Techimp Technologies S.r.l.

Techimp Hq S.r.l.

Andrea Cavallini

Gian Carlo Montanari

Gaetano Pasini

Stefano Serra

Fabiano Bettio

Davide Fabiani

Fabio Ciani

GianCarlo Montanari

Francesco Puletti

Dario Andreani

A device () for detecting and processing signals relating to partial electrical discharges in an electrical apparatus () powered by a square-wave () voltage modulated by a modulating wave () in such a way as to form an alternating voltage of predetermined frequency, comprises: a sensor () connectable to the apparatus () for detecting a discharge signal () representing the electrical pulses generated by the partial discharges; a processing unit () connected to the sensor () to receive the discharge signal () and derive the detection instants of each of the pulses detected with respect to a predetermined time reference, a synchronization module () designed to receive an electrical signal () representing the power supply voltage and equipped with a filter () configured for extracting from said power supply signal () a signal () representing the modulating wave (), the processing unit () being configured for associating with the pulses detected the values of a phase parameter (f) representing the phase of the modulating wave () at the pulse detection instants.

Device and method for detecting and processing signals relating to partial electrical discharges

A method for locating partial discharges occurring at a discharge site () in an electric apparatus () with elongate geometry and generating corresponding electric pulses () propagating in opposite directions along the apparatus () from the discharge site () comprises the steps of detecting () the electric pulses () picked up by a first and a second sensor (), operatively connected to the apparatus () and spaced out along it, and generating corresponding electric signals representative of the waveform of the pulses (), selecting () at least one pair of signals, detected in the consecutive sensors (), and representative of a pair of homologous pulses (), relating to the same partial discharge and propagating in opposite directions along the apparatus, deriving, for the signals of the selected pair of homologous pulses (), at least one attenuation parameter, correlated with a quantity that is variable depending on the distance travelled by the pulses (), calculating () the distance between the discharge site () and the sensors, based on processing the values of the attenuation parameter for the signals of the selected pair of homologous pulses ().

Device and method for locating partial discharges

A method for deriving the concentration of a gas dissolved in an electrical insulating oil () comprises the following steps:&#x2014;preparing a membrane () permeable to the gas, interposed between a container () of the oil () and a measuring chamber () that receives a part of the gas through the membrane ();&#x2014;measuring the value of gas concentration in the measuring chamber ();&#x2014;deriving an estimated value of the concentration of the gas in the oil () as a function of the measured value,&#x2014;the measuring step comprising taking at successive measuring instants a plurality of measurements of the values of gas concentration in the measuring chamber ();&#x2014;the deriving step comprising calculating the estimated value of gas concentration in the oil (), at an instant selected from said measuring instants, according to a non-linear function of the values measured at the selected measuring instant and at one or more of the measuring instants preceding the one selected.

Method and device for deriving the concentration of a gas dissolved in an electrical insulation oil

A method for monitoring an activity of partial electrical discharges in an electric apparatus powered with direct voltage comprises the following steps, repeated in succession at predetermined time intervals: measuring (1) analogue electrical signals and generating corresponding digital signals representative of the wave form of partial discharge impulses; deriving (2) for each of said digital signals, at least one shape parameter and at least one amplitude parameter; separating (3) the set of the measured data into homogeneous sub-sets with respect to the shape parameter; correlating (4) the sub-sets of signals having similar values of the shape parameter and measured in successive steps; selecting (5) the correlated sub-sets for which the amplitude parameter has a predetermined profile over time and attributing the signals of said subsets to partial discharge activities. The methods currently in use do not allow to monitor partial discharge activities in an apparatus in DC, because they do not allow to distinguish the signals relating to the partial discharges from those relating to noise or to disturbances.

Method and an apparatus for monitoring an activity of partial electrical discharges in an electrical apparatus powered with direct voltage

A method for locating partial discharges occurring at a discharge site () in an electric apparatus () with elongate geometry and generating corresponding electric pulses () propagating in opposite directions along the apparatus () from the discharge site () comprises the steps: () of detecting the pulses () picked up by a first and a second sensor (), connected to the apparatus () and spaced out along the same; () of deriving shape, phase and amplitude parameters for each of the signals detected; () of separating the sets of signals detected in each sensor into respective subsets which are uniform in terms of pulse waveform; () of identifying the subsets of signals relating to partial discharges and classifying them; () of correlating the subsets relating to different sensors and similarly classified, in order to derive a pair of subsets of signals relating to the same discharge site (); () of selecting, for the pair of correlated subsets, at least one pair of homologous pulses () detected in different sensors in the same time interval; and () of calculating the distance between the discharge site () and the sensors, based on the selected pair of homologous pulses ().

A method for detecting, identifying and locating partial discharges occurring in a discharge site along an electric apparatus comprises the following steps: detecting (1) electrical signals in a detection station; attributing (2) to each detected signal a value of a phase parameter; deriving (3) for each signal at least one shape parameter and one amplitude parameter; separating (4) the set of signals detected into subsets that are homogeneous relative to the shape parameter; identifying (5) sub-sets related to partial discharges and cataloguing them; repeating the above steps in a plurality of detection stations positioned along the apparatus; correlating (7) the sub-sets of signals detected in different detection stations and catalogued similarly; selecting (8) as a function of the amplitude and shape parameters of a sub-set among the correlated ones and locating (9) the partial discharges related to said sub-sets at the detection station of the selected sub-set. Known methods have poor effectiveness and/or reliability, especially for cables whose length exceeds 1-2 km or, alternatively, they require an excessively complex and costly field implementation.

Method for detecting, identifying and locating partial discharges occurring in a discharge site along an electric apparatus

A method for measuring and processing data pertaining to an activity of partial electrical discharges taking place in a three-phase electric machine () powered with square wave voltage, said data comprising a plurality of discharge signals and a plurality of sets of three values (e, e, e) of power supply voltage of the machine measured in concurrence with a corresponding discharge signal, comprises the following steps: &#x2014;transforming each set (e, e, e) of three voltage values measured into a corresponding pair (e, e) of voltage values; &#x2014;deriving a phase angle value from each of said pairs (e, e) of voltage values; &#x2014;attributing to each discharge signal the corresponding phase value, to assess the measured discharge signals as a function of corresponding phase values. Prior art techniques for processing data pertaining to activity of partial electrical discharges taking place in three phase electric machines powered with square wave voltage provide for assessing the measured discharged signals as a time sequence of events, with no possibility to place them effectively in relation to the power supply voltages, this entailing that any subsequent statistical processing of the measured data will have little significance.

Method for processing data pertaining to an activity of partial electrical discharges

An instrument () and a method for measuring pulses of partial electrical discharges in an electrical system comprise data processing means () operatively associated both with an input stage (), able to receive an analogue signal () representing said pulses and to provide a digital representation of the entire wave form of the pulses, to receive said digital representation, extract the value of predetermined parameters relating to the wave form of the pulses and transfer to and output stage () a processed digital signal comprising said values, the processing means () being able to operate substantially in real time, i.e. with no need for a memory for the intermediate storage of the data. Known solutions within the field of the measurement of partial discharge pulses for diagnostic purposes provide for the use of peak detector instruments, which are not able to measure all information useful for a diagnosis of the electrical system, and oscilloscopes interacting with a computer, disadvantageous in terms of costs and of calculation efficiency.

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San Pietro in Casale, Italy

Andrea Cavallini