Paolo Pinceti

Validation of ZnO surge arresters model for overvoltage studies

This paper presents an improvement of the procedure to determine the parameters of the simplified model for metal-oxide surge arresters, derived from the IEEE standard model. The main innovation introduced by the paper lays in the possibility to define an approximate dynamic model even if data about residual voltages for steep current pulse are not defined in the manufacturers data sheets. This model has a wide rangeability and its effectiveness is good for both medium- and high-voltage arresters. The effectiveness of the model was tested for several arresters of different manufacturers. The residual voltages reported in the datasheets and obtained by the manufacturers through a discharge test are compared with the simulations performed with Matlab. The possibility of defining a dynamic model for surge arresters even with missing data makes the proposed model a useful tool for insulation coordination studies involving steep front transients.

Definition of Power Quality Indices for DC Low Voltage Distribution Networks

The problem of definition of power quality assessment for low voltage dc distribution networks is addressed, with focus on: definition of meaningful electromagnetic phenomena; power quality indices and measurement methods; simulation and experimental results

An Algorithm for the Automatic Detection of Islanded Areas Inside an Active Network

Active networks require modifications of control logic and fast load/generator shedding actions to preserve system stability in case of the creation of islands. Today, industrial networks are designed to run both in parallel with the grid (if is present) and in islanded mode. The transmission system operator in public networks, on the other hand, does not allow islands. This will change as the detection of separated areas with generation capacity and loads will become crucial for the activation of the required control actions in public networks. Here, we describe an algorithm that automatically selects the events that may cause the system islanding, recognizes the island configuration, and calculates the amount of power to shed (when required). This algorithm is the very core of a power management system both for industrial applications today and for future public networks. It can be used to start all the required reactions to islanding, e.g., frequency control and load-shedding. The algorithm is for general-purpose and it does not require any customization for a specific network. The algorithm is based only on the network topology and it does not require data on the network parameters.

Voltage regulation via automatic load tap changing transformers: Evaluation of voltage stability conditions

Abstract The paper shows the role played by load tap changing (LTC) transformers, equipped with tap automatic control, in the analysis of voltage stability at the receiving end of transmission links. Owing to the slow nature of the process, voltage stability at load nodes is investigated with regard to the mid-term dynamics of synchronous generators and to the secondary voltage regulation. The importance of load models is also recognized so that voltage and frequency load characteristics are introduced and their effects on the voltage stability conditions are evaluated and discussed.

Detection of voltage transients to select and trigger control rules of SMES for power quality applications

The paper describes the preliminary results obtained in the HotSMESProject sponsored by the EU. The project has the goal to investigate the performances of the so-called High-Temperature Superconductor (HTS) when used in Superconducting Magnetic Energy Storage systems (SMES) used to improve the Power Quality (PQ).

FieldDC: An open frame application for fully exploiting the FDT/DTM technology

Currently Predictive Maintenance (PM) represents one of the most interesting topics in automation industry. The research of advanced predictive techniques is strictly connected with the availability of data provided by field devices inside a plant. The framework Field Data Catcher (FieldDC) presented in this paper proposes a solution to the problem of transporting information from field devices to a central database, where advanced diagnostic algorithms can be performed. A key feature of the framework is its possibility of operating regardless the type of field devices and communication protocols. To achieve this goal, the framework uses the functionality provided by FDT/DTM (Field Device Tool/Device Type Manager), an open technology that standardizes the communication and configuration interface between all field devices and host systems.

EMC testing of Fieldbus Interconnected Intelligent Positioners

The EMC test procedures and results for a set of intelligent positioners (IP) from several manufacturers are presented. IPs are Fieldbus interconnected intelligent control equipment and EMC test procedures have been conceived not only to test the withstanding capabilities (immunity) of the examined IPs, but also to collect meaningful results on the influence on overall equipment immunity of Fieldbus connection

Advanced Functions for Fieldbus based Integrated Control Systems

Since a few years ago Industrial Automation was classified into functional categories related to the controlled process: continuous process, factory automation, batch control, building automation, etc. Such a classification reflected the differences between the technologies used in the various areas. Automation systems for a refinery were intrinsically different from those used in car manufacturing, with no relationship with technologies used in HVAC control, and so on. Today these differences do not exist any more (or at least are quite dimmed). Independently from the application, the technological platform below almost all the automation applications is basically a network of digital devices (nodes) connected through a serial bus. The push toward this structure comes basically from three facts: The introduction on the market of Intelligent Field Devices (IFD) with sophisticated functionality and communication capacity The migration of the industrial automation from custom platforms toward standard platforms, mainly PC based The acknowledgement that every plant is a mix of different processes, so flexibility is required to the automation system to satisfy the different requirements.

EVALUATING CLOSED LOOP FAST VALVING PERFORMANCE IN POWER PLANTS

The stability of a generator following a sudden power imbalance, caused either by a short circuit or a load rejection, may be significantly increased adopting particular techniques of control of the turbine valves called “fast valving” (also “early valve actuation”). The control law is normally pre-defined on the bases of simulation studies of the power system dynamics, and may sometimes not match the precise system requirements in the real faulted conditions. A new control logic is proposed in the paper, based only on on-line measured variables, and probably better matching the system needs; this logic is called “Closed-Loop Fast Valving” (CLFV). The effectiveness of the CLFV is tested by means of computer simulations making use of the EMTP code.

EMERGENCY OPERATION OF ELECTRICAL POWER PLANTS: EFFECTS OF THERMAL UNIT CONTROLS ON FREQUENCY TRANSIENTS

Abstract The effect of thermal plant response on system frequency control is investigated in the paper using the results of computer simulation studies. Particularly, when islanding conditions for loss of generation or loss of heavy import are involved, the frequency deviation is largely influenced by the prime mover energy supply system as well as by the governing characteristics. As the response time frame of large steam units is on the order of minutes, the problem of the evaluation of grid frequency behaviour is cast in the so-called mid-term period. Consequently, interactions between the electrical grid and boiler turbine units are here evaluated on the basis of a mid-term modelling of the overall system. The time response of the system frequency and of some typical thermal variables are simulated for different operating modes of boiler turbine controls; the trends of such variables are correlated and compared in order to give an insight of the effects of the thermal dynamics on the frequency behaviour of an isolated power system.