CN106918796B - Online detection system and method for secondary circuit impedance of current transformer - Google Patents
Online detection system and method for secondary circuit impedance of current transformer Download PDFInfo
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Abstract
The invention discloses a current transformer secondary circuit impedance on-line detection system, which comprises: a signal generating unit for generating a sinusoidal voltage signal; the sinusoidal voltage signal injection unit is used for receiving a sinusoidal voltage signal and injecting the sinusoidal voltage signal into the secondary circuit of the current transformer; the high-frequency current signal coupling unit is used for coupling with the current transformer to obtain a coupling voltage signal; the amplitude comparison unit is used for comparing the amplitude of the coupling voltage signal with the detection threshold range of the phase-locked amplification unit and sending the comparison result to a server; the phase-locked amplifying unit is used for calculating an orthogonal component and an in-phase component according to the sinusoidal voltage signal and the coupling voltage signal and sending the orthogonal component and the in-phase component to the server; the server is used for adjusting the amplitude of the sinusoidal voltage signal generated by the signal generating unit according to the comparison result; and calculating the impedance of a secondary loop of the current transformer according to the orthogonal component and the in-phase component obtained by calculating the adjusted sinusoidal voltage signal.
Description
Technical Field
The invention relates to the field of impedance detection of current transformers, in particular to a system and a method for online detection of secondary loop impedance of a current transformer.
Background
At present, technical methods for analyzing the fault state of a secondary circuit of a current transformer and identifying an electricity stealing state are various, and many of the technical methods are analyzed by using the impedance of the secondary circuit as a characteristic quantity. Qualitative analysis of the impedance of the secondary loop, without quantitative calculation of the impedance of the secondary loop, leads to special cases, such as a transformation ratio of 2000: the large-impedance current transformer of 5 cannot distinguish normal connection and open circuit states, and the transformation ratio is 50: the small-impedance current transformer of 5 can not distinguish normal connection and short circuit state, so that reliable and direct data support can not be provided for fault diagnosis of current transformer winding faults, insulation abnormity and the like.
Therefore, how to detect the impedance of the secondary loop of the current transformer on line is a problem to be solved urgently.
Disclosure of Invention
The invention provides a system and a method for detecting the impedance of a secondary circuit of a current transformer on line, which aim to solve the problem of detecting the impedance of the secondary circuit of the current transformer on line.
In order to solve the above problem, according to an aspect of the present invention, there is provided an on-line current transformer secondary circuit impedance detection system, including: a signal generating unit, a sine voltage signal injecting unit, a high-frequency current signal coupling unit, a signal amplitude comparing unit, a phase-locking amplifying unit and a server,
the signal generating unit is respectively connected with the input end of the sinusoidal voltage signal injection unit, the input end of the phase-locked amplifier unit and the output end of the server, and is used for generating sinusoidal voltage signals and sending the sinusoidal voltage signals to the sinusoidal voltage signal injection unit and the phase-locked amplification unit;
the sinusoidal voltage signal injection unit is connected with the secondary circuit of the current transformer and used for receiving the sinusoidal voltage signal and injecting the sinusoidal voltage signal into the secondary circuit of the current transformer;
the high-frequency current signal coupling unit is respectively connected with the secondary circuit of the current transformer, the input end of the signal amplitude comparison unit and the input end of the phase-locked amplification unit, and is used for coupling with the secondary circuit of the current transformer to obtain a coupling voltage signal and respectively sending the coupling voltage signal to the signal amplitude comparison unit and the phase-locked amplification unit;
the amplitude comparison unit is connected with the server and used for comparing the amplitude of the coupling voltage signal with the detection threshold range of the phase-locked amplification unit to generate a comparison result and sending the comparison result to the server;
the phase-locked amplifying unit is respectively connected with the output ends of the high-frequency current signal coupling unit and the signal generating unit and the input end of the server, and is used for calculating an orthogonal component and an in-phase component according to the sinusoidal voltage signal and the coupling voltage signal and sending the orthogonal component and the in-phase component to the server; and
the server is used for adjusting the amplitude of the sinusoidal voltage signal generated by the signal generating unit according to the comparison result; and calculating the impedance of a secondary loop of the current transformer according to the orthogonal component and the in-phase component which are obtained by calculating the adjusted sinusoidal voltage signal and the corresponding coupling voltage signal.
