Simulation Approach in Evaluating the Electromagnetic Fields from the New Lines of Extra High Voltage (EHV) Circuits Near Residential Area in Malaysia

Transcription

1 European Journal of Scientific Research ISSN X Vol.40 No.2 (2010), pp EuroJournals Publishing, Inc Simulation Approach in Evaluating the Electromagnetic Fields from the New Lines of Extra High Voltage (EHV) Circuits Near Residential Area in Malaysia N. A. Rahman Department of Electric Engineering, Faculty of Engineering, University of Malaya Kuala Lumpur, Malaysia Tel: 60(3) ; Fax: 60(3) W. N. L. Mahadi Department of Electrical Engineering, Faculty of Engineering, University of Malaya Kuala Lumpur, Malaysia I. Said Department of Electrical Power, College of Engineering, Universiti Tenaga Nasional PutraJaya Campus, Kajang Selangor, Malaysia H. Hussain Department of Electrical Power, College of Engineering, Universiti Tenaga Nasional PutraJaya Campus, Kajang Selangor, Malaysia Abstract This paper presents a study which is carried out on the new lines of Extra High Voltage (EHV) transmission lines specifically on the quadruple circuits of 132kV and double circuits of 500kV tower designs. There were assumptions made by various clusters of communities in Malaysia highlighting the effects on EMF radiation emitted from towers to the surrounding area. These effects were somehow claimed to be standing within the dangerous limits and disturbed many residents. The radiation studies involving EHV transmission lines in Malaysia are rarely undertaken since a lot of work had been focused entirely on the low levels of high voltage lines. Authorities and the regulators such as Tenaga National Berhad (TNB) was pushed to draw the guidelines as well as producing firm decisions generally on the issues of EMF management and its protection strategy. An initial case had been identified which involve various sites which is visible and passing through the public residential areas. The lines were located within the Klang Valley areas which are having the highest density populated area in Malaysia. The study comprises work from the evaluation of the electric and magnetic fields of both design types and also simulation studies using Fields 2.0 software. This includes comparison of both results in actual site measurements and simulations with actual setting parameters as its input data. The outcome of this paper will be the results analysis on field characterizations during normal load operations and predictions on high load conditions progressing to justify the exact safety distances for publics.

2 Simulation Approach in Evaluating the Electromagnetic Fields from the New Lines of Extra High Voltage (EHV) Circuits Near Residential Area in Malaysia 190 Keywords: Electromagnetic Fields, Radiation Exposure, Transmission Lines, Extra High Voltages, Fields 2.0 program 1. Introduction The existences of power transmission lines in Malaysia were seen to be increasing significantly especially in the highly dense populated area. Major cities such as Klang Valley area had been steadily growth and were expected to have load demands higher than previous years. Authority in Malaysia has planned to upgrade the transmission line systems in capacity from High Voltage (HV) levels to the Extra High Voltage (EHV) levels. Previous line designs, which commonly used in Malaysia, were dominated by double circuit towers with voltage rating of 132kV and 275kV. These design lines had observed to be in difficulty to restore the power demands instead of prone to the various power outages. Now, higher voltage levels were proposed in order to build stronger power systems to the consumers with minimum failure events to their operations and activities. The implementations of upgrading the line systems by TNB had gone through a difficult time due to the issues of electromagnetic field radiations. Coincidently, these new transmission line routing has involve various residential areas within the Klang Valley area. The public rejections on the upgrading lines were quite high and intense from various clusters of communities. They believed that by increasing the voltages and circuits, by means of magnetic field will effect to children and had increased the risk of overexposure into double than normal circuit lines. The scientific researchers conducted by various international institutions also have indicated that there is a possibility of increasing childhood cancer for population within a few distances from the power lines. The exact findings also had shown an agreement with significant results on childhood cancers expose more than 4mG (Olsen.J,1993, Feychting.M,1993, Tynes.T,1997, UK childhood cancer, 2000, Kleinerman.R.A, 2000, Draper.G, 2005, Feizi A.A, 2007). As such, Malaysian authority is required to update the situations by evaluating the field strength from these lines. Normally, the EMF measurements were performed by following the procedures in IEEE/ANSI 644 standards. However, these actions have yet to achieve with public expectations especially when dealing with the dynamic strengths of EMF radiations. This is because the new lines not only increasing the voltages but also allocate substantial increment numbers of circuits in the towers. Currently, there are no international standards which regulate to perform modeling and simulation exercise during the implementations. It is only justified by utilities to use any simulation techniques to calculate the EMF values in a way to convince the people and is subjected to the exact accuracies (TNB Ranhill-BVI Project, 2000). 2. EMF Measurements The approach used in conducting EMF studies which commonly practiced by many researchers had proposed actual measurement data collection as a primary data. This is followed by identifying the hot spot areas or locations which had been affected as shown in table 1. A good measurement approach should also consider point of measurements located as follows: 1. Near the tower structure point 2. Underneath of the sag point Table 1: Site locations of the affected residential areas No Locations New Tower Design 1 Bukit Tinggi residential area 132kV Quadruple Circuit s 2 Taman Botanic residential area 3 Kapar residential area 4 Sungai Buloh residential area 500kV Circuit s 5 Bandar Baru Kota Puteri residential area

