Research on On-line Monitoring of Insulation of Metal Oxide Surge Arrester

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1 206 nternational Conference on Material Science and Civil Engineering (MSCE 206) SBN: Research on On-line Monitoring of nsulation of Metal Oxide Surge Arrester Yu-ting XU, Xiao-hua YUAN, Ya-li MO, Guo-tai DONG and De-cheng ZHU Shenyang nstitute of Engineering, Shenyang 036, Liaoning Province, China The commonly used on-line monitoring principle and methods of MOA are analyzed in the thesis. According to the operating characteristics of MOA, the harmonic generated by the harmonic voltage is obtained with a linear equivalent resistance. According to the relationship between phase s voltage and, the composition in the whole and interfering status of phases, the extraction algorithm of the fundamental and the third resistive is proposed. Keywords: Metal Oxide Surge Arrester; On-line monitoring; Resistive.. ntroduction After field operation showed that because of the zinc oxide lightning arrester are without a gap, so that the zinc oxide valve sheet long withstand power frequency voltage, during the running of the total flowing through the valve plate, plus on impulse voltage and internal moisture and other factors, cause valve arrester aging, increase the resistive leakage and power consumption increased, resulting in lightning arrester valve plate temperature increases until the thermal collapse, causing the accident of power network. 2. Principle of On Line Monitoring Device for Arrester n the normal operation of the power frequency voltage, the zinc oxide lightning arrester approaches the insulator, the flowing through it is very small, only milliampere; when the system has a high voltage or, over protection products of insulation resistance or through flow capacity, parallel arrester can automatically reduce the resistance. 328

2 2. The Principle of Monitoring the Resistance Current of MOA by the Method of Harmonic Analysis Figure. Equivalent circuit of MOA. As shown in Fig, the operating voltage of the MOA, the leakage. Power system voltage and waves meet the Dirichlet condition, therefore, can be decomposed into Fourier series: x U0 Ukm sin( kt+ k ) k. () ix 0 km sin( kt+ k ) k. (2) dux dc Due to i C C ux dt dt,small capacitance changes in the small area, so there is dc =0.The capacitive component of the leakage dt of the formula (): dux ic C Ck cos( kt+ k) dt k. (3) among it, Ck kcukm Let RX for the kth harmonic resistive amplitude can be that the resistive leakage and capacitive leakage at the same time harmonic 329

3 phase angle difference π, and the kth harmonic voltage and the K time harmonic 2 resistive phase, so the resistive ir 0 Rk sin( kt+ k ) k. (4) 3. Overall Structure of nsulation on Line Monitoring System Figure 2. Online monitoring system structure of MOA. As shown in Fig2, For MOA measurement, the measured voltage and signals are obtained from the voltage transformer (PT) and the bottom of the MOA. The voltage of the device is converted into low-voltage signal by PT, and the signal is sent to the front processing board (signal) by the cable. 4. On Line Monitoring Method of MOA s produced by the fundamental voltage on the nonlinear resistive fundamental, three times harmonic resistive changes to reflect the operation status of MOA, the leakage from the resistive is the key to determine the status of MOA. The arrangement of MOA in the field is more than one type, the A and C are far away, and the Phase interference between them can be ignored. A phase only considers the influence of B phase, B phase considering the influence of A and C phases, C phase is considered in the B phase, as shown in Fig

4 Figure 3. Phase interference of MOA. 2. An algorithm for extracting fundamental resistive. A phase leakage for the fundamental component AX : AX AR AC BA Phasor A, B, C phase fundamental is shown in Fig 4: AC AX U A AR 30 BA 90 U B BC U BX A. (5) U B BR B CB AB U C CX U C CC U B CR C 60 BC (a)a phase (b)b phase (C)C phase Figure 4. Fundamental phase diagram of A,B and C phase. The phase diagram of 4A, B, C three-phase fundamental can be obtained, such as (6) under the Department of type. 33

5 3 3 AX cosax AX BAC AR CBAUB AX sina AC BAC CAUA CBAUB 3 3 BXcosB BR CBC ABC 3 3 BR CCBUC CABUA (6) BX sinb BC CBC ABC CU B B CCBUC CABUA 3 3 CX cosc CR BCC CR CBCUB CX sinc CC BCC CCUC CBCUB Formula (6) in the six equations can be solved out of the six unknowns AR, BR, CR, Y,Y AB,Y BC, n which, AR, BR, CR, the fundamental wave voltage is generated on the MOA generated by the fundamental resistance. By, AR, BR, CR, The equivalent linear resistance of A, B and C three phase MOA can be obtained. U A U B UC R A R B R C AR, BR, CR 3. Three harmonic resistive extraction algorithm The three harmonic component of A phase leakage AX3 is AX 3 AR3 AC3 BAC3 Af 3. (7) As shown in Fig 5 (a).n the same way, the phase diagram of the three harmonic s can be drawn from the B and C phases, as shown in Fig 5 (b), (c). 332

6 AC 3 AX 3 BAC 3 U Af 3 A3 A3 ( U ) A3 B3 AR 3 BC 3 BX 3 Bf U U U B3 A3, C3 3 B 3 B3 ABC 3 CBC 3 ( ) BR3 CC 3 CX 3 U Cf BCC 3 ( U ) C3 B3 3 C 3 C 3 CR3 (a)a phase (b)b phase (c)c phase Figure 5. Third phase diagram of A,B and C phase. According to the relationship between the three (a) A phase 5 harmonic s, can be written (8). AX 3cos A3 AR3 Af 3cos A3 (8) sin sin AX 3 A3 AC3 BAC3 Af 3 A3 Similarly, according to figure 5 (b) B phase three harmonic s of the relationship, can be written (9) type. BX 3cosB3 BR3 Bf 3cos B3 (9) sin sin BX 3 B3 BC3 ABC3 CBC3 Bf 3 B3 According to the formula (9), BF3can be obtained, three harmonic resistive generated by the fundamental wave voltage of the B phase. Similarly, according to figure 5 (c) C phase three harmonic s of the relationship, can be written (0) type. 333

