Volt drop Calculation

The following example explains how volt-drop calculations can be carried out. Initially the subject is approached from a rigorous standpoint. Subsequently various simplifications are introduced, their results compared and their appropriateness discussed. The calculation sequence is -... 

Figure G.l is a simplified one-line diagram of a power generation and distribution system that would be suitable for most oil industry power systems that have their own power generating plants, e.g. an off-shore production platform. Figure G.2 is the equivalent diagram showing the basic symbols and configuration needed for the volt-drop calculation process. The example data are given below -...

With a current of 1 A, the voltage drop across a resistance of 1 Q is 1 V. This voltage is also represented by a current of 1 mA, through a resistance of 1 kQ, and a current of 1 ptA, through a resistance of 1 MQ. Thus, volts are calculated when the current is in amperes and the resistance in ohms, but also when the current is in miUiamperes and the resistance in kilohms, etc. A circuit can be drawn in electronic symbols, as illustrated in Figure 6.8. The symbol for a resistor in such a drawing is a sawtooth fine. 

Partition coefficients in the octanol-pH 7.4-phosphate-buffer system. c Nitrothiazole oxidation-reduction potentials (volts) as calculated from their half-wave potentials, as determined using a Polarecord E 261 polarograph (Metrohm AG, Herisau, Switzerland) and a saturated Ag/AgCl reference electrode. Measurements were performed at 20°C and a drop time of 1 drop/2.8 sec. The compounds were dissolved in 1 ml dimethyl formamide and added to 24 ml of a borax-potassium biphosphate buffer of pH 7.3 [prepared according to J. M. Kolthoff, J. Biol. Chem. (1925) 68, 135]. A pH of 7.4 resulted. Standard error of determination 3 mv. 

Appendix G gives detailed calculations of cable volt-drops for the starting and full-load running conditions of a 500 kW induction motor that is to be started direct-on-line in a power system that is fed by three 3125 kVA generators. This appendix demonstrates the following aspects of starting large motors -... 

Alternatively the volt-drop can be calculated by solving the circuit conditions shown in Figure 9.4, as follows... 

When calculating the volt-drop in low voltage motor feeder cables it is necessary to consider three factors in particular -... 

There are many commercially available computer programs for calculating fault currents. Some programs include other features such as load flow, harmonic penetration, transient stability, motor starting and volt-drop calcnlations, since these features tend to use the same database. Usually a program that calculates fault currents will have several special features for different types of fanlts e.g.,... 

Worked Example for the Calculation of Volt-drop in a Circuit Containing an Induction Motor... 

Figure G.l Simplified one-line diagram for calculating the volt-drop of a 500 kW HV motor.

CALCULATION OF VOLT-DROP IN A CIRCUIT CONTAINING AN INDUCTION MOTOR... 

Compare the calculated voltages and find the volt-drops. 

The voltage Vgs is within 1.5% of the rigorons case but too optimistic for the motor voltage. However, most of the volt-drop is due to the generator impedance in either case and so once some cases have been screened in this way then the more accurate method may be applied to the serious cases. Since the result is optimistic it therefore requires a safety margin of 2% to 5% to be added when this method is used. The percentage volt-drops can be calculated as follows -... 

Which makes the calculation of volt-drop much easier. However, all these impedances must be correctly reduced to the common system base as follows. It can be shown that the actual parameters may be easily converted to their per-unit system base parameters. The motor, load and generator impedances can be represented in terms of their kVA, or MVA, and voltage bases. 

Cyclic voltammetry (CV) is often used to determine the electrochemical properties of D-A copolymers. Usually, the CV setup consists of a Ag/AgNOs reference electrode, a platinum wire counterelectrode and a glassy carbon electrode with a drop-cast polymer film. First, the CV curve of ferrocene/ ferrocenium redox couple (Fc/Fc ) should be measured to calibrate the reference electrode. The polymer s HOMO energy level in electron volts is calculated from the onset of the oxidation peak ( ox) according to eqn (15.4). If the reduction peak of polymer is not clearly visible, the LUMO level can be approximated from the HOMO measured by CV and the bandgap measured by UV-vis. 

The standard redox potential is 1.14 volts the formal potential is 1.06 volts in 1M hydrochloric acid solution. The colour change, however, occurs at about 1.12 volts, because the colour of the reduced form (deep red) is so much more intense than that of the oxidised form (pale blue). The indicator is of great value in the titration of iron(II) salts and other substances with cerium(IV) sulphate solutions. It is prepared by dissolving 1,10-phenanthroline hydrate (relative molecular mass= 198.1) in the calculated quantity of 0.02M acid-free iron(II) sulphate, and is therefore l,10-phenanthroline-iron(II) complex sulphate (known as ferroin). One drop is usually sufficient in a titration this is equivalent to less than 0.01 mL of 0.05 M oxidising agent, and hence the indicator blank is negligible at this or higher concentrations. 

The electronic interaction of the relatively large molecules of phthalocyanine shows (Fig. 30) a considerable temperature effect (77a). In an experiment demonstrating this effect, the platinum foil (B in Fig. 2) was covered by the dye molecules until the work function was lowered to 4.32 volts at room temperature. If B was cooled by pouring liquid air into the upper tube of the photocell (a in Fig. 30), the photoelectric sensitivity increased and remained constant as long as liquid air was added. If the liquid air evaporated (6 in Fig. 30), the photoemission dropped to the original value at room temperature. This effect was arbitrarily reproducible. The calculation of the work function 4> and the constant M by the curves of Fowler [see Equation (5) in section III,la] in Fig. 31 gives = 4,32 volts, log M = —12.17 at room temperature (curve I), and = 4.15 volts, log M = —12.17 at low temperature (curve II). While... 

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