CN111679162B - Insulation monitoring method and device for transformer substation cable - Google Patents
Insulation monitoring method and device for transformer substation cableInfo
- Publication number
- CN111679162B CN111679162B CN202010488581.3A CN202010488581A CN111679162B CN 111679162 B CN111679162 B CN 111679162B CN 202010488581 A CN202010488581 A CN 202010488581A CN 111679162 B CN111679162 B CN 111679162B
- Authority
- CN
- China
- Prior art keywords
- current
- phase
- cable
- phase voltage
- voltage
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000009413 insulation Methods 0.000 title claims abstract description 51
- 238000012544 monitoring process Methods 0.000 title claims abstract description 35
- 238000000034 method Methods 0.000 title claims abstract description 33
- 230000032683 aging Effects 0.000 claims abstract description 49
- 230000008859 change Effects 0.000 claims abstract description 36
- 238000004458 analytical method Methods 0.000 claims abstract description 12
- 238000005457 optimization Methods 0.000 claims abstract description 7
- 238000005070 sampling Methods 0.000 claims description 98
- 238000012806 monitoring device Methods 0.000 claims description 17
- 238000009499 grossing Methods 0.000 claims description 14
- 238000012545 processing Methods 0.000 claims description 14
- 230000008569 process Effects 0.000 claims description 5
- 239000004020 conductor Substances 0.000 description 25
- 230000001052 transient effect Effects 0.000 description 14
- 239000003990 capacitor Substances 0.000 description 8
- 238000005516 engineering process Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Abstract
The invention provides an insulation monitoring method and device for a transformer substation cable, comprising the following steps: acquiring three-phase voltage, three-phase current, grounding wire current and joint temperature of a transformer substation cable; performing optimization treatment on the three-phase voltage, the three-phase current and the ground wire current to obtain the treated three-phase voltage, three-phase current and ground wire current; and analyzing the change trend of the processed three-phase voltage and three-wire current, comparing the joint temperature and the processed grounding wire current with corresponding preset thresholds respectively, and judging the aging condition of the insulating layer of the cable according to the analysis result and the comparison result. The cable is insulated and monitored from two aspects of an electrical value and a non-electrical value, the insulation aging condition of the cable can be comprehensively reflected from multiple angles, meanwhile, the error caused by the influence of uncontrollable factors on a monitoring result can be reduced by collecting various characteristic quantities, and the accuracy and the reliability of insulation monitoring are improved.
Description
Technical Field
The invention belongs to the field of insulation monitoring, and particularly relates to an insulation monitoring method and device for a transformer substation cable.
Background
With the maturity of the manufacturing technology of the cable and the reduction of the price, in order to improve the reliability of power supply and reduce the municipal land used for erecting the tower, and simultaneously avoid single-phase grounding faults caused by various reasons, the traditional overhead lines are increasingly replaced by the cable. With the increase of service life, the insulating layer of the cable is easily aged in various forms under the influence of electric field, temperature, humidity, chemical corrosion and mechanical stress, so that the insulating layer is broken down to cause single-phase grounding faults, and the reliability of urban power supply is affected
In order to effectively monitor the insulation state of the cable, the characteristic quantity monitored in the prior art is single and is easily influenced by noise of an operation environment, the aging degree is difficult to be comprehensively and effectively reflected, and the insulation aging monitoring effect is not ideal.
Disclosure of Invention
In order to solve the defects and shortcomings in the prior art, the invention provides an insulation monitoring method of a transformer substation cable, which comprises the following steps:
acquiring three-phase voltage, three-phase current, grounding wire current and joint temperature of a transformer substation cable;
Performing optimization treatment on the three-phase voltage, the three-phase current and the ground wire current to obtain the treated three-phase voltage, three-phase current and ground wire current;
And analyzing the change trend of the processed three-phase voltage and three-wire current, comparing the joint temperature and the processed grounding wire current with corresponding preset thresholds respectively, and judging the aging condition of the insulating layer of the cable according to the analysis result and the comparison result.
Optionally, the optimizing the three-phase voltage, the three-phase current and the ground line current to obtain the processed three-phase voltage, three-phase current and ground line current includes:
Smoothing the three-phase voltage U (T) and the three-phase current I 1 (T) at T acquired in the sampling total time T respectively through a root mean square formula to obtain continuous three-phase voltage U and three-phase current I 1;
the root mean square formula is:
Wherein T is the total sampling time, the unit is seconds, and the value range of T is a positive integer; n is the number of discrete values acquired in the total sampling time, and is calculated by the product of the total sampling time T and the sampling rate, and the value range of N is a positive integer; t is the sampling time; the value ranges of U, I 1、t、u(t)、i1 (t) are positive numbers.
Optionally, the optimizing processing is performed on the three-phase voltage, the three-phase current and the ground wire current to obtain the processed three-phase voltage, three-phase current and ground wire current, and the method further includes:
Smoothing the current I 2 (T) of the grounding wire at T time acquired in the sampling total time T through a root mean square formula to obtain a continuous current I 2 of the grounding wire;
the root mean square formula is:
Wherein T is the total sampling time, the unit is seconds, and the value range of T is a positive integer; n is the number of discrete values acquired in the total sampling time, and is calculated by the product of the total sampling time T and the sampling rate, and the value range of N is a positive integer; t is the sampling time; the value ranges of the I 2、t、i2 (t) are positive numbers.
