翻译原文.pdf

1 262 S6 Items Criteria Voltage 7651800 kV Tower Height 95 m COMPARISON OF ELECTRICAL ENVIRONMENTAL CHARACTERISTICS OF DIFFERENT EHV TRANSMISSION LINES Condition Nominal Max Average Jeong Boo Kim Dong I1 Lee Koo Yong Shin Korea Electric Power Research Institute Taejeon 305 380 Korea 19 m Insulation Clearance Abstract The present paper reports the analysis results by comparison of characteristics of electrical environment between different EHV transmission lines such as AN Audible Noise RI Radio Interference TVI Television Interference EMF Electric and Magnetic Field In Korea transmission lines with nominal voltage of 765 kV have been constructing since 1996 and Hungary energized a 750 kV line in 1978 However both EHV transmission lines have different line configuration Korea is a prime example of the first double circuit 765 kV line in the world and Hungary has been operating one of the single circuit 750 kV Phase to Phase Keywords Audible Noise Radio Interference Television Interference EMF Transmission Line Extra High Voltage Insulator Conductor I INTRODUCTION Suspension 300 kN Tension 400 kN Dia 3 04 cm 30 x 2 strings 28 x 3strings Cardinal x 6B Electricity utilities involved in transmission development maintenance and operation face increasingly serve challenges as result of heightened environmental awareness more comprehensive legislation and standards and growing public expectations and concerns These trends will have a major influence on the approach of companies to the management of both new projects and existing transmission assets Both countries Korea and Hungary studied the electrical environmental effects of both EHV transmission lines using the design parameters real measuring data through exchanging visits by governmental sponsoring Due to increasing of peak demand by more than 10 per annum Korea is constructing the first project 765 kV transmission lines of total 340 km and preparing the second 765 kV project In order to meet the need for economical bulk power transmission over the limited right of way with the least environmental impact to the people who live in the vicinity of these lines the 765 kV transmission lines of Korea adopted double circuit vertical line type with low reactance arrangement KEPRI developed an optimal design of 765 kV double circuit in the viewpoint of electrical environmental covering audible noise radio interference television interference magnetic field and electric field using corona cage and full scale 765 kV test line However in case of Hungary a single horizontal circuit of 750 kV transmission lines was adopted in 1978 due to the electric demand and different social circumstances Several countries have been using this type of single circuit transmission lines in worldwide In this paper beginning stage of constructing in the first double circuit 765 kV High Voltage Engineering Symposium 22 27 August 1999 Conference Publication No 467 D IEE 1999 Above SNR 40 dB Below TVI cr L Jermendy I Forgarasi Electric Large Laboratories Ltd H 1158 Budapest Vasgolyo St 2 Hungary All area Residential transmission line two different types of EHV transmission lines was analyzed by comparison of characteristics of electrical environment items such as AN RI TVI and EMF MF R 0 W 11 765 kV DOUBLE CIRCUIT VERTICAL TRANSMISSION LINE OF KOREA 1 000 mG 3 m From the direct nnder condiictnr II AN I Below 50 dBA I Residential area All area Above SNR 24 dB R I I I 3 5 7 0 kV m I Otherarea In order to make the guideline of 765 kV double circuit vertical transmission line as Table 1 KEPRI had been studying from 1984 to 1996 using corona cage and fidl scale 765 kV test line as shown in Fig 1 B Facilities and instrument system of 765 kV test line Maximum test voltage of test line which has total 700 m length with 3 spans of 200 m 300 m and 200 m is 850 kV line to line The voltage to the test line is supplied by 3 single phase auto transformers Each auto transformer is rated 3 MVA with a B E of 1425 kV Instrument system consist of Data Acquisition System and AN RI and TVI sensors which are installed along a lateral profile at midspan and were connected to their appropriate instruments located in the measuring house by long coaxial cables To measure AN Bruel i 40 j I 4 30 I J I 5 20 K 1 J i 10 I l L J 1 I 60 I 1 I I I 4 I I HI 0 0 Rain L5 I L50 Name Items U uu 0 1 2 2 158 500 8 0 W U 5 84 1 6 977 a 99 8 99 9 32333435363736394041 42434445464748495051 525354555657 AUDIBLE NOISE dBAI Fair L50 Fig 2 Cumulative distribution of audble noise Audible Noise Radio T I 1 T I 2 T I 3 I I I I I O O 2 7 1 1 0 1 I 5 f 52 5 418 42 7 AN3 A1 RI2 SNR SNR SNR Unit m Fig 1 Sensor located configuration of KEPRT Kochang test line To measure television interference biconical antennas US t y p e HK116 are installed at 3 m above ground The test receivers using QP detectors WS type ESVS30 are tuned to 75 MHz according to CISPER standards 2 C Results of Electrical Environmental Study using the 765 kV Full Scale Test Line In this paper we evaluated the environmental data of test line from Dct 95 to Nov 98 38months with KEPCO s 765 kV transmission line design criteria as Table 1 The summarized test results of Table 1 satisfy the design criteria of Table 1 Fig 2 shows the cumulative distribution of audble noise in rain weather at 15 m from outer conductor The curves have similar gradient for nominal voltage 765 kV and maximum voltage 800 kV The cumulative curves of RI sensors of Fig 3 show the characteristics of lateral profile Table 2 Summarized results of 765 kV test line Interference SNR dB 5 8 kV m 13 Electric Portable Field HI 3604 42 6 mG 4 1 Evaluation Datum SNR 71 Signal 45 3 Noise 25 7 2 