CN110672927B - Voltage fitting method based on target - Google Patents
Voltage fitting method based on target Download PDFInfo
- Publication number
- CN110672927B CN110672927B CN201911018159.5A CN201911018159A CN110672927B CN 110672927 B CN110672927 B CN 110672927B CN 201911018159 A CN201911018159 A CN 201911018159A CN 110672927 B CN110672927 B CN 110672927B
- Authority
- CN
- China
- Prior art keywords
- voltage
- data
- frequency
- fitting
- current
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000000034 method Methods 0.000 title claims abstract description 36
- 238000005259 measurement Methods 0.000 claims abstract description 26
- 230000003321 amplification Effects 0.000 claims abstract description 4
- 238000001914 filtration Methods 0.000 claims abstract description 4
- 238000003199 nucleic acid amplification method Methods 0.000 claims abstract description 4
- 238000006243 chemical reaction Methods 0.000 claims abstract description 3
- 238000005516 engineering process Methods 0.000 abstract description 8
- 238000004364 calculation method Methods 0.000 abstract description 3
- 238000004422 calculation algorithm Methods 0.000 description 11
- 238000012360 testing method Methods 0.000 description 11
- 238000012545 processing Methods 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000005672 electromagnetic field Effects 0.000 description 2
- 238000002847 impedance measurement Methods 0.000 description 2
- 230000001965 increasing effect Effects 0.000 description 2
- 230000001939 inductive effect Effects 0.000 description 2
- 230000004075 alteration Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000009795 derivation Methods 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/20—Measuring earth resistance; Measuring contact resistance, e.g. of earth connections, e.g. plates
- G01R27/205—Measuring contact resistance of connections, e.g. of earth connections
Abstract
The invention provides a voltage fitting method based on a target, which comprises the following specific steps: step 1, acquiring analog data of a grounding grid through a sensor, wherein the analog data comprises voltage data and current data; step 2, carrying out data amplification and filtering operation on the acquired voltage data and current data; step 3, converting the amplified and filtered analog data into digital data through an analog-to-digital conversion chip; and 4, performing voltage fitting based on a target according to the digital data in the step 3 to obtain a voltage fitting curve. Through the specific fitting method, the zero crossing point parameters of the voltage waveform can be effectively obtained, and the measurement error of the grounding impedance is greatly reduced. In the process of measuring and calculating the grounding impedance of the large-scale ground network, the grounding impedance value of a calculation field is quickly, effectively and accurately calculated, and the method is a technology which cannot be realized by the grounding impedance measuring technology at the present stage.
Description
Technical Field
The invention belongs to the field of measurement of large-scale grounding grid grounding impedance, and particularly relates to a voltage fitting method based on a target.
Background
The grounding impedance test of the grounding grid is mainly realized by measuring two physical quantities, namely test current injected into the grounding grid and dissipated through the grounding grid and potential rise of the grounding grid, and solving the two physical quantities through ohm's law. Generally, the grounding grid of the substation has a large area and a small grounding resistance. It is very difficult to accurately measure the ground resistance of the large-scale ground grid under strong external interference. In the engineering of measuring the grounding resistance of a large grounding grid, external interference is often serious and complex, so that the measurement error is increased, and the reliability of a measurement result is greatly reduced. External interference is the most main factor causing measurement errors (sometimes up to several volts in an operating transformer substation), and the interference can be divided into two parts, namely, induced voltage generated by an external electromagnetic field on a voltage pole measurement lead (such as induced voltage generated by mutual inductance coupling of a current pole test wire or coupling of a nearby operating power transmission line or equipment), voltage drop generated by interference current (such as system unbalanced current) in the ground on a grounding resistance of a grounding grid of the transformer substation, the grounding resistance of the grounding grid of the transformer substation is generally less than 0.5 ohm, and the voltage drop of tens of amperes of test current on the grounding resistance is not large. In addition, the external interference also comprises harmonic waves and high frequencies besides the power frequency, and the reading of the ordinary voltmeter influenced by the external interference is not the reference value of the power frequency, so that certain errors can be generated.
