阅读说明：本技术 一种变压器套管介损检测装置校正系统以及方法 (Transformer bushing dielectric loss detection device correction system and method ) 是由 周丹 马志钦 杨贤 饶章权 林春耀 欧阳旭东 于 2020-05-08 设计创作，主要内容包括：本发明公开了一种变压器套管介损检测装置校正系统以及方法,本发明包括：标准校正源、电流传感器、信号调理电路以及介损同步采集卡；电流传感器与信号调理电路相连接,信号调理电路与介损同步采集卡相连接；标准校正源包括电压校正模式和电流校正模式；标准校正源包括有第一输出端和第二输出端；本发明利用外加的标准校正源,通过调整标准校正源的输出模式从而计算电流二次测量回路、电压测量二次回路的固定相差,从而对变压器套管介损检测装置进行相位校核,在检测到相位出现偏差时,对偏差进行消除,避免由于设备自身参量变化及老化等因素导致测量结果可信度低的技术问题,有效提高监测数据的准确度。(The invention discloses a system and a method for correcting a transformer bushing dielectric loss detection device, wherein the system comprises the following steps: the device comprises a standard correction source, a current sensor, a signal conditioning circuit and a dielectric loss synchronous acquisition card; the current sensor is connected with the signal conditioning circuit, and the signal conditioning circuit is connected with the dielectric loss synchronous acquisition card; the standard correction source comprises a voltage correction mode and a current correction mode; the standard correction source comprises a first output end and a second output end; the invention utilizes an additional standard correction source, calculates the fixed phase difference of the current secondary measurement loop and the voltage secondary measurement loop by adjusting the output mode of the standard correction source, thereby carrying out phase check on the transformer bushing dielectric loss detection device, eliminating the deviation when detecting the deviation of the phase, avoiding the technical problem of low reliability of the measurement result caused by the parameters of the device, such as change and aging, and the like, and effectively improving the accuracy of the monitoring data.)

1. A transformer bushing dielectric loss detection device correction system is characterized by comprising a standard correction source, a current sensor, a signal conditioning circuit and a dielectric loss synchronous acquisition card; the current sensor is connected with the signal conditioning circuit, and the signal conditioning circuit is connected with the dielectric loss synchronous acquisition card; the standard correction source comprises a voltage correction mode and a current correction mode, and comprises a first output end and a second output end; when the standard correction source is in a current correction mode, the first output end is connected with the current sensor, and the second output end is connected with the dielectric loss synchronous acquisition card; when the standard correcting source is in a voltage correcting mode, the first output end is connected with the signal conditioning circuit, and the second output end is connected with the dielectric loss synchronous acquisition card.

2. The system of claim 1, wherein the current sensor is connected to the signal conditioning circuit via a signal transmission cable; when the standard correction source is in a voltage correction mode, the first output end is connected with the signal conditioning circuit through a signal transmission cable.

3. The system of claim 1, wherein the conditioning circuit comprises an amplifying circuit and a filtering circuit, and an output of the amplifying circuit is connected to an input of the filtering circuit.

4. The system of claim 1, wherein when the calibration source is in a current calibration mode, the first output terminal outputs a current signal to the current sensor, and the second output terminal outputs a voltage signal to the synchronous loss detection card;

when the standard correcting source is in a voltage correcting mode, the first output end outputs a voltage signal to the conditioning circuit, and the second output end outputs the voltage signal to the dielectric loss synchronous acquisition card;

the current sensor is used for collecting a current signal output by the standard correction source and transmitting the current signal to the signal conditioning circuit;

the signal conditioning circuit is used for amplifying and shaping the received voltage signal or current signal and transmitting the amplified and shaped voltage signal or current signal to the dielectric loss synchronous acquisition card;

the dielectric loss synchronous acquisition card is used for calculating the fixed phase difference of the transformer bushing dielectric loss detection device according to the received current signal and voltage signal.

5. The system according to claim 4, wherein the dielectric loss synchronous acquisition card is configured to calculate the fixed phase difference of the transformer bushing dielectric loss detection device by using a harmonic analysis method.

