because there is already a current flowing inside of it. An ohmmeter measures the current from the voltage that’s been being put out. So by applying an ohmmeter to a live network it will have an confusion between the live network and an ohmmeter voltage. http://wiki.answers.com/Q/Why_should_an_ohmmeter_never_be_used_on_an_energized_circuit 1. What is the voltage across a 220Ω resistor if the current through it is 5.6 mA? (Boylestad 131) Boylestad‚ Robert L
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nonthermal plasma discharge. A quartz coaxial DBD tube (ID: 6 mm‚ OD: 12 mm) at 400-mbar xenon-filled pressure has been used in the experiment. A unipolar pulselike voltage up to a −6-kV peak working at 30 kHz has been applied to the discharge electrodes for the generation of microdischarges. A single discharge is observed per applied voltage pulse. Visual images of the discharge and electrical waveform confirm the diffused-type discharges. The knowledge obtained by dynamic processes of DBDs in the discharge
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element and the characteristic of the circuit at the points where nonlinear elements are connected. The characteristics of a device are described as voltage vs. current. The devise must be experimentally determined by either the manufacturer or determined experimentally by a user. The characteristic of a resistor is a straight line‚ because voltage and current are proportional‚ through Ohms Law (V=IR or R=V/I). This equation shows that the slope is the value of the resistance which intercept at
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TABLE OF CONTENTS SI.NO Chapter Names Page No 1. Introduction 3 2.1 Substation 3 2.2 History 4 2.3 Duties 5 2.4 Linemen safety 7 2. Block diagram 9 3.5 Description of block diagram 10 3.6 Circuit description 11 3. Hardware requirement specification
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for underground transmission will be very heavy. Secondly‚ electric power has to be transmitted at high voltages for economic reasons. It is very difficult to provide proper insulation† to the cables to withstand such higher pressures. Therefore‚ as a rule‚ power trasmission over long distances is carried out by using overhead lines. With the growth in power demand and consequent rise in voltage levels‚ power transmission by overhead lines has assumed considerable importance. * 8.14 Methods of Reducing
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INTRODUCTION During the nineteenth century‚ when power supply was dc‚ dc motors were used extensively to draw power direct from the dc source. The motor speed could be varied by adjusting field current by a rheostat. That was an open loop control. Most of the drives were constant speed and the characteristics could not be matched with a job requirement. A vast development in the dc drives system took place when the ward Leonard Control System was introduced in the 1980s. The system
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technology changed from DC to AC. Power to be transmitted‚ voltage levels and transmission distances increased. FACTS (Flexible AC Transmission System) and HVDC (High Voltage Direct Current) are controllable devices whose functions are to enhance the security‚ capacity and flexibility of power transmission systems. Application of these components in power systems implies an improvement of transient and voltage stability‚ power oscillation damping and optimal power flow
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this circuit can be explained as follows: Let an alternating voltage v1 be applied to a primary coil of N1 turns linking a suitable iron core. A current flows in the coil‚ establishing a flux φp in the core. This flux induces an emf e1 in the coil to counterbalance the applied voltage v1 . This e.m.f. is e1 = N1 dφp . dt Assuming sinusoidal time variation of the flux‚ let φp = Φm sin ωt. Then‚ e1 = N1 ωΦm cos ωt‚ The r.m.s. value of this voltage is given by: E1 = 4.44F N1 Φm Now if there is a secondary
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transformer first introduced in high voltage electrical power system. In the early 1970s unit rating as large as 1100MVA were produced and 800KV and even higher KV class transformers were manufactured in year of 1980. Use of Power Transformer Generation of Electrical Power in low voltage level is very much cost effective. Hence Electrical Power are generated in low voltage level. Theoretically‚ this low voltage leveled power can be transmitted to the receiving end. But if the voltage level of a power is increased
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transform voltage from high to low‚ or the reverse‚ or perform any of several other important functions. Electric power may flow through several substations between generating plant and consumer‚ and its voltage may change in several steps. Substations may be owned and operated by a transmission or generation electrical utility‚ or may be owned by a large industrial or commercial customer. A substation may include transformers to change voltage levels between high transmission voltages and lower
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