CN110907673A - Magnetic resisting method applied to optical current transformer for lightning current measurement of power transmission system - Google Patents
Magnetic resisting method applied to optical current transformer for lightning current measurement of power transmission system Download PDFInfo
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- CN110907673A CN110907673A CN201911231002.0A CN201911231002A CN110907673A CN 110907673 A CN110907673 A CN 110907673A CN 201911231002 A CN201911231002 A CN 201911231002A CN 110907673 A CN110907673 A CN 110907673A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
- G01R1/02—General constructional details
- G01R1/18—Screening arrangements against electric or magnetic fields, e.g. against earth's field
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- 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
- G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
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Abstract
A magnetic resisting method applied to an optical current transformer for power transmission system lightning current measurement relates to the technical field of lightning current measurement. The invention aims to solve the problem that the measurement precision of the optical current transformer is reduced or even cannot be used under the interference of an external magnetic field. The magnetic resisting method applied to the optical current transformer for measuring the lightning current of the power transmission system combines the differential magnetic resisting with the optical current transformer, can effectively reduce the interference of an external magnetic field on the line lightning current measurement, and improves the current detection precision.
Description
Technical Field
The invention belongs to the technical field of lightning current measurement, and particularly relates to a magnetic resisting method of an optical current transformer.
Background
With the construction of power system security defense systems, efforts have been made to prevent large-scale destructive power system disasters. In a power system disaster, a high-risk lightning stroke fault is a main cause of line tripping, and accurate measurement of lightning parameters is a necessary prerequisite for analysis and design protection. The presence of non-periodic components in lightning current is a major cause of the inability of ferromagnetic coil type current transformers to accurately reflect current conditions. Therefore, optical current transformers with good dynamic response capabilities are beginning to be widely used.
The optical current transformer has a wide frequency band and good transient characteristics. Compared with a ferromagnetic coil current transformer, the current transformer can truly reflect primary current in a transient process, and is beneficial to improving the rapidity, the sensitivity and the reliability of relay protection. However, under the interference of the external magnetic field, the measurement accuracy of the optical current transformer is reduced or even cannot be used. This problem causes technical impediments to the practical use of optical current transformers.
Disclosure of Invention
The invention provides a magnetic resisting method applied to an optical current transformer for measuring lightning current of a power transmission system, aiming at solving the problems that the measurement precision of the optical current transformer is reduced or even cannot be used under the interference of an external magnetic field.
A magnetic resisting method applied to an optical current transformer for lightning current measurement of a power transmission system specifically comprises the following steps:
firstly, an optical current sensor is used for collecting lightning current magnetic fields transmitted on a line so as to output light intensity signals, the optical current sensor collects two magnetic fields with the same intensity and opposite polarities,
then, the light intensity signals corresponding to the two magnetic fields are subtracted, so that the interference in the light intensity signals is eliminated.
After the interference in the light intensity signal is eliminated, a lightning current magnetic field is obtained through a mathematical model of the optical current transformer, and a lightning current value is obtained according to the magnetic field.
In the magnetic resisting method, two identical optical current sensors are used for respectively collecting two magnetic fields on the same line, and the solenoid winding directions of the two optical current sensors are opposite and the axes of the two optical current sensors are arranged in parallel.
In the magnetic resisting method, the optical axes of the sensing heads of the two optical current sensors are on a straight line, or the optical axes of the sensing heads of the two optical current sensors are arranged in parallel.
In the magnetic resisting method, the lightning current magnetic field collected by the optical current sensor and the output light intensity signal can be represented as a linear relationship, and then the two optical current sensors have the following expressions:
wherein u is01And u02Respectively the light intensity signals output by the two optical current sensors,
H(x1) And H (x)2) Respectively the input signals of the two optical current sensors, namely the magnetic fields of the collected lightning current,
k is the sensitivity of the optical current sensor,
is an interference signal;
will u01And u02Subtracting, then there is:
u01-u02＝kH(x1)-kH(x2)
wherein, H (x)1)＝-H(x2)。
In the magnetic resisting method, a lightning current value i is obtained according to the following formula:
wherein L is the closed path of the solenoid,
h (x) is the magnetic field of the lightning current for current amplification.
The magnetic resisting method applied to the optical current transformer for measuring the lightning current of the power transmission system combines the differential magnetic resisting with the optical current transformer, can effectively reduce the interference of an external magnetic field on the line lightning current measurement, and improves the current detection precision.
Drawings
FIG. 1 is a schematic diagram of a sensor head of an optical current transformer;
FIG. 2 is a schematic diagram of the magnetic shielding method of the present invention;
fig. 3 is a schematic diagram of the arrangement of the optical current sensors according to the magnetic resisting method of the present invention, in which (a) the optical axes of the sensing heads of the two optical current sensors are aligned, and (b) the optical axes of the sensing heads of the two optical current sensors are parallel to each other.
Detailed Description
The first embodiment is as follows: the present embodiment is specifically described with reference to fig. 1 to 3, and the magnetic resisting method applied to the optical current transformer for lightning current measurement of the power transmission system in the present embodiment specifically includes the following steps:
firstly, as shown in fig. 3, the optical axes of the sensing heads of two identical optical current sensors are arranged on a transmission line of lightning current in a straight line or in a mutually parallel manner, and the winding directions of the solenoids of the two optical current sensors are opposite; two optical current sensors are used for respectively acquiring two magnetic fields with the same magnetic field intensity and opposite polarities on the same line, and then the optical current sensors respectively output light intensity signals.
