Santhakumar Raja

The method known as SCADA has long been used to control transmission systems, providing the operational flexibility and speed required for efficient and reliable performance. The use of SCADA in the distribution system is becoming increasingly important as utilities move into a deregulated, competitive environment. The acronym SCADA is being replaced by the generic term

After World War II, the drive to electrify the remaining rural and sparsely populated areas of the United States was renewed. Providing fully rated circuit breakers for switching loaded circuits was frequently beyond budget limitations. This created a need for new transmission and subtransmission voltage circuit-switching devices. One such device could be described as a

Sources : In circuit analysis, the goal is to start with a connected set of circuit elements such as resistors, capacitors, operational amplifiers, and other devices, and to find the voltages across and currents through each element, additional quantities, such as power dissipated, are often computed. To energize the circuit, sources of electric energy must

Definition of Electric Circuit : An electric circuit is a collection of electrical devices and components connected together for the purpose of processing information or energy in electrical form. An electric circuit may be described mathematically by ordinary differential equations, which may be linear or nonlinear, and which may or may not be time varying. The

GEO is also called as geosynchronous (or synchronous) orbits, which has 24 hour period of revolution but are inclined with respect to equator. Orbits that are below a mean altitude of about 36,000 km have periods of revolution shorter than 24 hours and hence are termed as non Geostationary Earth Orbit (GEO). Geostationary Earth Orbit

The communication is established to the satellite through earth station. The earth station can be located on the ship at the sea, or it can be located on the space craft or actually on the earth. The location of the earth station is decided depending upon the ease of control of satellite and the function

We know that the satellite can receive and transmit one of the bands given in Table For each band, the uplink and downlink frequencies are separate. Frequency division multiplexing of the complete uplink and downlink range of frequencies can be done to transmit and receive many channels simultaneously. For example for ‘C’ band, the bandwidth

In TDMA, the time slots are available to the ground stations with full bandwidth. In FDMA, the frequency bands are available to the ground stations with continuous time availability. By combining these two multiple access techniques, a hybrid technique called Code Division Multiple Access (CDMA) can be formed. Frequency hopping can be used so that

The uplink and downlink carriers of the satellite are required to be modulated by the signal to be transmitted. The modulation can be analog or digital. In the earlier satellites analog modulations were dominant and therefore they were used in communication satellites. The analog voice and video transmission systems use frequency. modulation and frequency division

The communications satellites are used to carry telephone, television and data signals. The television and telephone signals are normally analog. The satellite earth station transmits these signals on the same link by multiplexing. Time division multiplexing (TDM) and frequency division (FDM) are the commonly used multiplexing techniques. FDM/FM for Telephone Systems Fig shows the block