System and method for monitoring insulation state of extra-high voltage direct current bushing

Abstract

The invention discloses an extra-high voltage DC bushing insulation state monitoring system and method, and belongs to the technical field of bushing monitoring, and the system comprises a monitoring platform, a bushing partial discharge monitoring device, and a bushing dielectric loss, capacitance and leakage current monitoring device. The bushing partial discharge monitoring device comprises a high-frequency partial discharge acquisition module and a high-frequency pulse current sensor, and the high-frequency pulse current sensor, the high-frequency partial discharge acquisition module and the monitoring platform are in signal connection in sequence; the bushing dielectric loss, capacitance and leakage current monitoring device comprises a dielectric loss acquisition module, a leakage current sensor and a signal sampling unit, the leakage current sensor and the signal sampling unit are both in signal connection with the dielectric loss acquisition module, and the dielectric loss acquisition module is in signal connection with the monitoring platform. According to the invention, through integration of the monitoring platform and the monitoring equipment, comprehensive real-time monitoring of the running state of the sleeve is realized.

Description

Technical Field

[0001] The invention relates to the technical field of bushing monitoring, and in particular to a system and method for monitoring the insulation state of an ultra-high voltage direct current bushing. Background Art

[0002] As an important insulating element, the bushing in the UHV DC transmission system is a key high-voltage electrical component that plays the role of insulation support and electrical connection in the UHV transmission system. When the bushing is exposed to a complex high-voltage environment for a long time, it is easily affected by various factors, among which moisture has the most significant impact on its working stability.

[0003] Since transformer bushings usually use oil-paper insulation structure, once there is a problem with the sealing, moisture will penetrate into the insulation material, resulting in insulation aging, increased dielectric loss, partial discharge, and increased leakage current, which will further reduce the safety and reliability of the transformer bushing and generate leakage current. Once the internal insulation device passes the current, the insulation performance will be further reduced, which may cause partial discharge failure. Partial discharge will not only cause the deterioration and damage of the bushing insulation material, but also accelerate the overall loss of the transformer bushing.

[0004] At present, the operating status of the bushing is judged by regular inspection and power outage maintenance test, which consumes a lot of manpower and material resources and is difficult to find hidden dangers in time. The existing bushing operating status monitoring and fault warning technology has problems such as large measurement error and poor operating reliability.

[0005] In addition, existing bushing operation status monitoring devices often have problems such as poor grounding of the end screen, moisture on the main body, and system false alarms and missed alarms, which cannot meet the actual operation requirements. This has caused users to have concerns about the application of the equipment, and many online monitoring devices that have been put into operation have been deactivated or dismantled due to insufficient reliability. In addition, the monitoring technology of low-voltage bushings still faces many challenges, while the status monitoring technology of UHV DC bushings is almost in a blank stage. At present, the research on the evaluation and early warning of the insulation status of high-voltage bushings mainly stays at the discussion of theoretical methods, and has not yet formed a systematic engineering application plan. Summary of the invention

[0006] In view of this, the present invention aims at the deficiencies in the prior art and provides a system and method for monitoring the insulation status of an ultra-high voltage DC bushing.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a UHV DC bushing insulation status monitoring system, including a monitoring platform, a bushing partial discharge monitoring device, and a bushing dielectric loss, capacitance and leakage current monitoring device; the bushing partial discharge monitoring device includes a high-frequency partial discharge acquisition module and a high-frequency pulse current sensor, and the high-frequency pulse current sensor and the high-frequency partial discharge acquisition module are connected to the monitoring platform in sequence by signal; the bushing dielectric loss, capacitance and leakage current monitoring device includes a dielectric loss acquisition module, a leakage current sensor and a signal sampling unit, the leakage current sensor and the signal sampling unit are both connected to the dielectric loss acquisition module by signal, and the dielectric loss acquisition module is connected to the monitoring platform by signal.

[0008] Furthermore, the monitoring platform is developed based on a B / S architecture, has an independent database for storing and analyzing measurement data and abnormal records, and supports multi-directional display and flexible configuration of alarm thresholds.

