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An improved formula for the assessment of the external thermal resistance of three buried single-core, metal-sheathed, touching cables, laid in a flat formation, is proposed. The formula arises from the analysis based on a coupled electric-thermal model, as well as on the stochastic optimization method based on differential evolution. The effect of the new formula on cable rating is illustrated in a numerical example. Index Terms--External thermal resistance, numerical modeling, optimization methods, underground cables.

Expressions for computing the external thermal resistance ([T.sub.4]) of buried cables, in both the IEEE and the IEC standards, are applicable to a limited number of installation geometries. In this paper, a method for the computation of [T.sub.4] using the finite element approach is presented. With this method, a parametric study on how cable ampacity is affected by different configurations of the backfills is performed. The obtained results are compared with those of the IEC and IEEE standards (Neher-McGrath) and published extensions by El-Kady and Horrocks. Important differences can be observed for nonstandardized situations. Index Terms--Ampacity, backfill, cable thermal rating, external thermal resistance, finite element method, Neher-McGrath, underground cables.

This paper presents a new rigorous approach to the calculation of current ratings in pipe-type cables with slow circulation of the fluid. Detailed mathematical analysis is presented for the calculation of the hot-spot fluid temperature as a function of the cable geometry and the fluid inlet temperature. The emphasis is placed on real-time applications, in which the pipe-surface temperature is measured. A numerical example from an actual cable installation is presented. A comparison with the commonly applied method based on Buller's model is offered. Index Terms--Buller's model, pipe-type cables, rating calculations, slow fluid circulation.

This paper presents a new application of modern numerical algorithms, such as neural and probabilistic networks, for monitoring pressure system installations. Theoretical background as well as custom implementation of the algorithms is presented, and a complete system for monitoring high-pressure, fluid-filled (HPFF) cables is described. Index Terms--Dielectric fluid leak detection, neural networks, pipe type cables, probabilistic networks.

This paper presents results of an extensive study launched by Hydro One Networks aimed at determining air blast circuit breaker reliability measures from a statistical analysis of outage data. The study examines how the breaker failure rate depends on such factors as equipment age, voltage level, manufacturer, and number of repairs. Planned outage rates due to equipment maintenance were also investigated. Results presented in this paper are based on outage records involving 318 breakers and covering a period of 12 years. The results can form input information for probabilistic risk analysis studies. Index Terms--Air blast breakers, failure rates, outages, statistical analysis.

An algorithm to calculate the current-carrying capability of multicore cables is presented. The method takes into account the presence of air gaps and metallic conductors in the cable bundle. Under an assumption of a uniform loss density, analytical expressions, which take into account conduction inside the bundle and convection and radiation outside it, are developed. The method is illustrated with a numerical example of a telecommunication cable with 96 stranded cores. Experimental results are also reported for the same cable. Index Terms--Cable rating, conductor temperature, multicore cables, telecommunication cables.

In this paper a new method is proposed that allows estimation of conductor temperature and cable losses as a function of conductor current and some parameters corresponding to the nominal loading conditions. Such parameters include cable rating and loss factors computed by the cable manufacturer for the laying conditions specified by the user. There are two major application of the proposed approach: one relates to rating of power cable with current measurements alone and the other to the computation of the external thermal resistance with a nonunity load factor used in the Neher/McGrath approach. Both applications are examinee in this paper. Index Terms--Loss factor, Neher/McGrath method, power cables, real-time rating systems.

In this paper, an extension of the previously published method for the calculation of the derating factors for cables crossing external heat sources is proposed. The extension takes into account the longitudinal heat flow in cable metallic screen. The proposed algorithm is illustrated in a numerical example considering a practical situation of a high voltage cable crossing a steam pipe. Index Terms--Ampacity derating, cable crossings, power cables.

This paper presents a methodology to design an optimal bidding strategy for a generator according to his or her degree of risk aversion. A typical thermal plant is assumed to be located in the Ontario electricity system to apply this methodology for two types of participants: risk averse and risk seeker. Index Terms--Bidding strategy, open-access market, risk aversion.

This paper introduces a method for forecasting energy prices using artificial intelligence methods, such as neural networks and fuzzy logic, and a combination of the two. The new approach is compared with some of the exiting methods. Various factors affecting the market clearing price are investigated. Results for the Ontario electricity market are presented. Index Terms--Artificial intelligence, energy price forecasting, fuzzy logic, neural networks, open access market.

This paper describes the technical details of an advanced model for use in real-time cable rating systems. Real-time cable rating systems perform calculations of steady-state and emergency cable ratings in real time; several such systems have been installed to maximize asset utilization without compromising cable system reliability. An example of a complex tunnel installation, featuring four self-contained fluid-filled and cross-linked polyethylene cable circuits, is described in detail, highlighting key issues of relevance to real-time systems. Index Terms--Buried cables, cables in ducts, cables in tunnels, power cables, real-time ratings, state estimation.

The available transfer capability (ATC) is an important parameter for all companies participating in the power transaction activities. The main objective of this work is to propose a new methodology to determine the best points in the system to add new agents (sellers and buyers), in order to maximize the ATC, without violating a pre-established reliability level. In the process, the ATC probability density function is determined considering uncertainties from equipment un-availabilities. The proposed algorithm uses Monte Carlo simulation to select system state and linear programming with a dc power flow model, to analyze and optimize each selected state. The IEEE Reliability Test System (RTS) is used to illustrate the proposed methodology. Index Terms--Available transfer capability, composite reliability, Monte Carlo simulation, transmission capacity.

This paper reviews rating of cables installed in air. The following cable installations are investigated: (1) cables on riser poles, (2) cables in open and closed trays, (3) cables wrapped in fire protection covers, (4) cables in horizontal tunnels, and (5) cables in vertical shafts. The rating of cables in these installations is computed by solving energy balance equations for the unknown surface temperature with a given conductor current. In ampacity computations the conductor current is adjusted iteratively until permissible cable conductor and surface temperatures are achieved. It is shown in the paper how the same energy balance equations can be used to compute the ratings of all the above cable installations.

Cost considerations play a very important role in power system operation and planning. In traditional reliability analysis, these costs have rarely been taken into account, primarily because of the lack of suitable mathematical models. The aim of this paper is to introduce one set of such models. To model the economic aspects of component on system reliability, cost rates are introduced to the states and cost impulses to the transitions of the Markov chain. Then, the cost related reliability measures are defined and their relationship to the traditional reliability indices is illustrated. A brief discussion on the solution procedures for the modified Markov chain is offered followed by an illustrative numerical example.