Meanwhile, under the condition of strong electromagnetic environment, higher requirements are also put forward on the anti-interference capability of the detection equipment. There are powerful electrical devices in the vicinity of the data acquisition system, electromagnetic fields couple into sensors and transmission conductors in inductive or capacitive form; or the interference signal and the measured signal are connected in series and are superposed on the measured signal to become a part of the measured signal, and the part of the measured signal is sent to the amplifier for amplification, so that the influence is large, and the voltages of two input ends of the data acquisition and processing system are changed. No matter a power frequency or pilot frequency method is used, the signal-to-noise ratio of the test voltage is improved by using a traditional method, the signal processing means is limited, and a new signal processing means with the characteristic of measuring the resistance of the power grid is urgently needed to improve the measurement accuracy. At present, the digital measurement technology and the instrument are widely applied in the field of electric power test, a high-speed acquisition device is utilized to convert voltage analog quantity into digital quantity, and advanced digital signal processing technology can be utilized to carry out noise suppression or signal reconstruction, so that the measurement precision can be greatly improved.
In order to effectively solve the influence of zero sequence current on the measurement of the ground resistance, in the early 50 s of the 20 th century, a method for measuring the ground resistance of a grounding network by using test current different from power frequency, namely a method for measuring the frequency of injected current different from the frequency of the power network, is provided. The pilot frequency measurement method uses a variable frequency power supply, tests under the frequency deviating from the power frequency, and the grounding grid interference is eliminated through frequency selection filtering, so that the measurement result is not influenced by the system power supply, the grounding grid is not influenced by whether the grounding grid operates or the existence of an interference signal, the power frequency interference is effectively eliminated, and meanwhile, the high-frequency interference in the grounding grid is eliminated through frequency selection. Therefore, the influence of interference on the measurement result can be effectively eliminated by selecting the pilot frequency method to measure the grounding grid. The pilot frequency method is used, so that the interference of zero sequence current in the ground and the interference of external power frequency are theoretically solved, and the interference of high frequency, clutter interference and the interference of an electrified operation line are also easily solved. In addition, the pilot frequency method can be used under the condition that the transformer substation is not powered off. The technical requirement is high for ensuring the characteristics of the pilot frequency measurement grounding grid, so that the pass frequency band of voltage and current measurement equipment is required to be variable and narrow, and the instrument has high measurement precision and good anti-interference performance due to comprehensive consideration of hardware and software.
A general large-scale grounding network grounding impedance tester adopts a resistance frequency characteristic principle, firstly measures interference voltage according to a current-voltage method to obtain interference frequency, measures multiple frequencies of 40, 60, 94, 105, 111, 128Hz and the like within a frequency range of 40-128 Hz to obtain impedance under each frequency, measures and processes for multiple times, analyzes, obtains a resistance frequency characteristic curve by successive approximation curve fitting, and then directly interpolates on the curve to obtain power frequency, namely, power frequency grounding impedance can be obtained, and pure grounding impedance irrelevant to frequency can be obtained.
The method adopts successive approximation curve fitting to obtain a frequency-blocking characteristic curve, and then directly interpolates on the curve to obtain the power frequency. The error of one link is too large, so that the integral accumulated error is large, and the error is inevitably large due to too many indirect derivation links. When the grounding impedance detection equipment is designed, generally, a measurement voltage signal is assumed to be relatively stable within a short time, the assumption is relatively ideal in the application of a real measurement environment, and under the condition that power frequency interference or low-frequency interference changes, the caused measurement error is relatively large, and dynamic anti-interference cannot be realized. Therefore, there are deficiencies and drawbacks in principle that dynamic interference cannot be eliminated. Meanwhile, under the condition of large interference, the signal-to-noise ratio can be improved only by increasing the test current, and the anti-interference capability cannot be enhanced algorithmically. The design of instruments and equipment at the present stage is mainly focused on the measurement stage of signals, the essence analysis of measurement problems is lacked, and algorithm design of each link with pertinence is lacked.