6. A method for correcting a transformer bushing dielectric loss detection device, the method being based on any one of the claims 1 to 5, the method comprising the following steps:

setting a standard correction source as a current correction mode, setting the output of the standard correction source, and starting the standard correction source to output a voltage signal and a current signal with the same phase;

the current sensor collects a current signal output by a first output end of the standard correcting source and transmits the current signal to the conditioning circuit, and the conditioning circuit amplifies and shapes the current signal and transmits the current signal to the dielectric loss synchronous acquisition card; a second output end of the standard correction source outputs a voltage signal to the dielectric loss synchronous acquisition card;

calculating to obtain the phase deviation of the current secondary measurement loop according to the received voltage signal and current signal by the dielectric loss synchronous acquisition card;

setting the standard correction source into a voltage correction mode, setting the output of the standard correction source, and starting the standard correction source to output voltage signals with the same phase;

the first output end of the standard correcting source outputs a voltage signal to the conditioning circuit, the conditioning circuit amplifies and shapes the voltage signal and then transmits the voltage signal to the dielectric loss synchronous acquisition card, and the second output end of the standard correcting source outputs the voltage signal to the dielectric loss synchronous acquisition card;

calculating by a dielectric loss synchronous acquisition card according to the received voltage signal to obtain the phase deviation of the voltage secondary measurement loop;

and calculating the fixed phase difference of the transformer bushing dielectric loss detection device according to the phase deviation of the current secondary measurement loop and the phase deviation of the voltage secondary measurement loop, and performing software correction on the transformer bushing dielectric loss detection device according to the fixed phase difference.

7. The method for correcting the transformer bushing dielectric loss detection device according to claim 6, wherein the specific process of calculating the fixed phase difference of the transformer bushing dielectric loss detection device comprises the following steps:

and subtracting the phase deviation of the current secondary measurement loop from the phase deviation of the voltage secondary measurement loop to obtain the fixed phase difference of the transformer bushing dielectric loss detection device.

8. The method as claimed in claim 6, wherein when the standard calibration source is in the current calibration mode, the frequency and amplitude of the voltage signal output from the second output terminal and the current signal output from the first output terminal of the standard calibration source are set, and when the standard calibration source is in the voltage calibration mode, the frequency and amplitude of the voltage signal output from the first output terminal and the voltage signal output from the second output terminal of the voltage standard calibration source are set.

9. The method according to claim 8, wherein before calculating the phase deviation of the secondary current measurement loop according to the received voltage signal and current signal, the synchronous loss acquisition card further comprises:

the dielectric loss synchronous acquisition card performs analog-to-digital conversion and storage on the received voltage signal and current signal;

before the dielectric loss synchronous acquisition card calculates the phase deviation of the secondary voltage measurement loop according to the received voltage signal, the method further comprises the following steps:

the dielectric loss synchronous acquisition card performs analog-to-digital conversion and storage on the received voltage signals.

10. The method as claimed in claim 9, wherein when the calibration source is in a voltage calibration mode, the voltage output from the first output terminal and the voltage output from the second output terminal have different magnitudes.

Technical Field

The invention relates to the technical field of transformer bushing dielectric loss detection devices, in particular to a system and a method for correcting a transformer bushing dielectric loss detection device.

Background

The transformer bushing is an important supporting and insulating device of the transformer, and the insulating condition of the bushing is related to the safe and stable operation of the whole transformer, so that the insulation state monitoring of the bushing is particularly important in the current engineering application and subject research. The on-line monitoring of the bushing mainly measures a dielectric loss tangent tan which is used as a characteristic quantity for reflecting the size of the dielectric loss of the insulation, only depends on the dielectric property of the insulation material and is independent of the size and the like of a medium, and the dielectric loss tangent tan is very sensitive to finding insulation integrity defects and is not sensitive to local defects. In the online measurement of the dielectric loss of the sleeve, the bus voltage measured by PT or CVT is usually selected as a phase reference, a current sensor (synchronous acquisition) measures the current of a grounding wire at the end screen of the sleeve, and the phase difference between the voltage and the current is obtained through software calculation, so that the dielectric loss tangent value tan is obtained.

Because the tan value of the capacitive equipment is small (generally between 0.001 and 0.02), the dielectric loss tangent value tan of the sleeve is generally between 0.4 and 0.7 percent, and in addition, the running environment of the equipment is complex, and the design defects of the system per se cause that the accuracy and the stability of the monitoring system on site are difficult to ensure. The main factors influencing the field dielectric loss monitoring are as follows: harmonic waves, direct current drift, frequency fluctuation, interphase interference, ambient temperature and humidity, PT or CVT angular difference, angular difference of a current sensor and the like. Therefore, under the complex electromagnetic environment and the atmospheric variation operation condition, in addition to the parameters of the equipment, such as variation and aging, the online monitoring device has the phenomena of phase difference measurement absolute value deviation and data fluctuation, so that the measurement result has poor repeatability and low reliability, and the electrical parameters of the equipment and the insulation state of the evaluation equipment cannot be effectively reflected.

