CN112505397A - 10kV bus capacitance current monitoring method - Google Patents
10kV bus capacitance current monitoring method Download PDFInfo
- Publication number
- CN112505397A CN112505397A CN202011243672.7A CN202011243672A CN112505397A CN 112505397 A CN112505397 A CN 112505397A CN 202011243672 A CN202011243672 A CN 202011243672A CN 112505397 A CN112505397 A CN 112505397A
- Authority
- CN
- China
- Prior art keywords
- voltage
- current
- capacitance
- bus
- input
- 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.)
- Pending
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
-
- 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
- G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
- G01R27/2605—Measuring capacitance
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
Abstract
The invention discloses a 10kV bus capacitance current monitoring method, which adopts a voltage transformer accessed to a power grid by an open delta connection method to realize the input of a measurement signal, leads pins of a capacitor to penetrate through a hollow coil, obtains a voltage signal generated by the input current signal through a sampling resistor connected in series on the hollow coil, forms a real-time database, randomly extracts three groups of data to complete the capacitance current to ground capacitance and a system bus, avoids the direct contact with a tester and the power grid, thereby effectively improving the safety.
Description
The technical field is as follows:
the invention relates to a power grid detection method, in particular to a 10kV bus capacitance current monitoring method.
Background art:
the capacitance current level is a key indicator of the operation of the power distribution system. However, the accurate detection (monitoring) of the capacitance current is affected by various factors such as grid structure, operation mode, load variation, etc., and it is difficult for the current (monitoring) method to truly reflect the capacitance current value of the system. Firstly, the existing test mode is limited, although the capacitance current direct measurement method can ensure the measurement precision, the method is destructive and has high risk, and the method is mainly applied to type test verification of scientific research and detection instruments, capacitive current examination of special conditions and the like. Common indirect measurement methods comprise a neutral point plus capacitance method and a secondary injection method, the maximum measurement range of the conventional test instrument is 250A, but with the large amount of cables entering the ground, the capacitance current of a 10kV system in a local area exceeds 300A, for the distribution capacitance of a distribution network in a wider range, the conventional device or test platform cannot accurately obtain the distribution capacitance (the error is over 15 percent), and the large-range test instrument is extremely difficult to develop. The secondary injection method is characterized in that a test instrument injects non-power-frequency current at a PT opening triangle, the current respectively generates voltage drop in winding resistance R, leakage reactance XL and lead to ground capacitance of PT three phases, capacitance current of a system is calculated according to the relation between the capacitance and the impedance, and although the risk of the secondary injection method is low, the discreteness of a test result is large. The above measurement methods are limited by the system capacitance current level, operating equipment parameters, harmonic load and the like, and have certain problems in precision or safety.
The invention content is as follows:
the technical problem to be solved by the invention is as follows: the defects in the prior art are overcome, and the 10kV bus capacitance current monitoring method with high detection precision and good safety is provided.
The technical scheme of the invention is as follows: a10 kV bus capacitance current monitoring method comprises the following steps: step one, a voltage transformer is connected into a power grid by adopting an open delta connection method;
inputting a smaller current signal different from the power frequency voltage of the power grid at an open triangular end of the voltage transformer through a signal generator, enabling a pin of a capacitor to penetrate through the hollow coil, and acquiring a voltage signal generated by the input current signal through a sampling resistor connected in series on the hollow coil;
changing the frequency of the input current signal until at least five groups of input current signals and voltage signals are obtained, and removing the minimum value and the maximum value and then removing the average value of the remaining three groups to be used as a large group of current and voltage input data;
step four, repeating the step three at least five times, removing the maximum value and the minimum value, forming at least three groups of current signals and voltage signal input signals, and forming a real-time database;
step five, randomly extracting three groups from the database in the step four, and calculating the ground capacitance of the power grid;
and step six, calculating the capacitance current of the power grid ungrounded system bus according to the ground capacitance.
Further, the voltage transformer in the first step comprises a primary winding and a secondary winding, and the primary winding is directly connected with electricity
The three-phase bus and the secondary winding of the network are connected with a signal generator by adopting an open delta connection method.
Further, in the second step, the hollow coil is connected in series with a sampling resistor, and a voltage detection element for detecting the voltage on the sampling resistor is connected to the sampling resistor.