Disclosure of Invention
Aiming at the characteristics of the measurement of the grounding impedance, the induced voltage on the linear impedance is also the characteristic of the parameter similarity waveform under the condition of determining the characteristics of the test current source. According to the characteristics, a targeted voltage fitting method based on the target is provided. Through the specific fitting method, the zero crossing point parameters of the voltage waveform can be effectively obtained, and the measurement error of the grounding impedance is greatly reduced. In the process of measuring and calculating the grounding impedance of the large-scale ground network, the grounding impedance value of a calculation field is quickly, effectively and accurately calculated, and the method is a technology which cannot be realized by the grounding impedance measuring technology at the present stage.
The technical scheme of the invention is as follows:
a voltage fitting method based on a target comprises the following specific steps:
and 4, performing voltage fitting based on a target according to the digital data in the step 3 to obtain a voltage fitting curve.
The voltage fitting process in the step 4 comprises the following steps:
the target voltage waveform is set as:
wherein V is the target voltage, AvIs the current amplitude at voltage v, fvIn order to be the frequency of the voltage,
is a phase component, BvIs a direct current component;
the voltage corresponding to a series of data points of the acquired voltage waveform in the time series t (i) is v (i), wherein
v(i)＝v(1),v(2),v(3),v(4)…v(n) (2)
Fitting the measured parameters v (i) to the equation is
Frequency f of voltagevSet to the current frequency f of the current sourceIAnd the initial value of the direct current component is set to zero,
the above formula can be converted into
If the equation is the minimum value, it should satisfy
Is zero, i.e. is
Solving the ternary nonlinear equation set to obtain the coefficient A of the general expression of the positive selection functionv，
Bv，
And obtaining a voltage fitting curve. The target voltage waveform is set as:
wherein V is the target voltage, AvIs the current amplitude at voltage v, fvIn order to be the frequency of the voltage,
is a phase component, BvIs a direct current component;
the voltage corresponding to a series of data points of the acquired voltage waveform in the time series t (i) is v (i), wherein
v(i)＝v(1),v(2),v(3),v(4)…v(n) (2)
In order to fit the measured parameter v (i) to the above-mentioned voltage waveform equation, S is the variance of the measured voltage parameter, i.e.
Frequency f of voltagevSet to the current frequency f of the current sourceIAnd the initial value of the DC component is set to zero, the above formula can be converted into
If S is the minimum value, the following conditions are satisfied
Is zero, i.e. is
Solving the ternary nonlinear equation set to obtain the coefficient A of the general expression of the positive selection functionv，
BvThereby obtaining a voltage fitting curve.
Compared with the prior art, the invention has the beneficial effects that: the traditional fitting algorithm generally adopts a least square method, and aims to restore a real data waveform, so that the fitting algorithm is a universal fitting algorithm. Aiming at the characteristics of the measurement of the grounding impedance, the induced voltage on the linear impedance is also the characteristic of the parameter similarity waveform under the condition of determining the characteristics of the test current source. According to the characteristics, a targeted voltage fitting algorithm based on the target is provided. Through the specific fitting algorithm, the zero crossing point parameters of the voltage waveform can be effectively obtained, and the measurement error of the grounding impedance is greatly reduced. In the process of measuring and calculating the grounding impedance of the large-scale ground network, the grounding impedance value of a calculation field is quickly, effectively and accurately calculated, and the method is a technology which cannot be realized by the grounding impedance measuring technology at the present stage.
Drawings
Fig. 1 is a schematic diagram of the impedance measurement of the present invention.
Fig. 2 is a block diagram of a series circuit model of the ground impedance.
Fig. 3 is a graph of voltage waveforms under low frequency interference.
Fig. 4 is a graph of a voltage waveform of a least squares fit.
