HÉDIO TATIZAWA 1, ERASMO SILVEIRA NETO 2, GERALDO F. BURANI 1, ANTÔNIO A. C. ARRUDA 1, KLEIBER T. SOLETTO 1, NELSON M. MATSUO 1

Application of odelling and coputer siulation for the developent of a test setup for calibration of power quality easureent transducers for high voltage networks HÉDIO TATIZAWA 1, ERASMO SILVEIRA NETO 2, GERALDO F. BURANI 1, ANTÔNIO A. C. ARRUDA 1, KLEIBER T. SOLETTO 1, NELSON M. MATSUO 1 2 Copanhia de Transissão de Energia Elétrica Paulista ISA CTEEP 1 Instituto de Eletrotécnica e Energia da USP IEE/USP Av. Prof. Luciano Gualberto, 1289 São Paulo BRAZIL hedio@iee.usp.br http://www.iee.usp.br Abstract: - The ter power quality is, in general, closely related to the quality of the voltage. Considering the widespread presence of sensitive loads in the electric grid, and the increasing awareness of the consuers concerning the quality of the power supply, the control and easureent of power quality paraeters, for instance, haronics, interharonics, sags, swells, etc., are increasingly becoing uch ore iportant [1, 2, 3, 4]. Most of the necessary calibration procedures for power quality onitors and power quality analyzers are already defined in the international standards, ainly in the IEC 61000 series [5] and ANSI/IEEE Standards. This paper presents results of a research intended to develop a ethodology for the calibration of high voltage transducers for power quality easureents in high voltage networks, considering that such kind of procedures are not yet established in the pertinent standards. In this research it is also considered that the conventional high voltage laboratory is not suitable for power quality tests, so soe iproveents are necessary on this subject. In this developent, odelling and coputer siulation using ATP Alternative Transients Progra [6] were used for to assess the fruency response of the test setup, and the design of the reactive copensation of the test circuit. Key-Words: - high voltage transducers, capacitive voltage dividers, power quality easureents, haronics, IEC 61000 series, high voltage. 1 Introduction The control of power quality paraeters in transission and distribution networks deands qualified personnel, easureent uipent and suitable transducers for the power quality easureents. Considering the voltage transducers, the bibliographic survey perfored shows that there is not enough consensus defining the calibration procedures for high voltage levels typically found in transission and distribution networks [7, 8]. This paper suarizes the analysis perfored and the ain results of the research, aiing to develop a calibration test setup for high voltage transducers aiing to power quality easureents in power systes high voltage networks. 2 Test Setup Developent Capacitive voltage dividers (CVD) are in coon use for the easureent of power quality paraeters in power systes networks [9], thanks to its odularity and easy installation in transission and distribution substations environent. Fig. 1 shows a typical installation at field, in a 345kV transission substation. In this Fig. 1 the high voltage branch of the CVD is shown, coposed by six 500pF odular capacitances, noinal voltage 50kV. Referring to Fig. 2, all the capacitances of the high voltage branch (C1) are identical with noinal value of 500pF. For the easureents, the nuber of 500pF capacitances can be changed according to the expected voltage to be easured, in order to liit the voltage on the C2 capacitance of the secondary low voltage branch. This paper shows the developent of the test circuit for the calibration of voltage transducers, aiing to easureents of power quality disturbances in power systes high voltage networks. This kind of developent faces any levels of difficulties, considering that the generation of stabilized and well defined power quality disturbances, in the high voltage range (for exaple, over 1kV), for calibration purposes, ruires the adaptation of the conventional high voltage laboratory uipent. The conventional high voltage laboratory, in general, is uipped only with high voltage sources for generating power fruency (60Hz or 50Hz) and ipulse (atospheric ISSN: 1109-2777 880 Issue 9, Volue 7, Septeber 2008

