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International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of......

International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.

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  • 1. Urairat Fuangsoongnern et al Int. Journal of Engineering Research and Applications www.ijera.com ISSN : 2248-9622, Vol. 4, Issue 2( Version 5), February 2014, pp.51-58 RESEARCH ARTICLE OPEN ACCESS A measurement technique to identify and locate partial discharge in transformer with AE and HFCT Urairat Fuangsoongnern1, 2, Asst. Prof. Dr.Winai Plueksawan2 1 2 Provincial Electricity Authority, Bangkok, Thailand Faculty of Engineering Kasetsart University, Bangkok, Thailand ABSTRACT This paper proposes a measurement technique to identify and locate the occurrence of partial discharge (PD) in the insulation of oil immersed and dry type distribution transformers. With reference to IEEE Std. C57.1272007, four acoustic transducers type PD-TP500A were used to locate PD and one HFCT (High frequency current transducer) was used to identify PD. This process could accurately identify and locate the source of PD occurring at any position in a distribution transformer. The result of the findings enabled us to prevent damage and deploy defensive maintenance measure on the distribution transformer in time. Keywords - Partial Discharge, Oil Type Transformer, Dry Type Transformer, Acoustic Emission, High Frequency Current Transducer I. Introduction Transformer is the main equipment which used to modify the voltage in the high voltage from one level to another level in order to supply electricity through transmission lines or distribution lines. Transformers are used for 24 hours and transformers could be damaged by the PD occurring. The research is intended to detect PD in distribution transformers by measuring the PD and identify PD. The measured signal is the waveform shown through computer screen. Bring up the waveform and locate the source of PD occurring at any position in a distribution transformer to analyses for planning in order to prevent damage and preparing to maintenance distribution transformers to prevent damage in distribution transformers. II. Components Of The Transformer Most of the structure of the transformer consists of 3 major components: Core: iron core of a transformer is made from metal sheets, coated with dielectric laminate. Material of dielectric laminate, made from Ferromagnetic, has good magnetic properties. The high magnetic permeability help reducing the magnetic leakage phenomena. Winding: Conducting coil of a transformer is generally made of copper or aluminum wire, wrapped with insulation. Insulation: the insulation of transformer is intended to prevent winding’s exposure to the core steel and prevent each turn of coils from touching one another. In general, transformer consists of two types. Oil Immersed Transformer consists of winding, core, www.ijera.com insulation oil, tank, HV bushing, LV bushing and oil level gauge. Mineral oil is used as insulation and cooling. Dry Type Transformer consists of winding, core, connector and cooling fan. Resin is used as insulation III. Causes And Effects Of Transformer Damage The major cause of transformer insulation deterioration and damage is caused by Partial Discharge (PD). The insulation of the electrode, one side or both sides may be a solid, liquid or gas. Partial discharge occurs in the insulation. With a high electric field is not uniform or insulation is not uniform or homogeneous or other contaminating. Electric field stress at some point in the insulation is higher than the critical electric field stress. But may not have caused a complete breakdown. But it only partially [1, 2, 3, 4, 5]. IV. Theory Of The Measurements, Identification And Location Of The Occurrence Of Partial Discharge Measurement techniques and analysis signal can be divided into the two modes: Off-line Monitoring: Off Line Monitoring Partial Discharge measurement is being measured when all the devices stop working (Shut down system). On-line Monitoring: On Line Monitoring Partial Discharge measurement is conducted while all the devices are operating normally and being nonstop working. In the measurement of the partial discharge in this mode, the Partial Discharge occurs while supply being on only [6]. 51 | P a g e
