Luigi Parise

Ecodesign of Ever Net-Load Microgrids

The European Union has promoted the process of electrical market liberalization, extended to residential/commercial buildings, and a strong encouragement toward the rational use of energy. The European energetic policy aims to promote the installation of small renewable power sources, the use of highly efficient cogeneration, and the Nearly Zero-Energy Buildings (NZEBs) that have to be pursued as much as possible by local generation sufficient to supply the residual amount of energy. To avoid future chaotic phenomena in the existing distribution network, this paper highlights that the power flow of local generators has to be maintained locally: The users have to remain net-loads organized in ever net-load microgrids at least in a first evolution. The actual distribution network for low-voltage customers appears inadequate to comply with these improvements, and it has to change in order to accept microgrids organized by the union of customer groups. The authors suggest the ecodesign of the microgrids able to constitute the NZEB and to accomplish the goals of enhanced safety, high local power quality, dc distribution systems, common emergency systems, efficient load shedding, and energy management. The microgrids guarantee a reduced impact as ever net-load on the net supply.

Branch circuits ecodesign

The modeling of an industrial, commercial or residential electric power systems, pursuing goals on safety, energy and costs saving, operational performances, needs innovations and new approaches to be effective. In the aim of underlining parameters as guideline and indices of rules of thumb the paper approaches their definitions as much as possible in an easy manner for a suitable use by heart. Operational parameters like cable steady current S-density and transient current T-density, load current moment µ-density are introduced to support in a new way the selection and sizing of the cross sectional area S of circuit conductors and the understanding of their behavior. The introduced load current moments and joule moments are specific parameters that can assist the system design to guarantee energy saving, reduced voltage-drops and losses, a higher value of current densities, reduced volume of conductors and other related goals of efficiencies. The ecodesign needs a cultural change of classic approaches.

Microsystem criteria in electrical installations ecodesign

The ecodesign is developing a strong encouragement towards the energy saving balanced with other performances and requires new approaches that this paper begins to highlight. The distribution system management has to facilitate innovations, changes and the complying with these improvements. Together to energy saving, reduced voltage-drops and losses, the system modeling with components of smaller size allows to guarantee a higher value of current densities, reduced volume of conductors and other related goals of efficiencies. Microsystem criteria are highlighted introducing few specific parameters to assist the system design that rises generally as a comprehensive solution of a non linear system of many elements, grouping adequately the supplying loads, adopting circuit with conductors/cables in bunch, in loop or in rope design.

Wise Port and Business Energy Management: Port Facilities, Electrical Power Distribution

The paper deals with the relevance of analyzing the necessary development and of proposing a plan for research and remodeling the electrical infrastructures of port facilities. Good energy management principles, as well as electrical distribution architecture have a vital impact on performance of the installed system throughout its lifecycle. The ports are the interface of maritime transport and are integrated in the surrounding land. They are required to arrange their electrical power distribution system, possibly in microgrids that is, as a utility system, appropriate and adequate even to power the ship from shore. Harbors must have an energy master plan and their areas have to be considered as a unique territory. The energy service management for electrical distribution systems has to be carried out like a new occasion of economic business by the port authorities.

The Global Grounding System: Definitions and guidelines

The present paper presents the preliminary results of the ongoing Italian METERGLOB project on the contribution given by the exposed conductive parts to a Global Grounding System. One of the expected results of METERGLOB is to carry out guidelines for the identification of a Global Grounding System. These guidelines must be defined on the basis of the definitions and methods present in the current international standards on grounding and safety. In the paper some definitions and elements to be taken into account for the identification of a Global Grounding System are given.

Unprotected faults of electrical cords and extension cords in AC and DC systems

In electrical power systems all the wiring exposed to mechanical damages and other insulation stresses, such as flexible cords, can be involved in overheating, arcing and burning. Mechanical damages of the stranded bare conductors can degrade locally the effective sizing of the cross section and cause anomalous local conditions. The circuit protective devices can be unfit to detect the faults of cords that remain so energized and available to electric shock and fire hazards. Some fire ignitions result so special unprotected faults. To highlight the local incident energy in case of fault, the paper introduces the parameters steady current and transient current densities that assist to analyze these fault events. An efficient protection can be achieved by integration of active and passive techniques: - adopting Arc-fault Circuit Interrupters (AFCI) that recognize the arcing faults; - wiring the circuits with a grounding protection conductor to involve the ground in every faults that in AC systems are rapidly protected by residual current protective devices (RCDs or GFPDs). At this aim it is recommendable the use of special cables, Ground-Fault-Forced Cables, GFFCs particularly for cords and extension cords also supplying Class II equipment. The protection of DC systems requires a special care.

Microsystem criteria in branch circuits design

Microsystem criteria in branch circuits design consist in modeling their structure with components of smaller size, in grouping adequately the supplying loads, in adopting circuit with conductors/cables in bunch, in loop or in rope designs. The introduced operational parameters can assist the system design to guarantee, together to energy saving, reduced voltage-drops and losses, a higher value of current densities, reduced volume of conductors and other related goals of efficiencies. The microsystem ecodesign needs a cultural change of classic approaches and requires courage in innovating standardized series of components sizes and in revising parameters values.

Globality levels of grounding systems

IEC Standard 61936-1 “Power installations exceeding 1 kV a.c.” defines the “Global Grounding System” (GGS). It consists essentially in the interconnection of the MV/LV grounding systems, generally at least by means of the MV cables metal sheaths and/or of dedicated ground conductors buried along the MV cable lines. The interconnection of grounding systems involves a significant reduction of the apparent grounding resistance at the MV/LV substations, by creating a metallic ground-fault current path in parallel with the ground which drains away most of the fault current. Due to the mentioned ground resistance reduction, the IEC 61936-1 allows to adopt simplified, relaxed design criteria for the individual grounding systems. The paper suggests recognizing the four “globality” levels of grounding systems in a common zone of influence. It is highlighted the analysis of the interferences between more ground electrodes that can be sensitive for special power systems as data centers and hospitals. It suggests ways to mitigate transferred potentials and a graphical test by a rolling sphere that can be useful to verify the integration of aggregate of ground systems.

Current and voltage behaviour during a fault in a HV/MV system: Methods and measurements

When a single line to ground fault happens on the MV side of a HV/MV system, only a small portion of the fault current is injected into the ground by the ground-grid of the faulty substation. In fact the fault current is distributed between grounding electrodes and MV cables sheaths. In systems with isolated neutral or with resonant earthing this may be sufficient to provide safety from electric shock. Experimental measurements were performed on a real MV distribution network: a real single line to ground fault was made and fault currents were measured in the faulty substation and in four neighbouring substations. In this paper the problem of fault current distribution is introduced, the test system is described and the measurements results are presented.

Single grounding system intrinsically safe and global grounding system safe as set

This paper introduces a characterization of a single Grounding System (GS) or a set of interconnected GSs, according to their safety level and defines their condition of “conventionally safe” and “intrinsically safe”. GSs or a set of them are intrinsically safe, if they guarantee safe touch/step voltages permanently permissible for an assigned ground fault value. It is proposed a new definition of Global Grounding Systems (GGSs) revising that offered by the Standards IEC 61936-1/EN 50522. The paper suggests a safety criterion, useful for urban and industrial areas with reduced accessibility, that allows to identify the safety zone of influence and the intrinsically safe condition of a single GS and of a GGS, constituted by a set of interconnected single GSs.