Sebastian Dambone Sessa

Different Bonding Types of Scilla–Villafranca (Sicily–Calabria) 43-km Double-Circuit AC 380-kV Submarine–Land Cables

This paper describes and analyzes the extra-high-voltage double-circuit cable line between Sicily and Calabria which is a reinforcement of the Italian southern transmission grid. This is one of the longest ac submarine links in the world. The multiconductor cell analysis of this land-submarine double-circuit single-core cables has been compared with an electromagnetic transient program model with a very good agreement. The different choices of bonding systems implemented in the real Italian installation are theoretically justified by means of the two-software comparison.

Ground return current behaviour in HVAC insulated cables by means of MCA

The knowledge of ground return current in faulty occurrence plays a key role in the dimensioning of the earthing grid of substations and cable sealing end compounds, in the computation of rise of earth potential at substation sites and in electromagnetic interferences (EMIs) on neighbouring parallel metallic conductors (pipes, handrail, etc.). Moreover, the ground return current evaluation is also important in steady-state regime since this stray current can be responsible for EMIs and also for AC corrosion. In faulty situation and under some assumptions, the ground return current value at substation site can be computed by means of k-factors. The paper shows that these simplified and approximated approaches have a lot of limitations and only multiconductor approaches can show the ground return current behaviour along the cable (not only the two end values) both in steady-state regime and in short circuit occurrence (e.g. phase-to-ground and phase-to-phase-to-ground). Multiconductor Cell Analysis (MCA) considers the cable system in its real asymmetry without simplified and approximated hypotheses. The sensitivity of ground return current to circuit parameters (cross-bonding box resistances, substation earthing resistances, soil resistivity) is throughout presented.

A New Multiconductor Cell Three-Dimension Matrix-Based Analysis Applied to a Three-Core Armoured Cable

In this paper, a procedure based on three-dimension matrices is presented: it is the generalization of multiconductor cell analysis to any transmission line where the positions of all the active and passive conductors may change with continuity along their length. A meaningful example of this is given by a three-core single lead-screened armoured cable where cores and armour wires are wound helically with different lay lengths. Therefore, this generalization is presented with reference to these cables but it can be applied to any transmission line. The proposed matrix procedures can be implemented in any standard computer by means of a mathematical software (e.g., MATLAB). The computational complexity of this novel method is shown in comparison with the finite element method commercial software FLUX 3D, which takes 70 h for meshing and solving a 3-m long model. On the contrary, the present matrix algorithms take from minute fractions to maximum 2 min (depending on subconductor number) to obtain results having negligible differences with respect to FEM FLUX 3D ones if paramagnetic materials are involved and differences up to maximum 7% with ferromagnetic ones (which imply, for submarine cable installations, a current rating computation difference lower than 3%).

Finite Element model of a 3 m long three-core armoured submarine cable

This paper presents a complete three meter long 3D Finite Element Method (FEM) model of a three-core submarine armoured cable. In this model, the different laying pitches of cores and armour steel wires are correctly taken into account. For the first time in technical literature, a 3 meter long model has been successfully solved. The CPU times are very high i.e. about 70 hours (mesh plus solver). IEC 60287-1-1 gives a strong overestimation of armour and screen power losses and consequently an important underestimation of cable current rating. It is worth noting that IEC gives an overestimation even if a 2D model is considered i.e. the stranding is not taken into account.

Saving environmental impact of electrical energy transmission by employing existing/planned transport corridors

This paper deals with the development of a procedural approach for analysing the compatibility between high voltage alternating current/high voltage direct current power cables and existing/future structures by taking advantage of railway and highway transports. Several critical issues have been deeply analysed in order to ensure a reliable and safe operation of power cables hosted in railway/highway structures. The paper offers a perspective synergy that will have to be considered more and more in future electric networks due to the reduction of energy corridors. After a first assessment of the geometrical compatibility between insulated cables and hosting structures, the paper focuses on the fire behaviour of high voltage cables inside structures, some notes on the maximum length of high voltage alternating current cable links without the use of shunt reactive compensation and on the electromagnetic compatibility.

A free tool in Laplace domain for assessing the extra high voltage cable energization

The purpose of this paper is to present a free tool easily implementable in commercial mathematical software (e.g. Matlab) which allows computing the switching overvoltages due to the cable (in single or double circuit) energization. Also the use of shunt reactive compensation can be accounted for. In order to achieve this goal, the authors have made an extensive use of Lapalce domain. The paper shows both a numerical inverse Laplace transform and a novel method which does not need a numerical inverse transform. In fact, by representing the transmission line as a cascade of n cells constituted of lumped L-C ladder, it is straightforward to make the inverse Laplace transform of rational functions as polynomials.

43 km double-circuit AC 380 kV submarine-land cables in Italy between Sicily and Calabria

This paper describes and analyses the extra-high voltage double-circuit cable line between Sicily and Calabria which is a reinforcement of the Italian southern transmission grid. This is one of the longest ac submarine link in the world. The multiconductor cell analysis (MCA) of this land-submarine double-circuit single-core cables has been compared with an Electro Magnetic Transient Program (EMTP-RV) model with a very good agreement. The different choices of bonding systems implemented in the real Italian installation are theoretically justified by means of the two software comparison.

T-Ω formulation for eddy current problems with periodic boundary conditions

This paper presents a novel technique to perform the topological pre-processing needed in formulations based on an electric vector potential and a magnetic scalar potential when the eddy current problem being solved is subject to periodic boundary conditions (PBC). In this case, in fact, all the techniques to produce the generators for the first cohomology group introduced in literature cannot be used. The novel technique is very fast and it is used to model cables for power delivery.

Sodium-nickel chloride (Na-NiCl 2 ) battery safety tests for stationary electrochemical energy storage

In the paper a view of the tests carried out to verify the safety features of sodium-nickel chloride batteries for stationary energy storage installations is presented. In particular, the battery behaviour in very severe conditions has been analysed, by testing: the battery responses to strong vibrations in order to simulate a seismic event or the transport conditions; the battery damages after immersion in salt water; the battery damages after strong impacts; the battery damages after the battery was set on fire. Moreover, with the purpose of analysing the electrical safety of a sodium nickel chloride module, a short circuit test was performed, by inducing a short circuit between two cells inside the module, with deactivated battery protections.

Insulated cable systems with high current ratings, case studies and practical applications

Current rating computations for HV and EHV insulated cables play a crucial role in the planning phase of a new undergrounded line for both an entirely cable link and a mixed or hybrid (cascade connection of overhead and cable line) one. The paper gives a wide overview of the technical solutions which allow very high current ratings in undergrounded insulated cables. These solutions are examined from a theoretical standpoint and practical applications are shown and explained. The paper demonstrates that in underground insulated cables current rating up to 2500 A can be reached.