and switching) high voltage wavefors, used in dielectric tests of high voltage uipent insulation [10]. For calibration of high voltage transducers used in power quality disturbances easureents, additional wavefors are necessary, for instance, voltage haronics, sags (or dips), swells, etc. In this way, in this research, the following test circuit coponents were defined, in order to achieve the calibration circuit: tests, ainly considering high voltage levels found in transission systes, in the hundreds of kv range. The expected load for the test transforer, during the calibration tests, is supposed to be of capacitive nature, ainly capacitive voltage dividers (CVD) and capacitive voltage transforers (CVT). In general, CVTs present very high values of capacitance (few thousands of pf), becoing in this way a very heavy load for the high voltage test transforer. - Capacitive voltage dividers, coposed by 500pF odules, voltage 50kV. - Power quality analyzer for the transducers calibrations. In this research, a class A [11] coercial power quality analyzer was used. At the initial stage tests, a high voltage transforer with rated voltage 220V/100kV, rated power 10kVA, was used. The test circuit is shown in Fig. 2. Fig. 2 Tests perfored with the arbitrary wavefor voltage source test setup. Fig. 1 Capacitive voltage divider (CVD) installation for easureents in a 345kV substation. - arbitrary wavefor voltage source for generating sinusoidal wavefors, with low haronic distortion, considering haronic fruencies up to the 50th order (3000Hz), and generation of coposite wavefors (fundaental fruency + haronics), with enough power capacity for the calibration tests. In this research, a conventional coercial power quality generator was used for this purpose. - a step-up high voltage test transforer, fed at the low voltage side by the arbitrary wavefor voltage source, to produce in the high voltage side, the wavefors generated by the source (considering coposite wavefors and haronics), with enough power ruired by the calibration tests. The option of to generate high voltage wavefors in the way described above, was otivated by absence, or by the non availability, of high voltage sources for the wavefors ruired by the research in the calibration 2.1 Electric odel of the high voltage transforer The option of using a high voltage transforer to generate the high voltage for the calibration tests iplies in to introduce in the test circuit, a series uivalent reactance of the transforer. This option turned to be necessary, considering the non availability of a coercial high voltage source, with the capability for generating ruired wavefors for the calibration tests. The series association (su) of this leakage reactance with the load capacitances (CVD Capacitive Voltage Dividers and CVT Capacitive Voltage Transforers) results in a resonating (tuned) circuit for certain haronic fruencies. For the electrical odelling of the high voltage test transforer, the uivalent circuit was obtained by eans of ipedance voltage and no-load loss tests. The obtained uivalent circuit, for 60 Hz, is shown in Fig. 3. ISSN: 1109-2777 881 Issue 9, Volue 7, Septeber 2008

2.3 Test setup odelling and coputer siulation Aiing to analyze the test circuit behavior under haronic voltages, odelling and coputer siulation were perfored using ATP Alternative Transients Progra [6]. For the siulations, the odel of the test setup shown in Fig. 4 was used. The test setup fruency response, obtained with ATP progra, is shown in Fig. 5. There, transforer output voltage and CVD output voltage (ultiplied by 100) are shown for each fruency. A resonant fruency can be seen at 350 Hz. Fig. 3 Equivalent circuit of high voltage transforer where: R uivalent resistance,. uivalent leakage reactance, agnetizing reactance, Rp