Power Research

N. Maheswara Rao ¹, B. R. Vasudevamurthy ¹, Swaraj Kumar Das ¹, B. V. Raghavaiah ¹

Affiliations
1 Short-circuit Laboratory, Central Power Research Institute, Sir CV Raman Road, Bengaluru - 560080, IN

Abstract

The earth electrode is the main component of the earthing system which is in direct contact with the ground and thus provides a means of releasing or collecting any earth leakage currents. The electrode shall have good electrical conductivity and shall not corrode in a wide range of soil conditions. The design of these electrodes shall be such that they have good current carrying capacity under the earth fault conditions. This paper describes current withstand capability of these Earth Electrodes during earth fault conditions. Recent developments in Electrodes and their performance for different fault currents are given. Failure cases are studied from the laboratory tested Electrodes and appropriate recommendations were proposed. This can give an insight for estimating fault current withstand capability of a given dia and material of Electrode. Also different filler materials used for earth electrodes have been discussed.

Keywords

Earth Electrode, Pipe, Strip, Pipe in pipe, Strip in pipe, Short-circuit current, Coating Thickness Measurement, Touch Potential.

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G. Govinda Rao ¹, J. Santhosh ², B. V. Raghavaiah ³

Affiliations
1 Engineering Officer Grade 2, HPL, Central Power Research Institute, Bangalore - 560080, IN
2 Joint Director, HPL, Central Power Research Institute, Bangalore - 560080, IN
3 Additional Director, STDS, Central Power Research Institute, Bhopal - 462023, IN

Abstract

This paper elucidates the methods used in type testing and factory routine testing to ensure the tightness of SF₆ gas used in Medium Voltage (MV) and High Voltage (HV) switchgear as per the latest IEC and CIGRE guidelines. Gas insulated MV (>1 kV to ≤52 kV) and HV (>52 kV) switchgear are frequently being used in electrical power system throughout the world. Mostly, gas insulated MV and HV switchgear contains SF₆ as a pure gas or combined with other gases (i.e.: N2) to form a gas mixture. Recent times, distinct emphasis is being paid to reducing gas leakage during design, manufacturing and operation by enhancing gas handling procedures in compliance with Greenhouse gases emission regulations. Typically the assurance of gas tightness of MV and HV Switchgear shall be defined as the lowest possible quantity of SF₆ released to the atmosphere. Various test methods are used for tightness test measurement depends upon sensitivity of measurement, quantity and necessity

Keywords

Gas Insulated MV and HV switchgear, gas tightness test, SF6 leak detection methods.

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V. Ramachandrappa ¹, B. V. Raghavaiah ²

Affiliations
1 Joint Director, High Power Laboratory, CPRI, Bangalore - 560080, IN
2 Additional Director, STDS, Bhopal - 462 063, IN

Abstract

Short circuit test is one of the very important tests on electrical power equipment to verify its design aspects to withstand the critical severities under the condition of actual fault. To perform these tests a high power source is required. This source can be a grid supply with a high fault level or can be a high power short circuit generator. This paper gives the salient features of high power generator installed at Central Power Research Institute (CPRI), Bangalore. This 2500MVA short circuit generator is of highest capacity in the sub-continent of South Asia as on date. The design features are intricate in nature and complex in terms of stator, rotor damper winding and stator end winding. This paper presents the specification, design concept, constructional features, comparison between salient pole and turbo type of generators and other auxiliaries of the generator. Mechanism of achieving the maximum short circuit current is broadly discussed in this paper. This rare facility at CPRI meets high power testing requirement for the electrical industry and utilities of India and other part of the world. In this paper attempts are also made to bring out the highlights of operational features of capital intensive 2500 MVA SC generator. This generator has been used for short circuit testing of various power system components over the period of time.

Keywords

Short circuit generator, design, construction, testing capabilities

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S. Arjuna Rao ¹, Swaraj Kumar Das ¹, B. V. Raghavaiah ²

Affiliations
1 Short Circuit laboratory, Central Power Research Institute, Bangalore – 560 080, IN
2 Switchgear Testing & Development Station, Central Power Research Institute, Bhopal- 462 023, IN

Abstract

The development of wind power in India began in the 1990s, and has significantly increased in the last few years.India has the fifth largest installed wind power capacity in the world.As of 31 Jan 2013 the installed capacity of wind power in India was 18551.7 MW, mainly spread across Tamil Nadu (7134 MW), Gujarat (2,884 MW), &Maharashtra (2310.70 MW)whichare leading the top. All across the world, the demand for electricity from renewable energies is constantly growing. To meet this demand, wind farms must be as operable as conventional power plants and better integrated into the grid control mechanism. Our wind power plants should actively support the grid, fulfilling all necessary requirements and ensuring reliable energy supplies even during breakdowns. Wind power plants feed the grid with controlled reactive power. This allows for a constant voltage control, sustaining the line voltage. Even at temporary voltage dips the wind power plant remains connected to the grid and helps to keep it stable. If any frequency fluctuations occur the effective power of our wind turbines should automatically adjust according to the needs.

Keywords

Renewable Energy (RE),Wind Turbine Generator(WTG),Wind Power Plant(WPP),Doubly Fed Induction Generator (DFIG), Dynamic Voltage Restorer

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Arun Kumar Datta ¹, M. A. Ansari ¹, N. R. Mondal ¹, B. V. Raghavaiah ¹

Affiliations
1 Operation and Maintenance Division, Switchgear Testing and Development Station, Central Power Research Institute, Bhopal, IN

Abstract

Switchgear Testing and Development Station prevalently known as STDS was established in 1965 at Bhopal by the Government of India as one of the units of Central Power Research Institute. The predominant objective of setting up this institute was to cater the short-circuit testing needs of various LT/HT power equipments in switchgear, controlgear and transformer fi eld. Over the years, the unit has expanded and received all the national/international accreditations, and further became the member of Short Circuit Testing Liaison (STL). Today, CPRI’s short circuit laboratories of generator based and direct on-line based are one of the leading laboratories in south east Asia.

Year 2006–2007 was a test time for CPRI, Bhopal, when both the short-circuit generators have developed technical snag, resulting in an interruption of short-circuit testing. It was a challenge for CPRI as well as for the service provider to take repair work, as so many technical intricacies were involved including the reverse engineering process. Nation realized the importance of CPRI during the shutdown period. This paper discusses about the occurrence of failure, its detailed diagnosis, ischolar_main cause analysis and the action taken thereafter. Short-circuit generator is different from conventional one in many aspects. Repairing experiences of these generators, along with the re-commissioning process, are also shared herewith.

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Y. Agrawal ¹, M. K. Wadhwani ¹, B. V. Raghavaiah ¹

Affiliations
1 Switchgear Testing and Development Station, Central Power Research Institute, Bhopal, IN

Abstract

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.

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