3 191 N. A. Rahman, W. N. L. Mahadi, I. Said and H. Hussain Since the land issues are quite critical and massive in the Klang Valley, authorities such as TNB was urged to come out with a special scheme of protection to reduce risk of publics from over exposure of EMF radiations. The outcome of measurements also must be able to deduce conclusions that there are sufficient clearances within the Right of Way (ROW) under these lines in order to ensure public safety. At present the minimum clearances required by authority is 40m for double circuit type towers of 132kV, 275kV and quadruple circuit s while 50m clearances were set for the 500 kv double circuit tower (MESA, 2000). Since currently, Malaysian authority is following the international standard which is 1000 mg for public exposure (ICNIRP guidelines, 2000); the public had urged the authority to call for a standard review rather than adopting the limits suggested by the international standards. This is because fewer studies had been performed to relate electromagnetic radiations with various environmental factor involvements such as weather conditions, temperature, humidity and etc. The EMF measurement results in table 2 shows a typical value of EMF radiations from the new lines. The data have indicated normal power consumptions on the day of measurements with humidity around 50% to 60% and the temperature around 37 ºC to 40 ºC. In order to reduce the EMF impact, all phases were set as ABC-CBA or vertically inverse configurations on one side of the circuits. These results have shown better exposures as compared to international standards but unfortunately, were unable to convince people of the conclusive radiations from TNB systems. As a result, a routine work in monitoring of EMF radiation levels is suggested since it has been widely accepted by most of the authorities. Table 2: The results of magnetic fields at various points of tower measurements Descriptive Location Current (A) Left ROW (mg) Max. (mg) Right ROW (mg) Quadruple Lines (No.1) At sag point (between T- 33& T-34) Line 1 (I) = A Line 2 (I) = A Line 1 (I) = A Line 2 (I) = A Top Circuit Bottom Circuit Quadruple Lines (No.2) In between sag point to tower ( T-31 & T-32) Line 1 (I) = A Line 2 (I) = A Line 1 (I) = A Line 2 (I) = A Top Circuit Bottom Circuit kV Lines (No.3) In between sag point to tower ( T-12) Line 1 (I) = A Line 2 (I) = A kV Lines (No.4) In between sag point to tower ( T-53) Line 1 (I) = A Line 2 (I) = A kV Lines (No.5) At sag point (between T- 57& T-58) Line 1 (I) = A Line 2 (I) = A

4 Simulation Approach in Evaluating the Electromagnetic Fields from the New Lines of Extra High Voltage (EHV) Circuits Near Residential Area in Malaysia 192 The modeling and simulations techniques also require a detail data input from the lines under study in order to justify the accuracy of the model prior to the more advance study applications of magnetic fields. Figure 1 and 2 shows the significant reference models complete with line specifications in phases arrangements for quadruple and 500kV circuits. Figure 1: Reference model of EMF power line measurements for quadruple circuits Figure 2: Reference model of EMF power line measurements for 500kV circuits The above data were taken using emdex meter device with design and manufactured by enertech consultant. The device calculating the magnetic field results by averaging the result of magnetic fields using the formulation of B r = (B x + B y + B z ) (W.F.Horton and S.Goldberg, 1995).

5 193 N. A. Rahman, W. N. L. Mahadi, I. Said and H. Hussain 3. Simulation Modelling The research efforts on modelling and simulation exercise were incorporated in the studies as part of the main approach to support utilities in educating the public about the behaviour and the risk rate of radiation exposures. The advances of present electromagnetic software packages have enable studies on forecasting the radiation exposures to be applied using the same principle formulation as mentioned above. In this study, Field 2.0 software from Southern California Edison is used in prediction of magnetic field intensity with various power line performances. It calculates both elements of electric and magnetic fields instantaneously by projecting the field pattern for various applications. A good example is shown in figure 3 and 4 which representing the accuracy validation process between measurements and modelling values for both quadruple and 500kV tower lines. Figure 3: Accuracy validation process for quadruple lines Figure 4: Accuracy validation process for 500kV lines

