On the selection and installation of surge protection devices in a TT wiring system for equipment and human safety

This paper provides a comprehensive guidance for the selection and installation of transient protection devices, especially in a TT wiring system with the aim of safeguarding both the equipment concerned and the operators and users of equipment. A number of core and fringe issues with respect to surge protection have been discussed in details with the view of developing high level of electrical safety practices among engineers. The information presented can also be used as educational material that guides electrical engineers in addressing lightning protection issues of LV power systems and ELV signal systems. A number of real life examples and survey outcomes that reflect misinterpretation of standards and scientific practices, gathered in the South Asian region have also been discussed

A tutorial on the selection and installation of surge protection devices in a TT wiring system

This paper provides an easy-to-understand guidance for the selection and installation of transient protection devices, especially in a TT wiring system. Several fringe issues with respect to surge protection have also been discussed. The information presented can be used as educational material that guides electrical engineers in addressing lightning protection issues of LV power systems and ELV signal systems. A number of real life examples and survey outcomes that reflect misinterpretation of standards and scientific practices, gathered in the South Asian region have also been discussed

Lightning safety psyche

How is lightning protection ranked in the field of safety science? What is the general perception of the public with regard to the risk of receiving a lightning strike to their building? How do business entities manipulate the psyche of the public in upsizing financial gains? What is the true risk of public adopting lightning protection techniques that have not been included in major international standards? Is the research presented so far in condemning the lightning protection systems rejected by the scientific community, well-conducted? Is tabooing of some lightning protection technologies a productive strategy in driving the public to adopt protection systems recommended by international (IEC) standards? This paper makes comprehensive attempts to answer these questions

Defining lightning-safe structures for all socio-economic communities

Four levels of lightning-safe structures are defined based on the protection expected from various lightning injury mechanisms under thunderstorm conditions. This work, therefore, provides clarification for the long-standing issue of determining the most suitable recommendation for lightning safety in various socio-economic layers of society, especially in underprivileged communities. These globally uniform and consistent guidelines will help standard development committees, lightning safety seekers and donors of protection systems, state policy developers on disaster management, the insurance sector and industries that provide lightning protection, in determining the most appropriate lightning safety measures for a given target, based on the safety requirements, societal behaviour and affordability. Significance: Lightning safety module developers could confidently adopt the definition of safe structures provided here in their guidelines. The ambiguity on both indigenous and commercial lightning safe structures (purpose made) is cleared. Standards could specify the essential features of a structure that can be considered lightning safe

Lightning related human casualties in Mongolia

Lightning related casualties collected by the Institute of Meteorology in Mongolia from 2003 to 2015 have been analyzed. Being a country with one of the lowest population density, Mongolia records a relatively high human death rate per unit population per year, 15.4 dptm yr-1, which is much higher than that of many countries with similar isokeraunic level. During this period 57 deaths and 58 injuries have been reported, thus death to injury ratio is nearly 1:1. Around 88% of both deaths and injuries has been reported to be occurred while the victim is in wild area, typically the low-grown slopes in steppe climate. Other 12% of the death and injury cases have been located either in open spaces within the village or inside the fabric enclosed houses known as ger. Nearly 80% of the gender known deaths are of males. Almost 100% of the deaths of which the time of incident is known has happened between noon and midnight. Almost all case of injuries have also been reported during the same period. About 80% of the age-reported deaths were of people below 30 years. Slightly more than 50% of the deaths and 54% of the injuries have been reported from Central province

A multi-layer perceptron for scheduling cellular manufacturing systems in the presence of unreliable machines and uncertain cost

