2004 IEEElPES Transmission & Distribution Conference & Exposition: Latin America 1

Upgrading Urban High Voltage Transmission Line: Impact on Electric and Magnetic Fields in

the Environment M. L. Pereira Filho, Member IEEE, J. R. Cardoso, Member IEEE, C. A. F. Sartori, Member IEEE, M. C . Costa,

B. P. de Alvarenga, A. B. Dietrich, L. M. R. Mendes, I. T. Domingues, J . C . R. Lopes

Abstract- This paper presents a case study related to the electric and magnetic fields generated by an upgraded high voltage overhead transmission line in an urban environment. Consideration of risk perception recommends a previous analysis of electric end magnetic fields. A computational model based on charge simulation method to calculate electric field and Biot- Savart law to calculate magnetic field Is outlined. Model validation is done by simulation and measuring o f electric and magnetic fields on neighborhood of the existing transmission Line prior upgrade. Results of simulation of electric and magnetic fields with the new transmission line configuration were assessed to verify compliance with exposure limits recommended by World Health Organization. Magnetic and electric fields were measured considering the new configuration of transmission Line.

Index Term- Biological effects of electromagnetic radiation, Electric field measurement, Electromagnetic fields, Magnetic field measurement, Power transmission lines.

1. INTRODUCTION

pgrading voltage and current of high voltage Utransmission lines (TL) on urban environment brings out changes on electromagnetic field (EMF) in the environment and also impacts esthetical aspects.

To prevent problems with the community that lives along the TL right-of-way (ROW), it is recommendable to execute a plan of risk communication, demonstrating that the upgrade will not bring further risks to the community.

To address this concern, this paper presents a computational model to calculate electric and magnetic fields generated by TL, measured fields values in the ROW prior the upgrading for model validation, a survey of human exposure limits to EMF, a simulation of the new TL configuration to verify compliance with exposure limits and a new measurement with TL operating after upgrade.

This work was partially supported by Eletropaulo AES. M. L. Pereira Filho is with IPT - Instituto de Pesquisas Tecnologicas,

Brasil (e-mail: mleitc@ipt.br}. J. R. Cardoso, C. A. F. Sartori, M. C. Costa, B. P. de Alvarenga, A. 8 .

Dietrich are with LMAG - Laboratono de Eletromagnetismo Aplicado, Department of Electrical Engineering, Escola Politknica da USP, Brasil (e- mail: cardoso@pea.usp.br, sartori@pea.usp.br, caldora@pea.usp.br, bemardo@pea.up.br, alvaro@pea.usp.br ).

L. M. Rodrigues, 1. T. Domingues, J. C. R. Lopes are with AES Eletropaulo, B r a d (e-mai I: ligia.mendes@AES.com, ivo.domin~ues~AES.com, julio.lopes@AES.com).

The TL addressed belongs to Eletropaulo, 88 kV operating voltage, double vertical circuit, two ACSR conductors 636 MCM per phase. The upgrade consisted to adjust the isolation voltage for 138 kV and to increase the phase current capacity. The operating voltage remains 88 kV.

11. COMPUTATIONAL MODEL There are many papers and books on calculation of EMF

from TL. [l] and [2] are well known references. This section outlines calculation methods for electric and magnetic field, assuming low frequency decoupling, flat ground and 2-D approach.

A . Electric Field Calculation

To compute electric field a model based on a charge simulation method derived from a previous work [3] has been used.

The basic principle of the CSM is that the potential $i at a given point, generated by a discrete set of n charges Qj can be found by:

& = Z Pij . Qj , j = 1 t on (1)

The coefficients P i j depend on the types of charge elements, such as line, ring etc., as described in the literature 141. This application uses line elements, leading to change charge Q, by linear density of charge 0,. In order to determine 0, it is necessary to impose boundary condition vaIue of 4 at m points on the surface of conductors and then solve the matrix system:

Once the vector io] is knew, (1) is applied to obtain the potential at any point. [o] and [$I are complex vectors, considering amplitude and phase density.

Electric field is calculated by potential $.

. _ of potential and charge

numerical derivative of

0-7803-8775-9104/$20.00 Q2004 IEEE 788

B. Magnetic Field Calculation , 2 1 2 l I I I

Magnetic field is calculated by Biot-Savart law, assuming cables modeted by linear infinite segment. Fig. 1 shows a infinite conductor carrying a current I, in phasor notation, in the direction of z axis (reader direction).