According to the maintenance work of power transmission and transformation equipment in China, the dielectric loss test needs to be carried out on the transformer bushing in a periodical preventive test according to the preventive test regulations of electrical equipment. The preventive test has a certain effect on improving the reliability of the equipment, but the test period is long, the defects of the equipment cannot be found in time, and the power failure test is needed to influence the reliability of power supply. The online measurement of the dielectric loss of the sleeve can provide a certain maintenance basis for the state maintenance of the sleeve, and the insulation defect can be found in time, so that the development of the insulation fault in the sleeve can be effectively prevented. Before the dielectric loss on-line monitoring device is installed, the difference between the dielectric loss angle measured by the system and a standard dielectric loss measuring instrument is used as a correction value to correct the dielectric loss measurement in the later period. However, as the equipment operating conditions change and the equipment operating age increases, equipment and devices age, and the phase difference correction value before installation has an error.

With the development of digital and electronic technologies, in order to improve the accuracy of on-line monitoring of dielectric loss measurement systems, the following improvements have been made: software algorithm; temperature and humidity compensation; electromagnetic field shielding; and fourthly, hardware circuits. The improvement of the software algorithm is mainly to avoid measurement errors caused by power grid frequency change and harmonic existence and effectively inhibit spectrum leakage and barrier effect, and related researches show that the current algorithm can meet the requirement of the existing measurement precision, and the error can reach 10-6rad order of magnitude. Researches show that the influence of environmental temperature and humidity on casing dielectric loss measurement errors is large, the temperature and the humidity not only influence equivalent electrical parameters of a casing equipment body and a CVT, but also influence parameters of a secondary measurement loop mainly comprising a current sensor, a signal transmission cable and a signal conditioning unit, and therefore measurement errors are generated. In order to eliminate the influence of temperature and humidity, a temperature sensor and a humidity sensor are installed on a transformer on the site, temperature and humidity data on the site are uploaded to an upper computer, dielectric loss measurement data are corrected through software, and a corresponding early warning strategy is established (mainly, correction is carried out according to site operation experience). The electric field interference of dielectric loss measurement mainly comes from interphase interference, when A, B, C three-phase high-voltage bushings are tested, the A phase of a dielectric loss angle is large, the B phase is basically unchanged, the C phase is small (negative when serious), and the error of the interphase interference is generally eliminated by using a software method. The large space magnetic field exists around the field operation environment of the transformer, electromagnetic interference is generated on a hardware circuit, induced current is generated in a measurement loop, therefore, a signal transmission cable generally adopts a shielding cable, a cable joint needs to pay attention to moisture-proof treatment, and meanwhile, a circuit board is sealed in a shielding metal shell, so that external electromagnetic field interference is effectively shielded. The hardware circuit is mainly a signal conditioning circuit, the input and output signals of which require stable phase difference and are easily affected by external environmental factors, electromagnetic fields and aging of components,

in summary, the monitoring device for performing dielectric loss test on the transformer bushing in the prior art has the technical problem of low reliability of the measurement result due to the parameters of the device, such as change and aging.

Disclosure of Invention

The invention provides a system and a method for correcting a transformer bushing dielectric loss detection device, which are used for solving the technical problem of low reliability of a measurement result caused by the factors such as parameter change, aging and the like of equipment in a monitoring device for testing the dielectric loss of a transformer bushing in the prior art.

The invention provides a correcting system of a transformer bushing dielectric loss detection device, which comprises a standard correcting source, a current sensor, a signal conditioning circuit and a dielectric loss synchronous acquisition card, wherein the standard correcting source is connected with the current sensor; the current sensor is connected with the signal conditioning circuit, and the signal conditioning circuit is connected with the dielectric loss synchronous acquisition card; the standard correction source comprises a voltage correction mode and a current correction mode, and comprises a first output end and a second output end; when the standard correction source is in a current correction mode, the first output end is connected with the current sensor, and the second output end is connected with the dielectric loss synchronous acquisition card; when the standard correcting source is in a voltage correcting mode, the first output end is connected with the signal conditioning circuit, and the second output end is connected with the dielectric loss synchronous acquisition card.