[0009] Furthermore, the high-frequency pulse current sensor transmits the high-frequency pulse signal to the high-frequency partial discharge acquisition module through a shielded cable, and the high-frequency partial discharge acquisition module digitally processes the signal, extracts partial discharge characteristics and uploads them to the monitoring platform.

[0010] Furthermore, the leakage current sensor is a zero-flux current sensor, which is installed at the grounding wire of the end screen of the bushing by means of a through-hole buckle, and is used to collect the grounding current signal of the end screen of the bushing.

[0011] Furthermore, the signal sampling unit is installed on the bus PT / CVT secondary terminal and is used to collect the PT / CVT secondary voltage signal.

[0012] Furthermore, the dielectric loss acquisition module obtains the grounding current signal of the casing end screen and the PT / CVT secondary voltage signal, and uses the front circuit to convert the voltage and current signals into discrete digital quantities and then send them to the control chip. The two signals are filtered, amplified, and sampled for digital processing. The signals are calculated and processed in the time domain or frequency domain through Fourier transform to obtain the dielectric loss factor and capacitance value, which are then uploaded to the monitoring platform for analysis, display and storage.

[0013] Furthermore, the monitoring platform is connected to the bushing partial discharge monitoring device, and the bushing dielectric loss, capacitance and leakage current monitoring device in a wireless or wired manner.

[0014] A method for monitoring the insulation status of a UHV DC bushing comprises the following steps:

[0015] S1. Install a high-frequency pulse current sensor at the end screen of the transformer bushing. The high-frequency pulse current signal measured by the high-frequency pulse current sensor is transmitted to the high-frequency partial discharge acquisition module through a shielded cable. The high-frequency pulse current signal is subjected to hardware filtering, conditioning and amplification, and high-speed digital acquisition. The digital high-frequency pulse current signal is processed, calculated and analyzed through the intelligent algorithm embedded in the hardware to obtain partial discharge characteristics such as pulse time domain waveform, partial discharge amount, PRPD / PRPS spectrum, etc.; finally, the partial discharge characteristic results are transmitted to the monitoring platform in a wireless / wired manner to display the bushing partial discharge characteristics in all directions, and the partial discharge characteristics are further analyzed and identified;

[0016] S2. A zero flux current sensor is installed through the transformer bushing end screen grounding wire. The zero flux current sensor collects the bushing end screen grounding current signal and transmits it to the dielectric loss collection module.

[0017] S3. A signal sampling unit is installed on the busbar PT / CVT secondary terminal. The signal sampling unit collects the PT / CVT secondary voltage signal and transmits it to the dielectric loss collection module;

[0018] S4, the dielectric loss acquisition module uses the front circuit to convert the voltage and current signals into discrete digital quantities and then sends them to the control chip. The two signals are filtered, amplified, sampled and digitally processed, and the signals are operated and processed in the time domain or frequency domain through Fourier transform to obtain the dielectric loss factor and capacitance value, which are then uploaded to the monitoring platform for analysis, display and storage;

[0019] S5. The monitoring platform monitors the casing operation status in real time and automatically alarms for abnormal data.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The ultra-high voltage DC bushing insulation state monitoring system of the present invention obtains the high-frequency pulse current signal of the bushing end screen through the bushing partial discharge monitoring device, processes, calculates and analyzes it, obtains the pulse time domain waveform, partial discharge amount, PRPD / PRPS spectrum and other partial discharge characteristics, transmits them to the monitoring platform, displays the bushing partial discharge characteristics in all directions, and further analyzes and identifies the partial discharge characteristics; obtains the bushing end screen grounding current signal and PT / CVT secondary voltage signal through the bushing dielectric loss, capacitance and leakage current monitoring device, the two signals are filtered, amplified, sampled and digitally processed, the signals are calculated and processed in the time domain or frequency domain through Fourier transform, the dielectric loss factor and capacitance value are obtained, and then uploaded to the monitoring platform for analysis, display and storage; thereby, comprehensive and reliable monitoring of the transformer bushing insulation state is achieved.

