Steel lattice towers are also used in electronic and communication industries for communication of microwave signals through different types of antennas. Several antennae are fixed on the tower in different directions at different heights as per the requirement and usage. The antenna positions decide the height of the tower. Symmetrical cross sections are preferred for microwave towers due to reversal of wind direction. Generally steel lattice towers with square or triangular plan are used for microwave towers. Angle sections and tubes are commonly used for the fabrication of these towers. Microwave towers are generally self-supporting steel lattice towers. Guyed towers are also used for microwave communication, but are least preferred for supporting heavy disc antennae. Wind load on the tower body and antennae is the major load on the structure besides the self-weight of the tower. Microwave towers are generally supported either at ground or at rooftop of some buildings. The tip deflection of the tower is a governing parameter for the functional requirement. Typical configuration of a 102-m high microwave tower is shown in Figure. The tower is triangular in plan. The two-dimensional and three-dimensional views of the tower are shown.
Corona has many advantages and disadvantages. In the correct design of a high voltage overhead line, a balance should be struck between the advantages and disadvantages. ADVANTAGES (i) Due to corona formation, the air surrounding the conductor becomes conducting and hence virtual diameter of the conductor is increased. The increased diameter reduces the electrostatic stresses between the conductors. (ii) Corona reduces the effects of transients produced by surges. DIS-ADVANTAGES (i) Corona is accompanied by a loss of energy. This affects the transmission efficiency of the line. (ii) Ozone is produced by corona and may cause corrosion of the conductor due to chemical action. (iii) The current drawn by the line due to corona is non-sinusoidal and hence non-sinusoidal voltage drop occurs in the line. This may cause inductive interference with neighboring communication lines.
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