Inernaional Journal of Smar Grid and Clean Energy Developmen of Temporary Ground Wire Deecion Device Jing Jiang* and Tao Yu a Elecric Power College, Souh China Universiy of Technology, Guangzhou 5164, China Absrac In order o solve he safey problem of disassembling he ground wire emporarily for line mainenance, his paper proposes a new deecion mehod o preven ransmission lines closing wih ground wire, and invens a porable deecor o deec he saus of ground wires by making full use of modern power elecronics and digial signal processing echnology. Finally his paper developed he corresponding porable ground wire sae deecor. Descripions of he use of deecor, design ideas of hardware and key algorihms are represened. The deecor designed in his paper is simple-operaed, low cos, highly reliable, easy o promoe, ec. and i also can effecively preven human-induced acciden which is caused by ransmission lines closing wih ground wire. Keywords: Ground wire; elecric power overhaul; ransmission line; boos; comb filer 1. Inroducion Ground wire is imporan in mainenance and reformaions of power sysems. A presen, i mainly depends on he operaion icke and he performance degree of he operaing rules by he operaors in he process of ransmission line mainenance o avoid he risk. Therefore, here is a high probabiliy of missing-removing he ground wire, which can easily lead o serious acciden of swich on power ransmission wih ground. The Microcompuer Device avoids misoperaion by a series of logic judgmen and elecric chain and mechanical locks, bu for he misoperaion behavior of ransmission lines closing wih ground, which sill has serious hidden rouble and securiy leak [1]. A lo of measures and auxiliary devices have been designed o he managemen of emporary grounding o avoid closing wih a ground wire [-7]. Ground wire managemen sysem can enhance he reliabiliy of using ground wire and regulae he managemen of ground wire [-3] by replacing he exising ground wires, bu i demands sizable workload and he capial cos. An early-warning sysem of ground wire sae monioring can imely obain he working sae of ground wire [4], however, here is sill no suiable soluions for grounding-swich o avoid acciden by human-iniiaed-failure. Saus deecing device of ground wire which has been researched in [5-6] can make power sysem overhaul work achieve he aim of real ime on-line monioring, bu here are some deecion defecs by using ulrasonic ranging. These mehods and devices play a role in he ground wire misoperaion, bu mos echnical mehods are based on regulaions and human judgmen. They need high reconsrucion and sysem building cos, and can compleely avoid he acciden by human. Therefore, we should develop a porable inelligen device of ground wire by using he advanced power elecronics, signal processing, inelligen decision echnique for improving he accuracy and adapabiliy, and confirm he sae of ground wire in echnology o prevens he acciden of sending he elecriciy by closing earh line effecively.. Deecion Principle of Ground Wire In order o ensure he personal safey, here mus be ground wire near he ground when someone * Manuscrip received April, 1; revised Augus 15, 1. Corresponding auhor. Tel.: +86--8586976; E-mail address: ceeejiang@163.com.
Inernaional Journal of Smar Grid and Clean Energy, vol., no. 1, January 13 operaes wih he line, which is specified in he safey operaion. Therefore, he design mehod used by he deecor is as following: wih he las group deecion grounding wires remained and esed, hen remove or disconnec he las group afer making sure ha here is no addiional ground wires, which could avoid securiy risks caused by humans..1. Deecion principle of injecion volage The mehod of injeced volage measuremen is given as figure 1. One end of he signal source of he deecion insrumen is conneced o he ground line direcly, and he oher end is conneced o he earh hrough he auxiliary pole, which mehod is simple and pracical. In Fig. 1, he injec volage used sine wave volage wih adjusable ampliude. In order o avoid he effecs of ransformer, PT, phase-o-phase capaciance and ground capaciance, and eliminae he inerference of inducion signal, he wrier chose 4 Hz as he working frequency of injeced signal according o he resuls of simulaion and pracice esing requiremens. I can be seen from Fig. 1 ha wo ground wires form a loop when here is an addiional ground wire and he deeced curren value I is as he following: U I = R+ R3 + ( RL + jwxl)/3 (1) When here is no addiional ground wire, i can form a loop, and he curren I =. So we can judge he sae of ground wire by deecing he curren value. Fig. 1. Schemaic diagram of he injeced volage measuremen. Fig.. Schemaic diagram for he measuremen sysem of double clamp ype... Deecion principle of double-clamp inducion volage Double-clamp measuremen deecs he sae of ground wire direcly by he judgmen wheher here are loops beween wo phases. The specific deecion mehod is as shown in Fig.. When here is a loop, a volage signal source hrough he volage clamp in he measured circui generaes a consan AC volage. And he volage in he shor circui loop will generae a curren I:
Jing Jiang e al.: Developmen of Temporary Ground Wire Deecion Device 3 I = U RL+ jwxl+ (( RL+ jwxl)/) //( R + R ) 1 () Double-clamp deecion mehod eliminaes he influence of grounding resisances; i is accurae, convenience and safey. 3. Design of Hardware 3.1. Hardware srucure design According o he deecion principle of ground wire, he design of is hardware srucure diagram is as shown in Fig. 3. The design of he ground wire deecor mainly comprises daa processing chip TMS3LF47, volage and curren sampling circui, ani-jamming circui, filer circui, PWM driving circui, signal generaor, baery power supply monioring circui, LCD crysal display and keyboard inpu circui. Fig.3. Schemaic diagram of hardware srucure. 8 6 4 - -4-6 -8...4.6.8.3.3.34.36.38.4 6 4 - -4 Fig.4. Deecion circui simulaion analysis. -6...4.6.8.3.3.34.36.38.4 8 6 4 - -4-6 -8...4.6.8.3.3.34.36.38.4