7 cos cos CX 3 C3 CR3 Cf 3 C3 sin sin CX 3 C3 CC3 BCC3 Cf 3 C3 (0) According to the formula (0), CF3 can be obtained, that is, the C phase of the fundamental voltage generated by the three harmonic resistive. 5. Simulation and Experimental Results are Analyzed n order to verify the validity of the algorithm, the MOA valve patch model is analyzed by using the algorithm and the improved capacitive compensation method. The fundamental and the three harmonic components of the resistive are calculated. MOA valve slice model: i R = tan u k () Using the phasor method and the improved capacitive compensation method for analysis, the data obtained, such as Table, Table 2 (in A MOA as an example), the bracket is relative error value. Table. Resistive value of improved compensation method and phase method when U3=3%U and initial phase is different. Third harmonic amplitude 0 First phas e mproved Capacitive Current Compensation Method(μA) Resistive fundamental Three resistive Resistive fundamental Phasors (μa ) Three resistive 0 50.(-3.087%) 7.(-28.2%) 50.(-3.095%) 8.2(-.2%) (-2.507%) 7.6(-23.2%) 50.5(-2.705%) 8.8(-4.%) (-.733%) 9.0(-.%) 5.0(-.6%) 9.4(-5.05%) (0.386%) 0.4(5.05%) 52.3(.57%) 0.2(3.03%) U=3%U (.544%).7(8.%) 53.0(2.5%) 0.7(7.%) (3.473%) 2.5(26.2%) 53.2(2.905%).3(4.%) (3.667%) 3.0(3.2 %) 53.7(3.87%).7(8. %) 334

8 Table 2. Resistive value of improved compensation method and phase method when U3=5%U and initial phase is different. Third harmonic amplitude 0 First phase mproved Capacitive Current Compensation Method(μA ) Resistive fundamental Three resistive Resistive fundamental Phasors ( μa ) Three resistive 0 49.(-5.03%) 5.0(-45.3%) 49.0(-5.22%) 7.0(-4.8%) (-4.45%) 6.3(-36.3%) 49.8(-3.68%) 8.(-8.0%) U=5%U (-2.53%) 8.9(-0.0%) 5.3(-0.77%) 9.0(-5.04%) (.38%).3(4.%) 52.6(.74%) 0.6(7.06%) (3.86%) 3.9(40.4%) 54.(4.64%).6(7.0%) (6.93%) 4.9(50.5%) 55.2(6.77%) 2.4(25.%) (6.56%) 5.(52.3%) 55.3(6.95%) 2.9(30.5%) From Table and Table 2 can be seen, when the system contains a third harmonic voltage, quantity method effectively reduces the third harmonic resistive error, the main reason is the phasor method of MOA nonlinear resistors is equivalent to a linear and nonlinear resistance model, remove the harmonic voltage generated in the equivalent linear resistance of harmonic resistive. Also improved volume of compensation method for phase to phase coupling capacitance effect cannot be ruled out, when the phase interference is more serious to detect eigenvalue exist great error, and method in the analysis give full consideration to the phase interference effects, effectively remove the phase coupling capacitance caused by measurement error. Therefore, using the phasor method to carry out on-line monitoring has obvious effectiveness. 6. Conclusions Online monitoring data to judge the running status of the arrester provides very important basis, we must attach great importance to this work, to further improve the arrester on-line monitoring and inspection system, continue to explore and gradually establish to the actual state of the arrester repair and maintenance according to according to scientific maintenance method, to carry out arrester equipment evaluation and condition based maintenance, change the unreasonable 335

9 system of regular maintenance, reduce equipment of repeat outages or unnecessary power cut, reduce the human and financial resources waste, improve the reliability of power supply. Reference. Yunzhong Luo. nnovative installation of the 0kV line Zinc Oxide arrester. Enterprise technology development, 202, 3 (6). 2. Xinggui Wang, Qingling Li, Xiaozhen Li, et al., the application of Zinc Oxide surge arrester [J]. high voltage electrical equipment, 2008, 44 (2). 3. Wei Deng. Research on measurement method of resistive of metal oxide surge arrester [D]. Shanghai: Shanghai Jiao Tong University, Wenhu Hu, Xianggen Yin. Research and development of [J]. online monitoring technology of electrical equipment in North China electric power technology, 2003, 8 (2): Zuheng Niu. Based on the DSP of the zinc oxide arrester leakage online detection [J]. Journal of Shenyang nstitute of engineering, 200 (4): 338 a Huiwen Zeng. The principle and system of the on-line monitoring of the insulation of the Zinc Oxide arrester [D]. Sichuan University, Jianjun Qiang, Xinbo Huang, cloud chapter. Based on GPRS network of metal oxide to avoid electric porcelain to avoid the need for online monitoring system design [J] (6): Shijian Deng, Xingyu Zhu. Design of an online monitoring system for the [J]. industrial control computer, 2006 (5): Yuting Yan, Jian Wu, Zhong Jianling etc. Metal oxide to avoid the need for accident analysis and testing method of comparative study. nsulators and avoid the need for 20 (5): Changchang Wang, Fuqi Li, Sheng Gao Electrical equipment on-line monitoring and fault diagnosis [M]. Beijing: Tsinghua University Press, Ke Zhang. Research on the online monitoring technology of the resistive of the arrester of Zinc Oxide [J]. Master Thesis of North China Electric Power University,

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