Further, in the second step, the ampere loop law and the faraday electromagnetic induction law can be used to know that:
∮H·dl=I
B=μH
in summary, the voltage across the sampling resistor is:
wherein: n is the number of turns of the air core coil, d is the thickness of the air core coil, u is the magnetic conductivity of the air core coil, R1 and R2 are the center distance (inside and outside diameter) from the inner and outer rings of the air core coil to the capacitive pin, and dI/dt is the change rate of capacitive current.
Further, the capacitance to ground in the fifth step is calculated according to the following formula:
in the formula, C0 is capacitance to ground, i ═ 1, 2, and 3, and represents three groups of data detected when a current signal is input, Zi is equivalent impedance of a loop in each group of data, n1 is the number of turns of a primary winding, n2 is the number of turns of a secondary winding, uoi is a voltage value of a voltage signal measured in each group of data, io is a current value of the input current signal, ω i ═ 2 pi fi, and fi is a frequency of the current signal input in each group of data.
Further, the capacitance current I of the bus in the sixth step is calculated according to the following formula:
where ω is 2 π f, f is the frequency of the power frequency voltage in the grid, C0 is the capacitance to ground,the phase voltage of a bus in the power grid.
The invention has the beneficial effects that:
1. the invention realizes the input of the measuring signal by adopting the voltage transformer which is connected into the power grid by adopting an open triangle connection method, leads the pins of the capacitor to pass through the hollow coil, obtains the voltage signal generated by the input current signal through the sampling resistor which is connected in series on the hollow coil, forms a real-time database, randomly extracts three groups of data to complete the capacitance current of the ground capacitor and the system bus, and avoids the direct contact with the power grid by testers, thereby effectively improving the safety.
2. When the invention collects current and voltage data, group data is formed by removing the minimum value and the maximum value and then removing the average value, a plurality of group data are formed by removing the maximum value and the minimum value, at least three groups of current signals and voltage signal input signals are formed, a real-time database is formed, and then three groups of data are randomly extracted from the database to calculate the capacitance current, thereby solving the instability of the capacitance current and ensuring the accuracy of detection.
Description of the drawings:
fig. 1 is a flow chart of a 10kV bus capacitance current monitoring method.
The specific implementation mode is as follows:
example (b): see fig. 1.
A10 kV bus capacitance current monitoring method adopts a voltage transformer which is connected into a power grid by an open delta connection method to realize the input of a measurement signal, a pin of a capacitor penetrates through a hollow coil, a voltage signal generated by the input current signal is obtained through a sampling resistor which is connected in series on the hollow coil, a real-time database is formed, three groups of data are randomly extracted to complete the capacitance current of a ground capacitor and a system bus, the direct contact between a tester and the power grid is avoided, and therefore, the safety is effectively improved.
The present application will be described in detail below with reference to the drawings and examples.
Step one, a voltage transformer is connected into a power grid by adopting an open delta connection method;
the voltage transformer comprises a primary winding and a secondary winding, the primary winding is directly connected with a three-phase bus of a power grid, and the secondary winding is connected with a signal generator by adopting an open delta connection method.
Inputting a smaller current signal different from the power frequency voltage of the power grid at an open triangular end of the voltage transformer through a signal generator, enabling a pin of a capacitor to penetrate through the hollow coil, and acquiring a voltage signal generated by the input current signal through a sampling resistor connected in series on the hollow coil;
the hollow coil is connected with the sampling resistor in series, and a voltage detection element for detecting the voltage on the sampling resistor is connected with the sampling resistor.
From ampere's loop law and faraday's electromagnetic induction law:
∮H·dl=I
B=μH
in summary, the voltage across the sampling resistor is:
wherein: n is the number of turns of the air core coil, d is the thickness of the air core coil, u is the magnetic conductivity of the air core coil, R1 and R2 are the center distance (inside and outside diameter) from the inner and outer rings of the air core coil to the capacitive pin, and dI/dt is the change rate of capacitive current.
