Maria Gabriella Masi

Design and Performance Analysis of a Differential Current Sensor for Power System Applications

Current measurement is required to ensure the correct operation of power systems. Conventional current transformers are still widely employed in such networks, but their well-known limits make them not suitable for the incoming smart meters. In this paper, a current sensor based on proper measurements of the magnetic field produced by the primary current is proposed. Its main feature is the capability, owing to its particular geometry, of neglecting the effect of external fields without using traditional coil structure. An experimental analysis of its performance in both time and frequency domains is presented and discussed.

Toward a BITE for Real-Time Life Estimation of Capacitors Subjected to Thermal Stress

The use of a built-in test equipment (BITE) that is able to provide a real-time diagnostic of a monitored device allows increasing reliability and decreasing costs. The BITE operation can be based on a suitable life model of the device that must relate the time to failure to the “stress history” of the component. The life model is developed by exploiting the results of a proper measurement campaign. This paper investigates a life model for capacitors subjected to both constant and time-varying temperatures by illustrating the test system and discussing the achieved results.

A test set for LEDs life model estimation

Life models relate the time to failure to the applied stress. They can be derived starting from knowledge of chemical/physical phenomena involved in the ageing process caused by the stress or by means of regressive techniques on data acquired in ALT-based procedure. Anyway, experimental tests are needed. This paper deals with a test system implemented to estimate a life model for LEDs where the forward current is considered as stress.

Modeling of the physiological behavior of human vision system under flicker condition

The impression of visual unsteadiness caused by the fluctuation of the voltage supplying a lamp (flicker) is a power quality phenomena evaluated according to standards endorsed by both the IEC and IEEE. However, it is widely recognized that flicker measurements provide a correct estimation of the relevant human being annoyance only if a certain light source is considered (60 W, 120 V incandescent filament-lamp). In recent years, approaches based on the analysis of the light have been proposed. Nevertheless, all these lack of any kind of robust validation. In this respect, this paper presents the results of a study aimed at investigating on the performance of different methods for correlating the annoyance due to flicker with the behavior of some human physiological aspects.

A self-shielded current transducer for power system application

Current measurement is required to ensure the correct operation of power systems. Conventional current transformers are still widly employed in such networks but their well-known limits make them not suitable for the incoming smart meters. In this paper, a current transducer based on proper measurements of the magnetic field produced by the primary current is proposed. Its main feature is the particular geometry that allows neglecting the effect of external fields without using traditional coil-structure.

Toward a BITE for real time MTTF estimation of capacitors

The use of an equipment able to provide a real time diagnostic of a monitored device (BITE) allows to increase reliability and to decrease costs. BITE operates on the basis of a suitable life model of the considered device that must relate time to failure with past and present stresses. Model development can be carried out by exploiting the results of a proper measurement campaign. In this paper, a study of the life model for capacitor subjected to thermal stress is performed by presenting the test system and discussing the achieved results.

New Basis for the Development of the next-generation Flickermeters

Flicker severity is a parameter defined in the Standard EN 50160 that involves both power quality and physiological features. Due to practical and theoretical reasons, the Flickermeter described by the relevant International Standard may lead to incorrect results when used to correlate voltage variations with annoyance caused by fluctuations of light emitted by other types of lamps different than those based on the incandescent-filament principle. Therefore, its replacement is under consideration by some international organizations given that these last type of lamps will be no more available on the marked starting from the next year. This paper is aiming at providing a contribution to the study of a new theory to be used for the design of the next generation Flickermeter that must account for a wider variety of luminous sources. In particular the research is focused on finding a new method for detecting the human being annoyance in presence of luminous flicker. It is based on the measurement of the pupil diameter under flicker conditions. First preliminary results confirm that this measurement technique can be considered for the above purpose.

Flicker Effect Analysis in Human Subjects: New Noninvasive Method for Next-Generation Flickermeter

Flicker severity is a parameter defined in the Standard EN 50160 that involves both power quality and physiological features. Due to practical and theoretical reasons, the flickermeter described by the relevant International Standard may lead to incorrect results when used to correlate voltage variations with annoyance caused by fluctuations of light emitted by other types of lamps different from those based on the incandescent-filament principle. Therefore, its replacement is under consideration by some international organizations, given that this last type of lamps will no longer be available on the market starting next year. This paper aims at providing a contribution to the study of a new theory to be used for the design of next-generation flickermeters that must account for a wider variety of luminous sources. In particular, the research is focused on finding a new method for detecting human being annoyance in the presence of luminous flicker that is based on the measurement of the pupil diameter under flicker conditions. In this connection, this paper first investigates on the performance of an ad-hoc test system with the main goal to prove and evaluate its accuracy. Then, the results of tests on six volunteers are presented and discussed.

Dynamic stress-strength approach for reliability prediction

The role of reliability prediction during the design stage of a system is worldwide recognized. Simulation tools and proper experimental approaches are usually applied to get reliability properties. In this paper, an experimental method relying on the use the dynamic stress-strength approach is presented and applied on a simple electronic device. The obtained results are presented and discussed.

On the frequency response of semiconductive shields for power systems applications

Semiconductive materials are widely used in power systems components such as cables and connectors. Their role is to shield and control electric fields emitted by primary components thus helping to fulfill, amongst other things, electromagnetic compatibility (EMC) requirements of the kind of the apparatus in which they are used. In this paper the behavior vs. frequency of such semiconductive materials is studied and it will be shown the trend of shielding behavior vs. frequency. In particular at frequencies greater than very few kilohertz, such as those produced by higher harmonics or transient disturbances, such properties strongly decrease.