Preferably, the phase-locked amplifying unit includes: the device comprises a pre-amplification module, a band-pass filtering module, a trigger module, a 90-degree phase shift module, a correlation detection module and a low-pass filtering module.
Preferably, the adjusting, by the server, the amplitude of the sinusoidal voltage signal generated by the signal generating unit according to the comparison result includes:
if the comparison result shows that the amplitude of the coupled voltage signal is within the detection threshold range, the amplitude of the sinusoidal voltage signal generated by the signal generation unit is not changed;
if the comparison result is that the amplitude of the coupled voltage signal is larger than the upper limit of the detection threshold range, the amplitude of the sinusoidal voltage signal generated by the signal generation unit is reduced according to a preset adjustment amplitude threshold until the comparison result is that the amplitude of the coupled voltage signal corresponding to the adjusted sinusoidal voltage signal is within the detection threshold range;
and if the comparison result is that the amplitude of the coupled voltage signal is smaller than the lower limit of the detection threshold range, increasing the amplitude of the sinusoidal voltage signal generated by the signal generation unit according to a preset adjustment amplitude threshold until the comparison result is that the amplitude of the coupled voltage signal corresponding to the adjusted sinusoidal voltage signal is within the detection threshold range.
Preferably, the server calculates the impedance of the secondary loop of the current transformer according to the quadrature component and the in-phase component calculated by the adjusted sinusoidal voltage signal and the corresponding coupling voltage signal, and includes:
wherein Z is the impedance of the secondary loop of the current transformer, U0For injected sinusoidal voltage signals, n0Number of turns, n, of sinusoidal voltage signal injection unit2The number of turns of the high-frequency current signal coupling unit, R, x, y and y are numbers of turns of the high-frequency current signal coupling unit, sampling resistance of the high-frequency current signal coupling unit, in-phase component output by the phase-locked amplifying unit and quadrature component output by the phase-locked amplifying unit.
According to another aspect of the invention, an online detection method for the impedance of a secondary circuit of a current transformer is provided, and the method comprises the following steps:
injecting a sinusoidal voltage signal into the current transformer;
calculating the amplitude of a coupling voltage signal obtained by coupling of a secondary loop of the current transformer;
comparing the amplitude of the coupling voltage signal with a detection threshold range of a phase-locked amplifying unit to generate a comparison result, and adjusting the amplitude of the injected sinusoidal voltage signal according to the comparison result;
calculating a quadrature component and an in-phase component according to the injected sinusoidal voltage signal after adjustment and the corresponding coupling voltage signal; and
and calculating the impedance of a secondary loop of the current transformer according to the adjusted injected sinusoidal voltage signal, the orthogonal component and the in-phase component.
Preferably, the comparing the amplitude of the coupled voltage signal with a detection threshold range of a phase-locked amplifying unit to generate a comparison result, and adjusting the amplitude of the injected sinusoidal voltage signal according to the comparison result includes:
if the comparison result shows that the amplitude of the coupled voltage signal is within the detection threshold range, the amplitude of the sinusoidal voltage signal generated by the signal generation unit is not changed;
if the comparison result is that the amplitude of the coupled voltage signal is larger than the upper limit of the detection threshold range, the amplitude of the sinusoidal voltage signal generated by the signal generation unit is reduced according to a preset adjustment amplitude threshold until the comparison result is that the amplitude of the coupled voltage signal corresponding to the adjusted sinusoidal voltage signal is within the detection threshold range;
and if the comparison result is that the amplitude of the coupled voltage signal is smaller than the lower limit of the detection threshold range, increasing the amplitude of the sinusoidal voltage signal generated by the signal generation unit according to a preset adjustment amplitude threshold until the comparison result is that the amplitude of the coupled voltage signal corresponding to the adjusted sinusoidal voltage signal is within the detection threshold range.