  • 2. Urairat Fuangsoongnern et al Int. Journal of Engineering Research and Applications www.ijera.com ISSN : 2248-9622, Vol. 4, Issue 2( Version 5), February 2014, pp.51-58 In this article, the researchers measured the PD in the transformers using the On-line Monitoring described in AE method (Acoustic Emission: IEEE Std. C57.1272007) [9] and HFCT (High Frequency Current Transducer). 4.1 Acoustic Emission technique Acoustic Emission technique is testing by sending sound waves through an advanced non-destructive testing [7, 8]. The principle is to measure the frequency and the energy released when the crack expansion or when the phase change in the material and the energy that is released from the physical change in a solid material. Caused by external force or by a change in temperature such as the fluid and within the crack. Which the object is detected by the release of energy and precise to predict the position of the Partial Discharge [9, 10, 11]. can be viewed in trend, table view, 2D graph, 3D graphic and amplitude-pulse. 5.2 Description of equipment used in the test 5.2.1PD-TP500A PD-TP500A is a tool which is used for analysing signal and the findings signal of partial discharge of equipment. PD-TP500A has five channels consist of four of AE (Acoustic Emission) and a HFCT (High Frequency Current Transducer) sensors detecting the signal simultaneously, compare the signals to determine whether the signal originated from inside of the equipment or outside. When comparing all four signals from AE sensors, the location of the source can be determined. Figure 2. Power PD System Model (PD-TP500A) Figure 1. Illustration of typical propagation paths for the acoustic PD signal 4.2 High Frequency Current Transducer technique High Frequency Current Transducer technique has been specifically designed to measure the signal of Partial Discharge in contrast, it has a ferrite core to be suitable for the device to be measured. The main applications in the measurement the signal of Partial Discharge devices use HFCT consistent with ground wire of the transformer. Partial discharge test with HFCT on line transfer impedance measurement method is a technique in which units of measure are in the form 2.4 mV/1mA. V. 5.2.2 AE Sensor AE Sensor (Type R15I: Preamplifier 100x) has a sensitivity of 20 pC. Frequency range is from 50 kHz to 300 kHz. The sampling rate is 18 MHz. (max). The detected signals will be amplified 100 times for further processing. Figure 3. AE Sensor 5.2.3 HFCT Sensor HFCT Sensor (Type 50/100: 1mA/2.4mV) has a sensitivity of 5 pC. Frequency range is from 100 kHz. to 30 MHz. The sampling rate is 20 MHz (max). The signal rate is one to 2.4. The Equipments Used In The Experiment 5.1 Partial Discharge Signal Analysis is online The device which used to display on the computer screen called Power PD (PD-TP500A). It used for measuring the Partial Discharge online for transformers with Sensors 2 types of AE Sensor and HFCT Sensor is connected to the PD-TP500A via coaxial cable at a distance of 20 meters and connected to HFCT at a distance of 10 meters. The signals from four AE sensors and a HFCT are measured simultaneously and the data is saved in computer [12]. The software will analyze the frequency of measured signal, burst time, spectrum and the location of the source [13]. The data from the continuous monitoring www.ijera.com Figure 4. HFCT Sensor 5.3 Preparation for the test Equipment used in testing are: 5.3.1 AC power source 5.3.2 Sets of equipment PD-TP500A consists of AE Sensor and HFCT Sensor and computer to display the measurement and analysis of the signal Partial 52 | P a g e