Optionally, the analyzing the change trend of the processed three-phase voltage and three-wire current, comparing the joint temperature and the processed ground wire current with corresponding preset thresholds, and determining the aging condition of the insulating layer of the cable according to the analysis result and the comparison result, including:
Respectively acquiring the change rates of the processed three-phase voltage and three-phase current, matching the obtained change rates with the reference change rates in a pre-established fault database, and when the matching degree of the change rates of the three-phase voltage and the three-phase current is larger than a set fault threshold value, judging that the cable has faults due to ageing of an insulating layer and outputting fault alarm information;
If no fault warning information is output, judging that the cable is aged when the current of the grounding wire is larger than a preset current threshold value of the grounding wire, and outputting aging warning information; and when the joint temperature is greater than a preset cable joint temperature threshold, judging that the cable is aged, and outputting aging early warning information.
Optionally, the insulation monitoring method obtains three-phase voltage, three-phase current, grounding wire current and joint temperature of the substation cable through a sensor module, wherein the sensor module comprises a voltage acquisition module, a current acquisition module and a temperature acquisition module;
The voltage acquisition module comprises a voltage sensor for acquiring three-phase voltages and an amplifier for amplifying the acquired three-phase voltages;
The current acquisition module comprises a current sensor for acquiring three-phase current and ground wire current and an amplifier for amplifying the acquired three-phase current and ground wire current;
The temperature acquisition module comprises a thermistor for acquiring the joint temperature and an amplifier for amplifying the acquired joint temperature.
The invention also provides an insulation monitoring device of the transformer substation cable based on the same thought, wherein the insulation monitoring device comprises:
sampling device: the method comprises the steps of acquiring three-phase voltage, three-phase current, grounding wire current and joint temperature of a transformer substation cable;
A data processing device: the method comprises the steps of carrying out optimization treatment on three-phase voltage, three-phase current and grounding wire current to obtain treated three-phase voltage, three-phase current and grounding wire current;
Monitoring device: the method is used for analyzing the change trend of the processed three-phase voltage and three-wire current, comparing the joint temperature and the processed grounding wire current with corresponding preset thresholds respectively, and judging the aging condition of the insulating layer of the cable according to the analysis result and the comparison result.
Optionally, the data processing device is specifically configured to:
Smoothing the three-phase voltage U (T) and the three-phase current I 1 (T) at T acquired in the sampling total time T respectively through a root mean square formula to obtain continuous three-phase voltage U and three-phase current I 1;
the root mean square formula is:
Wherein T is the total sampling time, the unit is seconds, and the value range of T is a positive integer; n is the number of discrete values acquired in the total sampling time, and is calculated by the product of the total sampling time T and the sampling rate, and the value range of N is a positive integer; t is the sampling time; the value ranges of U, I 1、t、u(t)、i1 (t) are positive numbers.
Optionally, the data processing device is further configured to:
Smoothing the current I 2 (T) of the grounding wire at T time acquired in the sampling total time T through a root mean square formula to obtain a continuous current I 2 of the grounding wire;
the root mean square formula is:
Wherein T is the total sampling time, the unit is seconds, and the value range of T is a positive integer; n is the number of discrete values acquired in the total sampling time, and is calculated by the product of the total sampling time T and the sampling rate, and the value range of N is a positive integer; t is the sampling time; the value ranges of the I 2、t、i2 (t) are positive numbers.
Optionally, the monitoring device is specifically configured to:
Respectively acquiring the change rates of the processed three-phase voltage and three-phase current, matching the obtained change rates with the reference change rates in a pre-established fault database, and when the matching degree of the change rates of the three-phase voltage and the three-phase current is larger than a set fault threshold value, judging that the cable has faults due to ageing of an insulating layer and outputting fault alarm information;
If no fault warning information is output, judging that the cable is aged when the current of the grounding wire is larger than a preset current threshold value of the grounding wire, and outputting aging warning information; and when the joint temperature is greater than a preset cable joint temperature threshold, judging that the cable is aged, and outputting aging early warning information.
Optionally, the sampling device obtains three-phase voltage, three-phase current, grounding wire current and joint temperature of the substation cable through a sensor module, and the sensor module comprises a voltage acquisition module, a current acquisition module and a temperature acquisition module;
the voltage acquisition module comprises a voltage sensor for acquiring three-phase voltages of a transformer substation cable and an amplifier for amplifying the acquired three-phase voltages;
The current acquisition module comprises a current sensor for acquiring three-phase current and ground wire current of the transformer substation cable and an amplifier for amplifying the acquired three-phase current and ground wire current;
the temperature acquisition module comprises a thermistor for acquiring the joint temperature of the substation cable and an amplifier for amplifying the acquired joint temperature.
The technical scheme provided by the invention has the beneficial effects that:
The cable insulation monitoring device has the advantages that the conductor voltage current, the ground wire current and the joint temperature of the cable are respectively collected to serve as characteristic quantities, the cable is subjected to insulation monitoring from two aspects of an electrical value and a non-electrical value, the insulation aging condition of the cable can be comprehensively reflected from multiple angles, meanwhile, the collection of various characteristic quantities can reduce errors caused by influences of uncontrollable factors on monitoring results, and the accuracy and reliability of insulation monitoring are improved.
Drawings
In order to more clearly illustrate the technical solutions of the present invention, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic flow chart of an insulation monitoring method for a substation cable according to the present invention;
FIG. 2 is a circuit diagram of a three-phase voltage acquisition cable conductor;
FIG. 3 is a circuit diagram of the acquisition of three phase currents and ground currents of a cable conductor;
FIG. 4 is a circuit diagram of the junction temperature of the acquisition cable;
fig. 5 is a block diagram of an insulation monitoring device for a substation cable according to the present invention.