Preferably, the calculating the impedance of the secondary loop of the current transformer according to the adjusted injected sinusoidal voltage signal, the quadrature component and the in-phase component includes:
wherein Z is the impedance of the secondary loop of the current transformer, U0For injected sinusoidal voltage signals, n0Number of turns, n, of sinusoidal voltage signal injection unit2The number of turns of the high-frequency current signal coupling unit, R, x, y and y are numbers of turns of the high-frequency current signal coupling unit, sampling resistance of the high-frequency current signal coupling unit, in-phase component output by the phase-locked amplifying unit and quadrature component output by the phase-locked amplifying unit.
The invention has the beneficial effects that:
according to the technical scheme, the phase-locked amplifying unit utilizes the injected sinusoidal voltage signal and the corresponding coupling voltage signal to output to obtain the orthogonal component and the in-phase component, and calculates to obtain the secondary loop impedance of the current transformer according to the injected sinusoidal voltage signal, the orthogonal component and the in-phase component, so that the problems that the secondary loop of the existing large-impedance current transformer cannot distinguish a normal connection state and an open circuit state, and the secondary loop of the small-impedance current transformer cannot distinguish a short circuit state and a normal connection state can be effectively solved, and reliable and direct data support is provided for fault diagnosis of winding faults, insulation abnormity and the like of the current transformer.
Drawings
A more complete understanding of exemplary embodiments of the present invention may be had by reference to the following drawings in which:
fig. 1 is a schematic diagram of an on-line detection system 100 for secondary loop impedance of a current transformer according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a phase-locked amplification unit according to an embodiment of the invention;
FIG. 3 is an equivalent circuit diagram of a secondary circuit of the current transformer; and
fig. 4 is a flowchart of a method 400 for detecting the impedance of the secondary circuit of the current transformer on line according to an embodiment of the present invention.
Detailed Description
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same units/elements are denoted by the same reference numerals.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
Fig. 1 is a schematic diagram of an online detection system 100 for secondary loop impedance of a current transformer according to an embodiment of the present invention. As shown in fig. 1, the current transformer secondary loop impedance online detection system 100 is used for online detection of current transformer secondary loop impedance, and the current transformer secondary loop impedance online detection system 100 includes: the device comprises a signal generating unit 101, a sinusoidal voltage signal injecting unit 102, a high-frequency current signal coupling unit 103, a signal amplitude comparing unit 104, a phase-locked amplifying unit 105 and a server 106. The detection of the secondary loop impedance of the current transformer can effectively solve the problems that the secondary loop of the existing large-impedance current transformer (such as a transformation ratio of 2000: 5) cannot distinguish a normal connection state from an open circuit state, and the secondary loop of the existing small-impedance current transformer (such as a transformation ratio of 50: 5) cannot distinguish a short circuit state from a normal connection state, and simultaneously provides reliable and direct data support for fault diagnosis of winding faults, insulation abnormity and the like of the current transformer.
Preferably, the signal generating unit 101 is connected to the input end of the sinusoidal voltage signal injecting unit, the input end of the phase-locked amplifier unit, and the output end of the server, respectively, and is configured to generate a sinusoidal voltage signal and send the sinusoidal voltage signal to the sinusoidal voltage signal injecting unit and the phase-locked amplifying unit.
Preferably, the sinusoidal voltage signal injection unit 102 is connected to the secondary circuit of the current transformer, and is configured to receive the sinusoidal voltage signal and inject the sinusoidal voltage signal into the secondary circuit of the current transformer.
Preferably, the high-frequency current signal coupling unit 103 is connected to the input ends of the current transformer secondary circuit, the signal amplitude comparison unit and the phase-locked amplification unit, respectively, and is configured to couple with the current transformer secondary circuit to obtain a coupling voltage signal, and send the coupling voltage signal to the signal amplitude comparison unit and the phase-locked amplification unit, respectively.
Preferably, the amplitude comparing unit 104 is connected to the server, and configured to compare the amplitude of the coupling voltage signal with a detection threshold range of the lock-in amplifying unit, generate a comparison result, and send the comparison result to the server.
