Partial discharge detection device for an electric machine

Abstract

The present invention relates to a device for detecting partial discharges in an electric machine, comprising an antenna component (3) for receiving and transmitting signals in electromagnetic wave form; and an acquisition component (2) connected to the antenna component (3) for receiving the transmitted signals, the acquisition component (2) comprising a filter capable of filtering the received signals, allowing only partial discharge pulse frequency signals to pass through; a module capable of counting a number of partial discharges in a defined time interval; and a wireless device module; wherein the antenna component (3) is fixed internally to a connection box (4) of the machine.

Description

“PARTIAL DISCHARGE DETECTION DEVICE FOR AN ELECTRICAL MACHINE” FIELD OF INVENTION

[0001] The present invention relates to the monitoring of partial discharges in electrical machines. BACKGROUND OF THE INVENTION

[0002] The phenomenon of partial discharges, which comprise small electrical discharges that can occur within an insulation system, is known in the state of the art.

[0003] Partial discharges are low-energy discharges that, if sustained, prematurely degrade the insulation of electrical machines. Erosion results in a thinning of the insulating material, leading to progressive loss of dielectric properties until the breakdown voltage drops below the peak applied voltage, causing insulation failure.

[0004] In the case of medium-voltage electrical machines, the insulation system is designed to withstand partial discharges for long periods. In the case of low-voltage electrical machines with primarily organic insulation components, the insulation system tends to fail quickly under partial discharges.

[0005] Low-voltage motors driven by variable-frequency drives are particularly vulnerable to partial discharges. This susceptibility arises due to the nature of the voltage pulses generated by inverters, which often have high amplitude and steep rise times (high dV / dt). These rapid voltage changes can induce stress on the motor's insulation system, leading to the formation of partial discharges. Over time, these discharges can degrade the insulation, potentially resulting in reduced motor life, performance problems, or even complete failure.

[0006] Since partial discharges occur before failure, correct monitoring and detection of the occurrence of these discharges can provide sufficient time to carry out maintenance and prevention measures and, thus, increase the useful life of the insulation and, consequently, of the electrical machine. OJECTIVES OF THE INVENTION

[0007] It is one of the objectives of the present invention to provide a partial discharge detection device for an electrical machine and to allow the execution of maintenance and prevention measures.

[0008] It is another objective of the present invention to provide a partial discharge detection device for an electrical machine and to prevent the occurrence of insulation failures in the electrical machine.

[0009] It is yet another object of the present invention to provide a low-cost partial discharge detection device for an electrical machine.

[0010] It is another objective of the present invention to provide a partial discharge detection device for an electrical machine in operation (online), without the need for invasive interventions.

[0011] It is another object of the present invention to provide a partial discharge detection device for an electrical machine capable of counting the number of partial discharges in a defined time interval.

[0012] It is another object of the present invention to provide a partial discharge detection device for an electrical machine capable of wirelessly transmitting the occurrence of partial discharges. SUMMARY OF THE INVENTION

[0013] The present invention relates to a device for detecting partial discharges in an electrical machine. The device comprises an antenna component for capturing signals in the form of electromagnetic waves; and an acquisition component connected to the antenna component for receiving the signals, the acquisition component comprising a filter capable of filtering the received signals, selecting partial discharge pulse frequency signals, a module capable of counting a number of partial discharges in a defined time interval; and a wireless device module; wherein the antenna component is attached internally to a junction box of the machine.

[0014] In embodiments of the invention, the module capable of counting the number of partial discharges has configurable time intervals.

[0015] In one embodiment of the present invention, the antenna component comprises a coaxial cable, wherein a first end of the coaxial cable is configured to connect to the acquisition component and a second end of the coaxial cable is configured to connect to a junction box of the electrical machine.

[0016] In this embodiment, the second end of the coaxial cable can, but is not restricted to, being positioned near a terminal board in the junction box.

[0017] In one embodiment of the invention, the acquisition component filter is a high-pass filter.

[0018] The acquisition component may be housed in an enclosure and may, but is not restricted to, be battery powered, being a self-contained component that may be attached to the electrical machine or other support or device. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be described below in more detail, with reference to the attached drawings, in which:

[0020] Figure 1 - is a schematic illustration of the phenomenon of partial discharges;

[0021] Figure 2 is an illustration of a partial discharge detection device for an electrical machine according to an embodiment of the present invention;

[0022] Figure 3 is an illustration of the end of an antenna component of the partial discharge detection device according to an embodiment of the present invention;

[0023] Figure 4 is a schematic illustration of the connection between the antenna component of the partial discharge detection device according to an embodiment of the present invention and a connection box of an electrical machine;

[0024] Figure 5 is a schematic illustration of testing of the partial discharge detection device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] Figure 1 shows a schematic illustration of the phenomenon of partial discharges and its impact on the service life of the electrical machine.