[0022] The present invention uses a zero flux mutual inductor to monitor the leakage current. The zero flux mutual inductor uses external compensation technology to make the excitation current approach zero, thereby effectively resisting the interference of the excitation current, greatly improving the acquisition accuracy of small current signals, and significantly improving the accuracy of leakage current monitoring, meeting the monitoring needs of higher precision. The mutual inductor is installed on the grounding wire of the bushing by means of a through-hole clip, keeping the original grounding structure unchanged. Compared with the traditional grounding scheme in which the end screen lead extension rod is connected in series with the grounding wire, this installation method greatly reduces the safety risk and improves the safety and reliability of the system.

[0023] The present invention realizes comprehensive real-time monitoring of the casing operation status through the integration of the monitoring platform and the monitoring equipment. It has a flexible status early warning function, can automatically alarm for abnormal data, and supports the configuration of alarm thresholds according to different working conditions, further improving the flexibility and practicability of monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic diagram of the structural connection of Embodiment 1 of the present invention;

[0025] Figure 2 This is the organizational structure diagram of Example 1 of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0027] Example 1

[0028] like Figures 1-2 As shown, an embodiment of the present invention provides an ultra-high voltage DC bushing insulation status monitoring system, which mainly includes three parts: a monitoring platform, a bushing partial discharge monitoring device, and a bushing dielectric loss, capacitance and leakage current monitoring device. The high-frequency partial discharge monitoring device and the bushing dielectric loss, capacitance and leakage current monitoring device are connected to a router through an RJ45 cable and an interface, and then transmitted to the monitoring platform through the router through a 4 / 5G signal.

[0029] The casing partial discharge monitoring device includes a high-frequency partial discharge acquisition module and a high-frequency pulse current sensor, and the high-frequency pulse current sensor, the high-frequency partial discharge acquisition module and the monitoring platform are connected in sequence by signal; the high-frequency partial discharge acquisition module is connected to the DC12V power supply through a power cord, and the high-frequency pulse current signal obtained by the high-frequency pulse current sensor is transmitted to the high-frequency partial discharge acquisition module through a shielded cable for data processing and analysis; the high-frequency partial discharge acquisition module performs hardware filtering, conditioning and amplification, and high-speed digital acquisition on the high-frequency pulse current signal, and processes, calculates and analyzes the digital high-frequency pulse current signal through the hardware embedded intelligent algorithm to obtain the pulse time domain waveform, partial discharge amount, PRPD / PRPS spectrum and other partial discharge characteristics. Finally, the partial discharge characteristic results are transmitted to the monitoring platform in a wireless / wired manner to display the casing partial discharge characteristics in all directions, and further analyze and identify the partial discharge characteristics.

[0030] The bushing dielectric loss, capacitance and leakage current monitoring device comprises a dielectric loss acquisition module, a leakage current sensor and a signal sampling unit, wherein the leakage current sensor and the signal sampling unit are both connected to the dielectric loss acquisition module by signal, and the dielectric loss acquisition module is connected to the monitoring platform by signal; the leakage current sensor is a zero flux current sensor, which can monitor tiny leakage current with high precision and avoid electromagnetic noise interference, and is installed at the grounding wire of the bushing end screen by a through-hole buckle, and is used to collect the grounding current signal of the bushing end screen; the signal sampling unit is installed on the busbar PT / CVT secondary terminal, and is used to collect the PT / CVT secondary voltage signal; the dielectric loss acquisition module obtains the bushing end screen grounding current signal and the PT / CVT secondary voltage signal, and uses the front circuit to convert the voltage and current signals into discrete digital quantities and then send them to the control chip, the two signals are filtered, amplified, sampled and digitally processed, and the signals are operated and processed in the time domain or frequency domain by Fourier transform to obtain the dielectric loss factor and capacitance value, and then uploaded to the monitoring platform for analysis, display and storage.

[0031] This system is based on the principle of bushing dielectric loss, and proposes a technical solution for applying the absolute dielectric loss measurement method to transformer bushing side dielectric loss monitoring. This method obtains the bushing end screen grounding current signal through the leakage current sensor, obtains the bushing end screen voltage signal through the converter transformer valve side bushing end screen voltage detector, uses the waveform acquisition device to synchronously convert the time domain waveform into a digital discrete signal, and calculates the fundamental phase difference of the two signals through Fourier transform (FFT) to obtain the bushing dielectric loss angle, thereby judging the change of the bushing insulation state. The key to using the absolute dielectric loss measurement method is to effectively obtain the voltage and current fundamental wave signals, and then perform Fourier transform to transform the signal from time domain to frequency domain.