Fig. 5 is a graph of a voltage waveform based on a target voltage fit of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments 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 voltage waveform fitting algorithm based on a target, which is used for performing fixed parameter fitting on discrete voltage waveforms based on the frequency characteristics of a current source, and can greatly reduce errors caused by on-site dynamic interference. The basic measurement principle is shown in figure 1:
1. the current signal model can be generally expressed as:
suppose the current amplitude of the current source is A and the frequency is fIPhase angle of
The dc component is B. The current source is ideal sine wave and can be set initially
B is zero.
2. A series circuit model of the ground impedance is shown in fig. 2.
Z＝R+j2πfL
3. Assuming the field low frequency current interference is:
the total current is
4. Induced voltage after passing through the ground impedance is
The voltage waveforms in the presence of in-situ dynamic glitches are shown in FIG. 3:
5. voltage fitting algorithm
The traditional method is to adopt a least square method to fit the discrete signals, the fitted graph is shown in figure 4,
therefore, the zero crossing point time solving through the fitted waveform has a large error, and the ground impedance value calculated at this time can cause a large error. Thus, this patent proposes a selection target-based voltage fitting algorithm.
The voltage induced across the impedance must also be consistent with the frequency of the current source (whether it is a power frequency current source or a pilot frequency current source) regardless of whether it is a power frequency method or a pilot frequency method. The fitted voltage frequency is thus determined, i.e. coincides with the current source frequency. Since the ground impedance is a linear unit, the induced voltage of the standard current source on the impedance is also a standard sine wave, and only the phase difference exists. The phase difference depends on the magnitude of the inductive reactance in the ground impedance. The fitting algorithm process is as follows:
the target voltage waveform is set as:
the voltage corresponding to a series of data points of the acquired voltage waveform in the time series t (i) is v (i), wherein
v(i)＝v(1),v(2),v(3),v(4)…v(n)
Fitting the measured parameters v (i) to the equation is
Is the minimum value. If the method is based on a four-parameter method, namely the amplitude, frequency, phase and direct current components are unknown, the fitted voltage waveform contains the influence of other frequency components, and the zero crossing point error of the voltage is large. Thus, based on the above analysis, the target-based voltage fitting algorithm sets the voltage frequency to the current frequency, while the initial value of the dc component is set to zero.
The above formula can be converted into
Is the minimum value. If S in the equation is the minimum value, the following conditions are satisfied
Is zero, i.e. is
Solving the ternary nonlinear equation set to obtain the coefficient A of the general expression of the positive selection functionv，
Bv. The graph fitted to the above voltage waveform according to this method is fig. 5.
The voltage waveform amplitude and the zero crossing point moment are calculated through the fitting curve, the phase angle and the mode of the grounding impedance are analyzed by combining the waveform characteristics of the current source, and the accuracy of the grounding impedance measurement is improved.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (1)
1. A voltage fitting method based on a target is characterized by comprising the following specific steps:
step 1, acquiring analog data of a grounding grid through a sensor, wherein the analog data comprises voltage data and current data;
step 2, carrying out data amplification and filtering operation on the acquired voltage data and current data;
step 3, converting the amplified and filtered analog data into digital data through an analog-to-digital conversion chip;
step 4, performing voltage fitting based on a target according to the digital data in the step 3 to obtain a voltage fitting curve;
the voltage fitting process in the step 4 comprises the following steps:
the target voltage waveform is set as:
in the formula
In order to be the target voltage, the voltage of the power supply,
is at a voltage of
The magnitude of the current at the time of operation,
in order to be the frequency of the voltage,
in order to be the phase component of the signal,
is a direct current component;
for a series of data points of the acquired voltage waveform in time series
Corresponding voltage of
Wherein
To make the parameters measured
Fitting to the above voltage waveform equation (1), and S is the variance of the voltage measurement parameter, that is
Frequency of voltage
