Dec 2017 / by S. Roy Barman and M. Roy Barman
The grid disturbance episodes on 30 and 31 July, 2012 have drawn the attention of the policy makers to a very relevant issue of ensuring grid stability and reliability in the country. With the restructuring of the power sector, the responsibility of ensuring grid stability has been entrusted upon the system operators i.e. the Load Dispatch Centers at the state, regional and national levels. For any power system to operate efficiently, two unique requirements which must be continuously and exactly satisfied in order to maintain overall system stability and reliability is to maintain a constant balance between generation and load and to adjust generation to manage power flows within the constraints of individual transmission facilities. Therefore, system operators need some resources to balance grid during contingencies at short notice. These resources are commonly known as ancillary services. In costplus regulated regime, these resources can be built and operated under the instructions of system operators. However, in competitive, de-regulated regime, developing markets for such resources a necessity.
Nov 2017 / by Chirag Arora, Nagendra Kumar Swarnkar and Rahul Sharma
Main focus of this paper is to study and implementation of high efficiency DC-DC circuit, based on a boost DC/DC converter topology with high voltage gain. It is also about how to achieve high step up (efficient) DC/DC converter in the renewable power application due to low voltage of PV array. The proposed system having a solar photovoltaic module, a closed loop boost converter and a lighting module which is nothing but a DC load. Output voltage of renewable energy sources like PV modules, batteries and fuel cell is 20 V, which is boost to the range of 220V DC. If we want to connect them into grid the voltage level should be adjustable like electrical network accordingly. Performance of the system is affected by the efficiency of stepup DC-DC converter. Boost converter is used to convert a low level DC input voltage coming from solar PV module to a high level DC voltage output required for the DC load.
Keywords: High step-up, DC-DC converter, boost converter.
Nov 2017 / by Rakesh Kumar Khali
Tunnel T-48 the railway tunnel, is one of the main stretches of the 273 km long Udhampur-Srinagar-Baramullah, a new broad gauge rail project in the state of J&K, India covering a length of 10.2 km comprising the main tunnel and the escape tunnel of 10.20 km length, each of which are required to be bored with 7.12m and 4.5m of finished diameter respectively. Presently the tunnels – comprising 6 faces out of total 10 faces, i.e. 4 faces from adit-1, 4 faces from adit-2 and 2 faces from north portal – are under construction in accordance with the principle of New Austrian Tunnelling Method (NATM). The remaining 4 faces from Adit-2 are yet to be opened. Despite the very heterogeneous geological conditions, i.e., frequent changes of massy and completely fractured rock, and with partial high water ingress, the work is progressing without prolonged excavation related interruptions and delays. Tunnelling is a challenge on this stretch in the face of multifarious problems owing to extremely difficult and inaccessible terrain, compounded by technical problems and adverse security concerns. These prestigious tunnels are driven by conventional mined tunnelling methods, such as drill and blast and also by the most modern equipment like telescopic boomers, Schaeff loader, Volvo tippers, CIFA shotcrete machines, side tilt Libherr loaders, Terex tunnel loaders, PC-200 excavators with hydraulic breakers, transit mixers and swing stator batching plant (60m3/hr capacity) at each locations. Notwithstanding the difficult geology, extreme weather situations in winter and the hostile conditions of the area, we have been able to achieve the progress of construction of the tunnel, 24 meter per day. This paper deals with the planning process, with provisions for advancing with NATM in the very poor geological condition coupled with geological surprises, for and restoration of cavities with pipe roofing, SDR anchors, probe holes and extensive grouting to be followed by erection of lattice girders and shotcreting. The paper also interrogates the problems encountered as a result of extreme weather conditions and poor access available to the site where landslides owing to heavy rainfall during the winter season, are so common. The paper describes how we grappled with the adversities which broke our supply chain and how we overcame the same.
Keywords: Railway tunnel.
Nov 2017 / by Amartya Kumar Bhattacharya
The present paper starts by presenting an overview of the arsenic contamination in the groundwater in different parts of India. The paper goes on to present standards regarding arsenic in drinking water and then proceeds to give a statewise status of arsenic contamination. Adverse effects of arsenic on the health of human beings, accumulation of arsenic in the food chain and ill-effects of using arsenicladen water for irrigation are elaborated upon in the paper. The paper proceeds to explore technological options to deliver arsenic-free water by various ways and means. Providing medical relief to affected people is also included. A recommendation from the author to the government for the safe utilisation of arsenic-laden sludge from arsenic filters is also a key aspect of paper. The last portion of the paper points out the gaps in achieving the goal of ‘arsenic mitigation’.