The lightning current magnetic field collected by the optical current sensor and the output light intensity signal can be expressed as a linear relation, and then the two optical current sensors have the following expressions:
wherein u is01And u02Light intensity signals, H (x), respectively output by two optical current sensors1) And H (x)2) The input signals of the two optical current sensors, namely the magnetic field H (x) of the collected lightning current, k is the sensitivity of the optical current sensor,
is an interference signal.
As shown in FIG. 2, the measured lightning current vertically passes through the geometric center of the differential optical current sensor and generates a measured magnetic field HcWhen an interference magnetic field H exists outsidegThe magnetic induction intensity at the two optical current sensors is respectively Hc + HgAnd Hg-HcThe output of the differential optical current sensor is subtracted, and the measurement result does not contain an interference magnetic field Hg。
Further, according to the above principle, since the two optical current sensors collect two magnetic fields with the same magnetic field strength and opposite polarities on the same line, there is H (x)1)＝-H(x2) Then, the light intensity signals corresponding to the two magnetic fields collected by the optical current sensor are subtracted, so that the interference signal can be eliminated
Namely the following formula:
u01-u02＝kH(x1)-kH(x2)＝2kH(x)。
finally, after eliminating the interference in the light intensity signal, reversely deducing the lightning current magnetic field H (x) through a mathematical model of the optical current transformer, wherein the mathematical model of the optical current transformer has the following expression:
wherein uo is a light intensity signal output by the optical current transformer, and can be regarded as u in the embodiment01-u02＝u0L is the closed path of the solenoid and V is the Verdet constant, delta, of the magneto-optical material0Linear birefringence, x is the loop radius.
When the lightning current magnetic field h (x) is obtained, the lightning current value i can be reversely deduced according to the following formula:
wherein L is the closed path of the solenoid,
h (x) is the magnetic field of the lightning current for current amplification.
Claims (6)
1. A magnetic resisting method applied to an optical current transformer for lightning current measurement of a power transmission system is characterized in that,
firstly, an optical current sensor is used for collecting lightning current magnetic fields transmitted on a line so as to output light intensity signals, the optical current sensor collects two magnetic fields with the same intensity and opposite polarities,
then, the light intensity signals corresponding to the two magnetic fields are subtracted, so that the interference in the light intensity signals is eliminated.
2. The method of claim 1, wherein after eliminating the interference in the light intensity signal, the lightning current magnetic field is obtained by the mathematical model of the optical current transformer, and the lightning current value is obtained according to the magnetic field.
3. The method for preventing magnetism in an optical current transformer applied to lightning current measurement of a power transmission system according to claim 1 or 2, wherein two identical optical current sensors are used for respectively acquiring two magnetic fields on the same line, the solenoid winding directions of the two optical current sensors are opposite, and the axes of the two optical current sensors are arranged in parallel.
4. The method according to claim 3, wherein the optical axes of the sensing heads of the two optical current sensors are aligned or the optical axes of the sensing heads of the two optical current sensors are parallel to each other.
5. The method of claim 3, wherein the lightning current magnetic field collected by the optical current sensor and the output light intensity signal can be expressed as a linear relationship, and then the two optical current sensors have the following expressions:
wherein u is01And u02Respectively the light intensity signals output by the two optical current sensors,
H(x1) And H (x)2) Respectively the input signals of the two optical current sensors, namely the magnetic fields of the collected lightning current,
k is the sensitivity of the optical current sensor,
is an interference signal;
will u01And u02Subtracting, then there is:
u01-u02＝kH(x1)-kH(x2)
wherein, H (x)1)＝-H(x2)。
6. The method for resisting magnetism in the optical current transformer applied to the lightning current measurement of the power transmission system according to claim 2 is characterized in that a lightning current value i:
wherein L is the closed path of the solenoid,
h (x) is the magnetic field of the lightning current for current amplification.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201911231002.0A CN110907673A (en) | 2019-12-04 | 2019-12-04 | Magnetic resisting method applied to optical current transformer for lightning current measurement of power transmission system |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102818919A (en) * | 2012-08-27 | 2012-12-12 | 哈尔滨工业大学 | Optical current transformer and method for resisting external magnetic field interference |
| CN103149404A (en) * | 2013-02-28 | 2013-06-12 | 哈尔滨工业大学 | Clamp-on optical current transformer and anti-external magnetic field interference method and temperature drift inhibition method thereof |
| CN106526277A (en) * | 2016-10-13 | 2017-03-22 | 北京航天时代光电科技有限公司 | Novel optical path sensing unit for low-voltage optical current sensor |
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- 2019-12-04 CN CN201911231002.0A patent/CN110907673A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102818919A (en) * | 2012-08-27 | 2012-12-12 | 哈尔滨工业大学 | Optical current transformer and method for resisting external magnetic field interference |
| CN103149404A (en) * | 2013-02-28 | 2013-06-12 | 哈尔滨工业大学 | Clamp-on optical current transformer and anti-external magnetic field interference method and temperature drift inhibition method thereof |
| CN106526277A (en) * | 2016-10-13 | 2017-03-22 | 北京航天时代光电科技有限公司 | Novel optical path sensing unit for low-voltage optical current sensor |
Non-Patent Citations (1)
| Title |
|---|
| 张健: "光学电流互感器的抗磁场干扰技术和数字化技术研究", 《中国博士学位论文全文数据库 工程科技Ⅱ辑》 * |
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