uivalent no-load loss resistance. Considering the ipedance voltage and no-load loss tests, the value of the uivalent circuit paraeters are shown in Table 1. Table 1 Equivalent circuit of the high voltage test transforer Paraeter Values referred to low voltage side (Ω) Values referred to high voltage side (Ω) R (Ω) 0,151 31,2k (Ω) 0,673 139,0k Rp (Ω) 322,7 66,7M (Ω) 116,3 24,0M 2.2 Electric odel of the test setup Considering the obtained values of the step-up test transforer (referred to the high voltage side) and CVD, the uivalent circuit of the test setup is shown in Fig. 4. Fig. 5 Test circuit fruency response obtained with ATP progra, showing transforer high voltage output. Coputer siulation results show a non flat fruency response of the test circuit, with a resonant fruency at 352Hz (near 5th haronic). Experiental results of easureents ade at transforers low voltage side, using a power quality analyzer, and spectral analysis perfored, show accordingly results, with an aplifying effect at 5th haronic, caused by the proxiity with the resonating fruency. 2.4 Analysis of the circuit Considering the test setup odel, a siplified uivalent circuit results by calculating the series and shunt association of ipedances. This siplified circuit is shown in Fig. 6 and 7. Fig. 4 Electrical odel of the test setup, with step-up test transforer and capacitive voltage divider. Obs.: Resistance R5 is included for a better nuerical stability in coputer siulations, without affecting overall results for its very high value of 1.000.000MΩ. Fig. 6 Test circuit electrical odel. ISSN: 1109-2777 882 Issue 9, Volue 7, Septeber 2008

Fig. 7 Test circuit siplified electrical odel. Considering the uivalent circuit, the resonating fruency is caused by the series association of (step-up transforer leakage reactance) and Z (uivalent ipedance of the shunt association of CVD and agnetizing reactance of transforer). At resonating fruency: Where and With: c Z Z 1 c = jϖc = Z = = = // c. c c. c (1) c - agnetizing reactance of transforer = jϖl capacitive reactance of CVD. = jϖl (2) 2.5 Laboratory tests results Test setup developent Measureent results obtained with a power quality analyzer, and using an arbitrary wavefor generator at the high voltage transforer input showed that this test setup can generate high voltage haronics presenting low haronic distortion. Fig. 9 shows high voltage transforer output spectru, when a 60Hz sinusoidal wavefor is applied at input. The easureent was perfored at the capacitive voltage divider low voltage branch, using a power quality analyzer. In Fig. 8, a low haronic distortion can be seen, with very sall values of higher order voltage haronics. Fig. 8 Test transforer output voltage spectru, with a 60Hz voltage applied at input. Fig. 9 shows high voltage transforer output, when the input arbitrary wavefor generator is adjusted for coposite wavefor generation, with fruencies 60 Hz, 180Hz, 300Hz and 400Hz. The easureent was perfored using the power quality analyzer applied to the CVD output. Fig. 10 shows the output voltage spectru of the high voltage transforer. At resonating fruency: 1 L ϖ = 1 (3) L C L L where agnetizing inductance of transforer L and leakage inductance. By applying the nuerical values: ϖ = 2238,58rd / s So, the calculated resonating fruency f = 356.28 Hz, shows good agreeent with the coputer siulation results. Fig. 9 Test transforer output voltage, for input voltage with 60 Hz, 180Hz, 300Hz and 400Hz haronic coponents. ISSN: 1109-2777 883 Issue 9, Volue 7, Septeber 2008