Changing the frequency of the input current signal until at least five groups of input current signals and voltage signals are obtained, and removing the minimum value and the maximum value and then removing the average value of the remaining three groups to be used as a large group of current and voltage input data;
step four, repeating the step three at least five times, removing the maximum value and the minimum value, forming at least three groups of current signals and voltage signal input signals, and forming a real-time database;
step five, randomly extracting three groups from the database in the step four, and calculating the ground capacitance of the power grid;
the capacitance to ground is calculated according to the following formula:
in the formula, C0 is capacitance to ground, i ═ 1, 2, and 3, and represents three groups of data detected when a current signal is input, Zi is equivalent impedance of a loop in each group of data, n1 is the number of turns of a primary winding, n2 is the number of turns of a secondary winding, uoi is a voltage value of a voltage signal measured in each group of data, io is a current value of the input current signal, ω i ═ 2 pi fi, and fi is a frequency of the current signal input in each group of data.
And step six, calculating the capacitance current of the power grid ungrounded system bus according to the ground capacitance.
The capacitance current I of the bus is calculated according to the following formula:
where ω is 2 π f, f is the frequency of the power frequency voltage in the grid, C0 is the capacitance to ground,the phase voltage of a bus in the power grid.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and all simple modifications, equivalent variations and modifications made to the above embodiment according to the technical spirit of the present invention still fall within the scope of the technical solution of the present invention.
Claims (6)
1. A10 kV bus capacitance current monitoring method comprises the following steps: step one, a voltage transformer is connected into a power grid by adopting an open delta connection method;
inputting a smaller current signal different from the power frequency voltage of the power grid at an open triangular end of the voltage transformer through a signal generator, enabling a pin of a neutral point external capacitor to penetrate through the hollow coil, and acquiring a voltage signal generated by the input current signal through a sampling resistor connected in series on the hollow coil;
changing the frequency of the input current signal until at least five groups of input current signals and voltage signals are obtained, and removing the minimum value and the maximum value and then removing the average value of the remaining three groups to be used as a large group of current and voltage input data;
step four, repeating the step three at least five times, removing the maximum value and the minimum value, forming at least three groups of current signals and voltage signal input signals, and forming a real-time database;
step five, randomly extracting three groups from the database in the step four, and calculating the ground capacitance of the power grid;
and step six, calculating the capacitance current of the power grid ungrounded system bus according to the ground capacitance.
2. The 10kV bus capacitance current monitoring method as claimed in claim 1, wherein: the voltage transformer in the first step comprises a primary winding and a secondary winding, the primary winding is directly connected with a three-phase bus of a power grid, and the secondary winding is connected with a signal generator by adopting an open delta connection method.
3. The 10kV bus capacitance current monitoring method as claimed in claim 1, wherein: in the second step, the hollow coil is connected in series with the sampling resistor, and a voltage detection element for detecting the voltage on the sampling resistor is connected with the sampling resistor.
4. The 10kV bus capacitance current monitoring method as claimed in claim 1, wherein: in the second step, the ampere loop law and the faraday electromagnetic induction law can be known as follows:
∮H·dl=I
B=μH
in summary, the voltage across the sampling resistor is:
wherein: n is the number of turns of the air core coil, d is the thickness of the air core coil, u is the magnetic conductivity of the air core coil, R1 and R2 are the center distance (inside and outside diameter) from the inner and outer rings of the air core coil to the capacitive pin, and dI/dt is the change rate of capacitive current.
5. The 10kV bus capacitance current monitoring method as claimed in claim 1, wherein: in the fifth step, the capacitance to ground is calculated according to the following formula:
in the formula, C0 is capacitance to ground, i ═ 1, 2, and 3, and represents three groups of data detected when a current signal is input, Zi is equivalent impedance of a loop in each group of data, n1 is the number of turns of a primary winding, n2 is the number of turns of a secondary winding, uoi is a voltage value of a voltage signal measured in each group of data, io is a current value of the input current signal, ω i ═ 2 pi fi, and fi is a frequency of the current signal input in each group of data.