Preferably, the phase-locked amplifying unit 105 is connected to the output ends of the high-frequency current signal coupling unit and the signal generating unit, and the input end of the server, and is configured to calculate a quadrature component and an in-phase component according to the sinusoidal voltage signal and the coupling voltage signal, and send the quadrature component and the in-phase component to the server. Fig. 2 is a schematic diagram of a phase-locked amplifying unit according to an embodiment of the present invention. As shown in fig. 2, the phase-locked amplifying unit includes: the device comprises a pre-amplification module, a band-pass filtering module, a trigger module, a 90-degree phase shift module, a correlation detection module and a low-pass filtering module.
Preferably, the server 106 is configured to adjust the amplitude of the sinusoidal voltage signal generated by the signal generation unit according to the comparison result; and calculating the impedance of a secondary loop of the current transformer according to the adjusted sinusoidal voltage signal and the orthogonal component and the in-phase component which are obtained by calculating the corresponding coupling voltage signal. Preferably, the adjusting, by the server, the amplitude of the sinusoidal voltage signal generated by the signal generating unit according to the comparison result includes:
if the comparison result shows that the amplitude of the coupled voltage signal is within the detection threshold range, the amplitude of the sinusoidal voltage signal generated by the signal generation unit is not changed;
if the comparison result is that the amplitude of the coupled voltage signal is larger than the upper limit of the detection threshold range, the amplitude of the sinusoidal voltage signal generated by the signal generation unit is reduced according to a preset adjustment amplitude threshold until the comparison result is that the amplitude of the coupled voltage signal corresponding to the adjusted sinusoidal voltage signal is within the detection threshold range;
and if the comparison result is that the amplitude of the coupled voltage signal is smaller than the lower limit of the detection threshold range, increasing the amplitude of the sinusoidal voltage signal generated by the signal generation unit according to a preset adjustment amplitude threshold until the comparison result is that the amplitude of the coupled voltage signal corresponding to the adjusted sinusoidal voltage signal is within the detection threshold range.
Preferably, the server calculates the impedance of the secondary loop of the current transformer according to the quadrature component and the in-phase component calculated by the adjusted sinusoidal voltage signal and the corresponding coupling voltage signal, and includes:
wherein Z is the impedance of the secondary loop of the current transformer, U0For injected sinusoidal voltage signals, n0Number of turns, n, of sinusoidal voltage signal injection unit2The number of turns of the high-frequency current signal coupling unit, R, x, y and y are numbers of turns of the high-frequency current signal coupling unit, sampling resistance of the high-frequency current signal coupling unit, in-phase component output by the phase-locked amplifying unit and quadrature component output by the phase-locked amplifying unit.
According to the invention, the normal connection and open circuit state of the secondary circuit of the large-impedance current transformer and the normal connection and short circuit state of the secondary circuit of the small-impedance current transformer can be normally identified by accurately detecting the impedance of the secondary circuit of the current transformer. Fig. 3 is an equivalent circuit diagram of a secondary circuit of the current transformer, and as shown in fig. 3, the equivalent circuit diagram of the secondary circuit of the current transformer is composed of a current transformer equivalent circuit Z1 and a circuit conductor equivalent circuit Z2, where 1 indicates a current transformer terminal and 2 indicates a detection system terminal. The equivalent circuit Z1 of the current transformer consists of an equivalent inductor L1, an equivalent capacitor C1 and an equivalent resistor R1; the loop conductor equivalent circuit Z2 is composed of several equivalent resistances and equivalent capacitances. The total impedance Z of the secondary circuit of the current transformer is Z1+ Z2, and the calculation formula of the resistor Z1 is as follows:
when the injection signal is a 20K sinusoidal voltage signal, R1 ranges from about 0.05 to 0.5 ohm, C1 ranges from about 100pF to 10uF, L1 ranges from about 10uH to 100mH, and Z1 is calculated to range from about 0.5 ohm to 40 kOhm.
The loop conductor equivalent circuit Z2 is composed of several equivalent resistances and equivalent capacitances. When the injection signal is a sinusoidal voltage signal of 20K, the impedance corresponding to the loop conductor equivalent circuit Z2 in different connection states of the secondary loop of the current transformer is as follows:
when the secondary circuit of the current transformer is normally connected,
z2 ranges from about 0.1 to 0.8 ohms;
when the secondary circuit of the current transformer is open at the end of the current transformer (at 1 in figure 3),
z2 is above 300K ohm;
when the injection signal is 20K and the amplitude is 100mV of sine wave, and the secondary circuit of the current transformer is open at the detection end 2 in the figure 1, the value of Z2 is infinite.