Preferably, the current sensor is connected with the signal conditioning circuit through a signal transmission cable; when the standard correction source is in a voltage correction mode, the first output end is connected with the signal conditioning circuit through a signal transmission cable.

Preferably, the conditioning circuit comprises an amplifying circuit and a filtering circuit, and the output end of the amplifying circuit is connected with the input end of the filtering circuit.

Preferably, when the standard calibration source is in a current calibration mode, the first output end outputs a current signal to the current sensor, and the second output end outputs a voltage signal to the dielectric loss synchronous acquisition card;

when the standard correcting source is in a voltage correcting mode, the first output end outputs a voltage signal to the conditioning circuit, and the second output end outputs the voltage signal to the dielectric loss synchronous acquisition card;

the current sensor is used for collecting a current signal output by the standard correction source and transmitting the current signal to the signal conditioning circuit;

the signal conditioning circuit is used for amplifying and shaping the received voltage signal or current signal and transmitting the amplified and shaped voltage signal or current signal to the dielectric loss synchronous acquisition card;

the dielectric loss synchronous acquisition card is used for calculating the fixed phase difference of the transformer bushing dielectric loss detection device according to the received current signal and voltage signal.

Preferably, the dielectric loss synchronous acquisition card is specifically used for calculating the fixed phase difference of the transformer bushing dielectric loss detection device by adopting a harmonic analysis method.

A method for correcting a transformer bushing dielectric loss detection device is based on the correction system for the transformer bushing dielectric loss detection device, and comprises the following steps:

setting a standard correction source as a current correction mode, setting the output of the standard correction source, and starting the standard correction source to output a voltage signal and a current signal with the same phase;

the current sensor collects a current signal output by a first output end of the standard correcting source and transmits the current signal to the conditioning circuit, and the conditioning circuit amplifies and shapes the current signal and transmits the current signal to the dielectric loss synchronous acquisition card; a second output end of the standard correction source outputs a voltage signal to the dielectric loss synchronous acquisition card;

calculating to obtain the phase deviation of the current secondary measurement loop according to the received voltage signal and current signal by the dielectric loss synchronous acquisition card;

setting the standard correction source into a voltage correction mode, setting the output of the standard correction source, and starting the standard correction source to output voltage signals with the same phase;

the first output end of the standard correcting source outputs a voltage signal to the conditioning circuit, the conditioning circuit amplifies and shapes the voltage signal and then transmits the voltage signal to the dielectric loss synchronous acquisition card, and the second output end of the standard correcting source outputs the voltage signal to the dielectric loss synchronous acquisition card;

calculating by a dielectric loss synchronous acquisition card according to the received voltage signal to obtain the phase deviation of the voltage secondary measurement loop;

and calculating the fixed phase difference of the transformer bushing dielectric loss detection device according to the phase deviation of the current secondary measurement loop and the phase deviation of the voltage secondary measurement loop, and performing software correction on the transformer bushing dielectric loss detection device according to the fixed phase difference.

Preferably, the specific process of calculating the fixed phase difference of the transformer bushing dielectric loss detection device is as follows:

and subtracting the phase deviation of the current secondary measurement loop from the phase deviation of the voltage secondary measurement loop to obtain the fixed phase difference of the transformer bushing dielectric loss detection device.

Preferably, when the standard calibration source is in the current calibration mode, the frequency and the amplitude of the voltage signal output by the second output terminal and the frequency and the amplitude of the current signal output by the first output terminal, which are output by the standard calibration source, are specifically set, and when the standard calibration source is in the voltage calibration mode, the frequency and the amplitude of the voltage signal output by the first output terminal and the frequency and the amplitude of the voltage signal output by the second output terminal, which are output by the voltage standard calibration source, are specifically set.

Preferably, before the dielectric loss synchronous acquisition card calculates the phase deviation of the secondary current measurement loop according to the received voltage signal and current signal, the method further includes:

the dielectric loss synchronous acquisition card performs analog-to-digital conversion and storage on the received voltage signal and current signal;

before the dielectric loss synchronous acquisition card calculates the phase deviation of the secondary voltage measurement loop according to the received voltage signal, the method further comprises the following steps:

the dielectric loss synchronous acquisition card performs analog-to-digital conversion and storage on the received voltage signals.

Preferably, when the standard calibration source is in the voltage calibration mode, the voltage output by the first output terminal and the voltage output by the second output terminal have different magnitudes.