Set to current source current frequency
，
The above formula (3) can be converted into
If S is the minimum value, should satisfy
Is zero, i.e. is
Solving the ternary nonlinear equation set (6) to obtain the coefficient of the general expression of the sine function
，
，
，
And obtaining a voltage fitting curve.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911018159.5A CN110672927B (en) | 2019-10-24 | 2019-10-24 | Voltage fitting method based on target |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911018159.5A CN110672927B (en) | 2019-10-24 | 2019-10-24 | Voltage fitting method based on target |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN110672927A CN110672927A (en) | 2020-01-10 |
| CN110672927B true CN110672927B (en) | 2022-05-17 |
Family
ID=69084387
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201911018159.5A Active CN110672927B (en) | 2019-10-24 | 2019-10-24 | Voltage fitting method based on target |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN110672927B (en) |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101130261B1 (en) * | 2010-07-20 | 2012-03-26 | 한국 전기안전공사 | System for measuring ground parameter |
| CN103217584B (en) * | 2013-03-26 | 2015-09-16 | 广东电网公司电力科学研究院 | The measuring method of large-scale grounding network impedance ground |
| CN103913654B (en) * | 2014-03-17 | 2015-07-29 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | The recognition methods of System for HVDC System Earth Pole fault signature and equipment |
| CN104796116B (en) * | 2014-08-06 | 2017-08-01 | 中国航空工业集团公司北京长城计量测试技术研究所 | A kind of surge waveform peak measurement methods based on parameter fitting |
| CN108548962A (en) * | 2018-04-13 | 2018-09-18 | 国网上海市电力公司 | A kind of grounded screen alternating current and direct current and impulse resistance integrated test system and method |
| CN109683063B (en) * | 2019-02-22 | 2021-11-12 | 中国石油大学(华东) | Small current ground fault direction detection method using current and voltage derivative |
| CN110308332A (en) * | 2019-07-16 | 2019-10-08 | 国网湖南省电力有限公司 | A kind of grounding net of transformer substation impedance ground detection method, system and medium |
-
2019
- 2019-10-24 CN CN201911018159.5A patent/CN110672927B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN110672927A (en) | 2020-01-10 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN106291092B (en) | Constant charge soil interference monitoring and electricity method is remedied outside a kind of intelligent electric meter | |
| CN205103389U (en) | High frequency partial discharge detector verification system | |
| CN108318852A (en) | A kind of intelligent electric energy meter square wave influence test method | |
| CN106338237A (en) | Transformer winding deformation detection method based on frequency response impedance method | |
| CN114016041B (en) | Oil-gas pipeline potential detection method and device for cathodic protection | |
| CN107765084B (en) | Universal voltage input power frequency signal frequency measurement system | |
| CN110672927B (en) | Voltage fitting method based on target | |
| Amin et al. | Differential equation fault location algorithm with harmonic effects in power system | |
| CN108680843A (en) | A kind of method for detection of partial discharge of switch cabinet based on Radio Transmission Technology | |
| CN211086468U (en) | L CR tester | |
| KR101123539B1 (en) | A High Precision Ground Impedance Measurement Device | |
| CN207908626U (en) | A kind of simulation high frequency Partial discharge signal generating means | |
| CN105572482A (en) | Enclosed space electric field measurement device | |
| CN115808588A (en) | Pulse characteristic signal platform area topology identification method based on Rogowski coil | |
| CN108333475A (en) | A kind of contactless fault location signal processing method | |
| CN105572452A (en) | Gaussian beam bunch average current measuring method of particle accelerator in quasi-continuous running state | |
| CN103018637B (en) | Transmission line travelling wave measures noise-decreasing device and noise reducing method | |
| CN115015687A (en) | Four-end annular flexible direct-current power grid fault location method and system | |
| CN102169101A (en) | Conductive probe liquid holdup gauge | |
| CN112730990A (en) | Large-scale grounding grid impedance testing arrangement | |
| CN105445553A (en) | Method for precisely acquiring short-circuit impedance value of transformer at 50Hz | |
| CN106597113B (en) | Power line iron tower ground resistance on-line tester based on proportion detection | |
| CN102004854A (en) | Method for acquiring nonlinear load equivalent impedance parameters of distribution network in real time | |
| CN110907343A (en) | Method for detecting corrosion rate of grounding grid | |
| JP4100536B2 (en) | High frequency noise removal method in power quality diagnosis |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |