CN110702973A - Online measuring device for induced voltage of cable sheath - Google Patents
Online measuring device for induced voltage of cable sheath Download PDFInfo
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- CN110702973A CN110702973A CN201910975314.6A CN201910975314A CN110702973A CN 110702973 A CN110702973 A CN 110702973A CN 201910975314 A CN201910975314 A CN 201910975314A CN 110702973 A CN110702973 A CN 110702973A
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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
- G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
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- G—PHYSICS
- G08—SIGNALLING
- G08C—TRANSMISSION SYSTEMS FOR MEASURED VALUES, CONTROL OR SIMILAR SIGNALS
- G08C17/00—Arrangements for transmitting signals characterised by the use of a wireless electrical link
- G08C17/02—Arrangements for transmitting signals characterised by the use of a wireless electrical link using a radio link
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Computer Networks & Wireless Communication (AREA)
- Measurement Of Current Or Voltage (AREA)
Abstract
The invention is suitable for the technical field of power measurement, and provides an on-line measuring device for induced voltage of a cable sheath. The device is directly electrically connected with the metal protective layer of the cable to acquire signals, is not influenced by the magnitude of the induced voltage, has high measurement sensitivity and high accuracy, finds potential fault hidden dangers in time, provides technical basis and reference for adjusting and optimizing a cable circuit grounding mode and selecting the type of the protective layer protector for a cable operation unit, can effectively prevent operation accidents from happening, and prolongs the service life of the medium-high voltage crosslinked cable circuit.
Description
Technical Field
The invention relates to the technical field of power measurement, in particular to an online measurement device for induced voltage of a cable sheath.
Background
When alternating current flows through the core of the single-core power cable, an alternating magnetic field is generated around the alternating current to form magnetic flux linked with a cable loop, and the magnetic flux is simultaneously linked with the metal sheath of the cable, so that induced voltage is generated on the metal sheath. The induced voltage is related to the length of the cable, the longer the length, the higher the induced voltage.
For the safety of the cable, the national standard stipulates that the metal sheath of the ac single-phase cable must be directly grounded, and the normal induced voltage at any point on the metal sheath, which is not grounded, should comply with the following regulations: when the safety measure that the metal protective layer can not be contacted arbitrarily is not taken, the voltage is not more than 50V; unless otherwise, it must not be greater than 100V. In actual operation, the induced voltage of the sheath is abnormally increased due to the occurrence of a ground fault and the like. Therefore, the method has important significance for the online monitoring of the sheath induced voltage or the grounding circulation and the safe operation of the cable.
A conventional sheath induced voltage or ground line circulating current on-line monitoring device, as shown in fig. 1, employs a capacitive voltage divider to divide voltage, employs a CT (current transformer) or a PT (voltage transformer) to electrically isolate input signals, also performs voltage transformation, sends the voltage into a measurement circuit to perform measurement, and finally transmits the measurement result to a monitoring platform through a communication module. For example, the patents CN204575733U, CN209198494U, CN209296797U and CN101825657B all adopt the voltage or current on the CT or PT sensing cable to be sent to the detection circuit for detection.
However, since PT operates based on the electromagnetic induction principle, the primary stage must have enough current to generate an induced magnetic field, and the secondary stage can induce a corresponding voltage. This current is typically nominally 2 mA. The high-voltage-resistant capacitor of the capacitive voltage divider cannot be made large, so that the capacitive reactance is high, the output current of the voltage divider is small, and the primary input current of the PT is small. For example: the capacitance of the voltage divider is 0.1uF, the induction voltage frequency is 50Hz, and the capacitive reactance is 31.8 k; when the induced voltage reaches 50V, the current is 1.57mA, which is already lower than 2 mA. If the induced voltage is lower, the current output by the voltage divider will be smaller. When the primary input current of the PT is insufficient, the secondary output linearity and precision of the PT are poor, so that the whole measuring device is insensitive and low in accuracy. Through practical verification, when the induced voltage is lower than 10V, the conventional monitoring equipment adopting PT has very large measurement result error, and even the voltage cannot be measured completely.