According to the technical scheme, the embodiment of the invention has the following advantages:

the embodiment of the invention utilizes the additional standard correction source, calculates the fixed phase difference of the current secondary measurement loop and the voltage measurement secondary loop by adjusting the output mode of the standard correction source, thereby carrying out phase check on the transformer bushing dielectric loss detection device, eliminating the deviation when detecting the deviation of the phase, avoiding the technical problem of low reliability of the measurement result caused by the parameters of the device, such as change, aging and the like, and effectively improving the accuracy of the monitoring data.

Another advantage of another embodiment of the present invention is that:

the embodiment of the invention checks the transformer bushing dielectric loss detection device through the secondary measurement loop, does not need to perform power failure operation in the process, and improves the power supply reliability of a power system.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is also possible for those skilled in the art to obtain other drawings based on the drawings without inventive exercise.

Fig. 1 is a circuit wiring diagram of a transformer bushing dielectric loss detection apparatus calibration system and method according to an embodiment of the present invention when a standard calibration source is in a current calibration mode.

Fig. 2 is a circuit wiring diagram of a transformer bushing dielectric loss detection apparatus calibration system and method according to an embodiment of the present invention when a standard calibration source is in a voltage calibration mode.

Fig. 3 is a circuit configuration diagram of an amplifying circuit in a conditioning circuit of a transformer bushing dielectric loss detection device calibration system and method according to an embodiment of the present invention.

Fig. 4 is a circuit diagram of a filter circuit in a conditioning circuit of a transformer bushing dielectric loss detection device calibration system and method according to an embodiment of the present invention.

Fig. 5 is a flowchart of a method and a system for calibrating a transformer bushing dielectric loss detection apparatus according to an embodiment of the present invention.

Detailed Description

The embodiment of the invention provides a system and a method for correcting a transformer bushing dielectric loss detection device, which are used for solving the technical problem of low reliability of a measurement result caused by the factors such as parameter change, aging and the like of equipment in a monitoring device for testing the dielectric loss of a transformer bushing in the prior art.

In order to make the objects, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the embodiments described below are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention provides a correcting system of a transformer bushing dielectric loss detection device, which comprises a standard correcting source 1, a current sensor 6, a signal conditioning circuit 2 and a dielectric loss synchronous acquisition card 3, wherein the standard correcting source is connected with the current sensor; the current sensor 6 is connected with the signal conditioning circuit 2, and the signal conditioning circuit 2 is connected with the dielectric loss synchronous acquisition card 3; the standard correction source 1 comprises a voltage correction mode and a current correction mode, and the standard correction source 1 comprises a first output end 4 and a second output end 5; when the standard calibration source 1 is in a current calibration mode, the first output terminal 4 is connected with the current sensor 6, the second output terminal 5 is connected with the dielectric loss synchronous acquisition card 3, and the specific circuit connection diagram is shown in fig. 1; when the standard calibration source 1 is in the voltage calibration mode, the first output terminal 4 is connected to the signal conditioning circuit 2, and the second output terminal 5 is connected to the dielectric loss synchronous acquisition card 3, and the specific circuit connection diagram is shown in fig. 2.

It should be further noted that the standard calibration source 1 adopts a FLUKE 5080A CALIBRATOR, which can output a larger voltage and has a stronger circuit driving capability, is programmable, and can be used as a precision standard source. The amplitude of the alternating current voltage output by the correction source is 1 mV-1020V, and the output frequency is 45 Hz-1 kHz; the amplitude of the output alternating current is 20 muA-20.5A, the frequency is adjustable, and the correction source can simultaneously output voltage, current signals and double alternating current voltage signals with adjustable frequency and adjustable phase in practical application.

As a preferred embodiment, when the standard calibration source 1 is in the current calibration mode, the current sensor 6 is connected with the signal conditioning circuit 2 through the signal transmission cable 7; when the standard correction source 1 is in a voltage correction mode, the first output end 4 is connected with the signal conditioning circuit 2 through the signal transmission cable 7, and the signal transmission cable 7 is arranged, so that the interference of the surrounding environment on signals is reduced, and the detection accuracy is improved.