4 Inernaional Journal of Smar Grid and Clean Energy, vol., no. 1, January 13 3.. Deecion circui design The design of deecion circui needs o be obained from he curren sensor, a very weak signal which needs o be amplified o -3 V for 1 bi A/D converer for sampling. The accuracy and sabiliy of amplifying and filering will affec he performance of he deecing device direcly. So he preamplifier circui will use he precision, low power inegraed INA118 insrumenaion amplifier, and he filer use a wo sep low-pass, high-pass circui. The minimum curren value deeced is.1 ma, and he maximum is A. In order o ensure he accuracy of he measuremen, 8 channel digial conrolled swich CD451 is used o conrol he gain of he amplifier circui of muliples, realizing he auomaic funcion of swiching [7]. In order o verify he circui s performance, selecing he appropriae circui parameers, he wrier makes he simulaion of he circui as shown in Fig. 4. The inpu signal U1 includes inerference signals. Afer wo order band-pass filer, he noise componens are effecively removed, bu he ampliude of he signal is small, he noise raio does no mee he requiremens. So he signal U will be filered afer inermediae amplified. The resul of simulaion shows ha he noise raio is very high, and i s very beneficial for daa processing. 3.3. The design of he signal source In order o mee he requiremens of porable measuremen, 6V baery is used as power inpu by he insrumen. Since a 1 V, 1 W sandard sine wave signal source is needed, he insrumen adops boos circui and full bridge inverer echnology scheme [8], of which he program srucure diagram is as shown in Fig. 5. Fig. 5. Schemaic diagram of oupu power. The design of he Boos circui changes he inpu 6 V o 18 V DC volage, and invers o a high frequency AC square wave, and finally ges a 1 V RMS sandard sine wave hrough he LC filer circui. According o he power and he volume requiremens, he swich ubes of Boos circui and he full bridge circui use AP9971GD which has double MOS ransisors. AP9971 is a small volume, wih conducion loss, fas swiching speed, low cos and small power MOS ransisor, of which he volage and curren can reach o 6 V-5 A, on-resisance only 5 m ohm, especially suiable for he sysem of echnical parameers. The MOS ransisor driving chip uses high performance full bridge chip IR11, and his chip is a dual channel. The gae drive, high volage and high power devices monolihically inegraed drive module, grealy simplifying he logic circui of power device conrol requiremens, improving he reliabiliy of driving circui. IR11 has inernal boosrap circui, wih a separae high-end and low-end wo oupu channels, meanwhile i can simulaneously drive he same bridge arm wo MOS ransisors, and grealy simplify he circui srucure. 4. Deecion Algorihm Analysis Afer invesigaion, because of he same induced volage, here is a power frequency and is harmonics inerference signal. Due o he deeced curren signal is very weak, he inerference signal seriously affecs he correc deerminaion of he equipmen. In order o remove he inerference signal componen effecively, he deecion algorihm uses comb filer and digial filer processing. Comb filer has he funcion of enhancing or removing periodic signal componen, and is ransfer funcion is as following [9]:
Jing Jiang e al.: Developmen of Temporary Ground Wire Deecion Device 5 N 1 z 1+ ρ H 1 (z) = b, b = N 1 ρ z (3) 1 / N j πk / N Is poles are ρ e, k =,1..., N 1, and is ampliude-frequency response is as shown in Fig.6: Fig. 6. Ampliude-frequency response of comb filer From he ampliude-frequency response of comb filer, we can see ha i can effecively suppress he power frequency and is harmonics signals, and i s very suiable for he deecion of he sae of he ground line. 5. Conclusions This paper inroduces he porable ground wire deecor s deecion mehod, he key hardware and algorihm design in deail. This insrumen inhibis he leakage remove ground accidens by using deecion echnology. Is advanages are simple and convenien operaion, low cos, high reliabiliy, and so on. I doesn need for high cos of large-scale recificaion and i can be easily exended, and mached wih oher ground wire managemen sysem or process. As he las dich, i eliminaes he malignan acciden caused by arificial facors, and provides a reliable guaranee for he safe operaion of elecrical equipmen and safey of personnel. References [1] Tang CH, Song B, Hu G, e al. A new elecric Ani-maloperaion sysem based on IEC6185 sandard. Auomaion of Elecric Power Sysems, 9; 33(5):96-99. [] Xu JY, Dou WJ, Wang AH. On-line monioring sysem of ground wire working condiions. Elecric Power Auomaion Equipmen, 8; 8(7):111-113. [3] Zhang HL, Xu JY, Wang AH, e al. Research on ani-misoperaion managemen sysem of mobile ground-wire in power grid disribuion. Low Volage Apparaus, 8; 9(15):34-37. [4] Zhang ZL, Li DW, Guo XS, e al. A monioring and warning sysem for ransmission nework mainenance and ground wire working condiions. Auomaion of Elecric Power Sysems, 9, 33(16):11-115. [5] LIU Jiajun, MIAO Jun, e al. Visualized monioring of ground wire connecion saus for elecric power mainenance operaion. Elecric Power Auomaion Equipmen, 1; 3(7):134-136. [6] Liu JJ, Miao J. Research on new ype of elecric power overhaul ground wire device. Power Sysem Proecion and Conrol, 9; 37(3):119-11. [7] Hua CY, Tong SB. Basic Analog Elecronic Technology. Beijing: Higher Educaion Press; 6. [8] Liu FJ. Modern Inverer Technology and Is Applicaion. Beijing: Publishing House of Elecronics Indusry; 6. [9] Hu GS. Digial Signal Processing Theory, Algorihms and Implemenaion. Beijing: Tsinghua Publishing House; 3.