Electrical installation power factor

Power Supplies and Controls. Induction heating furnace loads rarely can be connected directiy to the user s electric power distribution system. If the load is to operate at the supply frequency, a transformer is used to provide the proper load voltage as weU as isolation from the supply system. Adjustment of the load voltage can be achieved by means of a tapped transformer or by use of a solid-state switch. The low power factor of an induction load can be corrected by installing a capacitor bank in the primary or secondary circuit. 

This chapter introduces the basic items of design and specification for the principal systems and components of an electrical industrial installation. Electrical supply systems are discussed with regard to interface with the supply authorities and the characteristics. Salient features of switchgear, transformers, protection systems, power factor correction, motor control equipment and standby supplies are identified and discussed together with reference to the relevant codes of practice and standards. The equipment and systems described are appropriate to industrial plant installations operating at typically 11 kV with supply capacities of around 20MVA. 

Electricity is normally charged for on the basis of power (kilowatts) and the supply authority must install plant whose rating (and therefore cost) is a function of the voltage of the system and the current which the consumer takes (i.e. kilo-volt-amps). The relationship between the two is kW = kVA x cos (j> where cos (j> is the power factor and is less than 1.0. In the case of loads which have a low power, factor the supply authority is involved in costs for the provision of plant which are not necessarily reflected in the kWh used. A penalty tariff may then be imposed which makes it economically worthwhile for the consumer to take steps to improve his power factor. Low power factors occur when the load is predominantly either inductive or capacitive in nature (as opposed to resistive). In most industrial circumstances where the load includes a preponderance of motors, the load is inductive (and the power factor is therefore lagging). Consequently, if the power factor is to be brought nearer to unity the most obvious method is to add a significant capacitive component to the load. 

The power factor at which consumers take their electricity from the local electricity supply authority is outside the control of the supply authority. The power factor of the consumer is governed entirely by the electrical plant and equipment that is installed and operated within the consumer s buildings. Domestic consumers do not have a bad power factor because they use very little inductive equipment. Most of the domestic load is neutral and at unity power factor. 

Electricity supply authorities discourage the use of equipment and installations with a low power factor because they absorb part of the capacity of the generating plant and the distribution network to no useful effect. They, therefore, penalize industrial consumers with a bad power factor through a maximum demand tariff, metered at the consumer s intake position. If the power factor falls below a datum level of between 0.85 and 0.9 then extra charges are incurred. In this way industrial consumers are encouraged to improve their power factor. 

The power factor of the consumer is governed entirely by the electrical plant and equipment that is installed and operated within the consumer s buildings. 

The non-polarized type is often found in electrical installation work for power-factor correction. A paper-dielectric capacitor is non-polarized and can be connected either way round. 

Diesels, gas turbines and steam turbines are the more commonly used prime movers for the generation of electrical power. Additionally, the steam turbine can be employed in combination with either the diesel or gas turbine for combined cycle operation. The following describes the basic operation of each of these prime movers in relation to its associated power-generating scheme and reviews the more significant factors affecting performance and efficiency. Further information on the actual plant and installation is given later in Section 15.6. 

Electrical power distribution within an industrial installation is most often at a voltage up to and including 33 kV. This section describes the types of cable suitable for power circuits for use up to 33 kV and considers the factors, which will influence the current-carrying capacity of such cables. 

Most phase I NAPs provide for NE allocations based on a general emission rate and predicted activity level. For example in The Netherlands (NL), new entrants are allocated allowances based on projected output or fixed cap factor multiplied by uniform emission rate in line with that of a combined-cycle gas turbine (CCGT). In France, Germany and Poland, C02-intensive power generators, such as coal-fired installations, receive the highest number of allowances per kW installed. The literature highlights the risk that NE provisions can create distortions (Harrison and Radov, 2002). In order to illustrate how these rules can impact electricity prices and C02 emissions in our GB simulations, we focus on two approaches one based on a uniform benchmark and one based on a fuel-specific benchmark. In both cases the forecast capacity factor of new entrants is fixed at 60%. 

Energy availability. Power and steam requirements are high in most industrial plants, and fuel is ordinarily required to supply these utilities. Consequently, power and fuel can be combined as one major factor in the choice of a plant site. Electrolytic processes require a cheap source of electricity, and plants using electrolytic processes are often located near large hydroelectric installations. If the plant requires large quantities of coal or oil, location near a source of fuel supply may be essential for economic operation. The local cost of power can help determine whether power should be purchased or self-generated. 

Another source of metallic contamination in the studied region comes from the residual oil combustion used for electric utilities and fluvial and terrestrial transportation. Using the selected emission factors (quantity of trace element released by quantity of material consumed) given by Nriagu and Pacyna (1988) and Nriagu (1989), the electric-power production installed in the Amazonian states and the fuel consumption used for transportation (Ministerio de Minas... 

I was about to send the computer off to Apple when I realized that it was winter. Normally this would not be a factor, but winters where I live (North Dakota) are extremely dry. Dry air promotes static electricity. At first I thought that my problem couldn t be that simple, but I was at the end of my rope. So, when I received my next set of new parts, I grounded myself with an antistatic strap for the time it took to install the components, and prayed while I turned on the power. Success The components worked as they should, and a new advocate of ESD prevention was born. ... 

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