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148 Fig. 8 Instead of feeding the parts of the telecommunication plant from a common central power plant, sectionalizing makes possible feeding from several smaller power supply plants. These can be placed near the parts of the telecommunication plant that are to be fed with power, which results in a considerable saving on cables. Voltage equality between the different parts of the telecommunication plant is maintained by means of a master voltage control system Sectionalizing of the power supply plant The contribution of the distribution cables to the total cost of the power supply plant increases relatively quickly when the mean length of the cables in the exchange exceeds a certain value. One of the reasons for this is that above this value the maximum permissible voltage drop will be decisive for the area of practically all cables. The cable costs will then be approximately equal to the square of the distribution distance, see fig. 7. By far the greater number of telecommunication exchanges of the SPC type have such distribution distances that a normal 48 V booster converter system will be cheaper than an alternative with a higher system voltage, for example 140 V. However, exchanges that extend over very large areas, where the cable costs could be decisive, cannot be ignored. In such cases LM Ericsson apply a method of dividing up the power equipment into a number of sections, each section supplying its own local part of the telecommunication equipment. In this way it is possible to cut down the distribution distances drastically, and hence also the cable costs, see fig. 8. It is clear from what is said below that, apart from improved cable economy when distribution distances are long, sectionalizing also has other important advantages. Requirement of voltage equality between the sections If a large telecommunication plant is
149 fed from a sectionalized power plant, the distribution voltages in the individual parts must be held at the same value to within very close limits. The requirements <strong>set</strong> by LM Ericsson are that the difference between voltages in the negative conductor at two arbitrarily selected rack fuses must not exceed 0.8 V and that the voltage difference at two corresponding points in the positive conductor must not exceed 0.6 V. Since the major part of this tolerance is used to cover the differences in voltage drop in the distribution cables, the permissible difference between different distribution racks constitutes only a small fraction of the values given above (
Page 1: ERICSSON REVIEW 3 1976 GEOSTATIONAR
Page 4 and 5: Geostationary Telecommunications Sa
Page 6 and 7: 112 forever silent. The next launch
Page 8 and 9: 114 Figs. 1—4 Figs. 5—8
Page 10 and 11: 116 Figs. 17—20 Figs. 21—24
Page 12 and 13: Electronic Push-button Telephone Se
Page 14 and 15: The bottom part (frame) ot the set
Page 16 and 17: Fig. 10 Buzzer unit Fig. 9 Tone rin
Page 18 and 19: Fig. 12 Impulsing unit and ring uni
Page 20 and 21: 126 Fig. 15 Transmission diagram Fi
Page 22 and 23: 128 ed by about 100 kohms. In order
Page 24 and 25: Fig. 20 DC characteristics (speech
Page 26 and 27: 132 use a microphone in which the o
Page 28 and 29: CCM - A Well- tried and Economic Ma
Page 30 and 31: 136 ] Do not allow more staff in th
Page 32 and 33: Ten Years Experience of CCM in the
Page 34 and 35: 140 Table 2 Existing staff requirem
Page 36 and 37: Optimization of Power Supply Equipm
Page 38 and 39: 144 Initial expenditure. This consi
Page 40 and 41: Table 1 Acquisition costs for diffe
Page 44 and 45: 150 Fig. 10 Apart from a highly sta
Page 46 and 47: Development, Production and Mainten
Page 48 and 49: 154 combined to meet the needs of e
Page 50 and 51: 156 duction and putting the package
Page 52 and 53: 158 Fig. 5 Working procedure when p
Page 54 and 55: 160 The error message is sent from
Page 56 and 57: Dr. Christian Jacobceus chaired the
Page 58 and 59: 164 Among the reasons that were giv
Page 60: TELEFONAKTIEBOLAGET LM ERICSSON PRI

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