Detailed Description
In order to make the structure and advantages of the present invention more apparent, the structure of the present invention will be further described with reference to the accompanying drawings.
Example 1
As shown in fig. 1, the invention provides an insulation monitoring method for a substation cable, which comprises the following steps:
s1: acquiring three-phase voltage, three-phase current, grounding wire current and joint temperature of a transformer substation cable;
S2: performing optimization treatment on the three-phase voltage, the three-phase current and the ground wire current to obtain the treated three-phase voltage, three-phase current and ground wire current;
s3: and analyzing the change trend of the processed three-phase voltage and three-wire current, comparing the joint temperature and the processed grounding wire current with corresponding preset thresholds respectively, and judging the aging condition of the insulating layer of the cable according to the analysis result and the comparison result.
Data capable of reflecting insulation aging conditions are collected from three angles of a conductor, a grounding wire and a connector of the cable respectively, the cable is subjected to insulation monitoring from two aspects of an electrical value and a non-electrical value, the insulation aging conditions of the cable can be comprehensively reflected from multiple angles, meanwhile, various characteristic quantities are collected, errors caused by the influence of uncontrollable factors on monitoring results can be reduced, and accuracy and reliability of insulation monitoring are improved.
The obtaining of the three-phase voltage, the three-phase current, the ground wire current and the joint temperature of the substation cable comprises the following steps: acquiring three-phase voltage and three-phase current of a cable conductor based on a preset sampling rate, and grounding wire current of the cable; the joint temperature of the cable is obtained through a temperature sensor.
A PCI bus-based data acquisition card PCI6221 is used by the american NI company that integrates a-D conversion and digital I/O functions. To ensure accurate measurement and reconstruction of the signal, the highest frequency of the ground line current and the nyquist sampling theorem are used as the sampling rate, which in this embodiment is 1.2MHz.
In the present embodiment, the model is selected to beThe voltage sensor is a capacitive sensor, and can effectively prevent overvoltage and overcurrent impact due to the fact that the piezoresistor and the fusing resistor are arranged in the sensor, and is good in linearity, high in measurement accuracy and capable of meeting the requirement of insulation monitoring. The circuit for collecting three-phase voltage of cable conductor is as shown in fig. 2, the diode VD1 that establishes ties in proper order, VD3 establishes ties with establishing ties in proper order with establishing ties with VD2 and VD4 parallelly connected, electric capacity C1 establishes ties with diode VD2, resistance R2 again establishes ties with electric capacity C1, transient diode TVS establishes ties at the both ends of resistance R2, electric capacity C2 establishes ties with resistance R3 again establishes ties with transient diode TVS again, electric capacity C2 connects ground with transient diode TVS's connected node, the inverted input of operational amplifier a is connected through resistance R4 in the connected node of resistance R3 and electric capacity C2, the homophase input of operational amplifier a is connected to electric capacity C3, the first end of resistance R4 links to each other with the first end of electric capacity C3, the second end of electric capacity C3 is grounded through resistance R6, resistance R5 connects between operational amplifier a's inverted input and output, diode VD5 establishes ties with VD6, operational amplifier's output passes through the intermediate node of diode VD5 and VD6, the second termination of diode VD 6. The input alternating voltage is 57.7V, the input voltage is regulated through the circuit structure, and the collected three-phase voltage of the cable conductor is obtained at the output end of the operational amplifier A.
In this embodiment, a current sensor of model SCT254FK type is selected, and the current can be converted from 0-5A to 0-2.5mA, so as to collect three-phase current of the cable conductor subsequently. The circuit for collecting three-phase current and ground wire current of cable conductor is as shown in figure 3, the diodes VD1, VD3 that establish ties in proper order are established ties with VD2 and VD4 that establish ties in proper order in parallel, electric capacity C1 establishes ties with diode VD2, VD4, electric capacity R2 establishes ties with transient diode TVS after establishing ties with electric capacity C1 again, electric capacity C2 establishes ties with transient diode TVS again after establishing ties with electric capacity R3, electric capacity C2 connects the inverting input terminal of fortune amplifier A through electric capacity R4 in the junction of electric capacity R3 and electric capacity C2, the homophase input of fortune amplifier A is connected to electric capacity C3, the first end of electric capacity R4 links to each other with the first end of electric capacity C3, the second end of electric capacity VD is earthed through electric capacity VD6, electric capacity R5 is connected between the inverting input of fortune amplifier A and output, diode VD5 establishes ties with 6, the output of fortune amplifier A passes through the intermediate node of diode VD5 and VD6, the second end of fortune amplifier VD6 is earthed, obtain the three-phase current of cable conductor of fortune amplifier A.
In the embodiment, a temperature sensor with the model number of JcJ G is selected, a thermal resistance type Pt1000 is selected as an input signal, the temperature measuring range is-50-340 ℃, and the output is direct current of 0-5V. The circuit for collecting the joint temperature of the cable is shown in fig. 4, the first end of the thermosensitive electric group R2 is connected with the first end of the diode VD5, the second end of the thermosensitive electric group R2 sequentially passes through the transient diode TVS, the resistor R3 and the resistor R4 to be connected with the inverting input end of the operational amplifier A, the first end of the capacitor C2 is connected between the resistor R3 and the resistor R4, the other end of the capacitor C2 is connected with the second end of the transient diode and grounded, the capacitor C3 is connected with the non-inverting input end of the operational amplifier A, the first end of the resistor R4 is connected with the first end of the capacitor C3 and grounded through the resistor R6, the resistor R5 is connected between the inverting input end and the output end of the operational amplifier A, the diodes VD5 and VD6 are connected in series, the output end of the operational amplifier A passes through the intermediate node of the diodes VD5 and VD6, the second end of the diode VD6 is grounded, and the current value corresponding to the joint temperature of the cable is obtained at the output end of the operational amplifier A.
