General guidelines for safekeeping of high voltage transformers - Part 1

Transformers such as HV/EHV (132 kV and above) are the most vital and costly equipment in power systems and large Industries. It is the prime duty of HV/EHV substation managers, asset managers, and substation Operation & Maintenance (O&M) engineers to look after transformers, beginning from receipt on-site through their lifecycle scrupulously with motherly feelings. Generally, OEM (Original Equipment Manufacturer) guidelines must be followed. This article is a significant and important contribution of experienced engineers in O&M and testing and commissioning up to 400 kV in HV/EHV substations. The authors deliberate all the aspects from receiving the consignment of an EHV Transformer on-site through its lifecycle, including O&M and life expectancy enhancement. This article serves as a guideline for substation managers, asset managers, and substation engineers in the absence of any guidelines issued by their utilities or in the industry

General guidelines for safekeeping of high voltage transformers - Part II

Transformers such as HV/EHV (132 kV and above) are the most vital and costly equipment in power systems and large Industries. It is the prime duty of HV/EHV substation managers, asset managers, and substation Operation & Maintenance (O&M) engineers to look after transformers, beginning from receipt on-site through their lifecycle scrupulously with motherly feelings. Generally, OEM (Original Equipment Manufacturer) guidelines must be followed. This article is a significant and important contribution of experienced engineers in O&M and testing and commissioning up to 400 kV in HV/EHV substations. The authors deliberate all the aspects from receiving the consignment of an EHV Transformer on-site through its lifecycle, including O&M and life expectancy enhancement. This article serves as a guideline for substation managers, asset managers, and substation engineers in the absence of any guidelines issued by their utilities or in the industry

Online refurbishment of old transformers

This article focuses on refurbishment / reconditioning for extension of life-expectancy of old transformers of EHV (extra high voltage 66 kV class and above) class, which were continuously in service for more than 20 years in the State Transmission Utility of Madhya Pradesh in India. The salient feature of this article for moisture refurbishment of old transformers was by adopting the criterion “% relative saturation of water in oil.” This selection criterion is different from the conventional practice in vogue of observing the deterioration trend of IR (Insulation Resistance) and PI (Polarization Index) values and the DGA (Dissolved Gas Analysis), etc. The reconditioning of all such old EHV transformers, precisely 205 units, was taken up “online” in a big way, avoiding long downtimes and frequent load shedding, etc., keeping in view dissatisfaction amongst the consumers at large. This project was completed over a period of five years

A qualitative study to understand patients\u27 experiences of foot pain and surgical consultation for hallux valgus and/or hallux rigidus

The foot is one of the most complex musculoskeletal systems in the body, playing a pivotal role in gait and posture. Epidemiological studies indicate that a high prevalence of foot problems is associated with a greater burden of pain, disability and decreased health-related quality of life. Disabling foot pain is likely to be multifactorial in origin, however to date there is limited evidence of the psychosocial impact of forefoot problems, as such the associated burden is unknown. The study was qualitative with the use of semi-structured interviews to explore patients\u27 experiences of their foot problem and of undergoing surgical consultation and/or intervention for hallux valgus and/or hallux rigidus. Sixteen patients participated: 14 females and 2 males; mean age of 61 years, SD 7.23 from a National Health Service secondary care hospital within an orthopaedic department, who required surgery for hallux valgus and/or hallux rigidus. Thematic analysis generated three themes; \u27the impact of pain\u27, \u27the decision-making process\u27 and \u27body image, the self and identity\u27. Forefoot problems present many issues for patients and impact on their physical, social and psychological health. Forefoot problems are multifactorial and patients should be supported using a biopsychosocial approach

Beam Switching Cylindrical Array Antenna System for Communication

The beam switching cylindrical array, which is a unique system, has been designed and developed to cover 360° in azimuth plane by generating 16 beams with specified elevation coverage.In this design, the concept of fast aperture selection (4 x 4) in microseconds from the total cylindrical array has been realised successfully to meet the requirement of point-to-multipoint communication. The components of the array, viz., radiating elements, powder dividers, switches, etc., are designed in printed circuit type, and hence, objectives of lightweight and ease of reproducibility are achieved. The lightweight of the array makes it accessible for easy mounting at a specified height for achieving longer communication range. Finally, a low-loss radome is incorporated to protect the array from environmental conditions. The various parameters, viz., return loss, gain, and switched-beam radiation patterns were measured over a bandwidth of 300 MHz in L- band and typical measured results are presented in this paper

Antihyperlipidemic activity of Chloroxylon swietenia in triton WR1339 induced hyperlipidemia

Background: Medicinal herbs are beneficial and effective either in the management and prevention of several metabolic disorders, associated with hyperlipidemia, hypertension and insulin resistance which increases the cardio-metabolic risk and demands for the life time therapy. Current allopathic medicines are expensive and reported with several adverse effects and hence, finding of a suitable herbal medicine for hyperlipidemic disorders is very important.Methods: Thirty albino rats weighing 200-230g were randomly divided into 5 groups were rendered hyperlipidemia with a single dose of triton WR 1339. Normal control, positive control, standard, aqueous and ethanolic extract groups were treated with tween-80, tween-80, atorvastatin, aqueous and ethanolic extracts of Chloroxylon swietenia respectively for seven days. At the end of the study, blood was collected for estimation of the lipid profile.Results: Both the aqueous and ethanolic extract groups significantly reduced the TG and VLDL levels.Conclusions: The extracts exhibited remarkable activity on one or either parameter of the lipid profile. It could be due to the presence of alkaloids, steroids, flavonoids, coumarins and phenols in the extracts

Quantum graphs where back-scattering is prohibited

We describe a new class of scattering matrices for quantum graphs in which back-scattering is prohibited. We discuss some properties of quantum graphs with these scattering matrices and explain the advantages and interest in their study. We also provide two methods to build the vertex scattering matrices needed for their construction.Comment: 15 page

Relaxation of Surface Profiles by Evaporation Dynamics

We present simulations of the relaxation towards equilibrium of one dimensional steps and sinusoidal grooves imprinted on a surface below its roughening transition. We use a generalization of the hypercube stacking model of Forrest and Tang, that allows for temperature dependent next-nearest-neighbor interactions. For the step geometry the results at T=0 agree well with the t^(1/4) prediction of continuum theory for the spreading of the step. In the case of periodic profiles we modify the mobility for the tips of the profile and find the approximate solution of the resulting free boundary problem to be in reasonable agreement with the T=0 simulations.Comment: 6 pages, Revtex, 5 Postscript figures, to appear in PRB 15, October 199

New iterative methods for linear inequalities

New iterative methods for solving systems of linear inequalities are presented. Each step in these methods consists of finding the orthogonal projection of the current point onto a hyperplane corresponding to a surrogate constraint which is constructed through a positive combination of a group of violated constraints. Both sequential and parallel implementations are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45240/1/10957_2004_Article_BF00939954.pd