secondary branch capacitance, three ethods where used, shown in Table 2. Fig. 10 Test transforer output voltage spectru, for input voltage with 60 Hz, 180Hz, 300Hz and 400Hz haronic coponents. According to Fig. 10, at transforer output only haronic coponents actually applied to the input were obtained (60Hz, 180Hz, 300Hz and 400Hz), showing the linear behavior of the transforer. Considering the voltages aplitudes for each haronic fruency, it depends on the transforer ratio and fruency response of the test setup. In this research, alternatives for to iprove fruency response where studied, by applying at the low voltage side of the test transforer passive coponents (resistances, capacitances and inductances), aiing at generating fundaental and haronic voltages (high voltages), without causing overflow of the voltage source (arbitrary wavefor generator), with rated power 5kVA. Good results where obtained in such studies (see section 4). 2.6 Measureent of CVD capacitances Capacitance and loss tangent values of the CVD coponents are of fundaental iportance, considering its role in the transforation ratio and phase error during easureents. So, easureents where perfored in the high voltage branch capacitances using Schering Bridge ethod, considering that in this ethod, easureents are perfored applying high voltages, with siilar conditions found in actual easureents using CVD. Those capacitance easureents where perfored with test voltages of 10kV and 30kV, and siilar results where obtained for the capacitance and loss tangent easureents for both test voltages. In actual conditions, the secondary branch capacitance of the CVD works under a voltage of about 200V (60Hz). For the easureent of that Table 2 Measureent of CVD secondary capacitance Measureent ethod Applied voltage during easureent (V) Fruency (Hz) Schering Bridge 200 60 (Tettex) Resonating Bridge 1 1k (QuadTech) Volt-apère Method 200 60 Measureent results in all three ethods where very siilar between each other, showing a little influence of test voltage and fruency in the capacitances values. 3 Test Setup For Calibration Of Voltage Transducers Considering high voltage easureents at field, in general instruent transforers are used, for power fruency voltages. However, for using such transducers in power quality studies, a calibration in a broader fruency range turn to be necessary, considering the various kinds of power quality disturbances. The capacitive voltage transforer (CVT) is a transducer coonly found in transission and distribution substations. A CVT, in general, presents a high capacitance (thousands of pf), arising, fro this fact, a technical difficulty for the test circuit ipleentation. This high capacitance, and associated low ipedance, ay becoe a proble for the voltage source (an arbitrary wavefor generator) to feed the test setup, considering its rating of 5kVA. For instance, a 4,000pF CVT, for use in a 230kV power syste, is a 27kVA load at rated voltage, above the rating of the arbitrary wavefor generator with rated power of 5kVA. This difficulty increases for higher order haronics. Fig. 11 shows the test setup for the calibration of a capacitive voltage transforer (CVT). ISSN: 1109-2777 884 Issue 9, Volue 7, Septeber 2008

The fruency response curve on Fig. 13 is siilar to Fig.5 one s, showing a non flat fruency response of the test setup, with a resonant fruency at 125Hz. Fig. 14 shows this sae curve, presented in log-log scale. 10 4 FS-CIRC-C-DPC-TPC-FONTE-BT>P2 Fig. 11 Test setup for the calibration of a capacitive voltage transforer, with voltage source (arbitrary wavefor generator), high voltage transforer, capacitive voltage divider (adopted as Reference Transducer) and test object (CVT). Fig. 12 shows the electrical uivalent odel of the test setup shown in Fig. 11 Voltage (V) 10 3 10 2 10 1 E 1 V 0,0317 Ω 0,3883H P 1 6 19,75 kω 242,04 10 H P 2 143,7 MΩ 6 15,6 10 H 539 10-6 µ F 539 10-6 µ F 0,213193 µf 4,4 10-3 µ F 0,38 kv / 300kV DPC TPC Fig. 12 Electric odel of the test setup shown on Fig. 11, with voltage source (arbitrary wavefor generator), high voltage transforer, capacitive voltage divider (adopted as Reference Transducer) and test object (CVT). The test transforer used in this circuit is a 300kV, 70kVA step-up transforer, where the uivalent circuit, again, was obtained by eans of no-load and ipedance voltage tests. Coputer siulation studies were perfored, using Alternative Transients Progra ATP, considering a hypothetical voltage source (aplitude 1V) applied at the circuit s input. Fig. 13 shows the fruency response curve of the circuit of Fig. 12, without reactive copensation. 