S. Dambone Sessa

Safety issues in tunnel installation of EHV power cables

This paper deals with tunnel installations of extra high voltage (EHV) power cables. Cross-bonding of the screens remains the usual earthing arrangements of cable systems, if their extension is greater than 1,5 km approximately. Such EHV cable systems need a functional earthing along the route in correspondence of each major section, at the sending and at the receiving ends. Given the difficulties involved with the realization of these earthing systems, other techniques should be sought for. In this paper two different methods to earth the cable screens are taken into account: the former is obtained by means of one or more earth continuity conductors (ECCs), whereas the latter relies on the tunnel steel reinforcement (TSR) itself. Each method is discussed and analyzed both in terms of safety issues and stray currents.

Phase-to-ground fault location methods in unearthed sub-transmission networks: A review

This paper provides a coherent classification of the existing methods for phase-to-ground fault location in power sub-transmission networks operated with unearthed neutral. The theoretical background of every approach is briefly presented, specifying whether each method is applicable on-line or off-line. The analysis is mainly focused on comparing the limitations of the algorithms, especially concerning the general properties of the lines of a sub-transmission power system.

A general electric model of sodium-nickel chloride battery

The paper presents the analysis of Sodium Nickel chloride batteries in transient operation, and proposes a very simple but quite precise model to represent both the transient and steady battery behaviours. The used modelling approach is based on steady state experimental measures. Sodium Nickel chloride batteries are one of the most promising technologies for electrical energy stationary storage in the high voltage network. Hence, the main purpose of this model is to foresee the battery voltage during the most important network services, which require very fast transition from the battery charge operation to the discharge one. In order to validate the model, several comparisons between experimental measures and model results are shown.

Impact of protective structures on EHV cable transient behaviour: Comparison between FEM, EMTP and measurements

Reliability of underground Extra High Voltage (EHV) cable systems is undermined by third party mechanical damages. In order to prevent long and expensive outages, the Italian TSO equipped some cable lines of strategical importance with additional protective structures. The presence of highly permeable and conductive material surrounding the cable installations has risen concerns about potential variations in the transient behaviour. The objective of this paper is to model a 380 kV single-core land cable system, by means of the Finite Element Method (FEM) software COMSOL and compare simulation results with measurements. The series impedance matrix as well as modal attenuations and velocities are significantly affected over a wide frequency range, whereas the self input impedance does not show any substantial changes either in short or open circuit conditions.

Sodium nickel chloride cell model for stationary electrical energy storage

The purpose of this paper is to present a reliable modelling of sodium-chloride battery in Simulink environment in order to have a powerful tool which is able to foresee the battery behaviour in both discharge and charge operations. The model is based on a wide set of measures (e.g. discharge and charge resistance for different depth of discharge and current rates, etc.). A comparison between the model results and real battery measures, in the same conditions, has been presented.