The three-phase voltage, the three-phase current and the ground wire current are optimized to obtain the processed three-phase voltage, the processed three-phase current and the processed ground wire current, wherein the three-phase voltage, the processed three-phase current and the processed ground wire current respectively carry out smoothing treatment on the discrete voltage and the discrete current acquired in the sampling total time T through a root mean square formula to obtain continuous three-phase voltage and continuous three-phase current;
the root mean square formula is:
Wherein T is the total sampling time, the unit is seconds, and T is a positive integer; n is the number of discrete values acquired in the total sampling time, and is calculated by the product of the total sampling time T and the sampling rate, and N is a positive integer;
U is continuous three-phase voltage, I 1 is continuous three-phase current, t is sampling time, three-phase voltage when U (t) is t, three-phase current when I 1 (t) is t, and U, I 1、t、u(t)、i1 (t) are positive numbers.
The three-phase voltage, the three-phase current and the ground wire current are optimized to obtain the processed three-phase voltage, three-phase current and ground wire current, and the method further comprises the step of respectively smoothing the ground wire current acquired in the sampling total time T through a root mean square formula to obtain continuous ground wire current;
the root mean square formula is:
Wherein T is the total sampling time, the unit is seconds, and T is a positive integer; n is the number of discrete values acquired in the total sampling time, and is calculated by the product of the total sampling time T and the sampling rate, and N is a positive integer;
I 2 is a continuous ground line current, t is a ground line current at sampling time, I 2 (t) is t, and I 2、t、i2 (t) is a positive number.
Since the voltage sensor and the current sensor are sampled based on a preset sampling rate, the acquired data is discrete. The cable insulation aging in practical application is a slow gradual change process, so that continuous data needs to be monitored, the aging condition of an insulation layer can be effectively reflected from the angle of data change trend, and the sensitivity of insulation monitoring is improved.
In this embodiment, the three-phase voltage, three-phase current and ground wire current of the conductor are optimized by the industrial personal computer, the IIPC4001D type industrial personal computer is selected as a hardware platform, and LabVIEW software is carried for data processing and display. The industrial personal computer is provided with the keyboard, is convenient to operate, is convenient for field work, is provided with the 5.7 inch TFT display screen, and can display data in real time. The industrial personal computer receives the collected three-phase voltage, three-phase current, grounding wire current and current corresponding to the joint temperature through a power carrier of the power system.
The power carrier uses the power line as a propagation medium, other channels are not required to be built by additional investment, and along with the continuous progress of technology, china develops into a power line capable of simultaneously transmitting data, voice, video and power in a four-wire manner in a medium-high voltage distribution line. The data obtained by the insulation monitoring can be transmitted by using a power carrier as well. When the power carrier wave is transmitted, the voltage sensor, the current sensor and the temperature sensor collect data, then a proper coding and modulation technology is selected to process the collected signals into high-frequency signals and transmit the high-frequency signals on a power line, and finally the high-frequency signals are demodulated through a demodulator, and the demodulated data are transmitted to an industrial personal computer.
The analysis of the change trend of the processed three-phase voltage and three-wire current, the comparison of the joint temperature and the processed grounding wire current with corresponding preset thresholds, and the judgment of the aging condition of the insulating layer of the cable according to the analysis result and the comparison result, comprises the following steps: respectively acquiring the three-phase voltage and the three-phase current change rate of the processed conductor; matching the obtained change rate with historical data in a fault database, and when the matching degree is simultaneously larger than a set fault threshold value, judging that the cable has faults due to ageing of an insulating layer, and outputting fault alarm information; if no fault warning information is output, comparing the ground wire current with a preset ground wire current threshold value, if the ground wire current is larger than the ground wire current threshold value, judging that the cable is aged, outputting ageing early warning information, simultaneously comparing the joint temperature with a preset cable joint temperature threshold value, and if the joint temperature is larger than the cable joint temperature threshold value, judging that the cable is aged, and outputting ageing early warning information.
The method for judging the aging condition of the insulating layer of the cable is realized based on LabVIEW software in the industrial personal computer, the fault early warning information and the aging early warning information can be displayed through a display screen of the industrial personal computer, and the phase voltages and the phase currents of the A phase, the B phase and the C phase of the cable conductor, the ground wire current value and the joint temperature value corresponding to the three-phase position are displayed on a monitoring interface, so that operation and maintenance personnel can conveniently check and know the aging condition of the insulating layer of the cable in time.
The insulation monitoring method of the substation cable is described below with reference to specific examples, and specifically includes:
Step one: based on the sampling rate of 1.2MHz, three-phase voltage of the cable conductor is obtained through a voltage sensor, three-phase current of the cable conductor and ground wire current of the cable are obtained through a current sensor, and meanwhile, a current value I 3 corresponding to joint temperature of the cable is obtained through a temperature sensor.
