Conductors size determination

Determine the minimum conductor size for a fault level of 50 kA for one second for an aluminium conductor. 

When high voltage motors are being considered, it is usually found that the minimum conductor size of the cable is determined by the let-through fault withstand capability rather than the full-load or starting current. Cable manufacturers provide graphical data for fault withstand capabilities of their cables, which are based on practical tests. These aspects are also associated with the protection system used for the motor, e.g. a contactor-fuse combination, a circuit breaker, the protective relay characteristics (thermal, inverse time with or without instantaneous or earth fault elements). 

During the planning stage, transmission capacity and reactive power compensation are normally studied. These studies mainly determine the cable route, the voltage level, the conductor size, and the amount and locations of shunt reactors. 

When the transmission development plan is set up for the cable, the cable route is studied further. One characterishc of cables, compared to overhead lines, is that the laying and soil conditions affect the planning studies in addition to the land availability. These factors affect the burial depth, soil thermal resistivity, and cable separation between phases, which may necessitate changes to the conductor size and the amount and locations of shunt reactors initially determined in the plarming studies. 

To determine the minimum size of ground conductor, consider a station grid made of Z coated steel, having the following parameters ... 

To determine the mininumi size of conductor for i required faith lev el. to account for the thermal effects only one can use the following formula to detertiiine the minimum size ol conductor for tiny fault level ... 

Figure 28.5 Determining the minimum size of conductor for a required fault level...

The production casing string for a certain well is to consist of 5-in. casing. Determine casing and corresponding bit sizes for the intermediate, surface and conductor string. Take casing data and bit sizes from Table 4-140. 

The current-carrying capacity of the wire is not directly related to the dielectric. This is determined by the conductor resistance and the heating effect that it produces in the wire. The required current-carrying capacity determines the size of the wire and thus the size of the insulator. The temperature rise caused by the current flow determines the type of insulation to be used. If the wire is limited to 140°F (60°C) service, the insulation can be one of those discussed above. If the wire is to operate at 300°F (150° C), another specification for plastic wire with better heat resistance such as TP polyester or PTFE is used. 

Abstract. Nanopowders of nonstoichiometric tungsten oxides were synthesized by method of electric explosion of conductors (EEC). Their electronic and atomic structures were explored by XPS and TEM methods. It was determined that mean size of nanoparticles is d=10-35 nm, their composition corresponds to protonated nonstoichiometric hydrous tungsten oxide W02.9i (OH)o.o9, there is crystalline hydrate phase on the nanoparticles surface. After anneal a content of OH-groups on the surface of nonstoichiometric samples is higher than on the stoichiometric ones. High sensitivity of the hydrogen sensor based on WO2.9r(OH)0.09 at 293 K can be connected with forming of proton conductivity mechanism. 

His mathematical analysis deals with the problem of determining how much of one powder A, must be added to another powder B, to obtain continuity of powder A in a random mixture of the two. When more than the minimum is added, more continuity will result. Continuity is expressed as the probability that pairs of particles of powder A have radii, the sum of which just equals the distance between their centers. Forscher s mathematical analysis leads him to conclude that for an aggregate of equal-size spheres A is probably discontinuous if the ratio of A to B is below Both A and B are continuous when A/B exceeds this ratio and eventually B becomes discontinuous if B/A falls below In the discussion given, powder A is a good conductor of electricity, and powder B, a poor conductor. The degree of continuity of powder A was assumed proportional to the over-all conductivity of the compound powder mixture. 

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