6 Simulation Approach in Evaluating the Electromagnetic Fields from the New Lines of Extra High Voltage (EHV) Circuits Near Residential Area in Malaysia Results and Discussions 4.1. Simulation by Phase Arrangement Configurations The results shown in Table 3 and 4 representing the prediction of radiation exposures of both towers which under studied during optimum and maximum line performances were undertaken. The results also used the existing phase arrangement which is ABC-CBA. The techniques which have been widely accepted and practiced by most of the utilities worldwide were recommended to be used in lowering the radiation exposure in certain stretch of power lines. It was forecasted that when 50% and 100% line performances, the magnetic field radiation at the boundary of right of way (ROW) is still below than 1000mG. However, great challenges were observed when the outcomes are not achievable as public expected that supposedly below than 4mG. This is well explained in table 2 where some of the exposures were found more than 4mG. Table 3: Simulation of quadruple tower magnetic field radiations under various lines performances Location Power Rate I (A) Magnetic Field (mg) (-99 ft) (-66 ft) (0 ft) (66 ft) (99 ft) No (1) 50% % No (2) 50% % Table 4: Simulation of 500kV tower magnetic field radiations under various lines performances Location Power Rate I (A) Magnetic Field (mg) (-99 ft) (-82 ft) (0 ft) (82 ft) (99 ft) normal No (3) 50% % normal No (4) 50% % normal No (5) 50% % In the case where phase arrangements are not able to reduce radiations into the desired levels, other options are suggested by improving the tower design structures. This can be done by proposing compaction design applied to the towers by allowing minimum clearances at horizontal and vertical directions. The magnetic field radiation would than altered according to the geometrical conductor positions at various levels. Table 5 and 6 proposed a good example in increasing the heights at two positions. Table 7, 8 and 9 served various compactions to the tower structure, while table 10, 11 and 12 proposed various horizontal compactions including table 13 which are combinations of vertical and horizontal compactions.

7 195 N. A. Rahman, W. N. L. Mahadi, I. Said and H. Hussain 4.2. Simulation by various line design compactions with nominal currents (250A) for double circuit lines Table 5: Increment of vertical height at the bottom phase conductors Table 6: Increment of vertical height at all phases Table 7: Compaction of vertical height between middle and bottom phases Table 8: Compaction of vertical height between middle and top phases

8 Simulation Approach in Evaluating the Electromagnetic Fields from the New Lines of Extra High Voltage (EHV) Circuits Near Residential Area in Malaysia 196 Table 9: Compaction of vertical height at all phases Table 10: Compaction of horizontal cross arm in all phases Table 11: Compaction of horizontal cross arm at top and bottom phases Table 12: Combination of horizontal and vertical compactions at top and bottom phases

9 197 N. A. Rahman, W. N. L. Mahadi, I. Said and H. Hussain Table 13: Combination of horizontal and vertical compactions 6. Conclusion From the studies, efforts to reduce the impact of high intensity magnetic field exposure from the power lines were conducted and examined using industrial based electromagnetic fields software applications. The protection scheme introduced in the studies includes height increments and phase compactions. The above results have indicated that tower structure modifications were viable in reducing magnetic field radiations by applying modelling and simulation approach. The input data for simulation case studies were based on the specifications of tower lines at the sites. The validity of all case studies were assessed by comparing the modelling and actual measurement results at sites. Options for the utilities to further minimize the radiation impact is justified by having of 20% design compaction on tower designs with 31.4% reductions at the ROW better than the phase arrangement methods. In the case where utilities requires for minor modifications, increment of bottom phase height solutions is recommended to be used with 26.9% reductions at the ROW better than the phase arrangement methods.

10 Simulation Approach in Evaluating the Electromagnetic Fields from the New Lines of Extra High Voltage (EHV) Circuits Near Residential Area in Malaysia 198 References [1] Olsen J, Nielsen A, Schulgen G, Residence near high voltage facilities and risk of cancer in children, British Medical Journal, 307(6909), pp [2] Feychting M, Ahlbom A, Magnetic fields and cancer in children residing near Swedish high-voltage power lines, Am. Journal Epidemiology, 138(7), pp [3] Tynes T, Haldorsen T, Electromagnetic fields and cancer in children residing near Norwegian high-voltage power lines, Am. Journal Epidemiology, 145(3), pp [4] UK Childhood Cancer Study Investigators, Childhood cancer and residential proximity to power lines, British Journal Cancer, 83(11), pp [5] Kleinerman RA, Kaune WT, Hatch EE, Wacholder S, Linet MS, Robison LL, Niwa S, Tarone RE, Are children living near high-voltage power lines at increased risk of acute lymphoblastic leukemia?, Am. Journal Epidemiology, 151(5), pp [6] Draper G, Vincent T, Kroll ME, Swanson J, Childhood cancer in relation to distance from high voltage power lines in England and Wales: a case-control study, British Medical Journal, 330(7503), pp [7] Feizi AA, Arabi MA, Acute childhood leukemias and exposure to magnetic fields generated by high voltage overhead power lines a risk factor in Iran, Asian Pacific Journal Cancer Preview, 8(1), pp [8] ICNIRP 1998; Guidelines for limiting exposure to time-varying electric and magnetic fields (up to 300 GHz), Health Physics, Vol.74, April [9] ANSI/IEEE Std , IEEE Standard Procedures For Measurement of Power Frequency Electric and Magnetic Fields from AC Power Lines, U.S.A [10] TNB Ranhill-BVI Project, R.W Beck, Inc, 2000 Transmission Line Design Manual, Kuala Lumpur. [11] Southern California Edison (SCE), Electric and Magnetic Fields Calculations Program FIELDS, Version 2.0, [12] Enertech Consultants, EMDEX II Linear Data Acquisition System (LINDA) User Manual, Version 2.2. [13] William F. Horton, Saul Goldberg, Power Frequency Magnetic Fields and Public Health, CRC Press, New York, 1995.