  • 3. Urairat Fuangsoongnern et al Int. Journal of Engineering Research and Applications www.ijera.com ISSN : 2248-9622, Vol. 4, Issue 2( Version 5), February 2014, pp.51-58 Discharge by connection Power PD (PD-TP500A) to computer via Port USB. 5.3.3 Equipment used to measure the partial discharge signal must be loading and running at all times. 5.3.4 When the equipment provided and installed to measure signal of partial discharge completed and then performed to detect and measure the signal. The result of signal to analysis and locate the source of the signal detected. If none of the sensors were able to detect any signals of PD Burst, it could be concluded that no PD occurred within the transformer, as shown in Figure 8. Figure 8. Display of No Partial Discharge Figure 5. Configuration of PD-TP500A VI. Reading Data And Signals Attained From The Experiment If signals were detected by AE sensors only, it could be concluded that the signals could either be a mechanical signal, floor vibration or some sort of loose parts inside the transformer, as shown in Figure 9, Figure 10, and Figure 11 respectively. Figure 6. Display of Software If PD Burst were detected from both AE sensors and HFCT sensor. It could be concluded that the PD occurred within the transformer, as shown in Figure 7. Figure 7. Display of Partial Discharge Detect www.ijera.com Figure 9. Display of a Mechanical Signal inside the transformer Figure 10. Display of Arcing signal inside the transformer 53 | P a g e
  • 4. Urairat Fuangsoongnern et al Int. Journal of Engineering Research and Applications www.ijera.com ISSN : 2248-9622, Vol. 4, Issue 2( Version 5), February 2014, pp.51-58 Figure 13. The position of AE sensor installation for Oil Immersed Transformer (Core Form: Single Phase) Figure 11. Display of Signal from inside of core vibration If signals were detected from the HFCT sensor only, it could be concluded that the signals could be mechanical signals or from arcing inside the transformer or it could be signals of PD caused by external transformer as shown in Figure 12. Figure 14. The position of AE sensor installation for Oil Immersed Transformer (Core Form: Three Phase) Figure 15. The position of AE sensor installation for Oil Immersed Transformer (Shell Form: Single Phase) Figure 12. Display of Partial Discharge outside the transformer VII. The Installation of AE Sensors And HFCT Sensor The installation of AE sensors referred to the IEEE Std C57.127-2007, Guide for the Detection and Location of Acoustic Emissions from Partial Discharge in Oil-Immersed Transformers and Reactors [9, 14, 15, 16]. AE 1: Installed at Top of Side 1 (HV Side), AE 2: Installed at Bottom of Side 2 (Left Side), AE 3: Installed at Top of Side 3 (LV Side) and AE 4: Installed at Bottom of Side 4 (Right Side) Figure 16. The position of AE sensor installation for Dry Type Transformer VIII. Case Study 8.1 Oil Immersed Transformer The experiment was conducted on May 31, 2011. The transformer being tested was an Oil Immersed Type www.ijera.com 54 | P a g e
  • 5. Urairat Fuangsoongnern et al Int. Journal of Engineering Research and Applications www.ijera.com ISSN : 2248-9622, Vol. 4, Issue 2( Version 5), February 2014, pp.51-58 with specifications of 2000 kVA, 22 kV/400-230 V, 50 Hz,3 Phases. The position of AE sensor installation referred to IEEE Std C57.127-2007 [9]. Figure 20. The result of measured signal of PD (Move AE and HFCT) Figure 17. The position of AE sensor and HFCT on transformer Figure 18. Signal of partial discharge detection with AE and HFCT As shown in Figure 20, after reposition the sensor 2, sensor 3, sensor 4 and HFCT, the PD location at sensor 1 could be confirmed. In order to reconfirm the PD location, all the AE sensors were repositioned along Y axis (vertical) and HFCT remained on case ground of side 2. Figure 21. The position of AE sensor and HFCT after repositioning Figure 18 shows the signals detection from AE sensor 1 and HFCT sensor. To confirm the location of PD, sensor 2, sensor 3 and sensor 4 were repositioned around sensor 1 and HFCT was moved to the position of on case ground of side 2. Figure 22. The result of measured signals of PD (AE sensors and HFCT repositioned) Figure 19. Position of AE sensors and HFCT on transformer www.ijera.com From Figure 22, after the AE sensors were installed along the Y axis, it could once again be confirmed that the PD occurred at the location of AE sensor 1. To make another reconfirmation, all the AE sensors were moved to the position of the top of side 1 while the HFCT remained at the same position. 55 | P a g e
  • 6. Urairat Fuangsoongnern et al Int. Journal of Engineering Research and Applications www.ijera.com ISSN : 2248-9622, Vol. 4, Issue 2( Version 5), February 2014, pp.51-58 Figure 23. The position of AE sensor and HFCT on transformer (After knowing the source of the signal) Figure 26. Signal of partial discharge detection with AE and HFCT From Figure 26, show the signal detection from AE sensors and HFCT. In order to reconfirm the PD location, all the AE sensors were repositioned along X axis (horizontal) and HFCT remained on case ground of side 4 as shown in Figure 27. Figure 24. The result of measured signal of PD (after AE sensors and HFCT repositioned) Figure 24, shows that the AE sensors and HFCT sensor were able to detect and locate the PD at the position of the top of side 1. The positions of the AE sensors are shown in Figure 23. 8.2 Dry Type Transformer The experiment was conducted on November 12, 2010. The transformer being tested was a Dry Type Transformer with specifications of 1600 kVA, 24 kV/400-230V, 50 Hz, 3 Phases. The position of AE sensor installation referred to IEEE Std C57.127-2007 [9]. Figure 25. The position of AE and HFCT on Dry Type Transformer www.ijera.com Figure 27. The position of AE sensor and HFCT after repositioning Figure 28. The result of measured signals of PD (AE sensors and HFCT repositioned) 56 | P a g e
  • 7. Urairat Fuangsoongnern et al Int. Journal of Engineering Research and Applications www.ijera.com ISSN : 2248-9622, Vol. 4, Issue 2( Version 5), February 2014, pp.51-58 From Figure 28, after the AE sensors were installed along the X axis, it could once again be confirmed that the PD occurred at the location of AE sensor 2. To make another reconfirmation, all the AE sensors were repositioned along Y axis (vertical) while the HFCT remained at the same position as shown in Figure 29. Figure 32. The result of measured signal of PD (after AE sensors and HFCT repositioned) Figure 29. The position of AE sensor and HFCT after repositioning From Figure 32, shows that the AE sensors and HFCT sensor were able to detect and locate the PD at the position of the top and middle of side 3. The positions of the AE sensors are shown in Figure 31. IX. Figure 30. The result of measured signal of PD (after AE sensors and HFCT repositioned) From Figure 30, after the AE sensors were installed along the Y axis, it could once again be confirmed that the PD occurred at the location of AE sensor 2. To make another reconfirmation, all the AE sensors were moved to the position of the top and middle of side 3 while the HFCT remained at the same position. X. Figure 31. The position of AE sensor and HFCT on transformer (After knowing the source of the signal) www.ijera.com Conclusion From the measurement of partial discharge in oil immersed transformer and dry type transformer with on-line monitoring methodology using the PDTP500A in conjunction with acoustic emission (AE) sensors (reference to IEEE Std. C57.127-2007) and a clamp-on type high frequency current transducer (HFCT) to detect and locate PD, it could be summarized as follow. 9.2 The equipments used for PD measurement, which are the PD-TP500A, AE sensors and HFCT, can be installed at the equipment being measured while it is running, no need to shut down the equipment and the power system. 9.3 This set of equipments is able to detect and analyze the problems occurring inside the transformer in the early state and inform how severe the problem is. More importantly, it is able to indicate whether the problem is caused by partial discharge, mechanical problems, arcing or loose part inside the transformer. 9.4 This method of partial discharge diagnosis is able to detect and correctly locate the partial discharge occurring inside the transformer which helps the transformer maintenance to be carried out effectively and then prevents the complete breakdown of the transformer which eventually reduces the cost occurring from repairing severely damaged transforme. Acknowledgments I would like to express my sincere thanks to my thesis advisor, Asst. Prof. Dr.Winai Plueksawan for her invaluable help and constant encouragement throughout the course of this research. Finally, I most gratefully acknowledge my parents and my friends for all their support throughout the period of this research. 57 | P a g e
  • 8. Urairat Fuangsoongnern et al Int. Journal of Engineering Research and Applications www.ijera.com ISSN : 2248-9622, Vol. 4, Issue 2( Version 5), February 2014, pp.51-58 REFERENCES Urairat Fuangsoongnern, Winai Plueksawan, and Promsak Apiratikul, Partial Discharge Analysis for Power Distribution Transformer Model, The Proceeding of 46th Kasetsart University Annual Conference, January 29 – February 1, 2008, 72-80. [2] F.H. Kreuger, Partial Discharge Detection in High-Voltage Equipment, Butterworths, London, England,1989. [3] H. Ogihara, Detection and location of coronas in oil-immersed transformer with corona detector. Electr. Eng. Jpn., vol. 84, 1964, 12-22. [4] S. A. Boggs, Partial discharge-Part III: Cavity-induced PD in solid dielectrics. IEEE Electr. Insul. Mag., vol. 6, no. 1, Jan./Feb. 1990, 11-20. [5] Winai Plueksawan, Promsak Apiratikul, and Urairat Fuangsoongnern, Partial Discharge Analysis for Power Distribution Transformer Model. EECON-31. 31st Electrical Engineering Conference, October 29-31, 2008, 299-302. [6] A. Santosh Kumar, Dr. R.P. Gupta, Dr. K. Udayakumar, and A. Venkatasami, Online Partial Discharge Detection and Location Techniques for Condition Monitoring of Power Transformers: A Review. IEEE International Conference on Condition Monitoring and Diagnosis, Beijing, China, April 21-24, 2008, 927-931. [7] R. T. Harold, Acoustical technology applications in electrical insulation and dielectrics. IEEE Trans. Electr. Insul., vol. 20, no. EI-1, Feb. 1985, 1-3. [8] B. R. Varlow, D. W. Auckland, and C. D. Smith, Acoustic emission analysis of high voltage insulation. IEE Proc.-Sci. Meas. Technol., vol. 146, no. 5, 1999. [9] IEEE Guide for the Detection and Location of Acoustic Emissions from Partial Discharge in Oil-Immersed Power Transformers and Reactors. IEEE Std. C57.127-2007. [10] IEEE Guide for Partial Discharge–Part XIV: Acoustic partial discharge detection– Practical application. IEEE Electr. Insul. Mag., vol. 8, no.1, Jan./Feb. 1992, 34-43. [11] IEEE Guide for Partial Discharge – Part XIII: Acoustic partial discharge detection – Fundamental considerations. IEEE Electr. Insul. Mag., vol. 8, no.1, Jan./Feb. 1992, 2531. [12] Prasanta Kundu, N. K. Kishore, and A. K. Sinha, Simulation and Analysis of Acoustic Wave Propagation due to Partial Discharge Activity. IEEE 2006 Annual Report Conference on Electrical Insulation and Dielectric Phenomena, 607-610. [1] www.ijera.com [13] R. T. Harold, Acoustical waveguide for sensing and locating electrical discharge in high voltage power transformers and other apparatus. IEEE Trans. Power App. Syst., vol. PAS-98, no. 2, 1979, 449-457. [14] Xiaodong Wang, Baoqing Li, Harry T. Roman, Onofrio L. Russo, Ken Chin, and Kenneth R. Farmer, Acousto-optical PD Detection for Transformer. IEEE Transactions on Power Delivery, Vol. 21, July 3, 2006, 1068-1073. [15] Su Su Win, Myo Myint Aung, and Wunna Swe, Partial Discharge Detection and Localization in Power Transformers. The 8th Electrical Engineering/ Electronics, Computer, Telecommunications and Information Technology (ECTI) Association of Thailand Conference, 2011, 673-676. [16] A. K. Lazarevich, Partial Discharge Detection and Localization in High Voltage Transformer using an Optical Acoustic Sensor. Master of Science Thesis, The Virginia Polytechnic Institute and State University, USA, 2003. 58 | P a g e