Step two: smoothing the discrete voltage and the discrete current acquired in each second through a root mean square formula to obtain continuous three-phase voltage and continuous three-phase current;
the root mean square formula is:
Wherein T is the total sampling time in seconds, t=1; n is the number of discrete values acquired in the total sampling time, and is calculated by the product of the total sampling time T and the sampling rate, and N is a positive integer;
U is continuous three-phase voltage, I 1 is continuous three-phase current, t is sampling time, three-phase voltage when U (t) is t, three-phase current when I 1 (t) is t, and U, I 1、t、u(t)、i1 (t) are positive numbers.
Smoothing the collected electric wire current in the sampling total time T through a root mean square formula to obtain continuous electric wire current;
the root mean square formula is:
Wherein T is the total sampling time in seconds, t=1; n is the number of discrete values acquired in the total sampling time, and is calculated by the product of the total sampling time T and the sampling rate, and N is a positive integer;
I 2 is a continuous ground line current, t is a ground line current at sampling time, I 2 (t) is t, and I 2、t、i2 (t) is a positive number.
Step three: and transmitting the I 3 obtained in the first step and the U, I 1、I2 obtained in the second step to the industrial personal computer through the power carrier.
Step four: the method comprises the steps of analyzing U, I 1、I2 and I 3 through LabVIEW software in an industrial personal computer, respectively obtaining the change rate of U, I 1 relative to the last second, matching the obtained change rate with historical data in a fault database, judging that a cable has faults due to ageing of an insulating layer when the matching degree is simultaneously more than 90%, and outputting fault alarm information; if no fault warning information is output, comparing the I 2 with a preset grounding wire current threshold value, if the current threshold value is larger than the grounding wire current threshold value, judging that the cable is aged, outputting ageing early warning information, simultaneously comparing the joint temperature corresponding to the I 3 with a preset cable joint temperature threshold value, and if the current threshold value is larger than the cable joint temperature threshold value, judging that the cable is aged, and outputting ageing early warning information.
Example two
As shown in fig. 5, the present invention proposes an insulation monitoring device 4 for a substation cable, the insulation monitoring device 4 comprising:
Sampling device 41: the method comprises the steps of acquiring three-phase voltage, three-phase current, grounding wire current and joint temperature of a transformer substation cable;
Data processing device 42: the method comprises the steps of carrying out optimization treatment on three-phase voltage, three-phase current and grounding wire current to obtain treated three-phase voltage, three-phase current and grounding wire current;
monitoring device 43: the method is used for analyzing the change trend of the processed three-phase voltage and three-wire current, comparing the joint temperature and the processed grounding wire current with corresponding preset thresholds respectively, and judging the aging condition of the insulating layer of the cable according to the analysis result and the comparison result.
Data capable of reflecting insulation aging conditions are collected from three angles of a conductor, a grounding wire and a connector of the cable respectively, the cable is subjected to insulation monitoring from two aspects of an electrical value and a non-electrical value, the insulation aging conditions of the cable can be comprehensively reflected from multiple angles, meanwhile, various characteristic quantities are collected, errors caused by the influence of uncontrollable factors on monitoring results can be reduced, and accuracy and reliability of insulation monitoring are improved.
The sampling device 41 is specifically configured to: acquiring three-phase voltage and three-phase current of a cable conductor based on a preset sampling rate, and grounding wire current of the cable; the joint temperature of the cable is obtained through a temperature sensor.
A PCI bus-based data acquisition card PCI6221 is used by the american NI company that integrates a-D conversion and digital I/O functions. To ensure accurate measurement and reconstruction of the signal, the highest frequency of the ground line current and the nyquist sampling theorem are used as the sampling rate, which in this embodiment is 1.2MHz.
In the present embodiment, the model is selected to beThe voltage sensor is a capacitive sensor, and can effectively prevent overvoltage and overcurrent impact due to the fact that the piezoresistor and the fusing resistor are arranged in the sensor, and is good in linearity, high in measurement accuracy and capable of meeting the requirement of insulation monitoring. The circuit for collecting three-phase voltage of cable conductor is as shown in fig. 2, the diode VD1 that establishes ties in proper order, VD3 establishes ties with establishing ties in proper order with establishing ties with VD2 and VD4 parallelly connected, electric capacity C1 establishes ties with diode VD2, resistance R2 again establishes ties with electric capacity C1, transient diode TVS establishes ties at the both ends of resistance R2, electric capacity C2 establishes ties with resistance R3 again establishes ties with transient diode TVS again, electric capacity C2 connects ground with transient diode TVS's connected node, the inverted input of operational amplifier a is connected through resistance R4 in the connected node of resistance R3 and electric capacity C2, the homophase input of operational amplifier a is connected to electric capacity C3, the first end of resistance R4 links to each other with the first end of electric capacity C3, the second end of electric capacity C3 is grounded through resistance R6, resistance R5 connects between operational amplifier a's inverted input and output, diode VD5 establishes ties with VD6, operational amplifier's output passes through the intermediate node of diode VD5 and VD6, the second termination of diode VD 6. The input alternating voltage is 57.7V, the input voltage is regulated through the circuit structure, and the collected three-phase voltage of the cable conductor is obtained at the output end of the operational amplifier A.