As a preferred embodiment, the conditioning circuit comprises an amplifying circuit and a filtering circuit, and the output end of the amplifying circuit is connected with the input end of the filtering circuit. The amplifying circuit and the filter circuit respectively realize amplitude adjustment and waveform adjustment of signals. Because the dielectric loss measurement current has a large change range, the adoption of a program control or automatic gain amplification circuit is more beneficial to signal acquisition. FIG. 3 shows an example of a gain-controllable amplifier AD603, in which the input front end of the gain-controllable amplifier AD603 adopts a resistor divider and a high-precision operational amplifier OP07 for voltage following, so as to increase the signal measurement range, and the division multiple is R₂/(R₁+R₂) The amplification factor of the AD603 is controlled by an external input voltage VG (pins 1 and 2 are respectively input by positive and negative control voltages), the linear change of gain of-10 dB to +30dB under the condition that-500 mV is less than or equal to VG and less than or equal to +500mV can be realized, and the external input voltage is provided by a high-precision D/A conversion chip controlled by a singlechip. The filter circuit adopts a second-order active low-pass filter, as shown in FIG. 4, with a cut-off frequency f_c＝1/(2πR₄C₂) Magnification factor A ═ 1+ R₅/R₆。

As a preferred embodiment, when the calibration source 1 is in the current calibration mode, the first output terminal 4 outputs a mA-level current signal to the current sensor 6, and the second output terminal 5 outputs a voltage signal with the same phase to the dielectric loss synchronous acquisition card 3, so that the dielectric loss synchronous acquisition card 3 can obtain the initial phase of the current signal;

when the standard calibration source 1 is in a voltage calibration mode, the first output end 4 outputs a voltage signal to the conditioning circuit, and the second output end 5 outputs a voltage signal with the same phase to the dielectric loss synchronous acquisition card 3, so that the dielectric loss synchronous acquisition card 3 can obtain a current signal initial phase;

the current sensor 6 is used for collecting a current signal output by the standard correction source 1 and transmitting the current signal to the signal conditioning circuit 2;

the signal conditioning circuit 2 is used for amplifying and shaping the received voltage signal or current signal, removing noise in the voltage signal or current signal, facilitating subsequent processing, and transmitting the amplified and shaped voltage signal or current signal to the dielectric loss synchronous acquisition card 3;

the dielectric loss synchronous acquisition card 3 is used for calculating the fixed phase difference of the transformer bushing dielectric loss detection device according to the received current signal and voltage signal. It should be further explained that the dielectric loss synchronous acquisition card 3 performs analog-to-digital conversion on the received current signal and voltage signal, and calculates the fixed phase difference of the transformer bushing dielectric loss detection device by using a harmonic analysis method, which comprises the following specific processes:

taking the standard calibration source 1 in the current calibration mode as an example, the second output terminal 5 of the standard calibration source 1 outputs a voltage signalThe first output terminal 4 outputs a current signalBoth satisfy the dirichlet condition and can be decomposed into:

similarly, the current can be expanded to:

in the formula: omega is the fundamental angular frequency; u shape₀、I₀Voltage and current direct current components respectively; u shape_k、I_kAmplitude of each harmonic of voltage and current α_k、β_kThe initial phase angles of the voltage and current harmonics respectively, and simultaneouslyIt can also be written as:

can obtain:

furthermore, because the voltage signal received by the dielectric loss synchronous acquisition card 3 is actually a discrete sequence, the period of the analog signal to be detected is set as T, the number of sampling points in one period is set as N, sampling is performed at intervals of T/N, and the data sequence of a single period is as follows: { U_K}＝U₀,U₁,U₂...U_N-1。

Performing discrete Fourier transform on the data sequence, so that the coefficient a of the discrete Fourier series_n、b_nComprises the following steps:

thus, in the fundamental component of the voltage signal:

the initial phase angle is:

similarly, the initial phase angle β of the fundamental wave of the current signal can be obtained₁Therefore, the current secondary measurement loop phase offset is:

as shown in fig. 5, a method for calibrating a transformer bushing dielectric loss detection device is based on the above-mentioned system for calibrating a transformer bushing dielectric loss detection device, and includes the following steps:

firstly, preparation work is needed, and due to the fact that a general current sensor 6 is of a through type, workers need to detach a tail screen outgoing line of a transformer bushing before a test, and a through hole of the current sensor 6 is reserved. Connecting a communication interface of the acquisition dielectric loss synchronous acquisition card 3 to a computer, so that the software can read phase data conveniently; meanwhile, the connector of the CVT secondary terminal outgoing line and the transmission cable is disconnected, the connection of the standard correction source 1 is facilitated, and an operator is in place after relevant instrument equipment is prepared.