When a high-frequency 20K sinusoidal voltage signal is injected, the total impedance Z of the secondary loop of the current transformer in different states is as follows:
when a large-impedance current transformer (such as a transformation ratio of 2000: 5) is normally connected, the loop impedance Z is Z1+ Z2, and the maximum value is about 40K ohms;
when the current transformer secondary circuit is open at the position 1 in fig. 3, the loop impedance Z is Z2, and the value is more than 300K;
when the current transformer secondary circuit is open at the position 2 in fig. 3, the circuit impedance Z-Z2 approaches infinity;
the loop impedance of the small-impedance current transformer (such as a transformation ratio of 50: 5) in normal connection is at least 0.5 ohm;
when the secondary loop of the current transformer is in short circuit, the loop impedance is between 0.1 ohm and 0.5 ohm.
From the above analysis, the impedance of the secondary circuit of the current transformer in the normal connection state is about between 0.5 ohm and 40K ohm, the circuit short-circuit state is when the impedance is less than 0.5 ohm, and the circuit open-circuit state is when the impedance is more than 40K ohm.
Fig. 4 is a flowchart of a method 400 for detecting the impedance of the secondary circuit of the current transformer on line according to an embodiment of the present invention. As shown in fig. 4, the current transformer secondary loop impedance online detection method 400 is used for online detection of current transformer secondary loop impedance, and the method 400 starts from step 101 and injects a sinusoidal voltage signal into a current transformer in step 401.
Preferably, the amplitude of the coupled voltage signal obtained through the current transformer secondary loop coupling is calculated in step 402.
Preferably, the amplitude of the coupling voltage signal is compared with a detection threshold range of the phase-locked amplifying unit in step 403, a comparison result is generated, and the amplitude of the injected sinusoidal voltage signal is adjusted according to the comparison result. Preferably, the comparing the amplitude of the coupled voltage signal with a detection threshold range of a phase-locked amplifying unit to generate a comparison result, and adjusting the amplitude of the injected sinusoidal voltage signal according to the comparison result includes:
if the comparison result shows that the amplitude of the coupled voltage signal is within the detection threshold range, the amplitude of the sinusoidal voltage signal generated by the signal generation unit is not changed;
if the comparison result is that the amplitude of the coupled voltage signal is larger than the upper limit of the detection threshold range, the amplitude of the sinusoidal voltage signal generated by the signal generation unit is reduced according to a preset adjustment amplitude threshold until the comparison result is that the amplitude of the coupled voltage signal corresponding to the adjusted sinusoidal voltage signal is within the detection threshold range;
and if the comparison result is that the amplitude of the coupled voltage signal is smaller than the lower limit of the detection threshold range, increasing the amplitude of the sinusoidal voltage signal generated by the signal generation unit according to a preset adjustment amplitude threshold until the comparison result is that the amplitude of the coupled voltage signal corresponding to the adjusted sinusoidal voltage signal is within the detection threshold range.
Preferably, the quadrature component and the in-phase component are calculated at step 404 from the adjusted injected sinusoidal voltage signal and the corresponding coupled voltage signal.
Preferably, the impedance of the secondary loop of the current transformer is calculated in step 405 according to the adjusted injected sinusoidal voltage signal, the quadrature component and the in-phase component. Preferably, the calculating the impedance of the secondary loop of the current transformer according to the adjusted injected sinusoidal voltage signal, the quadrature component and the in-phase component includes:
wherein Z is the impedance of the secondary loop of the current transformer, U0For injected sinusoidal voltage signals, n0N2 is the number of turns of the sine voltage signal injection unit, R is the sampling resistance of the high-frequency current signal coupling unit, x is the in-phase component output by the phase-locked amplification unit, and y is the quadrature component output by the phase-locked amplification unit.
In the embodiment of the invention, a sinusoidal voltage signal with a certain frequency and variable amplitude is generated by using a signal generation unit, and the turn ratio of a sinusoidal voltage signal injection unit is n01, the turn ratio of the high-frequency current signal coupling unit is 1: n2Signal amplitude comparison unit detects fig. 1
The amplitude value is fed back to the signal generation control unit, the phase-locked amplification unit outputs the orthogonal component y and the in-phase component x of the signal, and the server can calculate the amplitude A of the signal and the phase of the signal according to the orthogonal component y and the in-phase component x of the signal as follows:
thus, there are
Wherein, U0For known injected sinusoidal voltage signals, n0For sinusoidal voltage signal injection unit turns, n2The number of turns of the high-frequency current signal coupling unit, R sampling resistance of the high-frequency current signal coupling unit,x is the in-phase component output by the phase-locked amplifying unit, and y is the quadrature component output by the phase-locked amplifying unit.
The invention has been described with reference to a few embodiments. However, other embodiments of the invention than the one disclosed above are equally possible within the scope of the invention, as would be apparent to a person skilled in the art from the appended patent claims.
Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the [ device, component, etc ]" are to be interpreted openly as referring to at least one instance of said device, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.
Claims (3)
1. An on-line detection system for secondary loop impedance of a current transformer is characterized by comprising: a signal generating unit, a sine voltage signal injecting unit, a high-frequency current signal coupling unit, a signal amplitude comparing unit, a phase-locking amplifying unit and a server,
the signal generating unit is respectively connected with the input end of the sinusoidal voltage signal injection unit, the input end of the phase-locked amplifier unit and the output end of the server, and is used for generating sinusoidal voltage signals and sending the sinusoidal voltage signals to the sinusoidal voltage signal injection unit and the phase-locked amplification unit;
the sinusoidal voltage signal injection unit is connected with the secondary circuit of the current transformer and used for receiving the sinusoidal voltage signal and injecting the sinusoidal voltage signal into the secondary circuit of the current transformer;
the high-frequency current signal coupling unit is respectively connected with the secondary circuit of the current transformer, the input end of the signal amplitude comparison unit and the input end of the phase-locked amplification unit, and is used for coupling with the secondary circuit of the current transformer to obtain a coupling voltage signal and respectively sending the coupling voltage signal to the signal amplitude comparison unit and the phase-locked amplification unit;
the amplitude comparison unit is connected with the server and used for comparing the amplitude of the coupling voltage signal with the detection threshold range of the phase-locked amplification unit to generate a comparison result and sending the comparison result to the server;
the phase-locked amplifying unit is respectively connected with the output ends of the high-frequency current signal coupling unit and the signal generating unit and the input end of the server, and is used for calculating an orthogonal component and an in-phase component according to the sinusoidal voltage signal and the coupling voltage signal and sending the orthogonal component and the in-phase component to the server; and
the server is used for adjusting the amplitude of the sinusoidal voltage signal generated by the signal generating unit according to the comparison result; calculating the impedance of a secondary circuit of the current transformer according to the orthogonal component and the in-phase component which are obtained by calculating the adjusted sinusoidal voltage signal and the corresponding coupling voltage signal;
wherein, the server adjusts the amplitude of the sinusoidal voltage signal generated by the signal generating unit according to the comparison result, including:
if the comparison result shows that the amplitude of the coupled voltage signal is within the detection threshold range, the amplitude of the sinusoidal voltage signal generated by the signal generation unit is not changed;
if the comparison result is that the amplitude of the coupled voltage signal is larger than the upper limit of the detection threshold range, the amplitude of the sinusoidal voltage signal generated by the signal generation unit is reduced according to a preset adjustment amplitude threshold until the comparison result is that the amplitude of the coupled voltage signal corresponding to the adjusted sinusoidal voltage signal is within the detection threshold range;
if the comparison result is that the amplitude of the coupled voltage signal is smaller than the lower limit of the detection threshold range, the amplitude of the sinusoidal voltage signal generated by the signal generation unit is increased according to a preset adjustment amplitude threshold until the comparison result is that the amplitude of the coupled voltage signal corresponding to the adjusted sinusoidal voltage signal is within the detection threshold range;
the server calculates the impedance of the secondary loop of the current transformer according to the quadrature component and the in-phase component obtained by calculating the adjusted sinusoidal voltage signal and the corresponding coupling voltage signal, and the method comprises the following steps:
wherein Z is the impedance of the secondary loop of the current transformer, U0For injected sinusoidal voltage signals, n0Number of turns, n, of sinusoidal voltage signal injection unit2The number of turns of the high-frequency current signal coupling unit, R, x, y and y are numbers of turns of the high-frequency current signal coupling unit, sampling resistance of the high-frequency current signal coupling unit, in-phase component output by the phase-locked amplifying unit and quadrature component output by the phase-locked amplifying unit.