In this embodiment, a current sensor of model SCT254FK type is selected, and the current can be converted from 0-5A to 0-2.5mA, so as to collect three-phase current of the cable conductor subsequently. The circuit for collecting three-phase current and ground wire current of cable conductor is as shown in figure 3, the diodes VD1, VD3 that establish ties in proper order are established ties with VD2 and VD4 that establish ties in proper order in parallel, electric capacity C1 establishes ties with diode VD2, VD4, electric capacity R2 establishes ties with transient diode TVS after establishing ties with electric capacity C1 again, electric capacity C2 establishes ties with transient diode TVS again after establishing ties with electric capacity R3, electric capacity C2 connects the inverting input terminal of fortune amplifier A through electric capacity R4 in the junction of electric capacity R3 and electric capacity C2, the homophase input of fortune amplifier A is connected to electric capacity C3, the first end of electric capacity R4 links to each other with the first end of electric capacity C3, the second end of electric capacity VD is earthed through electric capacity VD6, electric capacity R5 is connected between the inverting input of fortune amplifier A and output, diode VD5 establishes ties with 6, the output of fortune amplifier A passes through the intermediate node of diode VD5 and VD6, the second end of fortune amplifier VD6 is earthed, obtain the three-phase current of cable conductor of fortune amplifier A.
In the embodiment, a temperature sensor with the model number of JcJ G is selected, a thermal resistance type Pt1000 is selected as an input signal, the temperature measuring range is-50-340 ℃, and the output is direct current of 0-5V. The circuit for collecting the joint temperature of the cable is shown in fig. 4, the first end of the thermosensitive electric group R2 is connected with the first end of the diode VD5, the second end of the thermosensitive electric group R2 sequentially passes through the transient diode TVS, the resistor R3 and the resistor R4 to be connected with the inverting input end of the operational amplifier A, the first end of the capacitor C2 is connected between the resistor R3 and the resistor R4, the other end of the capacitor C2 is connected with the second end of the transient diode and grounded, the capacitor C3 is connected with the non-inverting input end of the operational amplifier A, the first end of the resistor R4 is connected with the first end of the capacitor C3 and grounded through the resistor R6, the resistor R5 is connected between the inverting input end and the output end of the operational amplifier A, the diodes VD5 and VD6 are connected in series, the output end of the operational amplifier A passes through the intermediate node of the diodes VD5 and VD6, the second end of the diode VD6 is grounded, and the current value corresponding to the joint temperature of the cable is obtained at the output end of the operational amplifier A.
The data processing device 42 is specifically configured to perform smoothing processing on the discrete voltage and the discrete current acquired in the sampling total time T through a root mean square formula, so as to obtain continuous three-phase voltage and continuous three-phase current;
the root mean square formula is:
Wherein T is the total sampling time, the unit is seconds, and T is a positive integer; n is the number of discrete values acquired in the total sampling time, and is calculated by the product of the total sampling time T and the sampling rate, and N is a positive integer;
U is continuous three-phase voltage, I 1 is continuous three-phase current, t is sampling time, three-phase voltage when U (t) is t, three-phase current when I 1 (t) is t, and U, I 1、t、u(t)、i1 (t) are positive numbers.
The data processing device 42 is further configured to perform smoothing processing on the collected wire-connection currents in the sampling total time T through a root mean square formula, so as to obtain continuous wire-connection currents;
the root mean square formula is:
Wherein T is the total sampling time, the unit is seconds, and T is a positive integer; n is the number of discrete values acquired in the total sampling time, and is calculated by the product of the total sampling time T and the sampling rate, and N is a positive integer;
I 2 is a continuous ground line current, t is a ground line current at sampling time, I 2 (t) is t, and I 2、t、i2 (t) is a positive number.
Since the voltage sensor and the current sensor are sampled based on a preset sampling rate, the acquired data is discrete. The cable insulation aging in practical application is a slow gradual change process, so that continuous data needs to be monitored, the aging condition of an insulation layer can be effectively reflected from the angle of data change trend, and the sensitivity of insulation monitoring is improved.
In this embodiment, the three-phase voltage, three-phase current and ground wire current of the conductor are optimized by the industrial personal computer, the IIPC4001D type industrial personal computer is selected as a hardware platform, and LabVIEW software is carried for data processing and display. The industrial personal computer is provided with the keyboard, is convenient to operate, is convenient for field work, is provided with the 5.7 inch TFT display screen, and can display data in real time. The industrial personal computer receives the collected three-phase voltage, three-phase current, grounding wire current and current corresponding to the joint temperature through a power carrier of the power system.
The power carrier uses the power line as a propagation medium, other channels are not required to be built by additional investment, and along with the continuous progress of technology, china develops into a power line capable of simultaneously transmitting data, voice, video and power in a four-wire manner in a medium-high voltage distribution line. The data obtained by the insulation monitoring can be transmitted by using a power carrier as well. When the power carrier wave is transmitted, the voltage sensor, the current sensor and the temperature sensor collect data, then a proper coding and modulation technology is selected to process the collected signals into high-frequency signals and transmit the high-frequency signals on a power line, and finally the high-frequency signals are demodulated through a demodulator, and the demodulated data are transmitted to an industrial personal computer.
The monitoring device 43 is specifically configured to: respectively acquiring the three-phase voltage and the three-phase current change rate of the processed conductor; matching the obtained change rate with historical data in a fault database, and when the matching degree is simultaneously larger than a set fault threshold value, judging that the cable has faults due to ageing of an insulating layer, and outputting fault alarm information; if no fault warning information is output, comparing the ground wire current with a preset ground wire current threshold value, if the ground wire current is larger than the ground wire current threshold value, judging that the cable is aged, outputting ageing early warning information, simultaneously comparing the joint temperature with a preset cable joint temperature threshold value, and if the joint temperature is larger than the cable joint temperature threshold value, judging that the cable is aged, and outputting ageing early warning information.
