Power Research

V. Sreeram ¹, S. Sudhakara Reddy ²

Affiliations
1 Engineering Officer-2, High Power Laboratory, Central Power Research Institute, Bangalore - 560080, IN
2 Joint Director, High Power Laboratory, Central Power Research Institute, Bangalore - 560080, IN

Abstract

High Voltage Direct Current (HVDC) lines running parallel to AC transmission lines will encounter electromagnetic induction which will rise to substantial levels during a short circuit. The actual magnitude of induced current depends on several factors like distance between the lines, soil resistivity etc. The unenergised DC line will also have a voltage due to induction and the associated discharging equipment will have to carry the induced current. This paper attempts to study the levels of induction encountered by the HVDC line and associated equipment during a short circuit in the AC line. It was observed that magnitude of induced current during steady state and three phase fault did not exceed 5 A while the magnitude of induced current during single phase to ground fault exceeded 15 A

Keywords

Double Circuit Transmission Lines, Electromagnetic Induction, HVDC, Short Circuit Currents

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V. Sreeram ¹, D. H. Gopal ¹, M. R. Ravindra Mohare ¹

Affiliations
1 High Power Laboratory, Central Power Research Institute, Bangalore - 560080, IN

Abstract

Most short circuit generators have static excitation systems to supply field current to the rotor circuit. All synchronous alternators suffer a reduction in the terminal voltage due to high armature reaction which is a result of the extremely high magnitude short-circuit currents. The reduction in terminal voltage will lead to a corresponding reduction in the stator current magnitude. The short-circuit generators are expected to maintain a constant magnitude of current for specified duration to complete the tests as per corresponding standards. Hence the short-circuit generators invariably make use of super-excitation to maintain the required magnitude of short-circuit currents for specified duration. During circuit breaker testing, it is required to maintain the recovery voltage at pre-fault levels. This requires significant over excitation of the machine. This paper presents a brief review of the methodology and algorithm of super-excitation schemesadopted in short circuit testing along with actual data recorded at the High Power Laboratory at CPRI, Bangalore.

Keywords

Short-circuit generators, transient behavior, super-excitation

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V. Sreeram ¹, T Gurudev ¹, M. Rajkumar ¹, M. Maroti ¹, S. Sudhakara Reddy ¹

Affiliations
1 HPL, Central Power Research Institute, Bengaluru – 560012, Karnataka, IN

Abstract

The SFRA (Sweep Frequency Response Analysis) technique has become quite popular as a condition monitoring technique for transformers. The SFRA technique holds a vast repertoire of data in terms of the electromagnetic behaviour of the transformer. Much research has happened in comprehending this data but no effort has succeeded in determining a universal objective criterion for the interpretation of SFRA data. CIGRE study committee A2.53 has recently released Technical Brochure 812 which has been the result of nearly half a decade of international efforts in arriving at an objective criterion for the interpretation of SFRA. This paper discusses the state of the art in objective interpretation of SFRA data with special reference to TB 812. The paper also presents a case study in HPL where SFRA was compared to a conventional method.

Keywords

Frequency Response, Power Transformers, Statistical Analysis.

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Rajaramamohanarao Chennu ¹, S. Sudhakara Reddy ¹, Anupam Awasthi ¹, Gurudev T. Maroti ¹, S. Arun Kumar ¹, V. Sreeram ¹

Affiliations
1 Central Power Research Institute, Bengaluru – 560012, Karnataka, IN

Abstract

The market requirements for Medium Voltage (MV) metal enclosed switchgear are getting more and more stringent. Both building costs as well as the level of the transmitted and distributed electrical power have increased rapidly over the recent years and are expected to continue to rise. This means that switchgear manufacturers must bring more and more compact and powerful systems on the market, while being simultaneously as cost effective as possible. Internal Arc Classification (IAC) of switchgear according to IEC and IEEE standards is one of the most important requirements to guarantee safety in case of internal arc faults. Internal arcs cause a sudden pressure rise in electrical installations. This leads to an extreme pressure stress acting on switchgear compartments and switchgear rooms and could cause collapse of buildings This paper describes few important design rules and innovations, which were necessary to achieve best results during internal arc tests. Furthermore it demonstrates the effect of roof height during the internal arc test with the important case studies. Finally the best solution to eliminate the roof effect is also proposed.

Keywords

HP aignhe lSpeed Videography Analysis, IEC 62271-200 and IEEEC37.20.7, Internal Arc Test, Roof Height, Switch Gear panel.

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V. Sreeram ¹, M. Rajkumar ¹, S. Sudhakara Reddy ¹, T. Gurudev ¹, Maroti ¹

Affiliations
1 Central Power Research Institute, Bangalore - 560080, Karnataka, IN

Abstract

Cables form the backbone of modern power transmission and distribution systems. Even though, short circuit faults are more common with overhead transmission lines than with underground cables, the thermal and dynamic stress associated with short circuit make it a mandatory withstand requirement. High Power Laboratory has been regularly carrying out short circuit tests on LT and HT cables. This paper presents an overview of the tests carried out and their results.

Keywords

Cable, Short-circuit Currents, Thermal Stresses .

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