2. The system of claim 1, wherein the phase-locked amplification unit comprises: the device comprises a pre-amplification module, a band-pass filtering module, a trigger module, a 90-degree phase shift module, a correlation detection module and a low-pass filtering module.
3. A method for detecting the impedance of a secondary circuit of a current transformer on line is characterized by comprising the following steps:
injecting a sinusoidal voltage signal into the current transformer;
calculating the amplitude of a coupling voltage signal obtained by coupling of a secondary loop of the current transformer;
comparing the amplitude of the coupled voltage signal with a detection threshold range of a phase-locked amplifying unit to generate a comparison result, and adjusting the amplitude of the injected sinusoidal voltage signal according to the comparison result, including:
if the comparison result shows that the amplitude of the coupled voltage signal is within the detection threshold range, the amplitude of the sinusoidal voltage signal generated by the signal generation unit is not changed;
if the comparison result is that the amplitude of the coupled voltage signal is larger than the upper limit of the detection threshold range, the amplitude of the sinusoidal voltage signal generated by the signal generation unit is reduced according to a preset adjustment amplitude threshold until the comparison result is that the amplitude of the coupled voltage signal corresponding to the adjusted sinusoidal voltage signal is within the detection threshold range;
if the comparison result is that the amplitude of the coupled voltage signal is smaller than the lower limit of the detection threshold range, the amplitude of the sinusoidal voltage signal generated by the signal generation unit is increased according to a preset adjustment amplitude threshold until the comparison result is that the amplitude of the coupled voltage signal corresponding to the adjusted sinusoidal voltage signal is within the detection threshold range;
calculating a quadrature component and an in-phase component according to the injected sinusoidal voltage signal after adjustment and the corresponding coupling voltage signal; and
calculating the impedance of a secondary loop of the current transformer according to the adjusted injected sinusoidal voltage signal, the orthogonal component and the in-phase component, and the method comprises the following steps:
wherein Z is the impedance of the secondary loop of the current transformer, U0For injected sinusoidal voltage signals, n0Number of turns, n, of sinusoidal voltage signal injection unit2The number of turns of the high-frequency current signal coupling unit, R, x, y and y are numbers of turns of the high-frequency current signal coupling unit, sampling resistance of the high-frequency current signal coupling unit, in-phase component output by the phase-locked amplifying unit and quadrature component output by the phase-locked amplifying unit.
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| CN108957140B (en) * | 2018-07-02 | 2022-07-01 | 中国电力科学研究院有限公司 | Loop impedance measurement system and method with wide dynamic range |
| CN110488215A (en) * | 2019-09-17 | 2019-11-22 | 深圳市晶扬电子有限公司 | Current transformer tests circuit, method and device |
| CN112415287A (en) * | 2020-11-16 | 2021-02-26 | 中国电力科学研究院有限公司 | Method and system for identifying transformation ratio replacement of metering current transformer |
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| TW526327B (en) * | 1998-02-19 | 2003-04-01 | Sumitomo Metal Ind | Detection apparatus and method of physical variable |
| US9330875B2 (en) * | 2009-10-02 | 2016-05-03 | Semiconductor Components Industries, Llc | Method for determining a circuit element parameter |
| CN102087347B (en) * | 2009-12-08 | 2013-05-29 | 张建 | Charged test method for current transformer and application thereof |
| CN203037775U (en) * | 2013-01-08 | 2013-07-03 | 重庆渝电电力科技有限公司 | Fault detection device for metering current transformer |
| CN106569078B (en) * | 2016-10-25 | 2020-06-26 | 中国电力科学研究院 | State detection method and system for secondary circuit of current transformer |
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