阅读说明：本技术 配网ct校验方法 (Distribution network CT (computed tomography) calibration method ) 是由 蒋红亮 徐政 林振 王申华 方小方 方跃进 熊庄 管新涌 何华庆 金志武 吴辉 于 2020-05-09 设计创作，主要内容包括：本申请提出了配网CT校验方法,包括获取高压输电中直流电压中的交流部分,调用数字低通滤波器对交流部分进行滤波处理；基于函数相关性对滤波后的高压输电信号进行自相关运算,得到被检互感器与标准互感器的模拟输出；采用离散傅里叶变换对被检互感器与标准互感器的模拟输出量进行频谱分析以确定频率响应差异。通过依次执行直流滤波算法、信号时延测量算法、频谱分析算法,能够降低高压输电中直流电压和电流成分中因交流脉动信号导致被检直流合并单元输出的采样值波动较大的缺陷,从而提高其采集精度。(The application provides a distribution network CT (computed tomography) calibration method which comprises the steps of obtaining an alternating current part in direct current voltage in high-voltage power transmission, and calling a digital low-pass filter to filter the alternating current part; carrying out autocorrelation operation on the filtered high-voltage power transmission signal based on the functional correlation to obtain analog outputs of the detected mutual inductor and the standard mutual inductor; and performing spectrum analysis on the analog output quantities of the detected transformer and the standard transformer by adopting discrete Fourier transform to determine the frequency response difference. By sequentially executing the direct current filtering algorithm, the signal time delay measuring algorithm and the frequency spectrum analysis algorithm, the defect that the fluctuation of the sampling value output by the detected direct current merging unit is large due to alternating current pulse signals in direct current voltage and current components in high-voltage power transmission can be reduced, and the acquisition precision of the sampling value is improved.)

1. The distribution network CT verification method is characterized by comprising the following steps:

acquiring an alternating current part in direct current voltage in high-voltage power transmission, and calling a digital low-pass filter to filter the alternating current part;

carrying out autocorrelation operation on the filtered high-voltage power transmission signal based on the functional correlation to obtain analog outputs of the detected mutual inductor and the standard mutual inductor;

and performing spectrum analysis on the analog output quantities of the detected transformer and the standard transformer by adopting discrete Fourier transform to determine the frequency response difference.

2. The distribution network CT verification method according to claim 1, wherein the obtaining of the alternating current part of the direct current voltage in the high-voltage transmission and the filtering of the alternating current part by using a digital low-pass filter comprise:

determining a transfer function expression and a difference equation of the digital filter;

adjusting an expression of the digital filter based on a preset performance parameter;

and obtaining an error calculation formula of the digital low-pass filter which meets the requirement after adjustment.

3. The distribution network CT verification method of claim 1, wherein the autocorrelation operation is performed on the filtered high-voltage transmission signal based on the functional correlation to obtain analog outputs of the detected transformer and the standard transformer, and the method comprises the following steps:

obtaining an expression of an autocorrelation operation

In the above formula, x1(t) and x2(t) are respectively data received by the system at the same time, that is, analog outputs of the detected transformer and the standard transformer, D is delay, n1(t) and n2(t) are additive noises, which are assumed to be zero mean value and normal distribution random process with variance of 1, and are independent from the signal source s (t); the received correlation function of the data of the standard mutual inductor and the mutual inductor to be tested is as follows:

in the formula: rss represents the autocorrelation function of the source signal s (t), and E [. cndot. ] represents the mathematical expectation, where assuming that s (t), n1(t), and n2(t) are independent of each other, there are:

i.e. perfect orthogonality between the source signal and the noise and between the noise and the noise, then:

R₁₂(τ)＝R_ss(τ-D)

the autocorrelation function properties are:

|R_ss(τ-D)|≤R_ss(0)

in this case, when τ -D is 0, R_ss(τ -D) takes the maximum value, i.e., the peak value.

Technical Field

The invention belongs to the field of error checking, and particularly relates to a distribution network CT (computed tomography) checking method.

Background

With the development of urbanization, in order to improve the power supply reliability of a distribution network and improve the service quality and meet the requirement of the beautiful life of people on high-quality power supply service, countries and companies all invest a large amount of manpower and material resources to strengthen the construction, upgrading and transformation of the distribution network. Especially, a large number of distribution network automation devices all contain mutual inductor equipment (such as PT or CT), and the equipment cannot meet the requirements of live operation due to the quality, process, structure and the like, so that accidents occur. Therefore, aiming at the research of the uninterrupted operation technology of the distribution network automation equipment containing the mutual inductor, the problem that the equipment is damaged or broken due to improper operation to affect the safety of the equipment and operators can be reduced or avoided, the research of the uninterrupted operation technology of the distribution network automation equipment is developed for the first time, the blank of the company in the aspect is filled, the power failure of engineering prearrangement is reduced, and the power supply reliability is improved.

