The switching life of short-circuit contact breakers in power systems

Integral distributions of the actual values of short-circuit currents in the 100–500 kV networks, obtained by processing oscillograms of the transients in electrical transmission lines, are presented. It is shown that in the majority of newly established modern gas-filled contact breakers with spring-loaded drive mechanisms the switching and mechanical lives will not be exhausted after their useful life. Hence, planned repairs of such contact breakers can be predicted starting from their actual state and not from the fixed inter-repair periods. * JSC “Otdelenie Dal'nikh Peredach,” Russia. ** Electric Main Line Network Center (MéS Tsentra), Russia. *** IVTs Mosénergo, Moscow, Russia. **** Moscow Power Institute – Technical University, Moscow, Russia. ***** JSC “énergoservisproekt,” Russia. Translated from élektricheskie Stantsii, No. 10, October 2008, pp. 59–62.     

Does Allowing the Bells to Offer InterLATA Long-Distance Service Affect Entry into Local Telephony?

Following the 1984 divestiture of AT&T, local telephone service was provided by several Regional Bell Operating Companies (RBOCs). The RBOCs served as monopoly providers of local telephone service in their respective territories but were prohibited from offering long-distance service to their in-region subscribers. Section 271 of the landmark Telecommunications Act of 1996 allows an RBOC to offer in-region long-distance service if it demonstrates that the local telephone exchange market is open to competitive entry. This study empirically evaluates the efficacy of this policy by considering the impact of RBOC entry into long-distance on the development of competitive entry into local telephony. The results suggest that section 271 has been successful in promoting entry into local telephony. However, aggregate price data suggest that this entry has not been realized with lower rates for residential telephone subscribers.     

Means of improving the economy of water-preparation units at TPP

Developments directed toward refinement of heating systems and thermal deaeration of feed and make-up water using regenerative taps of extraction turbines are presented. The Ul’yanovsk No. 1 TPP is used as an example to demonstrate the feasibility of one of the proposed solutions at a specific thermoelectric power plant. __________ Translated from élektricheskie Stantsii, No. 7, July, 2007, pp. 32–36.     

Allowable gas temperature at outlet from furnace subject to slagging

The paper is devoted to substantiation and prediction of the allowable gas temperature at the outlet from a furnace subject to slagging. The non-optimality of values recommended by effective methodical instructions regarding the design of furnace devices is demonstrated. Utilizing knowledge gained from temperature measurements in boilers, and the situation regarding the slagging of heating surfaces located at the outlet from the furnace, new, frequently higher values are proposed. A method for evaluating the allowable gas temperature at the outlet froma furnace subject to slagging is suggested on the basis of data regarding the chemical composition of the mineral portion of coals. __________ Translated from élektricheskie Stantsii, No. 2, February, 2007, pp. 23–28.     

On Some Kinds of Damage in Drums of High-Pressure Boilers

Kinds of damage in drums of high-pressure powerplant boilers in the places of welding of separation devices by austenite electrodes are described. Results of a complex study of damaged metal are presented. The mechanism of damage caused by contact (electrochemical) corrosion on the interface of two metals with different values of electrode potential is established. Measures for preventing the described kinds of damage are recommended.     

Calculation of Maximum Permissible Load Currents under Cyclic Loading Conditions for Cables Laid in the Ground and in Pipes in the Ground

A method for calculating the maximum permissible load current under the conditions of cyclic daily load curve is developed. A system is suggested for parallel cables laid in the ground, including in pipes. The coefficients for determining permissible load currents are calculated for different laying variants. Calculated data for cables arranged in 2 × 2 and 2 × 4 blocks are presented.     

Management criteria for lake ecosystems applied to case studies of changes in nutrient loading and climate change

The aim of this paper is twofold: to present and discuss practically useful management criteria from different perspectives of lake management (fishery, recreation, conservation, monitoring of water quality and use of water for irrigation and drinking), and to put these criteria into the context of a holistic lake ecosystem model, LakeWeb, which accounts for production, biomasses, predation and abiotic/biotic feedbacks related to nine key functional groups of organisms constituting the lake ecosystem. These are phytoplankton, benthic algae, macrophytes, bacterioplankton, herbivorous zooplankton, predatory zooplankton, zoobenthos, prey fish and predatory fish. The LakeWeb model also includes a mass‐balance model for phosphorus and calculates bio‐uptake and retention of phosphorus in these groups of organisms. It also includes submodels for the depth of the photic zone and lake temperature. The LakeWeb model is driven by few and readily accessible driving variables and it has been extensively tested and shown to capture fundamental lake foodweb interactions very well, which should lend credibility to the scenarios discussed in this paper regarding the conditions in Lake Batorino, Belarus. The LakeWeb model offers a tool to address important, often very complex, scientific problems in a realistic manner. The first scenario describes the changes after 1990 when there was a drastic reduction in the use of fertilizers in agriculture because of political changes and the corresponding changes in lake characteristics and foodweb structures utilizing the given management criteria. The second scenario describes, for comparative purposes, the probable alterations in the lake foodweb related to global climatic changes; in this case, warming and increased temperature variations. This study indicates that there are several similarities between eutrophication and increases in temperatures, which are discussed in this paper along with the mechanistic reasons related to such changes by using a set of general management criteria.