Busbar installation

Each unit cost contains all the costs involved in the installation of that unit. For motors installed costs include the starter, conduit, wire, and a proportionate share of the service panelboard and busbars. The motor cost is not included since this will be part of the equipment cost. In the case of lighting, the installed cost includes the lighting fixtures, the conduit and wire, and a proportional share of the hghting panelboard and service switching costs. 

In the cubicle construction of a switchgear assembly the busbar chamber is normally located at the top of the assembly and runs through the length of it. It is usually suitable for extension, through fish joints at either end, if required at a later date. For installations having top cable entry, the busbar chamber may also be located at the bottom of the assembly or the depth of the panel increased, with an additional shroud between the top busbar chamber and cable chamber. From these main busbars are tapped the vertical buses for each vertical panel. Manufacturers may adopt different practices for horizontal and vertical busbar arrangements to economize on their cost of production. We illustrate the most common types of busbar arrangements. 

On the supply side of the interrupter, an equivalent busbar, inductance and lumped capacitance with a provision to connect p.f. correction capacitors, if required, to represent a replica of the actual installation. 

The second method of improving the power factor of an installation is to provide static capacitor banks. These can be installed as a single block at the point of supply busbar, as a set of switchable banks or as individual units connected to specific loads. For an installation where no synchronous machines are installed for other purposes (i.e. as prime movers or generators) then static capacitor banks are almost invariably the most cost-effective way of improving the power factor. 

Capacitors as bulk units can be connected to the supply busbar via a fuse switch, molded-case circuit breaker of air circuit breaker. In this type of installation control is purely manual, and in cases of a reasonably constant load and where the amount of power factor correction is limited such a manually controlled system is perfectly adequate. The supply authority may, however, require to be informed that a capacitor bank is permanently connected to the supply. Capacitors are more generally connected either in banks controlled from a VAR sensitive relay or across individual loads (e.g. motors). 

Despite the advanced technology of the AQUATECH System, its installation is not complex. In fact, it is simpler and less costly than conventional electrolysis processing. AQUATECH Systems need only two electrodes for an entire 100-150 cell unit stack, avoiding complicated busbar arrangements. Furthermore, scale-up and installation of the unit are facilitated by the modular skid mounted cell stack design. 

Most commercial multistory installations contain busways that serve as the primary source of electrical power to various floors. Busways that incorporate sandwiched busbars are susceptible to nonlinear loading, especially if the neutral bus carries large levels of triplen harmonic currents (third, ninth, etc.). Under the worst possible conditions, the neutral bus may be forced to carry a current equal to 173% of the phase currents. In cases where substantial neutral currents are expected, the busways must be suitably derated. Table 4.10 indicates the amount of nonlinear loads that may be allowed to flow in the phase busbars for different neutral currents. The data are shown for busways with neutral busbars that are 100 and 200% in size. 

To protect the system from prolonged high voltage it is the usual practice to install an overvoltage relay (59) in each of the generator circuit breakers or at their common busbar. The relay settings are usually set to operate at 115%, with a time delay between 0.5 and 10.0 seconds. 

Install a vertical ground bus in each rack (as illustrated in Fig. 10.270). Use about l-y2-in.-wide, y4-in.-thick copper busbar. Size the busbar to reach from the bottom of the rack to about 1 ft short of the top. The exact size of the busbar is not critical, but it must be sufficiently wide and rigid to permit the drilling... 

Busbars can be cut, welded, bent, punched, drilled, plated, and insulated to meet specifications. They are most practical when configurations must be precise, terminal points inflexible, and installation locations confined. 

At Rovno NPP, each of the two additional diesel generators has a priority connection to Unit 3 or 4. A cross-switching would be possible when two additional busbars for reliable station service (3BJ and 3BK) are also installed in Unit 3. The emergency backup of some additional consumers can be provided. Two important safety related consumers are connected to the additional diesel generators ... 

Check the position of the meter. The Electricity Supply Regulations require it to be installed in the consumer s premises unless it is more reasonable for it to be located elsewhere, in which case it should be accessible to the consumer. This is more likely to occur in blocks of flats and housing in multiple occupation. In such premises the supply authority may bring in only one service cable on to a busbar and then feed each tenant via cables in conduit or sometimes in MIMS cable. The latter is not a good choice because the insulation is hygroscopic and if the end seals fail, the cable can break down. It may also fail if subject to HV transients, so such cables should be fitted with suppressors. If the conduit or sheath of the MIMS cable is used as the earthing conductor, check that the connections are satisfactory and of low resistance and any joints in the conduit provide adequate continuity. 

Post-World War II installations will usually have a consumer unit, which is a small distribution board with a double pole isolating switch and a phase busbar to feed the fuses or MCBs controlling the final circuits. There will be terminal blocks for the neutrals and protective conductors. The earth terminal block may be utilised as the consumer s earthing terminal. Some of the older models may have wood frames and/or may be backless. As BS 7671 requires connections to be made in non-flammable enclosures, the wooden framed type do not comply and the backless ones are acceptable only if mounted on non-flammable material. If rewirable fuses to BS 3036 are used, check that the correct size of fuse wire has been used. For cartridge fuses, check that blown fuses have not been repaired with a bit of fuse wire spanning the contacts or the cartridge replaced by a nail, hairpin or the like. There should be only one final circuit connected to each fuse carrier or MCB. 

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