The method for judging the aging condition of the insulating layer of the cable is realized based on LabVIEW software in the industrial personal computer, the fault early warning information and the aging early warning information can be displayed through a display screen of the industrial personal computer, and the phase voltages and the phase currents of the A phase, the B phase and the C phase of the cable conductor, the ground wire current value and the joint temperature value corresponding to the three-phase position are displayed on a monitoring interface, so that operation and maintenance personnel can conveniently check and know the aging condition of the insulating layer of the cable in time.
The various numbers in the above embodiments are for illustration only and do not represent the order of assembly or use of the various components.
The foregoing is illustrative of the present invention and is not to be construed as limiting thereof, but rather, the present invention is to be construed as limited to the appended claims.
Claims (8)
1. An insulation monitoring method for a substation cable, which is characterized by comprising the following steps:
acquiring three-phase voltage, three-phase current, grounding wire current and joint temperature of a transformer substation cable;
Performing optimization treatment on the three-phase voltage, the three-phase current and the ground wire current to obtain the treated three-phase voltage, three-phase current and ground wire current;
Analyzing the change trend of the processed three-phase voltage and three-wire current, respectively comparing the joint temperature and the processed grounding wire current with corresponding preset thresholds, and judging the aging condition of the insulating layer of the cable according to the analysis result and the comparison result;
the analysis of the change trend of the processed three-phase voltage and three-wire current, the comparison of the joint temperature and the processed grounding wire current with corresponding preset thresholds, and the judgment of the aging condition of the insulating layer of the cable according to the analysis result and the comparison result, comprises the following steps:
Respectively acquiring the change rates of the processed three-phase voltage and three-phase current, matching the obtained change rates with the reference change rates in a pre-established fault database, and when the matching degree of the change rates of the three-phase voltage and the three-phase current is larger than a set fault threshold value, judging that the cable has faults due to ageing of an insulating layer and outputting fault alarm information;
If no fault warning information is output, judging that the cable is aged when the current of the grounding wire is larger than a preset current threshold value of the grounding wire, and outputting aging warning information; and when the joint temperature is greater than a preset cable joint temperature threshold, judging that the cable is aged, and outputting aging early warning information.
2. The insulation monitoring method of a substation cable according to claim 1, wherein the optimizing the three-phase voltage, the three-phase current and the ground line current to obtain the processed three-phase voltage, three-phase current and ground line current comprises:
Smoothing the three-phase voltage U (T) and the three-phase current I 1 (T) at T acquired in the sampling total time T respectively through a root mean square formula to obtain continuous three-phase voltage U and three-phase current I 1;
the root mean square formula is:
Wherein T is the total sampling time, the unit is seconds, and the value range of T is a positive integer; n is the number of discrete values acquired in the total sampling time, and is calculated by the product of the total sampling time T and the sampling rate, and the value range of N is a positive integer; t is the sampling time; the value ranges of U, I 1、t、u(t)、i1 (t) are positive numbers.
3. The insulation monitoring method of a substation cable according to claim 1, wherein the optimizing process is performed on the three-phase voltage, the three-phase current and the ground line current to obtain the processed three-phase voltage, three-phase current and ground line current, and further comprising:
Smoothing the current I 2 (T) of the grounding wire at T time acquired in the sampling total time T through a root mean square formula to obtain a continuous current I 2 of the grounding wire;
the root mean square formula is:
Wherein T is the total sampling time, the unit is seconds, and the value range of T is a positive integer; n is the number of discrete values acquired in the total sampling time, and is calculated by the product of the total sampling time T and the sampling rate, and the value range of N is a positive integer; t is the sampling time; the value ranges of the I 2、t、i2 (t) are positive numbers.
4. The insulation monitoring method of a substation cable according to claim 1, wherein the insulation monitoring method obtains three-phase voltage, three-phase current, ground wire current and joint temperature of the substation cable through a sensor module, and the sensor module comprises a voltage acquisition module, a current acquisition module and a temperature acquisition module;
The voltage acquisition module comprises a voltage sensor for acquiring three-phase voltages and an amplifier for amplifying the acquired three-phase voltages;
The current acquisition module comprises a current sensor for acquiring three-phase current and ground wire current and an amplifier for amplifying the acquired three-phase current and ground wire current;
The temperature acquisition module comprises a thermistor for acquiring the joint temperature and an amplifier for amplifying the acquired joint temperature.
5. An insulation monitoring device of a substation cable, characterized in that the insulation monitoring device comprises:
sampling device: the method comprises the steps of acquiring three-phase voltage, three-phase current, grounding wire current and joint temperature of a transformer substation cable;
A data processing device: the method comprises the steps of carrying out optimization treatment on three-phase voltage, three-phase current and grounding wire current to obtain treated three-phase voltage, three-phase current and grounding wire current;
Monitoring device: the method comprises the steps of analyzing the change trend of the processed three-phase voltage and three-wire current, comparing the joint temperature and the processed grounding wire current with corresponding preset thresholds respectively, and judging the aging condition of an insulating layer of the cable according to an analysis result and a comparison result;
the monitoring device is specifically used for:
Respectively acquiring the change rates of the processed three-phase voltage and three-phase current, matching the obtained change rates with the reference change rates in a pre-established fault database, and when the matching degree of the change rates of the three-phase voltage and the three-phase current is larger than a set fault threshold value, judging that the cable has faults due to ageing of an insulating layer and outputting fault alarm information;
If no fault warning information is output, judging that the cable is aged when the current of the grounding wire is larger than a preset current threshold value of the grounding wire, and outputting aging warning information; and when the joint temperature is greater than a preset cable joint temperature threshold, judging that the cable is aged, and outputting aging early warning information.