Disclosure of Invention
The invention aims to provide an on-line measuring device for induced voltage of a cable sheath, which adopts a mode of a measuring board and a main control board to replace a PT acquisition mode, and the measuring board transmits a detection signal to the main control board in a wireless transmission mode so as to achieve the purpose of adopting PT for electrical isolation. Because PT is not adopted, an induced voltage signal on the cable metal sheath is directly input into the detection circuit for signal detection after being subjected to voltage division by the capacitive voltage divider, and the defect that the PT can be detected only by larger input current is avoided; the measuring circuit with high input impedance is adopted, large input current is not needed, and normal measurement can still be carried out under the conditions that the induction voltage is small, the voltage of the voltage divider is low, and the output current is small. Therefore, the problems of poor measurement sensitivity, low accuracy and even incapability of measurement under the same condition by adopting PT are solved.
In order to achieve the above object, an embodiment of the present invention provides an online measurement device for induced voltage of a cable sheath, including an electrical connection line, a voltage divider, a measurement board and a main control board, wherein the measurement board includes a measurement board CPU, a measurement circuit and a communication module in wireless communication with the main control board; the main control board comprises a main control board CPU and a communication module which is in wireless communication with the measuring board; the measuring circuit comprises a high input impedance in-phase amplifier, an active rectifying circuit and a filter circuit; the CPU also includes an AD conversion module. The measurement circuit transmits the filtered signals to an AD conversion module of a CPU of the measurement board, the AD conversion module converts analog signals into digital signals and transmits the digital signals to a CPU processor, and the CPU processor analyzes and processes the received digital signals to obtain the magnitude of induction voltage and transmits the magnitude of the induction voltage to a main control board through a wireless communication module.
Furthermore, an isolating switch power supply is also arranged on the measuring board, and the power supply module of the main control board supplies power to the measuring board through the isolating switch power supply.
Furthermore, the main control board also comprises a communication module communicated with the control center.
Further, the voltage divider adopts a capacitive voltage divider.
The invention provides an effective technical means for detecting the induction voltage of the medium-high voltage cable sheath, so as to realize normal and accurate detection and evaluation when the induction voltage of the sheath is small, find potential fault hidden dangers in time, provide technical basis and reference for adjusting and optimizing the grounding mode of a cable line and selecting the type of a sheath protector for a cable operation unit, effectively prevent the occurrence of operation accidents and prolong the service life of the medium-high voltage crosslinked cable line.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments of the present invention or in the description of the prior art will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a prior art induced voltage sensing circuit for a cable metal sheath;
FIG. 2 is an induced voltage detecting apparatus of a metal sheath of a cable according to the present invention;
fig. 3 is a measurement circuit on the measurement board in the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
The following description provides many different embodiments, or examples, for implementing different features of the invention. The particular examples set forth below are illustrative only and are not intended to be limiting.
As shown in fig. 2, an online measurement device for induced voltage of a cable sheath comprises an electrical connection line, a voltage divider, a measurement board and a main control board; one end of the electric connecting wire is directly connected to the outer surface of the cable metal sheath, the other end of the electric connecting wire is connected with the voltage divider, the output end of the voltage divider is connected with the measuring board, and the measuring board is wirelessly connected with the main control board.
The measuring board comprises a measuring board CPU, a measuring circuit and a communication module in wireless communication with the main control board; the main control board comprises a main control board CPU and a communication module which is in wireless communication with the measuring board;
the measuring circuit comprises a high input impedance in-phase amplifier, an active rectifying circuit and a filter circuit; the measuring board CPU also comprises an AD conversion module connected with the output end of the filter circuit of the measuring circuit.