7000 6000 5000 4000 3000 2000 1000 0 0 200 400 600 800 1000 (file FS-CIRC-C-DPC-TPC-FONTE-BT.pl4; x-var t) v:p2 Fig. 13 Fruency response curve of the circuit shown on Fig. 12, without reactive copensation - Output voltage applied to the Capacitive Voltage Transforer (CVT) 10 0 10 3 10 4 10 5 10 6 10 7 Fruency (Hz/1000) Fig. 14 Fruency response curve of the circuit shown on Fig. 12, without reactive copensation, presented in log-log scale - Output voltage applied to the Capacitive Voltage Transforer (CVT). Fig. 15 shows the voltage source electrical current output for each haronic fruency. In this Fig., a resonant fruency can be seen at about 125Hz, showing a current peak at this fruency. Current (A) 10 2 10 1 10 0 10-1 10-2 FS-CIRC-C-DPC-TPC-FONTE-BT>FONTE -A (Type 8) 10 3 10 4 10 5 10 6 10 7 Fruency (Hz/1000) Fig. 15 - Fruency response curve of the circuit shown on Fig. 12, without reactive copensation, presented in log-log scale - Electrical current at voltage source output for each haronic fruency. Considering the fruency response curve shown on Fig. 15, high values of electrical current are to be expected at the arbitrary wavefor generator output, showing the necessity of soe kind of fruency dependent copensation to be provided. By eans of coputer siulation using ATP progra, any alternatives of reactive copensation circuits were studied, aiing to generate high values of output voltage applied to the Capacitive Voltage Transforer, and concoitantly, low values electrical currents at the voltage source output. ISSN: 1109-2777 885 Issue 9, Volue 7, Septeber 2008

4 Test setup with shunt reactive copensation In order to obtain the necessary high voltage wavefors for the calibration tests, additional studies were ade, considering the use of passive coponents (resistances, inductances and capacitances), aiing at reactive copensation considering haronic fruencies. Those studies where perfored using Alternative Transients Progra ATP, considering a hypothetical voltage source (aplitude 1V) applied at the circuit s input. Those coputer siulations aied at evaluating the output voltage applied to the CVT, for each haronic fruency. Also, those studies analyzed the voltage output in any different situations, by applying resistances, capacitances and inductances at the high voltage and/or low voltage sides of the step-up transforer, for to iprove the fruency response curve of the test circuit, aiing at obtaining in the test setup higher values of voltage output together with lower values of input electrical current. Fig. 16 shows the electric odel of the test setup for the calibration of a 230kV CVT, capacitance 5,300pF, with reactive copensation provided by the shunt capacitance and shunt inductance. This reactive copensation is intended for to obtain low intensity of electrical current at 60Hz and, siultaneously, high values of voltage for haronic voltages applied to the CVT. The diensioning of the shunt capacitance and inductance was perfored with the aid of the ATP progra coputer siulation. the shunt capacitance and inductance values for reactive copensation. Table 3 shows values of reactive copensation for other haronic fruencies, considering a 5,300pF - 230kV capacitive voltage transforer. Table 3 Reactive copensation for each haronic fruency, for 5,300pF CVT CVT Capacitance (pf) Fruency (Hz) Shunt inductance (H) Shunt capacitance (µf) 120 0.35 15,000 5,300 180 1.2 2,300 300 1.2 650 660 1.4 117 Figs. 17 and 18 shows the fruency response of the test setup (without the 0.5Ω series resistance), with reactive copensation for 300Hz, for test transforer voltage (high voltage side) and voltage source output current, respectively. Voltage (V) 10 4 10 3 10 2 10 1 FS-CIRC-C-DPC-TPC-FONTE-BT-IND-PARAL-1.5MH-CAP-PARAL-600UF-SCAN1-COR-IND>P2 (Type 4) Fruency (Hz/1000) Fig. 17 Test setup