Setting a standard correction source 1 as a current correction mode, setting the output of the standard correction source 1, connecting a first output end 4 of the standard correction source 1 with a current sensor 6, connecting a second output end 5 with a dielectric loss synchronous acquisition card 3, and starting the standard correction source 1 to output voltage signals and current signals with the same phase;

the current sensor 6 collects current signals output by the first output end 4 of the standard correcting source 1 and transmits the current signals to the conditioning circuit, and the conditioning circuit amplifies and shapes the current signals and transmits the current signals to the dielectric loss synchronous acquisition card 3;

the dielectric loss synchronous acquisition card 3 simultaneously receives the voltage signal output by the second output end 5 of the standard correction source 1, and performs analog-to-digital conversion and current signal on the received voltage signal and current signalStoring and calculating to obtain the phase deviation of the current secondary measurement loop

Setting a standard correcting source 1 into a voltage correcting mode, setting the output of the standard correcting source 1, connecting a first output end 4 of the standard correcting source 1 with a conditioning circuit, connecting a second output end 5 with a dielectric loss synchronous acquisition card 3, and starting the standard correcting source 1 to output voltage signals with the same phase;

the first output end 4 of the standard correcting source 1 outputs a voltage signal to a conditioning circuit, the conditioning circuit amplifies and shapes the voltage signal and then transmits the voltage signal to the dielectric loss synchronous acquisition card 3, and the second output end 5 of the standard correcting source 1 outputs the voltage signal to the dielectric loss synchronous acquisition card 3;

the dielectric loss synchronous acquisition card 3 performs analog-to-digital conversion and storage on the received voltage signal and current signal, and calculates to obtain the phase deviation of the voltage secondary measurement loop

Calculating the fixed phase difference of the transformer bushing dielectric loss detection device according to the phase deviation of the current secondary measurement loop and the phase deviation of the voltage secondary measurement loop, and regulating the phase differenceThe lead is positive and the lag is negative, and the fixed phase difference of the dielectric loss secondary measurement loop is calculatedAnd comparing the fixed phase difference of the secondary measurement loop of the historical data record, performing software correction on the transformer bushing dielectric loss detection device, eliminating the measurement error caused by the change of the fixed phase difference, recovering the original wiring on the site, and finishing the test.

As a preferred embodiment, when the calibration source 1 is in the voltage calibration mode, the voltage output from the first output terminal 4 and the voltage output from the second output terminal 5 have different magnitudes. The first output terminal 4 is the voltage output signal of the analog CVT, typically 100/V3V; the second output end 5 is a reference phase voltage signal, the amplitude is 2-3V, and collection by a collection card is facilitated.

As a preferred embodiment, when the calibration source 1 is in the current calibration mode, the frequency and amplitude of the voltage signal output by the second output terminal 5 and the current signal output by the first output terminal 4, which are output by the calibration source 1, are specifically set, and when the calibration source 1 is in the voltage calibration mode, the frequency and amplitude of the voltage signal output by the first output terminal 4 and the voltage signal output by the second output terminal 5, which are output by the calibration source 1, are specifically set. It should be further noted that, in this embodiment, when the standard calibration source 1 is in the current calibration mode, the current amplitude of the first output terminal 4 is several milliamperes to several tens milliamperes, specifically determined according to the actually measured bushing end screen grounding current, and the frequency power frequency is 50 Hz; the voltage amplitude of the second output end 5 is 2-3V, and the frequency power frequency is 50 Hz; when the standard correction source 1 is in a voltage correction mode, the amplitude of the voltage output by the first output end 4 is 100/V3V, and the frequency is 50 Hz; the amplitude of the voltage output by the second output end 5 is 2-3V, and the frequency power frequency is 50 Hz.

It can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units can refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus, and method can be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is merely a logical division, and in actual implementation, there can be other divisions, for example, multiple units or components can be combined or integrated into another system, or some features can be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection can be an indirect coupling or communication connection of some interfaces, devices or units, and can be in an electric, mechanical or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, i.e. may be located in one place, or may also be distributed over a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the scheme of the embodiment.

In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each of the units may exist alone physically, or two or more units may be integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, can be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention essentially or partially contributing to the prior art, or all or part of the technical solution can be embodied in the form of a software product stored in a storage medium, and including instructions for causing a computer device (which can be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, and an optical disk.

The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments can still be modified, or some technical features of the foregoing embodiments can be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.