6. The 10kV bus capacitance current monitoring method as claimed in claim 1, wherein: in the sixth step, the capacitance current I of the bus is calculated according to the following formula:
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CN202011243672.7A CN112505397A (en) | 2020-11-10 | 2020-11-10 | 10kV bus capacitance current monitoring method |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CN202011243672.7A CN112505397A (en) | 2020-11-10 | 2020-11-10 | 10kV bus capacitance current monitoring method |
Publications (1)
Publication Number | Publication Date |
---|---|
CN112505397A true CN112505397A (en) | 2021-03-16 |
Family
ID=74955740
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CN202011243672.7A Pending CN112505397A (en) | 2020-11-10 | 2020-11-10 | 10kV bus capacitance current monitoring method |
Country Status (1)
Country | Link |
---|---|
CN (1) | CN112505397A (en) |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN101021554A (en) * | 2007-03-16 | 2007-08-22 | 长沙理工大学 | Neutral-point earth-free distributing network direct-to-ground capacitance current measuring method |
CN103063901A (en) * | 2012-12-28 | 2013-04-24 | 上海市电力公司 | Pilot frequency injection detection method of power grid ungrounded system busbar capacitance current |
CN106771647A (en) * | 2016-12-30 | 2017-05-31 | 国网天津市电力公司 | A kind of low current neutral grounding electric network capacitance current measurement method |
-
2020
- 2020-11-10 CN CN202011243672.7A patent/CN112505397A/en active Pending
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN101021554A (en) * | 2007-03-16 | 2007-08-22 | 长沙理工大学 | Neutral-point earth-free distributing network direct-to-ground capacitance current measuring method |
CN103063901A (en) * | 2012-12-28 | 2013-04-24 | 上海市电力公司 | Pilot frequency injection detection method of power grid ungrounded system busbar capacitance current |
CN106771647A (en) * | 2016-12-30 | 2017-05-31 | 国网天津市电力公司 | A kind of low current neutral grounding electric network capacitance current measurement method |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
Liu et al. | A study of the sweep frequency impedance method and its application in the detection of internal winding short circuit faults in power transformers | |
Jayasinghe et al. | Winding movement in power transformers: a comparison of FRA measurement connection methods | |
Li et al. | Research on a composite voltage and current measurement device for HVDC networks | |
Wu et al. | A new testing method for the diagnosis of winding faults in transformer | |
Cataliotti et al. | Current transformers effects on the measurement of harmonic active power in LV and MV networks | |
CN112710930A (en) | Online evaluation method for insulation state in capacitor voltage transformer | |
CN110687408B (en) | Cable insulation monitoring method and device | |
CN107656174A (en) | One kind is used for deformation of transformer winding and carries out inline diagnosis method and system | |
Wang et al. | A differential self-integration D-dot voltage sensor and experimental research | |
CN109521391A (en) | The detection device and method of generator voltage mutual inductor winding interturn short-circuit failure | |
CN111289858A (en) | Method for judging partial discharge inside transformer | |
CN104750989A (en) | Single-core cable transient state thermal circuit model conductor temperature calculating method and device | |
CN116449162A (en) | Simulation test device and monitoring method for turn-to-turn discharge defects of large power transformer | |
CN104111438B (en) | Primary large-current loop monitoring method in current transformer error test | |
CN112505397A (en) | 10kV bus capacitance current monitoring method | |
CN106610464B (en) | Determine the system and method for deformation of transformer winding tester frequency-selective filtering performance | |
Sharma et al. | Development of reference SFRA plot of transformer at design stage using high frequency modelling | |
Gao et al. | Quantitative Research on Accumulative Effect of Transformer Winding Deformation and Its Influence Degree Based on Time-Frequency Analysis of Vibration Signal | |
Wang et al. | Analysis of influencing factors on site fault diagnosis of inter-turn short circuit fault of dry-type air-core shunt reactor | |
CN105182116B (en) | A kind of transformer winding working state detecting method based on weighted gradient structural similarity | |
Pham et al. | FRA-based transformer parameters at low frequencies | |
CN209606602U (en) | The detection device of generator voltage mutual inductor winding interturn short-circuit failure | |
CN112526412A (en) | Method and system for testing polarity of current transformer of transformer lifting seat | |
CN113589213B (en) | Method for testing metering characteristics of mutual inductor under special load condition of power grid | |
CN110658398A (en) | Transformer vibration fundamental frequency signal separation method based on power factor angle correction |
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 | ||
RJ01 | Rejection of invention patent application after publication | ||
RJ01 | Rejection of invention patent application after publication |
Application publication date: 20210316 |