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Wadhwani, M. K.
- Parameters Affecting the Performance of Transformers Under Short Circuit - A CPRI Experience
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1 Switchgear Testing and Development Station, Central Power Research Institute, Bhopal, IN
1 Switchgear Testing and Development Station, Central Power Research Institute, Bhopal, IN
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Power Research, Vol 7, No 2 (2011), Pagination: 123–130Abstract
Transformers are basic electrical machines and they form a very vital link in any electrical power transmission networks. During its service life, a transformer may experience number of short circuits in the system in addition to the abnormal overloading and switching impulses. Such abnormal conditions can cause the movement of the windings and failure of the supporting structures due to electro – mechanical forces and may result in total failure due to inadequacy in design and defective manufacturing process. Further, the rapid growth of fault level in the system network is major a concern for short circuit withstand capability of a transformer in service for a long period of time. With advanced modern technology and available short circuit test facilities, transformer manufacturing industry is now enabling to produce the reliable and safe transformers. Performance evaluation during ability to withstand short circuit test in a fully equipped testing laboratory is still final measure of checking the overall quality of the transformer from the point of design, material used, production process and quality control. Central Power Research Institute (CPRI), is having an experience of more than fifty years in the fi eld of short-circuit testing. The roles of various factors which affect the performance of transformers under short-circuit conditions are discussed along with the analysis of the failure cases during the short circuit testing.- Interpretation of NSDD and Restrike in Capacitive Current Switching Test on Medium Voltage Vacuum Circuit Breaker
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1 Switchgear Testing and Development Station, Central Power Research Institute Govindpura, Bhopal – 462023, Madhya Pradesh, IN
1 Switchgear Testing and Development Station, Central Power Research Institute Govindpura, Bhopal – 462023, Madhya Pradesh, IN
Source
Power Research, Vol 17, No 2 (2021), Pagination: 81-87Abstract
Capacitor banks are installed in an increasing number to control power quality issues and improving the power factor to counteract the reactive power in the transmission and distribution networks. Due to load fluctuations switching of capacitor banks is a typical phenomenon. Capacitor bank is normally having concentrated capacitance in contrast with distributed capacitance. It generally draws more current than unloaded cableor line in practical cases up to several hundred amperes. Hence, switching of capacitor bank causes a very high rate of rise of transient recovery voltage across circuit breaker contacts. This scenario can be simulated in testing laboratories by a voltage source connected to a circuit breaker which again is connected to a large capacitance in terms of IEC called capacitive current switching test. Non-sustained disruptive discharge (NSDD) is a voltage breakdown after the vacuum circuit-breaker open the fault current which will not cause the recovery of power frequency current. Restrike is different from NSDD, the recovery of power frequency current between the contacts will make the breaker failed. It’s not easy to show the distinction between NSDD and restrike during some type tests. The paper presents the study of performance evaluation of the circuit breaker during the capacitor current switching duties. A statistical analysis of failure of circuit breaker during capacitor current switching tests are included in the paper to help the manufacturers & utilities, so that the care can be taken for trouble free services. The paper also discusses the changes made in the IEC 62271 – 100, Amendment1:2012 for conducting the capacitive current switching tests.Keywords
Capacitor Switching Duty Cycle, Non-sustained Disruptive Discharge (NSDD), Voltage Breakdown, Capacitive Current Switching Test,Current Switching Test, Inadequate Synchronization.References
- Thielens DW. Circuit Influences on Non-Sustained Disruptive Discharges in Vacuum Switching Devices. Eindhoven University, M.Sc. report S433649; 2003.
- Smeets RPP, Wiggers R, Bannink H, Kuivenhoven S, Chakraborty S, Sandolache G. The impact of switching capacitor banks with very high inrush current on switchgear. CIGRE Conference, paper A3; 2012.
- IEC 62271-100; 2008.
- IEEE C37.012.