1

X

Fig. I , Application of Biot-Savart law

The amplitude of magnetic field density B is given by

IBI = pJ/ (2nR)

with R = sqrt((x - x,)’ + (y ~ yC)’)

Bx and By components are given by:

(3)

(4)

To calculate the total magnetic field Bt from a TL with N conductors on a point P (x,y), it’s necessary to do a summation over all the phase conductors, taking into account that both Bx and By are phasors:

Btx = C Bxi , i from 1 to N

Bty=CByi , i f iom 1 toN ( 5 )

IBtJ (rms) = sqrt(Btx2 + Bt$)

C. ModeI Validation The validation of the model was carried out through

simulations with the configuration of the TL prior the upgrade and measuring the values of the generated fields.

Fig. 2 shows the double circuit TL cross section. The horizontal clearance between circuits is 4 m. Clearance between phases of same circuit is 3.5 m. Lowest phase height is 7.8 in at middle span. Phase sequences on right and left circuit are respectively B-C-A and B-A-C, direction upward.

I - 0

...,,.,*.............:

kht-of-way 10 mwide I Fig. 2. Cross section of double circuit TL

Electric and magnetic fields were measured and simulated over the two lines indicated in Fig. 2, one at a horizontal profile at 1.3 m height, crossing the entire ROW, to assess fields values on people walking along streets under the TL.

The other line is a vertical profile at ROW edge, 5 m from the ROW center, to assess fields values on constructions already placed at the edge. These constructions have maximum height of 6 m. The vertical profile runs from 0 to 20 m height, In fact, the distance of measurement points to phase conductor is about 1.7 m, because it was necessary to use a mechanical safety device.

Magnetic field measurement was executed with an isotropic meter with three perpendicular field coils, with indication of each spatial field component as well the true rms value.

Electric field measurement was executed with a displacement current type meter, orientation of sensor determines the spatial component measured.

Fig 3 shows simulated and measured values of magnetic field on horizontal profile at 1.3 m height above ground. There is a good agreement between measured and simulated values. The deviations suggest a systematic error, perhaps on phase conductor height. However, typical difference is 13 YO, with higher values in simulated results.

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3

0 2 4 6 8 10 Distance from T L right-of-way center (m)

~

-Simulated H Measured

Fig 4 shows simulated and measured values of magnetic field on vertical profile at 1.7 m from ROW center, with height from 0 to 20 m.

100

m 80

Z 60

3' 40

- 90

.- a 70

5 % 50

.- U 30

2 0 A ! ! I ! : ! ; I : ! : !

- -U

r=

z 20 SI 10

0 2 4 6 8 10 12 14 16 18 20

Height from ground (m)

Fig. 4. Simulated and measured magnetic field values on vertical profile at 3.7 m from ROW center, with height from 0 to 20 m.

There is a good agreement between measured and simulated vaIues. Largest deviation is 18%. This result is consistent with an expected variation on distance between meter and phase conductor. Fig. 5 shows a typical measurement on vertical profile.

Fig 6 shows simulated and measured values of electric field vertical component on horizontal profite at 1.3 m height above ground.

There is a good agreement between measured and simulated values. The deviations have the same pattem of Fig. 3, with high values in simulated results. In this case, there is a tall wall at ROW edge, causing a reduction on electric field near ground.

Fig. 5. Typical measurement on vertical profile,

1-Simulated -+-Measured

0 2 4 6 8 10

Distance from right-of-my center (m)

Fig. 6. horizontal profile at 1.3 m height above ground.

Simulated and measured electric field vertical component Ey on

Fig 7 shows simulated and measured values of electric field horizontal component on vertical profile at I .7 m from ROW center, with height from 0 to 20 m.

It was not possible to use optical cable for this measurement and to avoid the presence of operator in the maintenance basket. As a result, electric field was disturbed. To minimize this disturbance, only the horizontal component was considered. There is a good agreement between measured and simulated values at phase conductors heights, with maximum deviation of 19%.

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4

-Simulated -+-Measured

I

I I 5 14 e

I I f I + t

0 5 10 1s 20

Height from ground (m)

w

Fig, 7. Simulated and measured electric field horizontal component Ex on vettical profile at 3.7 tn from ROW center, with height from 0 to 20 m.

Another set of comparison between measured and simulated values was performed on a garden square with higher phase conductor height. The results show good agreement either.

111. REGULATORY REQUIREMENTS There is no federal regulatory requirement for TL below

230 kV at the moment in Brazil. There is a technical standard NBR 5422 [SI from Brazilian Standards Association, d i n g a 5 kV/m electric field strength at ROW edge.

License contract from electric power regulatory agency ANEEL stipulate maximum magnetic field 83.3 pT. It's the same value recommended by ICNlRP [6], a non-governmental organization recognized by WHO - World Health Organization.

WHO established the International EMF Project in 1996 to assess the scientific evidence of possible health effects of EMF. The International EMF Project has compiled a worldwide standards database limiting exposure to EMF [7].

