International Research Journal of Engineering and Technology (IRJET) Volume: 04 Issue: 03 | Mar -2017
www.irjet.net
e-ISSN: 2395 -0056 p-ISSN: 2395-0072
Fractional Frequency Transmission System Somesh Sadalge1, Suraj Bhoskar2, Amol Chavan3, Rohit Kabaj4, P. M. Maskar5 1234 5
Students, Electrical, Sanjay Ghodawat institute, Atigre, India
Professor, Dept. of Electrical Engineering, Sanjay Ghodawat institute, Maharashtra, India
---------------------------------------------------------------------***--------------------------------------------------------------------Abstract -The fractional frequency transmission system (FFTS) is a newly developing concept in power transmission system. In this system, electrical power is transmitted at a reduced frequency (One third of the rated frequency).This approach would be effective in long- distance transmission system of electrical power. Transmitting power at a reduced frequency reduces the electrical length of the transmission line (i.e., more amount of electrical power can be transmitted using the same length of the line at reduced frequency than at rated frequency).This paper introduces the basic concept of FFTS and primary results. The primary objective of this paper is design of frequency converter that is required at each end of the transmission line in order to change the frequency. The experiment uses cycloconverter as a frequency changer, which is used at the sending end to step down the frequency to 50/3Hz. Similarly, at the receiving end another frequency converter is used to step- up the frequency back to 50Hz.The FFTS approach proposes new strategy for expanding the transmission capacity. Key Words: Frequency converter, Fractional frequency Transmission System, Transmission System.
1. INTRODUCTION In the history of the ac transmission system, increasing distance and capacity mainly depends on raising voltage rating of transmission lines. Now day, the highest voltage level of the ac power transmission system in operation is 750 kV. To further upgrade, the voltage level encounters difficulties of material and environmental issues. The transmission and distribution losses in India currently stand at 27% of the total power is generated. Another method i.e., employed to increase the transmission capacity is the high voltage DC (HVDC) transmission system. A HVDC transmits DC power at a very high voltage level. However, at the generation is in AC, it has to employ current converters at transmitting and the receiving ends and these current converters are very expensive device. Apart from that, up to now the HVDC practices have been limited to the point-to-point transmission system. It is difficult to operate a multi- terminal HVDC system. In 1994, the fractional frequency transmission system was developed, which uses lower frequency (50/3 Hz) to reduce the electrical length of the ac transmission line, and thus, its transmission capacity can be increased. This paper presents the experimental installation of FFTS and primary experimental results. The experiment uses cycloconverter as a frequency changer is used at the sending end to step the frequency down to 50/3Hz. Similarly, at the receiving end another frequency tripler is used to step-up the frequency back to 50Hz.[13] Thus, a another FACTS device is successfully established in this experiment.
2. METHODOLOGY Power transmission using FFTS involves frequency changes at four stages: 1. In such a system, electrical power is transmitted at a reduced frequency (One third of the rated frequency=50/3 Hz). 2. Transmitting power at a reduced frequency reduces the electrical length of the transmission line (i.e., more amount of power can be transmitted using the same length of the line at reduced frequency than at rated frequency). 3. At the sending end, cycloconverter is use for reducing frequency. 4. Similarly, at the sending end frequency tripler is use for converting frequency back to 50 Hz before feeding to utility grid. The basic schematic diagram of FFTS is as shown below:-
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