[0032] The following is a detailed introduction to the dielectric loss measurement method:

[0033] First, assume that the signal sequence is collected continuously for 1s.

[0034]

[0035] Transforming the sequence yields:

[0036]

[0037] Where N is the number of sampling points, because the voltage and current sequences in the system are real sequences, so:

[0038]

[0039] And in the formula:

[0040]

[0041] At this time, the amplitude and phase of the signal can be expressed as:

[0042]

[0043] After processing the total current I, the fundamental amplitude and initial phase angle can be obtained. By processing the voltage signal U, the fundamental initial phase angle can be obtained The phase angle difference can be obtained Based on the dielectric loss vector diagram, the dielectric loss angle can be obtained as The dielectric loss tanδ is calculated and the insulation loss is judged by the size of tanδ.

[0044] The monitoring platform is developed based on B / S architecture and has an independent database. It can automatically save measurement data, analysis results, abnormal operation records and other information, realize historical data query and analysis, and facilitate comprehensive understanding of the operating status of the monitored bushing. The monitoring platform 1 undertakes the core functions of system control management and information interaction, and is responsible for storing, displaying and comparing and analyzing the bushing insulation status data monitored from the high-frequency partial discharge monitoring device 3, bushing dielectric loss, capacitance and leakage current monitoring device 4, and comprehensively manages the online monitoring terminal.

[0045] When the monitoring results show that the bushing has insulation abnormalities such as partial discharge or leakage current, maintenance measures should be taken immediately, such as replacing damaged parts or repairing them.

[0046] If the monitoring results indicate that the casing is in good condition, routine maintenance and inspections can be performed as planned.

[0047] Example 2

[0048] An embodiment of the present invention provides a method for monitoring the insulation status of a UHV DC bushing, comprising the following steps:

[0049] S1. Install a high-frequency pulse current sensor at the end screen of the transformer bushing. The high-frequency pulse current signal measured by the high-frequency pulse current sensor is transmitted to the high-frequency partial discharge acquisition module through a shielded cable. The high-frequency pulse current signal is subjected to hardware filtering, conditioning and amplification, and high-speed digital acquisition. The digital high-frequency pulse current signal is processed, calculated and analyzed through the intelligent algorithm embedded in the hardware to obtain partial discharge characteristics such as pulse time domain waveform, partial discharge amount, PRPD / PRPS spectrum, etc.; finally, the partial discharge characteristic results are transmitted to the monitoring platform in a wireless / wired manner to display the bushing partial discharge characteristics in all directions, and the partial discharge characteristics are further analyzed and identified;

[0050] S2. A zero flux current sensor is installed through the transformer bushing end screen grounding wire. The zero flux current sensor collects the bushing end screen grounding current signal and transmits it to the dielectric loss collection module.

[0051] S3. A signal sampling unit is installed on the busbar PT / CVT secondary terminal. The signal sampling unit collects the PT / CVT secondary voltage signal and transmits it to the dielectric loss collection module;

[0052] S4, the dielectric loss acquisition module uses the front circuit to convert the voltage and current signals into discrete digital quantities and then sends them to the control chip. The two signals are filtered, amplified, sampled and digitally processed, and the signals are operated and processed in the time domain or frequency domain through Fourier transform to obtain the dielectric loss factor and capacitance value, which are then uploaded to the monitoring platform for analysis, display and storage;

[0053] S5. The monitoring platform monitors the casing operation status in real time and automatically alarms for abnormal data.

[0054] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art can still modify or make equivalent substitutions to the specific implementations of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims of the present invention to be approved.