fruency response, with reactive copensation for 300Hz, without the 0.5Ω series resistance. Test transforer output voltage (high voltage side). FS-CIRC-C-DPC-TPC-FONTE-BT-IND-PARAL-1.5MH-CAP-PARAL-600UF-SCAN1-COR-IND>FONTE -A (Type 8) 10 2 10 1 Fig. 16 Electric odel of the test setup, for calibration of a 230kV CVT. At left, is shown the shunt capacitance and inductance, and the 0.5Ω resistance for reactive copensation. In this test setup, the values of the shunt inductance and capacitance are adjusted for each haronic fruency. For instance, for the calibration of the CVT in haronic fruency of 300Hz (5th haronic), a 1.5H inductance and a 650µF capacitance are used. The 0.5 Ω resistance in series with the voltage source akes soother the fruency response curve, siplifying the tuning of Currente (A) 10 0 10-1 10-2 Fruency (Hz/1000) Fig. 18 Test setup fruency response, with reactive copensation for 300Hz, without the 0.5Ω series resistance. Voltage source (arbitrary wavefor generator) output current. Fig. 18 shows that at 300Hz, a iniu value of voltage source output current is obtained. Also, for ISSN: 1109-2777 886 Issue 9, Volue 7, Septeber 2008

60Hz there is another iniu, aking this test setup suitable for applying, during the calibration tests, a coposite wavefor with a 60Hz and 300Hz voltage haronic coponents. 3 2 FS-CIRC-C-DPC-TPC-FONTE-BT-IND-PARAL-1.5MH-CAP-PARAL-600UF-SCAN1-COR-IND>A - (Type 8) Fig. 19 shows the voltage at priary (low voltage side) side of the step-up transforer, for each haronic fruency. The priary side voltage reains stable, iplying in stability of the arbitrary wavefor generator voltage source output. Current (A) 1 1.5 FS-CIRC-C-DPC-TPC-FONTE-BT-IND-PARAL-1.5MH-CAP-PARAL-600UF-SCAN1-COR-CAP>A - (Type 4) 0 Fruency (Hz/1000) Fig. 21 Electrical current in the shunt inductance, at the priary side of the step-up transforer. Voltage (V) 1.0 Fig. 22 shows the electrical current in the shunt capacitance at the low voltage side of transforer. 0.5 2.0 FS-CIRC-C-DPC-TPC-FONTE-BT-IND-PARAL-1.5MH-CAP-PARAL-600UF-SCAN1-COR-CAP>A - (Type 8) 1.8 1.6 0.0 Tie (s) Fig. 19 Voltage at priary (low voltage side) of step-up transforer considering haronic fruencies. Current (A) 1.4 1.2 1.0 0.8 Fig. 20 shows the electrical current at this sae low voltage side of the step-up transforer. High values of electrical current (200A range at test voltage) are expected at 60Hz fruency for transforer priary side. Current (A) FS-CIRC-C-DPC-TPC-FONTE-BT-IND-PARAL-1.5MH-CAP-PARAL-600UF-SCAN1-COR-IND>A -TB (Type 8) 10 2 10 1 10 0 0.6 0.4 0.2 0.0 Fruency (Hz/1000) Fig. 22 - Electrical current in the shunt capacitance, at the priary side of the step-up transforer.. 4.1 - Influence of the series resistance Fig. 23 shows the test setup uivalent circuit, with series 0.5Ω resistance, shunt 1.5H and 600F capacitance for passive reactive copensation applied at the low voltage side of the step-up transforer. 10-1 0,5 Ω P 1,75 kω P 2 6 0,0317 Ω,3883H 0 242,04 10 19 H 539 10-6 µ F 10-2 Fruency (Hz/1000) Fig. 20 - Electrical current at priary (low voltage side) of stepup transforer. Fig. 21 shows the electrical current in the shunt inductance, at the priary side of the step-up transforer. High values (200A range at test voltage) of electrical current are expected at 60Hz fruency. E 1 V 1,5 H 600 µ F 143,7 MΩ 6 15,6 10 H 539 10-6 µ F 0,213193µF 4,4 10-3 µ F 0,38 kv / 300 kv DPC TPC Fig. 23 - Electric odel of the test setup, with series 0.5Ω resistance, shunt 1.5H and 600µF capacitance for passive reactive copensation applied at the low voltage side of the step-up transforer. Fig. 24 shows output voltage of the test setup, applied to CVT. ISSN: 1109-2777 887 Issue 9, Volue 7, Septeber 2008