- Smeets RPP, Lathouwers AGA, Falkingham LT. Assessment of Non-Sustained Disruptive Discharges (NSDD) in Switchgear. Test experience and standardisation status. CIGRE Conference, paper A3-303; 2004.
- Performance Evaluation of Circuit Breakers under Asymmetrical Fault Condition (Test Duty T100a)
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Authors
Affiliations
1 Central Power Research Institute, Govindpura, Bhopal – 462023, Madhya Pradesh, IN
1 Central Power Research Institute, Govindpura, Bhopal – 462023, Madhya Pradesh, IN
Source
Power Research, Vol 17, No 2 (2021), Pagination: 113-119Abstract
Among several switchgear equipment largely used in high voltage Transmission systems, which change the grid configuration, isolates faulty parts from the grid, etc. circuit breaker is a remarkable one. For the reason to analyse the interrupting capabilities, a circuit breaker has to undergo various test duties according to IEC 62271-100 among which Test duty T100a is considered as the most onerous one. During this test the breaker has to prove its Interrupting capability during maximum arc energy condition. This article focuses on the Performance evaluation of circuit breaker under asymmetric condition Test duty T100a.Keywords
Asymmetrical Fault, Circuit Breaker, IEC 62271-100, Luminous Electric Discharge, Test Duty T100a.References
- High Voltage switchgear and control gear for Alternating circuit breakers, IEC 62271-100, 2017 Edition 2.0.
- Cigre Guide for Application part-2 of IEC 62271-100 & IEC 62271-1 for making and breaking tests.
- Guide to the interpretation of IEC 62271–100: Edition 2.0 2008-04 High-voltage switchgear and control gear part 100: High-voltage alternating-current circuit-breakers, Issue 9.0, 01-05-2011.
- Failure Analysis of OLTC during Transition Resistor Test
Abstract Views :127 |
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Authors
Affiliations
1 CPRI, Bhopal - 462023, Madhya Pradesh, IN
1 CPRI, Bhopal - 462023, Madhya Pradesh, IN
Source
Power Research, Vol 18, No 2 (2022), Pagination: 121-125Abstract
Emerging modern technologies and ever-changing demands compete with each other to bring new changes to the sociotechnical life of human beings. OLTC is one such equipment connected as an integral part of the transformer to change the turns ratio while the transformer is in energized condition, to adjust the output voltage. Changing times and technology brought many changes in the OLTC techniques, design and operation. Traditionally OLTC is a complex mechanical device, which has some deficiencies. OLTC design elements are checked during the transition resistor test. Thus, OLTC testing for transition resistors is a method to enhance the reliability of OLTC design. This paper discusses a typical failure case of OLTC during the transition resistor test conducted in CPRI.Keywords
On Load Tap Changer (OLTC), Transition Resistor and Mechanical Device.References
- IEC standard 60214- 1: Tap changers Part 1: Performance requirements and test methods; 2014.
- Redfern MA, Handley WRC. Duty based maintenance for on-load transformer tap changers. IEEE; 2001. p. 1824-29. https://doi.org/10.1109/PESS.2001.970355 DOI: https://doi.org/10.1109/PESS.2001.970355
- Gao D. A new scheme for on-load tap changer of transformer. IEEE; 2002. p. 1016-20.
- Martins HJA, et al. Failures/Solutions in on load tap changer, 145kV. IEEE. 1998. p. 43-48.
- Govindappa BV. Recent trends in on-load tap changer technology- A study. Tutorial on- On load tap changer as per IS & IEC standards; 2011. p. 97-118.
- Pathak S. Switching test On-Load Tap Changer (OLTC). Tutorial on- On load tap changer as per IS & IEC standards; 2011. p. 69-96.
- Rogers DJ, Green TC. A hybrid diverter design for distribution level on-load tap changers. IEEE; 2010. p. 1493-1500. https://doi.org/10.1109/ECCE.2010.5618245 DOI: https://doi.org/10.1109/ECCE.2010.5618245