The working principle of the on-line measuring device for the induced voltage of the cable sheath is as follows: the device comprises a metal sheath, a voltage divider, a high input impedance in-phase amplifier, an active rectification circuit, a filter circuit, an AD conversion module, a CPU processor, a wireless communication module and a power supply module, wherein one end of an electric connection wire is connected to the surface of the metal sheath of a cable, the electric connection wire is electrically connected with the metal sheath, the other end of the electric connection wire is connected with the voltage divider, the voltage divider is used for reducing the voltage and is connected to the in-phase input end of the high input impedance in-phase amplifier of a measuring circuit, the signal is amplified by the high input impedance in-phase amplifier and then rectified by the active rectification circuit and filtered by the filter circuit and then output to the AD conversion module of the CPU of the. The main control board CPU receives the information, and when the detected induction voltage value exceeds a certain threshold value, the main control board CPU automatically sends alarm information to prompt surrounding people to keep away as soon as possible so as to avoid safety accidents.
Furthermore, an isolating switch power supply is arranged on the measuring board, and the power supply module of the main control board supplies power to the measuring board through the isolating switch power supply, so that the electrical isolation between the measuring board and the rear-end control circuit is further ensured.
Furthermore, the main control board also comprises a communication module communicated with the control center, the communication module transmits the measured induction voltage information to the control center for unified management, when the induction voltage value exceeds a safety threshold value, an automatic alarm is started to prompt a worker of cable fault at the position, and the worker is dispatched to overhaul the cable fault.
The invention provides an on-line measuring device of induced voltage of a cable sheath, which does not adopt PT for electrical isolation, but directly connects the induced voltage of a metal sheath to a detection circuit of a measuring board for measurement, the measuring board is powered by an isolation power supply, and the measuring result is transmitted to a main control board at the rear end in a serial port isolation mode, thereby achieving the electrical isolation effect of a signal acquisition end and a rear end control end. Because the signal acquisition is directly electrically connected with the metal protective layer of the cable, the device is not influenced by the magnitude of the induced voltage, and has high measurement sensitivity and high accuracy.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (6)
1. An on-line measuring device for induced voltage of a cable sheath is characterized by comprising an electric connecting wire, a voltage divider, a measuring board and a main control board, wherein,
one end of the electric connecting wire is directly and electrically connected with the surface of the cable sheath, the other end of the electric connecting wire is electrically connected with one end of the voltage divider, and the other end of the voltage divider is electrically connected with the measuring plate;
the measuring board comprises a measuring board CPU, a measuring circuit and a communication module in wireless communication with the main control board;
the main control board comprises a main control board CPU and a communication module which is in wireless communication with the measuring board;
the voltage divider, the measuring board and the main control board are respectively grounded.
2. The apparatus for on-line measurement of sheath induced voltage of claim 1 wherein said measurement circuit comprises a high input impedance in-phase amplifier, an active rectification circuit, and a filter circuit;
the output end of the voltage divider is connected with the non-inverting end of a high-input-impedance non-inverting amplifier of the measuring circuit, and the inverting end of the high-input-impedance non-inverting amplifier is connected with a feedback signal;
the output end of the high-input-impedance in-phase amplifier is sequentially connected with the active rectifying circuit and the filter circuit, the output end of the filter circuit is connected with an AD conversion module in the measuring board CPU, signals passing through the AD conversion module are transmitted to the measuring board CPU, and the measuring board CPU analyzes and processes received digital signals to obtain an induction voltage value.
3. The apparatus for on-line measurement of induced voltage of sheath of cable as claimed in claim 1 or 2, wherein the measurement board is further provided with a power supply of a disconnecting switch, and the power supply module of the main control board supplies power to the measurement board through the power supply of the disconnecting switch.
4. The apparatus for on-line measurement of sheath induced voltage of claim 3, wherein the voltage divider is a capacitive voltage divider.
5. The apparatus for on-line measurement of sheath induced voltage as recited in claim 4, wherein said main control board further comprises a communication module for communicating with a remote control center.
