ENGINEERING ARTICLES

At the earliest practical time in a project the engineers will need to identify areas of engineering and design where interfaces are necessary. An efficient system of communication and exchange of information should be established and implemented at regular intervals. Meetings should be arranged to discuss problem areas and short-falls in information. The following generally summaries what is needed, particularly during the feasibility and conceptual stage of a project. In order to be able to engineer an economical and efficient power system it is desirable for the electrical engineer to have: • A basic understanding of the hydrocarbon and chemical processes and their supporting utilities e.g. compression, pumping, control and operation, cooling arrangements. • A procedure for regular communication with engineers of other disciplines, e.g. instrument, process, mechanical, safety, telecommunications, facilities, operations and maintenance. • An appreciation of the technical and economic...

• Switchboards and motor control centre name and tag number. • Bus-section numbers or letters. • Cubicle numbers or letters. • Line voltage, number of phases, number of wires, frequency, busbar continuous current rating. • Busbar nominal fault breaking capacity in kA at 1 or 3 seconds. • Identification of all circuit breakers, fuse-contactor units, and their nominal current ratings. • Neutral earthing arrangements, e.g. connections to the incomers. • Protective devices of all incomers, bus-section circuit breakers, busbars, and outgoing circuits. • Interlocking systems in schematic form. • Local and remote indication facilities. • Details of special devices such as transducers, automatic voltage regulators, synchronising schemes, fault limiting reactors, reduced voltage motor starters, busbar trunking. • Rating, ratio and accuracy class of current and voltage transformers. • Identification of spare and unequipped cubicles. • Refere...

Single-line diagrams are the most essential documents that are developed during the detail design phase of a project. They identify almost all the main items of power equipment and their associated ancillaries. Initially they define the starting point of a project. Finally they are a concise record of the design, from which all the design and purchasing work evolved. The final single-line diagrams should contain at least the following information. Complicated power systems may require the single-line diagrams to be sub-divided into several companion diagrams, in which aspects such as protection, interlocking and earthing are treated separately. This ensures that the diagrams are not overly congested with information. The end results should be unambiguous and be easily read and understood by the recipient. The Key Single Line Diagram Switchboards and motor control centres: • All switchboards and motor control centre names, bus-section numbers, line voltages, number of phases, number of ...

The rating of a motor should exceed that of its driven machine by a suitable margin. The selection of this margin is often made by the manufacturer of the driven machine, unless advised otherwise. The actual choice depends on various factors e.g. Approximate rating of the motor or machine (kW) Margin of the motor rating above the machine rating (%) Up to 15 125 16.0 to 55 115 `Above 55 110 • The absolute rating of either the motor or the driven machine i.e. small or large machines. • The function of the driven machine e.g. pump, compressor, fan, crane, conveyor. • Expected operating level e.g. often near to maximum performance, short-term overloading permitted. • Shape of the operating characteristic of the machine e.g. pressure (head) versus liquid flow rate in a pump. • Change in energy conversion efficiency of the machine over its working range. • Machine is driven at nearly constant speed. • Machine is driven by a variable speed motor. • Harmonic currents w...

Some basic and important points, in relation to a modern power system, are summarized below: 1. Generation, transmission and distribution of electric power in our country is carried out as 3-phase system at 50 Hz. 2. Three most important conventional methods of power generation in out country are: coal based thermal plants, Hydel plants and nuclear plants.  3. Load centers (where the power will be actually consumed) are in general situated far away from the generating station. So to transmit the large amount of power (hundreds of MW) efficiently and economically over long distance, high transmission voltage (such as 400 kV, 220 kV) is used.   4. Material used for transmission lines is bare is bare copper conductors which are supported at regular intervals by steel towers. Stack of disk type ceramic insulators are used between the HV line and the steel tower.   5. Level of current decides the section of the line conductor and the level of voltag...

Nuclear power plants are thought to be the solution for bulk power generation. The present day atomic power plants work on the principle of nuclear fission of 235 U. In the natural uranium, 235 U constitutes only 0.72% and remaining parts is constituted by 99.27% of 238 U and only about 0.05% of 234 U. The concentration of 235 U may be increased to 90% by gas diffusion process to obtain enriched 235 U. When 235 U is bombarded by neutrons a lot of heat energy along with additional neutrons are produced. These new neutrons further bombard 235 U producing more heat and more neutrons. Thus a chain reaction sets up. However this reaction is allowed to take place in a controlled manner inside a closed chamber called nuclear reactor. To ensure sustainable chain reaction, moderator and control rods are used. Moderators such as heavy water (deuterium) or very pure carbon 12 C are used to reduce the speed of neutrons. To control the number neutrons, control rods made of cadmium or boron steel ar...

In a hydral power station , water head is used to drive water turbine coupled to the generator. Water head may be available in hilly region naturally in the form of water reservoir (lakes etc.) at the hill tops. The potential energy of water can be used to drive the turbo generator set installed at the base of the hills through piping called pen stock. Water head may also be created artificially by constructing dams on a suitable river. In contrast to a thermal plant, hydel power plants are eco-friendly, neat and clean as no fuel is to be burnt to produce electricity. While running cost of such plants are low, the initial installation cost is rather high compared to a thermal plants due to massive civil construction necessary. Also sites to be selected for such plants depend upon natural availability of water reservoirs at hill tops or availability of suitable rivers for constructing dams. Water turbines generally operate at low rpm, so number of poles of the alternator are high. For e...