METHOD FOR PROCESSING DATA PERTAINING TO AN ACTIVITY OF PARTIAL ELECTRICAL DISCHARGES

• US 20100114509A1
• Filed: 01/25/2008
• Published: 05/06/2010
• Est. Priority Date: 02/08/2007
• Status: Active Grant

• Current Assignee: I.S.A. - Altanova Group Srl (ESCO Technologies, Inc.)
• Original Assignee: Techimp Technologies S.r.l.
• Inventors: Montanari, Gian Carlo, Pasini, Gaetano, Cavallini, Andrea
• Granted Patent: US 8,234,085 B2
• Time in Patent Office: Days
• US Class Current: 702/58
• CPC Class Codes: G01R 31/1272 of cable, line or wire insulation, e.g. using partial discharge measurements locating faults in cables G01R31/083
• CPC Class Codes: G01R 31/343 in operation
• CPC Class Codes: G01R 31/346 Testing of armature or field windings
• CPC Class Codes: H02K 11/35 Devices for recording or transmitting machine parameters, e.g. memory chips or radio transmitters for diagnosis

Abstract

A method for measuring and processing data pertaining to an activity of partial electrical discharges taking place in a three-phase electric machine (1) powered with square wave voltage, said data comprising a plurality of discharge signals and a plurality of sets of three values (e_u, e_v, e_w) of power supply voltage of the machine measured in concurrence with a corresponding discharge signal, comprises the following steps: -transforming each set (e_u, e_v, e_w) of three voltage values measured into a corresponding pair (e_d, e_q) of voltage values; -deriving a phase angle value from each of said pairs (e_d, e_q) of voltage values; -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.

Claims

1. A method for processing data pertaining to an activity of partial electrical discharges taking place in a three-phase electric machine (1) powered with square wave voltage, said data comprising a plurality of discharge signals associated with said partial electrical discharges and a plurality of sets of three values (e_U, e_V, e_W) of power supply voltage of the machine (1), each set measured in concurrence with a corresponding discharge signal,

characterised in that it comprises the following steps:

transforming each set (e_U, e_V, e_W) of three voltage values measured into a corresponding pair (e_d, e_q) of voltage values;

deriving a phase value from each of said pairs (e_d, e_q) of voltage values;

attributing to each discharge signal associated with a corresponding partial electrical discharge the corresponding phase value, to assess the measured discharge signals as a function of corresponding phase values.

2. Method as claimed in claim 1, wherein said three phase electric machine (1) is powered by a converter (2) operating in PWM logic.

3. Method as claimed in claim 1, wherein said transformation step comprises multiplying each measured set of three voltages (e_U, e_V, e_W) times a predetermined matrix, able to remove from said set of three voltages the zero sequence component.

4. Method as claimed in claim 3, wherein said predetermined matrix is a matrix obtainable multiplying a Park matrix times any 2×

2 matrix of maximum rank.

5. Method as claimed in claim 1, comprising a step of separating the discharge signals into classes on the basis of the respective attributed phase values.

6. Method as claimed in claim 5, wherein said classes are three and correspond to predetermined phase intervals.

7. Method as claimed in claim 6, wherein said phase intervals are substantially the following:

[85, 95] and [215, 325] for the first class;

[205, 215] and [335, 85] for the second class;

[325, 335] and [95, 205] for the third class.

8. Method as claimed in claim 1, comprising a step of statistically processing the values of amplitude of the discharge signals as a function of the phase values attributed.

9. Method as claimed in claim 5, comprising a step of statistically processing the values of amplitude of the discharge signals of a predetermined class, as a function of the phase values attributed.

10. Method as claimed in claim 1, comprising a step of rejecting noise, on the basis of said phase values attributed to the discharge signals.

11. Method as claimed in claim 1, wherein said plurality of discharge signals is measured through a sensor (3) common to all three phases.

12. Method for assessing for diagnostic purposes an activity of partial electrical discharges taking place in a machine (1) powered with square wave voltage, comprising, for the measurement of the data to be processed, the following steps:

measurement of a plurality of discharge signals, associated with said partial electrical discharges;

measuring a set of three values of voltage (e_U, e_V, e_W) powering the machine, in concurrence with each measured discharge signal,

And comprising, with regard to the processing of said data, the following steps;

transforming each set of three voltage values measured into a corresponding pair of voltage values (e_d, e_q);

deriving a phase value from each of said pairs of voltage values;

attributing to each discharge signal the corresponding phase value, to assess the measured discharge signals as a function of corresponding phase values.