A expressive number of national organizations have formulated guidelines establishing limits for occupational and residential EMF exposure based on ICNlRP 163 publication. In this paper, ICNIRP [61 exposure reference levels were adopted as safety for human exposure to electric and magnetic field.

Reference levels for general public exposure for 60 Hz frequency are 4,16 kVlm for electric field and 83,3 pT for magnetic field density. These reference levels are applied to continuous exposition.

Iv. SIMULATION OF NEW CONFIGURATION

A. Technical Data Major changes on the new design were nominal current

980 A per phase, higher line height, with lowest phase at 1 I m from ground and, in some places, clearance between circuits

was 7 m.

voltage of 88 kV. Electric field simulation was performed with nominal

B. Simulation Results

Fig. 8 shows a magnetic field simulation on a horizontal profile at I .5 m height, Maximum magnetic field amplitude is 12.7 pT at ROW center.

0 2 4 6 8 10

Distance from right-of-way center (m)

Fig. 8. Simulated magnetic field values on horizontal profile at 1 . 5 m height above ground.

Fig 9 shows simulated and measured values of magnetic field on vertical profiles at ROW edge and 1.5 m outside ROW edge.

_ _ _ _ _ _ . 5.0 m -6.5 m

0 5 10 15

Height from ground (m)

Fig. 9. Simulated magnetic field values on vertical profile at 5.0 and 6.5 m from ROW center, with height from 0 to 20 m

Conceming magnetic field, Fig. 8 shows compliance with exposure limit 83.3 pT in ROW at 1.5 m height. Fig 9 shows compliance of magnetic field in height lesser than 8.8 m and greater than 18.2 m at ROW edge (5.0 m). Zoning regulation in this area requires a setback 1.5 m for build construction. In Fig. 9, 1.5 m away ROW edge is represented by curve 6.5 m, so, every build obeying zoning regulation will comply with exposure standard.

Fig. IO shows a electric field simulation on a horizontal

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profile at 1.5 m height. Maximum electric field strength is 1.53 kVlm at ROW center, I I

1 I I I 1

Of I I I I 0,O 2SJ 4,O 6,O 8,O 10,o

I Distance from ROW center (m) I Fig. 10. Simulated electric field strength on horizontal profile at 1.5 m height above ground.

Fig I 1 shows simulated values of electric field strength on vertical profiles at ROW edge and 1.5 m outside ROW edge.

*...._. 5.0 m -6.5 m

0 5 10 15 20

Height from ground (m)

Fig. 11. Simulated magnetic field values on vertical profile at 5.0 and 6.5 m from ROW center, with height from 0 to 20 m

Concerning electric field, Fig. 10 shows compliance with exposure limit 4.16 kV/m in ROW at 1.5 m height. Fig 11 shows compliance of electric field in height lesser than 8.2 m and greater than 18.6 m at ROW edge (5.0 m). In Fig. 11, 1.5 m away ROW edge is represented by curve 6.5 m, so, every build obeying zoning regulation will comply with exposure standard, same situation presented to magnetic field.

C. Measurement with new configuration

Measurements were carried out in horizontal profile 1 .O m height. A maximum electric and magnetic field value was 1.7 kV/m and 8.9 pT, respectively. Magnetic field is lower than expected because TL flow power was lower than nominal value.

Measurements were camed out in vertical profile 6.5 m from ROW center, corresponding to a setback 1.5 m, a maximum electric and magnetic field value was 8.3 kV/m and 56 pT, respectively. Magnetic field is lower than expected because TL flow power was lower than nominal value.

V. CONCLUSIONS Simulated and measured results for the upgraded

configuration indicate that magnetic and electric field in horizontal profile along ROW will not exceed the reference levels specified by ICNIRP [6]. Constructions already placed at ROW edge also comply with exposure standard, because they have height lower than 6.0 m.

At ROW edge, in the vertical profile, there is a stretch at same height of TL phases where electric and magnetic fields values are greater than reference levels. Zoning regulation must be enforced in this case. Constructions erected 1.5 m from edge ROW will comply with exposure standard.