[0026] Thus, the figure shows the occurrence of partial discharges (number of pulses) over time and the moment at which insulation failure occurs. of the stator, when there is an increase in voltage to a level above the breakdown voltage.

[0027] The present invention relates to a device for detecting partial discharges in electrical machines, preferably low voltage electrical machines 1, which, in the illustrated embodiment, comprises an acquisition component 2 and an antenna component 3 for capturing electromagnetic waves.

[0028] As best illustrated in Figure 3, in the illustrated embodiment, the antenna component 3 comprises a coaxial cable comprising a central conductor covered by an insulator, an outer conductor with apertures and a jacket.

[0029] In one embodiment of the invention, the antenna component 3 of the device of the present invention can advantageously be arranged in the junction box 4 of an electric motor (see exemplary illustration in Figure 4), eliminating the need to open the machine to make the connection or the need for any adaptation to the machine housing or even decoupling of the load. In this way, the machine can be fully operational when the antenna component 3 can be mounted and dismounted from the machine.

[0030] Thus, a first end of the coaxial cable may be configured to connect to the acquisition component 2 and a second end of the coaxial cable may be stripped to form the antenna.

[0031] In one embodiment of the invention, the second end of the coaxial cable is configured to be positioned within the junction box 4 of the electrical machine, as close as possible to the opening of the stator housing of the machine.

[0032] As illustrated in figure 4, in the illustrated embodiment, the connection to the connection box 4 can be made by positioning the conductor of the antenna component 3 inside the connection box 4, close to the terminal board 5 of the connection box 4, and, more specifically, in a region closer to the opening that gives access to the internal volume of the machine.

[0033] In the embodiment illustrated in the figures, the acquisition component 2 comprises a filter, such as a high-pass filter, capable of letting pass the frequency signals of the partial discharge pulses, a module capable of count the number of partial discharges in a time interval and a wireless communication module.

[0034] In one embodiment of the invention, the module capable of counting the number of partial discharges in a defined time interval comprises a series of latch comparators for driving the signal to a microcontroller.

[0035] In this sense, it should be emphasized that partial discharge pulses present particularities that can differentiate them from other signals, and the technician in the subject is generally aware of the characteristic frequency spectrum of partial discharges of the equipment being analyzed.

[0036] It should also be noted that a module capable of counting the number of partial discharges in a time interval can reduce the amount of data to be transmitted wirelessly.

[0037] The module capable of counting the number of partial discharges can also be configured to count the number of discharges at different time intervals.

[0038] In the illustrated embodiment of the present invention, the acquisition component 2 may be housed in a housing configured to be attached to the electrical machine, preferably external to the junction box 4, or to another base or support. The acquisition component 2 may, but is not limited to, be powered by batteries, making it portable and independent. Partial discharges may be detected while the machine is operating.

[0039] Figure 5 illustrates the detection of partial discharges in motors with inverters with different voltage variation characteristics at the time of switching, showing the detected partial discharges in the lower graphs and the lateral comparative graph showing the operating time until the occurrence of failures.

[0040] Having described examples of embodiments of the present invention, it should be understood that the scope of the present invention encompasses other possible variations of the described inventive concept, being limited solely by the content of the claims alone, including possible equivalents.

Claims

CLAIMS 1. Device for detecting partial discharges in an electrical machine, characterized by the fact that it comprises: an antenna component (3) for capturing and transmitting signals in the form of an electromagnetic wave; and an acquisition component (2), connected to the antenna component (3) for receiving the transmitted signals, the acquisition component (2) comprising a filter capable of filtering the received signals, allowing only partial discharge pulse frequency signals to pass, a module capable of counting a number of partial discharges in a defined time interval; and a wireless communication module; in which the antenna component (3) is fixed internally to a junction box (4) of the machine.

2. Device according to claim 1, characterized in that the antenna component (3) comprises a coaxial cable, wherein a first end of the coaxial cable is configured to connect to the acquisition component (2) and a second end of the coaxial cable is configured to connect to the junction box (4) of the electrical machine.

3. Device according to claim 2, characterized in that the second end of the coaxial cable is positioned close to a terminal board (5) of the junction box.

4. Device according to claim 1, characterized in that the module capable of counting the number of partial discharges has configurable time intervals.

5. Device according to any one of claims 1 to 4, characterized in that the filter of the acquisition component (2) is a high-pass filter.

6. Device according to any one of claims 1 to 5, characterized in that the acquisition component (2) is housed in a housing.

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