Fig. 24 Output voltage of test setup, applied to CVT, with series 0.5Ω resistance, shunt 1.5H and 600µF capacitance for passive reactive copensation. Fig. 25 shows the voltage source output current, with series 0.5Ω resistance, shunt 1.5H and 600µF capacitance for passive reactive copensation. Magnitude (Mag) FS-CIRC-C-DPC-TPC-FONTE-BT-RES-SERIE-05-IND-PAR-1.5MH-CAP-PARAL-600UF- SCAN1>FONTE -A (Type 8) FS-CIRC-C-DPC-TPC-FONTE-BT-RES-SERIE-05-IND-PAR-1.5MH-CAP- PARAL-600UF-SCAN1>P2 4 (Type 4) 10 103 Voltage (V) 102 101 0 100000 200000 300000 400000 Fruency Hz/1000 500000 600000 2.0 1.5 1.0 0.5 0.0 Fruency Hz/1000 Fig. 25 Voltage source output current, with series 0.5Ω resistance, shunt 1.5H and 600µF capacitance for passive reactive copensation. Figs. 24 and 25 shows that the presence of the series 0.5Ω resistance provides an soothing effect on the peaks of the fruency response curves (copare with Figs. 17 and 18), at the resonant fruencies. This feature is advantageous, aking easier the tuning of the test circuit, in the sense that the specification and adjustent of the values of the capacitances and inductances used for reactive copensation are less strict, without the necessity of being too precise concerning its design specification. 5 Conclusions Considering the obtained experiental results, it was possible to assure the effectiveness of this test setup for generating sinusoidal high voltage wavefors, keeping under control, at low values, the total haronic distortion. Also, with this test setup coposite wavefors were produced, at high voltage level, keeping under control the haronic distortion, with the aid of reactive copensation. Additionally, with reactive copensation, it was possible to keep under acceptable low values, the voltage source output current considering 60Hz and other higher order haronic current coponents. This test setup also showed the feasibility of to test, at high voltage levels, test objects with high capacitance (capacitive voltage transforers with thousands of pf capacitance), for 60Hz and higher order haronics, using reactive copensation. References [1] Panoiu M., Panoiu C., Osaci M., Muscalagiu I., Siulation Result about Haronics Filtering using Measureent of Soe Electrical Ites in Electrical Installation on UHP EAF, WSEAS Transactions On Circuits And Systes, Issue 1, Volue 7, January 2008. [2] Tung.N., Fujita. G, Masou. M.A.S, Isla.S.M, Ipact of Haronics on Tripping Tie and Coordination of Overcurrent Relay, 7th WSEAS International Conference on Electric Power Systes, High Voltages, Electric Machines, Venice, Italy, Noveber 21-23, 2007. [3] Yang Han, Mansoor, Gang Yao, Li-Dan Zhou, Chen Chen, Haronic Mitigation of Residential Distribution Syste using a Novel Hybrid Active Power Filter, WSEAS Transactions on Power Systes, Issue 12, Volue 2, Deceber 2007, ISSN 1790-5060. [4] Seifossadat S.G., Razzaz M., Moghaddasian M. Monadi M., Haronic Estiation in Power Systes Using Adaptive Perceptrons Based on a Genetic Algorith, WSEAS Transactions On Power Systes, Issue 11, Volue 2, Noveber 2007, ISSN 1790-5060. [5] International Eletrotechnical Coission, IEC 61000 Standard series, Electroagnetic copatibility (EMC) - (various parts). [6] ATP Alternative transients progra Rule Book, Bonneville Power Adinistration, 1987. [7] Bradley DA, Bodger PS, Hyland PR, Haronic response tests of voltage transducers for the New Zealand power systes, IEEE T-PAS, vol PAS-104, nº 7, 1985. ISSN: 1109-2777 888 Issue 9, Volue 7, Septeber 2008

[8] Seljeseth H, Saethre EA, Ohnstad T, Voltage transforer fruency response. Measuring haronics in Norwegian 300kV and 132kV power systes. Proceedings IEEE 8º International Conference on Haronics and Quality of Power ICQHP 98, Athens, 1998. [9] Dugan, RC, McGranaghan, MF,Santoso, S, Beaty, HW, Electrical power systes quality, 2nd Edition, McGraw-Hill, 2004. [10] International Eletrotechnical Coission, IEC 60060-1 Standard, High voltage test techniques1994. [11] International Eletrotechnical Coission, IEC 61000-4-7 Standard, Electroagnetic copatibility (EMC) - Test and easureent techniques General guide on haronics and interharonics easureents and interpretation, for power supply systes and uipent connected thereto 2º edition 2002. ISSN: 1109-2777 889 Issue 9, Volue 7, Septeber 2008