In this paper, a new method is proposed for short-term period scheduling of dynamic cellular manufacturing systems in the presence of bottleneck and parallel machines. The aim of this method is to find best production strategy of in-house manufacturing and outsourcing in small and medium scale cellular manufacturing companies. For this purpose, a multi-period scheduling model has been proposed which is flexible enough to be used in real industries. To solve the proposed problem, a number of metaheuristics are developed including Branch and Bound; Simulated Annealing algorithms; Fuzzy Art Control; Ant Colony Optimization and a hybrid Multi-layer Perceptron and Simulated Annealing algorithms. Our findings indicate that the uncertain condition of system costs affects the routing of product parts and may induce machine-load variations that yield to cell-load diversity. The results showed that the proposed method can significantly reduce cell load variation while finding the best trading off values between in-house manufacturing and outsourcing

Hydrogen as an energy carrier: prospects and challenges

This paper provides an insight to the feasibility of adopting hydrogen as a key energy carrier and fuel source in the near future. It is shown that hydrogen has several advantages, as well as few drawbacks in using for the above purposes. The research shows that hydrogen will be a key player in storing energy that is wasted at generation stage in large-scale power grids by off-peak diversion to dummy loads. The estimations show that by the year of 2050 there will be a hydrogen demand of over 42 million metric tons or 45 billion gallon gasoline equivalent (GGE) in the United States of America alone which can fuel up 342 million light-duty vehicles for 51 × 1011 miles (82 × 1011 km) travel per year. The production at distributed level has also been discussed. The paper also presents the levels of risk in production, storage and distribution stages and proposes possible techniques to address safety issues. It is shown that the storage in small to medium scale containers is much economical compared to doing the same at large-scale containers. The study concludes that hydrogen has a promising future to be a highly feasible energy carrier and energy source itself at consumer level

Surge protection of low voltage systems and relevant standards

This paper discusses the components and techniques of protecting low voltage systems from lightning generated electrical transients and the adequacy of International Standards in addressing the transient protection issues. Our analysis question the suitability of 8/20 μs test current impulse in representing characteristics such as the time derivative or the energy content of lightning currents. The 10/350 μs test current impulse better represents the integrated effect of the energy content of impulse component and long continuing current. A new waveform is required to be specified for testing the ability of protective devices to respond to the fast leading edges of subsequent strokes that may come 100s of millisecond after the preceding stroke. The test voltage waveform 1.2 / 50 μs should also be modified to test the response of protective devices for fast leading edges of induced voltage transients. A surge protective device that is tested for lightning transients may not be able to provide defense against other transients

Transients that may affect low voltage electrical systems

A comprehensive review has been done on the types of transients that may affect low voltage electrical systems. The paper discusses various characteristics of lightning, switching, nuclear and intentional microwave impulses giving special attention to their impact on equipment and systems. The analysis shows that transients have a wide range of rise time, half peak width, action integral etc. with respect to both source and coupling mechanism. Hence, transient protection technology should be more specific with regard to the capabilities of the protection devices

Design of a Lightning Protection System for an Overhead 3 kV DC Electrified Railway Line: A Case Study from South Africa

A protection scheme is proposed for the 3 kV DC railway, in Kwa-Zulu Natal province, a region with a high lightning occurrence density. The surge protection was sought by implementing three metal-oxide surge arresters and an overhead ground wire. The purpose of these arresters is determined by their location in the circuit and the points that are vulnerable to adverse lightning effects: an arrester is installed to protect insulators between overhead lines and the supporting metallic mast, an arrester is installed to protect the point of contact between a stationary power supply wire and the train, and an arrester is installed to protect apparatus associated with the running tracks (return rail). An isolated earthing system is explored, and the effects of surge impedances and footing resistances are discussed. The voltage dropped across relevant vulnerable components and energy absorbed by the system components are determined by the simulation software Simulink. These results are compared with a railway system outfitted with the designed lightning protection mechanisms. Lightning currents are injected into the system using Heidler function where the parameters are in compliance with lightning protection standards. It is observed that the protection mechanisms defend susceptible components to a specified level. This demonstrates the success of the design in accordance with arrester protection levels (73.3 kV) and equipment withstand capabilities (a basic insulation level of 143 kV). This offers a protection margin of 95%. The largest percentage overshoot in the system is 39%, and this value is substantiated using reflection phenomena