Evaluation Datum SNR 54 S al 14 Noise 40 3 Maximum Voltage 800 kV case 4 Current 1000 A case Ill 2a 30 32 34 36 3a 40 42 44 46 4a 50 52 54 FIELD STRENGTH dBuV m Fig 3 Cumulative probability of radio interference at 475 kHz TVI cumulative frequency dntribution at 75 MHz in fair weather of T11 sensor is as shown in Fig 4 The electric field along the lateral line was measured and compared with the calculated as shown inFig 5 The magnetic field was calculated with 1000 A current condition The peak value of magnetic field shows 42 6 mG in the lm above ground level on the center of test line as shown in Fig 6 3 1 264 S6 45 0 7 6 I 5 5 2 9 4 03 5 I w a LL 2 W 1 0 10 20 30 40 50 LATERAL DISTANCE FROM C L ml Fig 5 Lateral profile of electric field strength 250 a U i i 200 SO 0 10 0 I 5 0 0 0 I I I I I I 111 750 kV SINGLE CIRCUIT HORIZONTAL TRANSMISSION LINE OF HUNGARY E RI I 50dB A Design of the transmission line In the 1970s a transmission line and a substation of large capacity was needed to be built to extend the cooperation of the interconnected electrical power system of the East European countries Therefore accordng to the requirement and to the connecting line parameters of that time a single circuit horizontal line was built All area 15 kV d 10 5 kV m ResidatiaV Road crossing I rI R 0 W I 40m From the dired under I condudor At that time the rad10 interference and the electric field was taken into account as environmental parameters In course of the operation all the environmental characteristics were checked under the existing line B Measuring apparatuses of the 750 kV transmission line The radiated electromagnetic waves were detected in the frequency range between 0 2 30 MHz by a ferrite aerial and by a selective microvoltmeter For TVI measurements the meter used met the prescription of CISPR and had a bandwidth of 120 kHz A real time analyzer and an MV 102 t y p e microphone was used to the determination of the acoustic noise C Results obtained on actual 750 kV transmission line In order to make a statistical evaluation of the rad0 interference caused by actual line a number of measurements were performed Fig 7 demonstrates general results of the 750 kV line 20 m from the outer phase in Merent spans In every case the maximal grabent is given which was calculated taking into account the line parameters and the actual voltage The interference on the line is the most intensive below 1 MHz The Qsturbances observed in substation vary randomly in a relative wide range Frequency spectra of TVI at four distances from 20 to 100 m from the transmission line were obtained at one midspan of the 750 kV line caused by a microgap see Fig 8 Actual line measurement can practically be performed for auQble noise at EHV level in fair weather The corona generated audible noise as shown in Fig 9 recorded by microphone placed in a height of 1 8 m above ground 70 I I 0 15 0 3 0 5 1 2 4 6 10 20 30 MHzl Fig 7 Radio interference of 750 kV transmission line in function of the frequency Fig 8 Frequency spectra of TVI generated by gap discharges in the midspan of the 750 kV transmission line From the Fig 9 can be seen the most noticeable AN tone is the hum Neither the other harmonic components nor the A weighted noise play an important role The line can be characterized form point of view audible noise by the A weighted noise level measured at the edge of R O W 1 265 S6 In this case the AN level of the 750 kV line is equal to 37 5 A in fair weather 1 0 i 80 m 20 0 1 0 2 0 40 Fig 9 Audible noise octave band and A weighted levels in the vicinity of a 750 kV transmission line Electric and magnetic field problems arising from the transmission lines and substations have been studied in Hungary practically from the erection of the 750 kV line in the last twenty years At the beginning the activity was focused to development of measuring device for electric then later for magnetic field Fig 10 gives the geometric configuration of the 750 kV lines at the place where measurements were performed The magnetic induction developing as a function of distance measured fiom the axis of the central conductor projected to ground has been measured at points notma1 to the axis of the line at a height of 1 5 m above ground at the maximal sag Change of the magnetic induction in the function of distance is shown in Fig 11 then the line operated with about a half capacity Fig 10 Electric field strength at the level of 1 8 m above the ground for the 750 kV transmission line About the same value could be registered in dwelling houses in the vicinity of transmission line i e there was practically no difference between the values of magnetic induction inside and outside of the building With respect to the personal carrying out live line work the following effect developed in the body on 750 kV line in case of a current of 1000 A 25 1 pT working on vertical structure as well as 45 pT on horizontal structure Concerning the mitigation in case of electric field measures are taken in the 750 kV substation where the corridors on the field are screened by grounded wires The live line work is performed in electrostatic clothes The agricultural machines have a grounding chain against charging the large metal body d t Fig 1 1 50 Hz magnetic induction in the function of the distance in the vicinity of the 750 kV line IV CONCLUSIONS Comparison can be made between environmental characteristics of EHV transmission lines of sigtllficantly different parameters and that of different design philosophy and technology In this manner the test line results can be adapted to the actual line The larger difference of the conductor arrangements makes possible extrapolation of t