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Technical Article 1

Consulting engineers have a very important role to play in the successful completion of any project. He is concerned with three specific aspects of project implementations viz. Technical, financial and management.

The most important responsibility of the consulting engineer is to provide competent and appropriate technical advice. For this, he depends on the technical education that he has under zone, coupled with the practical experience of many years he has been in the field of project engineering. More often a purely theoretical solution has to be tempered with a practical approach, arising out of the experience. This brings out the outmost importance of experience in the successful practice of consultancy services.

It is very important that consulting engineers keep abreast with the latest technological developments and new products/processes introduced in the field of his specialisation. Books, periodicals, product catalogues, technical seminars etc. provide the necessary inputs.

The best technical solution need not be satisfactory if the cost attached to it is exorbitant. This aspect is often overlooked and sometimes resented by consulting engineers. However, it is to be borne in mind that the business/project to which advice is given has to operate in a fiercely competitive market and the cost of the final product depends on the cost of the project/capital equipment that is required to be put up. It is the responsibility of the consulting engineers to project a realistic cost estimate so that adequate financial budgets are provided for execution of the work. In case of any revision necessitated by changed requirement/process during the execution stage, cost revision should immediately be intimated to the authorities for necessary sanctions.

Project management is an important role of consulting engineers. In India, unfortunately, project management practices are usually not followed seriously. The reasons for it are many: lack of adequate technical staff from contractor's side etc. However, the usefulness of project management techniques can not be ignored. As a key agency, responsible for execution of the job,consulting engineers can influence adoption of project management techniques in the construction industry.

In all the above aspects, role of consulting engineers is complementary to the staff from the clients side. Success or otherwise of consulting engineers in project execution depends largely on the accuracy of inputs from the owners/users and the support he receives from them.

Technical Article 2
H.K.Shivaram B.E (Electrical), Director (Tech) and H. N. Radhakrishna B.E (Electronics ), Manager (Designs ) PROK DEVICES PRIVATE LIMITED, Bangalore

The current and voltage waveforms in power systems are frequently distorted by harmonics. Power system harmonics are known to be generated by a number of sources in the power network. With increase in co - generation and solid state applications, larger quantities of harmonic currents are expected to be injected into the AC transmission and distribution networks. The nature of loads has changed, as the loads are becoming highly non - linear in characteristics, because of application of solid state devices in motor control and energy conservation methods. The operation of non - linear devices under unbalanced conditions cause harmonic problems in power systems. The harmonic distortion to communication interference. The harmonic contents in the network at any point must be measured so that harmonic counter measures can be properly designed. Harmonic meters are important instruments for such harmonic measurement studies.

There are also many harmonic problems related to unbalanced operation of power systems. With unbalanced conditions, the generation and propagation of harmonics are more complicated. Unbalance may also produce non-characteristic harmonics in the system. It is important to evaluate the effects of these harmonics since no filters are generally installed to nullify them. In view of the fact that there is always some degree of unbalance and that the harmonics are more sensitive to unbalances, than to that of fundamental component, measurement of unbalance in the system along with harmonic content measurement is a must.

The main harmonic sources in the systems are :

  • Transformer with magnetization non - linearities.
  • Rotating machines
  • Arc furnaces
  • Fluorescent lighting
  • Thyristor converters

The main effects of current and voltage harmonics are:

  • Amplification of harmonic levels resulting from series and parallel resonance.
  • Reduction of efficiency of power generation, transmission and utilization.
  • Aging of insulation of electrical plant components and thus shortening of their useful life.
  • Plant mal-operation, in particular, the relays.
  • Interference with communication.

Most of the harmonic sources are at the load points and electric supply utilities are putting stringent restrictions on industries to limit the harmonic contents within the stipulated value. This is required to ensure the quality supply to other customers. While effectively designing the filters to maintain the harmonic distortion within the accepted limit, economy is to be looked into. Harmonic meters are required to measure the harmonic contents in the system and design the filters economically to ensure proper quality of power supply

In order to maintain an efficient and effective electricity supply it is necessary to define the level of distortion that can be permitted on the power systems. This need has resulted in the development of a series of measuring instruments. These instrument technology and sophistication are steadily increasing leading to the present day generation of microprocessor based measuring instruments.

Harmonic analysis is the process of finding the frequency contents and their phase angle for a time domain signal. Using this information one can measure the highest frequency present in the signal. Once this information is known, cut off frequency for the low pass filter and sampling frequency (fs) can be determined.


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