Claims

1. A UHV DC bushing insulation status monitoring system, characterized by: It includes a monitoring platform, a casing partial discharge monitoring device, and a casing dielectric loss, capacitance and leakage current monitoring device; the casing partial discharge monitoring device includes a high-frequency partial discharge acquisition module and a high-frequency pulse current sensor, and the high-frequency pulse current sensor and the high-frequency partial discharge acquisition module are sequentially connected to the monitoring platform by signal; the casing dielectric loss, capacitance and leakage current monitoring device includes a dielectric loss acquisition module, a leakage current sensor and a signal sampling unit, and the leakage current sensor and the signal sampling unit are both connected to the dielectric loss acquisition module by signal, and the dielectric loss acquisition module is connected to the monitoring platform by signal.

2. The UHV DC bushing insulation status monitoring system according to claim 1, characterized in that: The monitoring platform is developed based on the B / S architecture and has an independent database for storing and analyzing measurement data and abnormal records, and supports multi-directional display and flexible configuration of alarm thresholds.

3. The UHV DC bushing insulation status monitoring system according to claim 1, characterized in that: The high-frequency pulse current sensor transmits the high-frequency pulse signal to the high-frequency partial discharge acquisition module through a shielded cable. The high-frequency partial discharge acquisition module digitally processes the signal, extracts partial discharge characteristics and uploads them to the monitoring platform.

4. The UHV DC bushing insulation status monitoring system according to claim 1, characterized in that: The leakage current sensor is a zero-flux current sensor, which is installed at the grounding wire of the end screen of the bushing by means of a through-hole buckle, and is used to collect the grounding current signal of the end screen of the bushing.

5. The UHV DC bushing insulation status monitoring system according to claim 4, characterized in that: The signal sampling unit is installed on the bus PT / CVT secondary terminal and is used to collect the PT / CVT secondary voltage signal.

6. The UHV DC bushing insulation status monitoring system according to claim 5, characterized in that: The dielectric loss acquisition module obtains the grounding current signal of the end screen of the bushing and the secondary voltage signal of the PT / CVT, and uses the front circuit to convert the voltage and current signals into discrete digital quantities and send them to the control chip. The two signals are filtered, amplified, and sampled for digital processing. The signals are calculated and processed in the time domain or frequency domain through Fourier transform to obtain the dielectric loss factor and capacitance value, which are then uploaded to the monitoring platform for analysis, display and storage.

7. The UHV DC bushing insulation status monitoring system according to claim 1, characterized in that: The monitoring platform is connected to the bushing partial discharge monitoring device and the bushing dielectric loss, capacitance and leakage current monitoring device in a wireless or wired manner.

8. A method for monitoring the insulation status of a UHV DC bushing, characterized in that: The following steps are involved: S1. Install a high-frequency pulse current sensor at the end screen of the transformer bushing. The high-frequency pulse current signal measured by the high-frequency pulse current sensor is transmitted to the high-frequency partial discharge acquisition module through a shielded cable. The high-frequency pulse current signal is subjected to hardware filtering, conditioning and amplification, and high-speed digital acquisition. The digital high-frequency pulse current signal is processed, calculated and analyzed through the intelligent algorithm embedded in the hardware to obtain partial discharge characteristics such as pulse time domain waveform, partial discharge amount, PRPD / PRPS spectrum, etc.; finally, the partial discharge characteristic results are transmitted to the monitoring platform in a wireless / wired manner to display the bushing partial discharge characteristics in all directions, and the partial discharge characteristics are further analyzed and identified; S2. A zero flux current sensor is installed through the transformer bushing end screen grounding wire. The zero flux current sensor collects the bushing end screen grounding current signal and transmits it to the dielectric loss collection module. S3. A signal sampling unit is installed on the busbar PT / CVT secondary terminal. The signal sampling unit collects the PT / CVT secondary voltage signal and transmits it to the dielectric loss collection module; S4, the dielectric loss acquisition module uses the front circuit to convert the voltage and current signals into discrete digital quantities and then sends them to the control chip. The two signals are filtered, amplified, sampled and digitally processed, and the signals are operated and processed in the time domain or frequency domain through Fourier transform to obtain the dielectric loss factor and capacitance value, which are then uploaded to the monitoring platform for analysis, display and storage; S5. The monitoring platform monitors the casing operation status in real time and automatically alarms for abnormal data.

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