VI. REFERENCES

[J. J, Laforest (Ed.), ‘Transmission line reference Book 345 kV and above”, Palo Alto: EPRI, 1982, Zd edition, ch 8. IEEE Magnetic Fields Task Force, “Magnetic fields from electric power lines theory and comparison to measurements IEEE Truns. Power Delivery, vol. 3, pp. 2127-2136,Oct. 1988. M. L. Pereira Filho, C. A. F. Sartori, V. C. Silva, J. R. Cardoso, ”

Electric field shielding for reducing induced voltage under transmission lines,” in Proc. COMPUMG 2003, 14th ConJ Computution of EZecf“gne?ic Fields., Saratoga Springs, July 13 - 17,2003. N. H, Malik, “A Review of the charge simulation method and its applications“, IEEE Trans. Electrical Insulation, Vol 24, No 1, p 3-20, 1989. Projeto de linhas &reus de transmissEo de energia elitrica, ABNT NBR 5422, 1985 (in Portuguese). Guidelines for Limiting Exposures Exposure to Time-Varying Electric, Mugnetic, and Electromugnelic Fields p p to 300 GHz), ICNIRP - Intemational Commission on Non-lonizing Radiation Protection , Health Physics, Vol74, pp 494-522, 1998. EMF WORLD WID.€ S T m A R I J S - World Health Organization lntemational EMF Project.. [Online]. Available: http://www.who.intl docstore/peh-emWEMFStandards/who~102iWorldmapS.htm

VII. BIOGRAPHIES

Mhrio k i t e Pereira Filho was born in C d , Brazil, in 1957. He obtained the Electrical Engineer degree in 1980 and the MSc degree in 1999 from Escola Politkcnica da Universidade de S b Paulo, in Brazil. He i s member of IEEE EMC Society His current research interests are grounding, EMC and numerical field computation.

Jod Roberto Cardoso was born in 1949. He obtained the B.Sc., M.Sc.and Ph.D. from Escola Polittcnica da Universidade de %io Paulo (EPUSP), Brazil, in 1974, 1979, and 1985 respectively. Since 1999 he is Full Professor in the Dept. of Electrical Engineering, EPUSP. In 1988 he founded the LMAG - Laboratdrio de Eletromagnetismo Aplicado. He was the COMPUMAG’97 chairman. He is member of IEEE PES. His current research interests include electromagnetic field computation by FEM and electrical machines.

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Carlos A. F. Sartori received the B.Sc., M Sc., and the Ph D from Escola Politbcnica of University of SBo Ligia Maria Rodrigues Mendes was bom in Slo Paulo. He is the Vice-president of the Brazilian Paulo, Brazil, in 1955 She received BSc. degrees In Society on Electromagnetics He is also an IEEE Chemical and Civil Engineenng, respectively from senior member, an EMCS Board Member, member of FAAP and FESP. She works at Eletropaulo since the IEEE Educatron Society and ICs His current 1986. Her Interest area is transmission lines research interests include the time-domain modeling of foundations EMC problems

Mauricio Coldora Costa was bom in Slo Paulo, Brazil, in 1973. He obtained the BSc. and M.Sc degrees from Escola Politicnica da Universidade de Si30 Paulo, Brazil, in 1995 and 1998, respectively. He obtained the Ph.D. degree in Electrical Engineering from Laboratoire d’Electrotechnique de Grenoble, France, in 2001. His current research interests are optimization, software development and electromagnetic field computation.

Bernard0 Pinheiro de Alvarenga graduated in Electrical Engineeering from Universidade de Brasilia in 1990. He obtained the M Sc degree in Electrical Engineering from Universidade de Uberlbdia em 1993 and the Ph.D. in Electrical Engineering from Escola Politecnica da Univenidade de SO Paulo in 2004. He is associate teacher of Escola de Engenharia Elbtrica da UFG. He is a member both o f Nccleo de Pesquisa em Processamento de Energia e Qualidade - PEQiUFG and of Laboratbrio de Eletromagnetismo

Aplicado - LMAG/PEA/ EPUSP. His current research interests include special electrical machines, electromagnetic field computation by FEM and EMC.

Alvaro Batista Dietrich was born in Slo Paulo,

degrees in Electncal Engineer from Escola Poltttcnica da Univenidade de Sao Paulo, in 1997 and 2000, respectively His current interests are hysteresis and material modeling, software development and FEM applications in electromagnetism.

Brazil, in 1971 He obtained the B Sc. and the M Sc

Ivo Teixeira Domingues was bom in SBo Paulo, Brazil, in 1964. He graduated from UMC- Universidade de Mogi das Cruzes in Electricai Engineering. He obtained the MSc degree in Power Systems from E.P.U.S.P. He works at Eletropaulo since 1986 and their interest areas are materials standards, protection and distribution lines construction.

JuIio Cesar b m o s Lopes was born in SZo Jose do Rio Preto, Brazil, on September 16, 1954. He graduated from Escola Polithica da Universidade de SBo Paulo. His employment experience included CESP, Ligth and Eletropaulo, SBo Paulo, Brazil. His fields of interest include electromagnetic fields (emf), substations, overhead and underground transmission lines. He received an International Executive MBA degree from Faculdade de Economia e Aclministm@o of University of SZo Paulo.

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