The live-line disconnection drainage wire is the most basic conventional live-line work project of a 10kV overhead distribution line and accounts for about 60% of the live-line work times of each unit of a power company every year. In order to ensure the safety of live working, safety regulations require that when a no-load line is disconnected and connected in a live state, a circuit breaker (switch) and an isolating switch (knife switch) at the other end of the line are required to be confirmed to be disconnected, and a transformer and a voltage transformer which are connected to the line side can be carried out after the transformer and the voltage transformer are confirmed to be withdrawn from operation. However, with the overall progress of the automatic transformation work of the distribution lines of the urban power grid, various load switches are widely used, and a transformer (energy-taking PT for short) for providing power for a controller and an operating device of the load switch cannot quit operation during live-line work. Whether the energy taking PT can be installed in a charged state or not and the drainage wire with the PT is disconnected become the difficult problems which need to be solved urgently in the current charged work.

The mutual inductor is an important component of an electric energy metering device and is a legal metering appliance for performing fair and fair trade settlement between a power generation company and a power grid company, between the power grid company and a power supply company, between the power supply company and power users and accurately calculating and checking technical and economic indexes in a power system. According to the current national verification regulations, the transformers (including voltage transformers and current transformers) used for metering in the power grid must be regularly subjected to error characteristic detection. According to the conventional detection method, the error characteristic detection can be carried out only by taking an operating transformer off-line, which inevitably affects the power supply reliability. And the electric power system in China has a huge number of power transformers, the error performance workload of the power system in power failure test is huge, time and labor are wasted, and real data in a three-phase electrified state cannot be obtained.

Disclosure of Invention

In order to solve the defects in the prior art, the invention provides a distribution network CT (computed tomography) verification method, which comprises the following steps:

acquiring an alternating current part in direct current voltage in high-voltage power transmission, and calling a digital low-pass filter to filter the alternating current part;

carrying out autocorrelation operation on the filtered high-voltage power transmission signal based on the functional correlation to obtain analog outputs of the detected mutual inductor and the standard mutual inductor;

and performing spectrum analysis on the analog output quantities of the detected transformer and the standard transformer by adopting discrete Fourier transform to determine the frequency response difference.

Optionally, the obtaining an alternating current portion in a direct current voltage in high voltage power transmission, and calling a digital low-pass filter to perform filtering processing on the alternating current portion includes:

determining a transfer function expression and a difference equation of the digital filter;

adjusting an expression of the digital filter based on a preset performance parameter;

and obtaining an error calculation formula of the digital low-pass filter which meets the requirement after adjustment.

Optionally, the performing autocorrelation operation on the filtered high-voltage power transmission signal based on the functional correlation to obtain analog outputs of the detected transformer and the standard transformer includes:

obtaining an expression of an autocorrelation operation

In the above formula, x1(t) and x2(t) are respectively data received by the system at the same time, that is, analog outputs of the detected transformer and the standard transformer, D is delay, n1(t) and n2(t) are additive noises, which are assumed to be zero mean value and normal distribution random process with variance of 1, and are independent from the signal source s (t); the received correlation function of the data of the standard mutual inductor and the mutual inductor to be tested is as follows:

in the formula: rss represents the autocorrelation function of the source signal s (t), and E [. cndot. ] represents the mathematical expectation, where assuming that s (t), n1(t), and n2(t) are independent of each other, there are:

i.e. perfect orthogonality between the source signal and the noise and between the noise and the noise, then:

R₁₂(τ)＝R_ss(τ-D)

the autocorrelation function properties are:

|R_ss(τ-D)|≤R_ss(0)

in this case, when τ -D is 0, R_ss(τ -D) takes the maximum value, i.e., the peak value.

The technical scheme provided by the invention has the beneficial effects that:

by sequentially executing the direct current filtering algorithm, the signal time delay measuring algorithm and the frequency spectrum analysis algorithm, the defect that the fluctuation of the sampling value output by the detected direct current merging unit is large due to alternating current pulse signals in direct current voltage and current components in high-voltage power transmission can be reduced, and the acquisition precision of the sampling value is improved.

Drawings

In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.

Fig. 1 is a schematic flow chart of a distribution network CT verification method proposed in the present application;

FIG. 2 is a FIR direct type structure proposed in an embodiment of the present application;

FIG. 3 is a schematic diagram of a phase relationship proposed in the embodiment of the present application;

fig. 4 is a schematic diagram of a butterfly form of an 8-point FFT proposed in the embodiment of the present application.

Detailed Description

To make the structure and advantages of the present invention clearer, the structure of the present invention will be further described with reference to the accompanying drawings.