Description:
Unplanned power system islanding is usually seen as a major risky operating condition and specific countermeasures are applied in order to avoid it. However the capability of voluntary disconnection f... see morerom the external grid and autonomous operation is often a requirement for some industrial power systems and power plants. The panel session at the 2012 IEEE Innovative Smart Grid Technologies Conference on
“Power system islands, autonomous microgrids and relevant instrumentation” aims at providing an occasion to exchange ideas and experiences in order to envisage situations in which voluntary power system islanding may be useful and to define the instrumentation required for a reliable operation in islanded conditions. This paper, provided by the organizers, reviews some activities recently carried out on this topic at their institution.
Description:
Monitoring units for the measurement of high frequency voltage transients have been in operation at three different busses of an Italian medium voltage (MV) distribution feeder, mainly composed by ove... see morerhead lines, in March 2007 – August 2008. The feeder is located in a region characterized by a high ground flash density value (4 flashes/km2/yr); many of the recorded voltage transients may be correlated with the lightning events detected for the same region by the Lightning Location System (LLS) CESISIRF. The paper presents some experimental results obtained using the monitoring units and their comparison with computer results obtained using a LIOV-EMTP model of the considered MV feeder. A procedure aimed at achieving the best fit between measurements and calculations, which takes into account the uncertainties associated with LLS data, is also presented.
Authors:A. Borghetti, F. Napolitano, C.A. Nucci, M. Paolone, M. Bernardi, W. Schulz
X International Symposium on Lightning Protection, 9th-13th November, 2009 – Curitiba, Brazil
Description:
This paper deals with the calculation of lightning induced overvoltages on medium-voltage (MV) and low-voltage (LV) distribution networks taking into account the presence of MV–LV distribution trans... see moreformers and, in particular, the surge transfer through them. The influence of the high-frequency model adopted for the representation of the power transformer on the calculation results is analyzed, with regards to two different models, both identified and validated by means of laboratory measurements: namely, a simple π of capacitances, and the more complex one introduced by Morched, Marti, and Ottevangers in 1993. Accurate simulation results provide information on the adequacy of both models for the calculations of interest. Additional results, useful to evaluate the expected level of power quality and the benefits achievable by a proper installation of protection devices, are presented making reference to a realistic and complex configuration of an overhead distribution system
Authors: Alberto Borghetti, Atef Morched, Fabio Napolitano, Carlo Alberto Nucci, Mario Paolone,
IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 24, NO. 1, JANUARY 2009
Description:
The switching of medium voltage electrical motors is typically realized by means of vacuum circuit breakers (VCBs) essentially in view of their elevated number of switching cycles. As known, switching... see more of VCBs generates important transient recovery voltages (TRVs)
that need to be properly evaluated in both VCB sizing and in the power system insulation coordination. As large medium voltage electrical motors are installed into plants typically controlled by means of Supervisory Control And Data Acquisition (SCADA) systems,
maneuvers that involve the motor inrush followed by its sudden de-energization (due, in general, to the intervention of an automatic diagnostic function), resulting into important TRVs, are not unusual. The paper aims at investigating the TRVs due to this specific type of
VCB switching by means of a model implemented in the EMTP-RV simulation environment. By making reference to a real plant, the validation of the implemented models is obtained by comparing the simulation results with some experimental transients provided by the plant data fault recorder. The paper finally discusses the adequacy of different countermeasures by analyzing their effectiveness for the TRVs limitation.
Authors: A. Borghetti, F. Napolitano, C.A. Nucci, M. Paolone, M. Sultan, N. Tripaldi
CIGRE - International Symposium “Assessing and Improving Power System Security, Reliability and Performance in Light of Changing Energy Sources” Recife, Pernambuco, Brazil, April 3-6, 2011
Topic 3 – System technical performance
Subtopic 3.5 – Switching and lightning transient on power systems. Impact on performance and measurements
Description:
The following example demonstrates the coupling effect between 3 adjacent transmission lines.
The case study consists of the implementation of a third transmission line next to two existing... see more lines. The data of the geometrical configuration are entered in the DATA LINE module and are stored in the "line_couplin_CP.lin". The generated model was obtained using the CP option and are loaded to the CP m-phase module using the data included in the "line_coupling_CP_rv.csv" file. The results are very close to the measurements provided in "H.W. DOMMEL ET AL, CASE STUDIES FOR ELECTROMAGNETIC TRANSIENTS, P.1,1991".