6. The apparatus for on-line measurement of induced voltage in sheath of cable of claim 5, wherein an automatic alarm is activated when the remote control center monitors that the induced voltage value exceeds a certain threshold.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910975314.6A CN110702973A (en) | 2019-10-14 | 2019-10-14 | Online measuring device for induced voltage of cable sheath |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910975314.6A CN110702973A (en) | 2019-10-14 | 2019-10-14 | Online measuring device for induced voltage of cable sheath |
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| CN110702973A true CN110702973A (en) | 2020-01-17 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN201910975314.6A Pending CN110702973A (en) | 2019-10-14 | 2019-10-14 | Online measuring device for induced voltage of cable sheath |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112730952A (en) * | 2020-12-29 | 2021-04-30 | 康威通信技术股份有限公司 | High tension cable sheath ground connection case detection device |
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|---|---|---|---|---|
| CN201229389Y (en) * | 2008-07-24 | 2009-04-29 | 福建省泉州电业局 | Cable sheath insulation on-line monitoring device |
| CN101825657A (en) * | 2010-05-12 | 2010-09-08 | 国网电力科学研究院 | Medium-high voltage single-core crosslinked cable induction voltage and circular-current online detection method and device |
| CN201945681U (en) * | 2010-12-22 | 2011-08-24 | 上海市电力公司 | Online monitoring device for capacitor voltage transformer |
| CN202994894U (en) * | 2012-12-17 | 2013-06-12 | 湖南继善高科技有限公司 | High-precision isolated measurement device for high-voltage signals |
| US20160238648A1 (en) * | 2015-02-12 | 2016-08-18 | Hagenuk Kmt Kabelmesstechnik Gmbh | Circuit Arrangement for Cable Checking, Cable Testing, Cable Diagnosis and/or Cable Fault Localization and Device with a Circuit Arrangement of that Type |
| CN109298268A (en) * | 2018-11-09 | 2019-02-01 | 深圳供电局有限公司 | High-voltage cable monitoring device |
| CN109521335A (en) * | 2018-11-16 | 2019-03-26 | 国网江苏省电力有限公司盐城供电分公司 | It is a kind of to take the high-voltage cable insulating state on-line detecting system that powered based on self-induction |
| CN209446711U (en) * | 2019-02-01 | 2019-09-27 | 北京杰安源科技有限公司 | High-tension cable is cross interconnected and insulated on-line monitoring system |
-
2019
- 2019-10-14 CN CN201910975314.6A patent/CN110702973A/en active Pending
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201229389Y (en) * | 2008-07-24 | 2009-04-29 | 福建省泉州电业局 | Cable sheath insulation on-line monitoring device |
| CN101825657A (en) * | 2010-05-12 | 2010-09-08 | 国网电力科学研究院 | Medium-high voltage single-core crosslinked cable induction voltage and circular-current online detection method and device |
| CN201945681U (en) * | 2010-12-22 | 2011-08-24 | 上海市电力公司 | Online monitoring device for capacitor voltage transformer |
| CN202994894U (en) * | 2012-12-17 | 2013-06-12 | 湖南继善高科技有限公司 | High-precision isolated measurement device for high-voltage signals |
| US20160238648A1 (en) * | 2015-02-12 | 2016-08-18 | Hagenuk Kmt Kabelmesstechnik Gmbh | Circuit Arrangement for Cable Checking, Cable Testing, Cable Diagnosis and/or Cable Fault Localization and Device with a Circuit Arrangement of that Type |
| CN109298268A (en) * | 2018-11-09 | 2019-02-01 | 深圳供电局有限公司 | High-voltage cable monitoring device |
| CN109521335A (en) * | 2018-11-16 | 2019-03-26 | 国网江苏省电力有限公司盐城供电分公司 | It is a kind of to take the high-voltage cable insulating state on-line detecting system that powered based on self-induction |
| CN209446711U (en) * | 2019-02-01 | 2019-09-27 | 北京杰安源科技有限公司 | High-tension cable is cross interconnected and insulated on-line monitoring system |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112730952A (en) * | 2020-12-29 | 2021-04-30 | 康威通信技术股份有限公司 | High tension cable sheath ground connection case detection device |
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Application publication date: 20200117 |
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