of harmonics on the power system equipment and loads, with special attention given to the circumstances in ships, is discussed. Some guidelines are given for the computation of additional harmonic losses in power cables and transformers. It is also shown, that if the system is rich in harmonics, these losses must be taken into account when sizing the equipment.

The effect of harmonics on electrical machines is also discussed. The influence on induction machines is usually small. However, in large synchronous machines a significant degree of harmonic losses may be expected. Especially in the high voltage system the harmonics must be taken into account when selecting the machine ratings.

Also the harmonic resonances, which may arise when using reactive power compensation capacitors, are discussed. Due to the risk of harmonic resonances, the use of capacitors is not recommended in marine power systems.

Also the immunity of different load devices to harmonic distortion is discussed. The equipment considered are resistive loads, discharge lamps, universal machines and electronic equipment. Finally a brief survey is given on the standards and recommendations for the maximum distortion levels allowed.

Activity unit

VTT Energy, Energy Systems, Tekniikantie 4 C, P.O.Box 1606, FIN-02044 VTT, Finland

ISSN and series title1235-0605 VTT TIEDOTTEITA - MEDDELANDEN - RESEARCH NOTES

ISBN951-38-4877-9

LanguageEnglish

Class (UDC) Keywords

621.431.74:629.1.066:62-83 power equipment, ships, propulsion, drives, electric drives, electric propulsion, equipment, marine propulsion, electric power generation

Sold by VTT Information ServiceP.O.Box 2000, FIN-02044 VTT, Finland

Pages Price group

Phone internat. + 358 0 456 4404Fax + 358 0 456 4374

24 p. A

VTT TIEDOTTEITA - MEDDELANDEN - RESEARCH NOTES

VTT ENERGIA - VTT ENERGI - VTT ENERGY

1621 Lehtonen, Matti, Karkkainen, Seppo & Partanen, Jarmo. Kokonaisvaltainen sahkolaitos- automaatiokonsepti Suomessa. 1995. 68 s. + liitt. 35 s.

1623 Takala, Juha. Siirtotiedoston rakennemaarittely. Versio 2.0. 1995. 25 s.

1628 Jokiniemi, forma, Kilpi, Klaus, Lindholm, Dona, Makynen, Jouni, Pekkarinen, Esko, Saira- nen, Risto & Slide, Ari. Vakavien reaktorionnettomuuksien ilmidt. 1995. 103 s.

1631 Halttunen, Veikko & Hokkanen, Markku. Tuotetiedonhallinta. Taustaa ja ratkaisuvaihto- ehtoja. 1995. 75 s.

1634 Isotalo, forma, Katainen, Antero, Lehtonen, Mikko, Pesonen, Olavi, Salonen, Tapio, Saaski, fuha, Hokkanen, Markku & Halttunen, Veikko. Konepajan piirrepohjainen tuotteen- ja tuotannonsuunnittelu. KOPSU-projektin loppuraportti. 1995. 86 s.

1635 Lehtonen, Matti (editor). EDISON - research programme on electricity distribution auto­mation 1993 - 1997. Interim report 1994. 1995. 89 p. + app. 7 p.

1637 Hanhijarvi, fussi & Takala, fuha. Tietosuojasta. 1995. 23 s.

1638 Takala, fuha, Uuspaa, Pentti & Silventoinen, Marko. Uudet tiedonsiirtotekniikat. 1995. 82 s. + liitt. 31s.

1648 Solantausta, Yqd & Kurkela, Esa. Feasibility of electricity production from biomass by gasification systems. 1995. 51 p.

1653 Ahonen, Markku, Kosonen, Risto, Kekkonen, Veikko & Wistbacka, Magnus. Kaukolam- mdn paluuvetta hyodyntava rakennuksen ilmastointi- ja lammitysjaijestelma. 1995. 65 s. + liitt. 16 s.

1660 Koponen, Pekka, Lemstrom, Bettina & Ikonen, fuhani. Sahkonjakelun energianhallintajar- jestelma. Rajapinnat ja tiedonsiirtotarpeet. 1995. 74 s. + liitt. 23 s.

1668 Farin, fuho, Lehtonen, Matti & Leino, Kalevi. Sahkdntoimituksen keskeytykset ja muut sahkdn laatutekijat sahkontoimitusehdoissa. 1995. 20 s. + liitt. 20 s.

1670 Kekkonen, Veikko, Sipila, Kari & Ahonen, Markku. Kaukolammdn kayttovarmuuden optimointi. 1995. 43 s. + liitt. 1 s.

1671 Vanttola, Timo. Reaktoriturvallisuuden tutkimusohjelma (RETU) vuosiksi 1995-1998. 1995. 43 s. + liitt. 12 s.

1677 Lemstrom, Bettina, Peltola, Esa & Lehtonen, Matti. Tuulivoima ja keskijanniteverkon jan- nitetason hallinta. 1995. 59 s.

1678 Lehtonen, Matti, Harmand; Yves, Huber, Andreas, di Lembo, Giorgio & de Vylder, fulius. Fault management in electrical distribution systems. 1995. 28 p.

1681 Lemettinen, Lotta, Virtanen, Yrjo & funttila, Vesa. Energiajaijestelmien elinkaaritietojen laatuarviointi. "Okoinventare fiir Energiesysteme" -tietokanta. 1995. 34 s. + liitt. 68 s.

1686 Laitinen, Heikki & Ranta, Tapio. Puupolttoaineisiin kytkeytyvan liiketoiminnan kuvaami- nen. 1995. 66 s.

1692 Aakko, Paivi, Kytd, Matti, Kokko, fussi, Rantanen, Leena, Karintaus, Antti & Pentikainen, fuha. Moottoribensiinin reformulointi paastojen vahentamiseksi Suomen oloissa. Bensiinin aromaattien, olefiinien ja T90-lampotilan vaikutus paastdihin. 1995. 63 s. + liitt. 30 s.

1695 Edelmann, Kari, Malinen, Pekka, Ryymin, Risto, Karlsson, Markku, Kaijaluoto, Sakari & Timofeev, Oleg. Tulistettu hoyry paperin kuivatuksessa. 1995. 24 s. + liitt. 34 s.

1696 Farin, fuho, Koponen, Pekka & Takala, fuha. Sahkdn laadun seuranta kaukoluettavalla energiamittarilla (Laatuvahti). 1995. 23 s. + liitt. 27 s.

1697 Lehtila, Antti. Uusien energiatekniikoiden ja paasttinvahennyksen potentiaali Suomessa. 1995. 73 s. + liitt. 8 s.

1706 Fagemas, Leena. Chemical and physical characterisation of biomass-based pyrolysis oils. Literature review. 1995. 113 p. + app. 2 p.

1722 Lehtonen, Matti. Harmonics in power systems of ships with electrical propulsion drives. Part 1. Effects on the equipment. 1996. 24 p.

1723 Lehtonen, Matti. Harmonics in power systems of ships with electrical propulsion drives. Part 2. Comparison between different converters. 1996. 30 p. + app. 4 p.

In this report the effect of harmonics on the power system equipment and loads, with special attention given to the circumstances in ships, is discussed. Some guidelines are given for the computation of additional harmonic losses in power cables and transformers.

The effect of harmonics on electrical machines is also considered. The harmonic resonances, which may arise when using reactive power com­pensation capacitors, are discussed. Next the immunity of different load devices to harmonic distortion is discussed. The equipment considered are resistive loads, discharge lamps, universal machines and electronic equip­ment. Finally a brief survey is given on the standards and recommendations for the maximum distortion levels allowed.

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ffects on the equipment