6. The insulation monitoring device of a substation cable according to claim 5, wherein the data processing device is specifically configured to:
Smoothing the three-phase voltage U (T) and the three-phase current I 1 (T) at T acquired in the sampling total time T respectively through a root mean square formula to obtain continuous three-phase voltage U and three-phase current I 1;
the root mean square formula is:
Wherein T is the total sampling time, the unit is seconds, and the value range of T is a positive integer; n is the number of discrete values acquired in the total sampling time, and is calculated by the product of the total sampling time T and the sampling rate, and the value range of N is a positive integer; t is the sampling time; the value ranges of U, I 1、t、u(t)、i1 (t) are positive numbers.
7. The insulation monitoring device for a substation cable according to claim 5, wherein the data processing device is further configured to:
Smoothing the current I 2 (T) of the grounding wire at T time acquired in the sampling total time T through a root mean square formula to obtain a continuous current I 2 of the grounding wire;
the root mean square formula is:
Wherein T is the total sampling time, the unit is seconds, and the value range of T is a positive integer; n is the number of discrete values acquired in the total sampling time, and is calculated by the product of the total sampling time T and the sampling rate, and the value range of N is a positive integer; t is the sampling time; the value ranges of the I 2、t、i2 (t) are positive numbers.
8. The insulation monitoring device for a substation cable according to claim 5, wherein the sampling device obtains three-phase voltage, three-phase current, ground wire current and joint temperature of the substation cable through a sensor module, and the sensor module comprises a voltage acquisition module, a current acquisition module and a temperature acquisition module;
the voltage acquisition module comprises a voltage sensor for acquiring three-phase voltages of a transformer substation cable and an amplifier for amplifying the acquired three-phase voltages;
The current acquisition module comprises a current sensor for acquiring three-phase current and ground wire current of the transformer substation cable and an amplifier for amplifying the acquired three-phase current and ground wire current;
the temperature acquisition module comprises a thermistor for acquiring the joint temperature of the substation cable and an amplifier for amplifying the acquired joint temperature.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010488581.3A CN111679162B (en) | 2020-06-02 | Insulation monitoring method and device for transformer substation cable |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010488581.3A CN111679162B (en) | 2020-06-02 | Insulation monitoring method and device for transformer substation cable |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN111679162A CN111679162A (en) | 2020-09-18 |
| CN111679162B true CN111679162B (en) | 2024-07-09 |
Family
ID=
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN205720418U (en) * | 2016-06-21 | 2016-11-23 | 上海谷元电气科技有限公司 | High tension cable circulating current detector |
| CN108490329A (en) * | 2018-03-12 | 2018-09-04 | 国网江苏省电力有限公司徐州供电分公司 | Power distribution network crosslinking polyethylene-insulated cable insulation state monitoring apparatus and monitoring method |
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN205720418U (en) * | 2016-06-21 | 2016-11-23 | 上海谷元电气科技有限公司 | High tension cable circulating current detector |
| CN108490329A (en) * | 2018-03-12 | 2018-09-04 | 国网江苏省电力有限公司徐州供电分公司 | Power distribution network crosslinking polyethylene-insulated cable insulation state monitoring apparatus and monitoring method |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN103675623B (en) | GIS partial discharge detection method and system under a kind of surge voltage | |
| WO2021098611A1 (en) | Platform for testing leakage current difference factor of aged xlpe cable, and method | |
| CN107064648B (en) | The detection device and method of the lightning-arrest lead resistance value of blower fan pylon based on leakage cable | |
| CN115407255B (en) | Current transformer error online monitoring device and method | |
| CN107247204B (en) | State monitoring system and monitoring method for voltage limiters in ultra-high and extra-high voltage series compensation device | |
| CN110286319B (en) | One-time and two-time complete column switch integrated test method | |
| CN111458652A (en) | Fault determination method, device and equipment for direct current charging pile | |
| CN202025054U (en) | Portable creepage current electrified detecting system for support insulator | |
| CN111007366A (en) | Oil type casing hidden danger monitoring system and method | |
| CN112363017A (en) | Line fault positioning method based on wavelet transformation | |
| CN111679162B (en) | Insulation monitoring method and device for transformer substation cable | |
| CN113805007A (en) | High-voltage cable health state online monitoring system and monitoring method thereof | |
| CN107765084B (en) | Universal voltage input power frequency signal frequency measurement system | |
| CN117554880A (en) | Method and device for detecting faults of secondary circuit of high-voltage transformer for metering | |
| CN105353236A (en) | On-line remote detection method and device for detecting state of disc-type insulator | |
| CN115656719B (en) | High-voltage cable sheath defect online diagnosis method based on sheath current transaction | |
| CN110645887A (en) | Winding deformation judgment method based on short-circuit reactance | |
| CN108646145B (en) | Method and system for positioning flashover tower of power transmission line | |
| CN215005567U (en) | Broadband carrier module with electricity stealing prevention detection function | |
| CN111289837A (en) | Method and system for evaluating latent fault of power distribution network equipment | |
| CN111679162A (en) | Insulation monitoring method and device for transformer substation cable | |
| CN115684717A (en) | High-voltage line harmonic detection device and method based on electric field coupling | |
| CN1328586C (en) | Electric energy quality monitoring, recording and analyzing system | |
| CN114384377A (en) | Cable insulation condition monitoring method and system based on QGA-VMD | |
| CN217443434U (en) | Arrester resistive current on-line monitoring device with temperature correction |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant |