CN114089115A - Method and device for identifying secondary cable of transformer substation - Google Patents
Method and device for identifying secondary cable of transformer substation Download PDFInfo
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Abstract
The invention provides an identification method for a secondary cable of a transformer substation, which comprises the following steps: clamping the outer layer of the cable by using a detection clamp, and adding voltage to a shielding layer in the cable; step two, replacing the detection clamp to adjust the contact area of the detection clamp and the cable, and repeating the measurement process in the step one; step three, adjusting the voltage added to the shielding layer in the cable, and repeating the measuring process in the step one; adjusting the position of the detection clamp for clamping the cable, and repeating the measurement process in the first step; and step five, detecting and analyzing the electrical parameters measured in the step one to the step four in real time, and presenting the results according to the interactive device. A device for identifying a secondary cable of a transformer substation structurally comprises a detection clamp, a power supply transmitter and a detection identification end; when the device is used, the detection clamp is connected with the outer surface of the outer insulating layer of the cable, and the power emitter is connected with the shielding layer in the cable.
Description
Technical Field
The invention relates to a method and a device for identifying a secondary cable of a transformer substation, and belongs to the field of cable inspection devices.
Background
At present, a large number of secondary cables are used in a transformer substation as signal transmission media among equipment control systems, so that a large number of secondary cables are stacked in a cable trench; when a transformer substation needs to be transformed or overhauled, workers often cannot replace secondary cables, the removed cables are directly placed in the cable trench, and new cables are mixed with the removed cables, so that the cables in the cable trench slowly become too many to be processed; some transformer substations can also adopt another method for processing, after workers remove one end of a cable needing to be replaced, as a plurality of cables cannot be pulled out, universal meters can be adopted for identifying the cable, and the identified cable is cut short for removing operation, but as secondary cables in a cable trench are complicated and complicated, and the interlayer light of the cable trench is dark, the identification rate of the universal meters is low, when the workers remove waste cables and the like, the cable identification error is easy to occur, so that the cable is cut mistakenly, serious safety accidents are caused, serious threats are brought to the personal safety of the workers, or large-area power failure is caused, and serious economic losses and influences are caused to the economic development and the production life of the society.
At present, many secondary cable detection devices mostly adopt an off-line detection method, power failure treatment is often needed to be carried out on a secondary cable line, and then the secondary cable detection device is accessed for detection and identification, and the detection means needs power failure detection to cause that the operation of the whole line is influenced, and wastes time and labor, and high-frequency detection is difficult to realize; the development of some technologies can enable the detection of the cable to be realized continuously in the process of detecting and identifying the cable, namely the identification of the cable is realized by means of current or square waves and the like, but the detection can avoid power failure, but the device has larger weight and volume, the portable carrying can not be realized in the process of carrying out position moving of workers, a large amount of manpower and material resources are still spent to access the testing device, the identification rate of the device is low, and once the fault occurs, serious economic loss can be caused, and even the personal safety of the workers can be threatened.
Disclosure of Invention
The invention provides a method and a device for identifying a secondary cable of a transformer substation, and aims to solve the problem that the damage degree of a cable cannot be detected when a waste cable is dismantled.
The technical solution of the invention is as follows: an identification method for a substation secondary cable, the method comprising the steps of:
clamping the outer layer of a cable by using a detection clamp, adding voltage to a shielding layer in the cable, and leading out connecting wires at two ends of the shielding layer and the detection clamp to monitor electrical parameters between the shielding layer and the detection clamp;
step two, replacing the detection clamp to adjust the contact area of the detection clamp and the cable, and repeating the measurement process in the step one;
step three, adjusting the voltage added to the shielding layer in the cable, and repeating the measuring process in the step one;
adjusting the position of the detection clamp for clamping the cable, and repeating the measurement process in the first step;
step five, detecting and analyzing the electrical parameters measured in the step one to the step four in real time, and presenting results according to the interactive device;
and a strict execution sequence is not required among the second step, the third step and the fourth step.
Furthermore, in the first step, the shielding layer is led out from two ends of the shielding layer and the detection clamp, the conductive connecting line is led out from two ends of the detection clamp and is connected with the detection identification end, and the detection identification end monitors the electrical parameters between the shielding layer and the detection clamp; in the second step, when the contact area of the detection clamp and the cable is adjusted, the detection clamp for adjustment comprises clamping jaws with different lengths and clamping jaws with different radiuses, so that the contact areas of the detection clamp and the outer insulating layer of the cable are changed, the charge distribution on the clamping jaws under different contact areas is slightly different, and the error detection when the cable is partially damaged is avoided through multiple measurements; the multiple measurement means that the clamping jaws with different lengths are replaced more than twice, and the clamping jaws with different radiuses are replaced more than twice.
Further, in the third step, the voltage added to the shielding layer in the cable is adjusted to be pulse voltage; adjusting voltage added to a shielding layer in the cable, specifically adjusting duty ratio, frequency and amplitude of the voltage; the duty ratio is set to be 30%, 50% or 70%, and the frequency is selected to be a 500 +/-100 Hz frequency band; the voltage is 5V or 12V or 24V, the voltage amplitude is adjusted from small to large, and the small voltage cannot accurately measure data due to different specifications of the cable and the fact that when the cable is large, the voltage added to the shielding layer in the cable needs to be adjusted for multiple times to carry out repeated measurement; the repeated measurement of the voltage added to the shielding layer in the cable line by the multiple times of adjustment is to measure the voltage added to the shielding layer in the cable line by three times of adjustment, if no signal exists in all the three times, the measurement is continuously adjusted, and the adjustment frequency is preferably not more than six times.
Further, in the fourth step, the position of the cable clamped by the detection clamp is changed, and a damaged cable segment and a nondestructive cable segment of the cable are found out through a plurality of times of measurement; in the fifth step, the electrical parameters measured in the first step to the fourth step are detected and analyzed in real time, and the specific results according to the presentation result of the interactive device are as follows: detecting and analyzing the electrical parameters measured in the first step to the fourth step in real time through the detection and identification end, and presenting the result according to the interactive device; the interaction device comprises a display screen and a sound box on the detection identification end.
Further, the cable line includes an inner portionThe conductor and the outer insulating layer see the inner conductor (copper wire) as an infinitely long straight wire, the outer insulating layer is a good insulator, and the relative dielectric constant of the outer insulating layer is epsilonrThe detection clamp comprises a metal clamp sheet, the detection clamp is clamped on a cylindrical surface coaxial with the central conductor, the area of the detection clamp is S, the distance from the axis of the inner conductor to the outer surface of the outer insulating layer is k, and the radius of the inner conductor is k1Then, from poisson's equation and the first class boundary condition, equation (1) can be derived:
wherein epsilon0F (r) is a distance vector from the detection clamp to the inner conductor, E (r, t) is the electric field intensity generated by the potential of the inner conductor at the position of the detection clamp,
is the inner conductor potential; under the action of an electric field, inductive charges Q appear on the surface of the metal electrode of the detection clamp, a minimum area infinitesimal dS is taken on the surface of the metal electrode of the detection clamp, and the normal direction of the area infinitesimal dS is the same as the direction of the electric field E (r, t); then, according to the gaussian theorem, the induced charge amount generated on the area bin dS is shown in the formula (2):
as can be seen from the formula (2), the induced charges generated on the area micro-element dS change with the change of the electric field intensity generated by the potential of the inner conductor at the position of the detection clamp, so the induced charges are induced on the inductive resistor Z connected with the output cablecableThe resulting voltage is shown in equation (3):
the resulting current is shown in equation (4):
I＝Uout/Zcable (4)。
furthermore, the contact area S between the detection clamp and the cable is adjusted by replacing the detection clamp, and the formula (3) shows that the voltage value generated on the induction resistor is in direct proportion to the contact area S, the generated current value is in direct proportion to the contact area S, the change rate of the measured voltage and current relative to S is kept consistent after the contact area S is changed, and when the cable is damaged, the epsilon of the damaged part is kept consistentrChange occurs, the voltage value is influenced by epsilonrInfluence, the change rate of the measured voltage and current relative to the contact area S can be changed after the contact area S is changed; and when the change rate of the measured voltage or current relative to the contact area S is changed after the contact area S is changed, judging that the cable wire is damaged.
Further, by adjusting the position of the detection clamp for clamping the cable, if the cable is not damaged, according to the formula (1) -the formula (4), all parameters are not changed, so that the measured voltage value and the measured current value are kept unchanged, the measured first non-zero voltage or non-zero current is used as a comparison parameter, the voltage and the current which are measured after the position of the detection clamp is changed do not exceed 2% of the change of the comparison parameter, the change is considered to be not large, the voltage and the current are considered to be unchanged, and the change amplitude is considered to be large when the change exceeds 2%, and the detected position is judged to be damaged.
A device for identifying a secondary cable of a transformer substation structurally comprises a detection clamp, a power supply transmitter and a detection identification end; the detection clamp is connected with the detection identification end; when the cable is used, the detection clamp is connected with the outer surface of the outer insulating layer of the cable, and the power supply emitter is connected with the shielding layer in the cable.
Further, the detection clamp comprises a metal clamp sheet and a metal clamp insulation handle; one end of the metal clip sheet is connected with the metal clip insulating handle, and the metal clip sheet is connected with the detection identification end through a conductive connecting wire; the metal clamping sheets comprise two metal fan-shaped sheets which are oppositely arranged to form a clamping jaw, and one end of each of the two metal fan-shaped sheets is fixedly connected with the metal clamping insulating handle; when the cable clamp is used, the two metal fan-shaped sheets form a clamping jaw with a fan-shaped sheet, the clamping jaw with the fan-shaped sheet is clamped on the outer surface of the outer insulating layer of the cable and is in contact with the outer surface of the outer insulating layer, and the other ends of the two metal fan-shaped sheets are connected through a buckle, so that the two metal fan-shaped sheets are tightly wrapped on the outer layer of the cable; when the cable conductor needs to be detected, the power supply emitter is connected with the shielding layer in the cable conductor through the lead and injects voltage, the detection clamp and the shielding layer form a parallel capacitor structure at the moment, an electric field is arranged inside the detection clamp, the metal clamping sheets on the detection clamp can sense electric charges, and the detection device detects the electric charges on the detection clamp and records the electric charges.
Furthermore, the detection clamp is connected with an induction resistor, the induction resistor is fixedly arranged in the detection identification end, one end of the induction resistor is connected with the detection clamp, the other end of the induction resistor is grounded through an output cable, the detection clamp can generate voltage on the induction resistor, and the detection identification end judges the quality of the cable through analyzing the voltage and the current; if the change degree of the voltage or the current does not exceed the threshold value, the cable wire is not damaged; if at least one of the voltage and the current has a change amplitude exceeding a threshold value, the detection position corresponding to the cable is damaged; if at least one of the voltage and the current is zero, the corresponding detection position of the cable wire is broken or seriously damaged.
The invention has the beneficial effects that:
1) the identification method for the secondary cable of the transformer substation, provided by the invention, can be applied to the transformer substation, so that the workload of workers can be well reduced when the workers perform safety measures, demolish waste cables and other work;
2) according to the invention, the related data is obtained by detecting the voltage of the cable, and the data is detected in real time to realize the discrimination of the cable, so that the identification of the multi-core cable containing the armor layer can be realized;
3) the process data of the invention is adjusted for many times, so that the damage degree of the secondary cable can be accurately detected, and the subsequent judgment and recycling are convenient;
4) the invention adopts the principle of electromagnetic induction, provides a method for testing cables on site, and is easy to realize in a detection device; the detection process of the invention is divided into a plurality of times, which can deal with the detection of the cable with most of the existing specifications and can reduce the condition of error detection.
Drawings
FIG. 1 is a schematic view of a model of a contact measurement of a detection clamp with a cable line.
Fig. 2 is a schematic model diagram of an equivalent parallel capacitor.
Fig. 3 is a schematic structural diagram of a substation secondary cable identification device.
Fig. 4 is a schematic structural view of the inspection jig.
FIG. 5 is a schematic view showing a connection model of the inspection jig and the cable.
In the attached drawing, 1 is a shielding layer, 2 is an inner conductor (the inner conductor is the inner core of a cable), 3 is an outer insulating layer, 4 is a metal clip sheet, 5 is an equivalent parallel capacitor, 6 is a buckle, 7 is the anode of an analog parallel capacitor, 8 is the cathode of the analog parallel capacitor, 9 is the cable, 10 is an external grounding device, 11 is a detection identification end, 12 is a power supply transmitter, 13 is a metal clip insulating handle, and 14 is a conductive connecting wire.
Detailed Description
A method for recognizing a secondary cable of a transformer substation acquires related data by detecting the voltage of the cable and detects the data in real time to realize the discrimination of the cable.
An identification method for a substation secondary cable, the method comprising the steps of:
clamping the outer layer of a cable by using a detection clamp, adding voltage to a shielding layer 1 in the cable, and leading out connecting wires from two ends of the shielding layer 1 and the detection clamp to monitor electrical parameters between the shielding layer 1 and the detection clamp;
step two, replacing the detection clamp to adjust the contact area of the detection clamp and the cable, and repeating the measurement process in the step one;
step three, adjusting the voltage added to the shielding layer 1 in the cable, and repeating the measuring process in the step one;
adjusting the position of the detection clamp for clamping the cable, and repeating the measurement process in the first step;
and step five, detecting and analyzing the electrical parameters measured in the step one to the step four in real time, and presenting the results according to the interactive device.
And a strict execution sequence is not required among the second step, the third step and the fourth step.
In the first step, conductive connecting wires are led out from two ends of the shielding layer and the detection clamp and are connected with a detection identification end, and the detection identification end monitors electrical parameters between the shielding layer and the detection clamp.
In the second step, when the contact area of the detection clamp and the cable is adjusted, the detection clamp for adjustment comprises clamping jaws with different lengths and clamping jaws with different radiuses, so that the contact area of the detection clamp and the outer insulating layer 3 of the cable is changed, the charge distribution on the clamping jaws under different contact areas is slightly different, and the error detection when the cable is partially damaged can be avoided through multiple measurements; the multiple measurement means that the clamping jaws with different lengths are replaced more than twice, and the clamping jaws with different radiuses are replaced more than twice.
In the third step, the voltage added to the shielding layer 1 in the cable line is preferably adjusted to be a pulse voltage.
In the third step, the voltage added to the shielding layer in the cable is adjusted, specifically, the duty ratio, the frequency and the amplitude of the voltage are adjusted; the duty ratio is generally set to 30%, 50% and 70%, the frequency is selected from a frequency in a specified range, and the preferred frequency of the frequency in the specified range is a frequency band of 500 +/-100 Hz; the amplitude is generally selected from typical voltages, the typical voltages are preferably 5V, 12V and 24V, the voltage amplitude is adjusted from small to large, and due to the fact that specifications of cables are different, when the cable is large, the small voltage is added, data cannot be accurately measured, and therefore the voltage added to a shielding layer in the cable needs to be adjusted for multiple times to be measured repeatedly; the voltage added to the shielding layer in the cable is preferably adjusted three times to measure repeatedly, if no signal exists in the three times, the measurement is continuously adjusted, and the adjusting frequency is preferably not more than six times.
In the fourth step, the position of the detection clamp for clamping the cable is changed, and the damaged segment and the nondestructive segment of the cable are found out through a plurality of times of measurement, so that the recovery and utilization are facilitated; the several measurements described here are specifically: the secondary cable is divided into a head section, a middle section and a tail section, and each section is measured at least once.
In the fifth step, the electrical parameters measured in the first step to the fourth step are detected and analyzed in real time, and the specific results according to the presentation result of the interactive device are as follows: detecting and analyzing the electrical parameters measured in the first step to the fourth step in real time through the detection and identification terminal 11, and presenting the results according to the interactive device; the interaction device comprises a display screen and a sound box on the detection identification end 11.
In the fifth step, the detecting and analyzing of the electrical parameters measured in the first to fourth steps specifically includes: the detection clamp is connected with an induction resistor, the induction resistor is fixedly arranged in the detection identification end 11, one end of the induction resistor is connected with the detection clamp, the other end of the induction resistor is grounded through an output cable, the detection clamp can generate voltage on the induction resistor, and the detection identification end 11 judges the quality of the cable through analyzing the voltage and the current; if the change degree of the voltage or the current does not exceed the threshold value, the cable wire is not damaged; if at least one of the voltage and the current has a change amplitude exceeding a threshold value, the detection position corresponding to the cable is damaged; if at least one of the voltage and the current is zero, the corresponding detection position of the cable wire is broken or seriously damaged.
The cable comprises an inner conductor and an outer insulating layer, the inner conductor (copper wire) is regarded as an infinite straight wire, the outer insulating layer is a good insulator, and the relative dielectric constant of the outer insulating layer is epsilonrThe detection clamp comprises a metal clamp sheet, the detection clamp is clamped on a cylindrical surface coaxial with the central conductor, the area of the detection clamp is S, the distance from the axis of the inner conductor to the outer surface of the outer insulating layer is k, and the radius of the inner conductor is k1Then, from poisson's equation and the first class boundary condition, equation (1) can be derived:
wherein epsilon0F (r) is a distance vector from the detection clamp to the inner conductor, E (r, t) is the electric field intensity generated by the potential of the inner conductor at the position of the detection clamp,
is the inner conductor potential; under the action of an electric field, inductive charges Q appear on the surface of the metal electrode of the detection clamp, a minimum area infinitesimal dS is taken on the surface of the metal electrode of the detection clamp, and the normal direction of the area infinitesimal dS is the same as the direction of the electric field E (r, t); then, according to the gaussian theorem, the induced charge amount generated on the area bin dS is shown in the formula (2):
as can be seen from the formula (2), the induced charges generated on the area micro-element dS change with the change of the electric field intensity generated by the potential of the inner conductor at the position of the detection clamp, so the induced charges are induced on the inductive resistor Z connected with the output cablecableThe resulting voltage is shown in equation (3):
the resulting current is shown in equation (4):
I＝Uout/Zcable (4)。
the contact area S between the detection clamp and the cable is adjusted by replacing the detection clamp, and the formula (3) shows that the voltage value generated on the induction resistor is in direct proportion to the contact area S, the generated current value is in direct proportion to the contact area S, the change rate of the voltage and the current measured after the contact area S is changed relative to the S is kept consistent, and when the cable is damaged, the epsilon of the damaged part is kept consistentrChange in voltage value by ∈rInfluence, voltage, current measured after changing the contact area S, relative to the contactThe rate of change of the contact area S will change; when the change rate of the measured voltage or current relative to the contact area S is changed after the contact area S is changed, judging that the cable is damaged; it is preferable that the cable wire is judged to be damaged when the rate of change in the measured voltage or current with respect to the contact area S fluctuates by more than 2% after the contact area S is changed.
Changing the potential of the inner conductor by adjusting the voltage applied to the shield 1 in the cable
Its purpose is in order to make voltage and cable specification match, the observation of being convenient for.
Through adjusting the position that detects anchor clamps centre gripping cable conductor, if the cable conductor is harmless, according to equation (1) -formula, each parameter can not change, therefore the voltage value and the current value that record keep unchangeable, regard as the contrast parameter with the first non-zero voltage or non-zero electric current that measures, consider signal attenuation, detect anchor clamps centre gripping inaccurate and other human factors, the voltage that measures after changing the detection anchor clamps position, the electric current does not exceed 2% relative to contrast parameter change and can be considered to change little, can be regarded as voltage, the electric current is unchangeable, exceed 2% then consider that the change amplitude is great, the position judgement that detects at this moment is impaired.
A method for identifying a secondary cable of a transformer substation further comprises the step of arranging a plurality of clamps to clamp different positions of the cable at the same time, namely combining the steps two to four into a whole, and clamping the plurality of positions to measure different sections of the cable at the same time, so that the measuring speed is improved.
A device for identifying a secondary cable of a transformer substation structurally comprises a detection clamp, a power supply transmitter 12 and a detection identification end 11; wherein, the detection clamp is connected with the detection recognition end 11; when the device is used, the detection clamp is connected with the outer surface of the outer insulating layer 3 of the cable, and the power emitter is connected with the shielding layer 1 in the cable.
The power supply transmitter 12 is connected with a shielding layer in the cable line through a lead; the power transmitter 12 is preferably a pulsed power source.
The detection clamp comprises a metal clamp sheet 4 and a metal clamp insulating handle 13; one end of the metal clip sheet 4 is connected with a metal clip insulating handle 13, and the metal clip sheet 4 is connected with the detection device 11 through a conductive connecting wire 14; when the cable is used, the metal clip sheet 4 is in contact with the outer surface of the outer insulating layer 3 of the cable, the metal clip insulating handle 13 is convenient for a person to operate and use, and the metal clip insulating handle 13 is used for electric insulation to avoid electric charge loss from the metal clip insulating handle 13; the metal clip sheet 4 is connected with the detection device 11 through the conductive connecting line 14, so that the detection device can conveniently detect the charges on the detection clamp.
The metal clip sheet 4 comprises two metal fan-shaped sheets which are oppositely arranged to form a clamping jaw, and one end of each of the two metal fan-shaped sheets is fixedly connected with the metal clip insulating handle 13; when the cable clamp is used, the two metal fan-shaped sheets form a clamping jaw with a fan-shaped sheet, the clamping jaw with the fan-shaped sheet is clamped on the outer surface of the outer insulating layer 3 of the cable and is in contact with the outer surface of the outer insulating layer 3, and the other ends of the two metal fan-shaped sheets are connected through the buckle 6, so that the two metal fan-shaped sheets are tightly wrapped on the outer layer of the cable; when the cable conductor needs to be detected, the power emitter 12 is connected with the shielding layer 1 in the cable conductor through the lead and injects voltage, the detection clamp and the shielding layer 1 form a parallel capacitor structure at the moment, an electric field is arranged inside the detection clamp, the metal clamping sheets 4 on the detection clamp sense electric charges, and the detection device detects the electric charges on the detection clamp and records the electric charges.
The length of the two metal fan-shaped sheets is used as the length of the clamping jaw of the detection clamp, and the width of the two metal fan-shaped sheets is used as the radius of the clamping jaw of the detection clamp; the detection clamp comprises a plurality of detection clamps with different clamping jaw sizes, and detection clamps with clamping jaws of different lengths and radiuses are prepared according to needs.
When the multi-core cable line identification device works, the shielding layer of the detected cable line simulates the positive electrode of a parallel capacitor, the metal clamping sheet 4 simulates the negative electrode of the parallel capacitor, an equivalent parallel capacitor is simulated between the shielding layer 1 and the metal clamping sheet 4, the required target cable line is judged and identified by establishing the parallel capacitor and detecting charges, the multi-core cable line identification device can be used for multi-core cable line identification, and the identification speed and accuracy of the cable line are improved; the cable detected in the invention comprises a substation secondary cable.
Example 1
Referring to fig. 1 to 5, the present embodiment discloses a method for identifying a secondary cable of a substation, which is used for identifying a target cable from a bundle or a plurality of cables in the substation.
The detection copper clamp is directly clamped on a target cable line as a detection clamp by a detection person, the detection copper clamp is reliably connected with the cable line to prevent the cable line from falling off, and the target cable line and the surrounding cable line keep a distance of about 1 cm to prevent the influence caused by the surrounding cable line during detection; the power supply transmitting end of the power supply transmitter 12 is arranged to provide a pulse power supply for the cable, so that an armored shielding layer of the cable and the detection copper clip form a parallel capacitor, the armored shielding layer of the target cable is equivalent to the anode of the parallel capacitor, a copper sheet of the detection copper clip is equivalent to the cathode of the parallel capacitor, and a changed electric field can enable the copper sheet of the detection copper clip to generate induced charges; and then, induced charges on the copper clamp are led into a detection identification end through a lead, and after the detection end identifies a charge signal, electric parameters such as charge current, voltage and the like are recorded.
And after one group of detection is finished, the clamp, the voltage regulation and the position regulation are respectively replaced for repeated detection, the detected four groups of data are mutually contrasted, the damage condition of the target cable is obtained according to the average electrical parameter level, if the target cable is not damaged, the target cable can be recycled, and if part of the target cable is damaged, the target cable can be cut. Under the condition that cables are not stacked seriously or when the number of cables to be detected is large, a plurality of clamps are arranged on one cable to measure and analyze electrical parameters simultaneously.
Claims (10)
1. A method for identifying a secondary cable of a transformer substation is characterized by comprising the following steps:
clamping the outer layer of a cable by using a detection clamp, adding voltage to a shielding layer in the cable, and leading out connecting wires at two ends of the shielding layer and the detection clamp to monitor electrical parameters between the shielding layer and the detection clamp;
step two, replacing the detection clamp to adjust the contact area of the detection clamp and the cable, and repeating the measurement process in the step one;
step three, adjusting the voltage added to the shielding layer in the cable, and repeating the measuring process in the step one;
step four, adjusting the position of the detection clamp for clamping the cable, and repeating the measurement process in the step one;
step five, detecting and analyzing the electrical parameters measured in the step one to the step four in real time, and presenting results according to the interactive device;
and a strict execution sequence is not required among the second step, the third step and the fourth step.
2. The method for identifying the secondary cable of the transformer substation according to claim 1, wherein in the first step, the shielding layer is led out from two ends of the shielding layer and the detection clamp, the conductive connecting line is led out from two ends of the detection clamp and is connected with the detection identification end, and the detection identification end monitors the electrical parameter between the shielding layer and the detection clamp; in the second step, when the contact area of the detection clamp and the cable is adjusted, the detection clamp for adjustment comprises clamping jaws with different lengths and clamping jaws with different radiuses, so that the contact areas of the detection clamp and the outer insulating layer of the cable are changed, the charge distribution on the clamping jaws under different contact areas is slightly different, and the error detection when the cable is partially damaged is avoided through multiple measurements; the multiple measurement means that the clamping jaws with different lengths are replaced more than twice, and the clamping jaws with different radiuses are replaced more than twice.
3. The identification method for the secondary cable of the transformer substation according to claim 1, wherein in the third step, the voltage added to the shielding layer in the cable line is adjusted to be a pulse voltage; adjusting voltage added to a shielding layer in the cable, specifically adjusting duty ratio, frequency and amplitude of the voltage; the duty ratio is set to be 30%, 50% or 70%, and the frequency is selected to be a 500 +/-100 Hz frequency band; the voltage is 5V or 12V or 24V, the voltage amplitude is adjusted from small to large, and the small voltage cannot accurately measure data due to different specifications of the cable and the fact that when the cable is large, the voltage added to the shielding layer in the cable needs to be adjusted for multiple times to carry out repeated measurement; the repeated measurement of the voltage added to the shielding layer in the cable line by the plurality of times of adjustment is to measure by adjusting the voltage added to the shielding layer in the cable line by three times, if no signal exists in all the three times, the measurement is continuously adjusted, and the adjusting times are preferably not more than six times.
4. The identification method for the secondary cable of the transformer substation according to claim 1, wherein in the fourth step, the position of the detection clamp for clamping the cable is changed, and a damaged cable segment and a nondestructive cable segment of the cable are found out through a plurality of measurements; in the fifth step, the electrical parameters measured in the first step to the fourth step are detected and analyzed in real time, and the specific results according to the presentation result of the interactive device are as follows: detecting and analyzing the electrical parameters measured in the first step to the fourth step in real time through the detection and identification end, and presenting the result according to the interactive device; the interaction device comprises a display screen and a sound box on the detection identification end.
5. A method according to claim 1, wherein the cable line comprises an inner conductor and an outer insulating layer, the inner conductor being seen as an infinitely long straight conductor, the outer insulating layer being a good insulator, the outer insulating layer having a relative dielectric constant erThe detection clamp comprises a metal clamp sheet, the detection clamp is clamped on a cylindrical surface coaxial with the central conductor, the area of the detection clamp is S, the distance from the axis of the inner conductor to the outer surface of the outer insulating layer is k, and the radius of the inner conductor is k1Then, from poisson's equation and the first class boundary condition, equation (1) can be derived:
wherein epsilon0F (r) is the distance vector from the detection clamp to the inner conductor, E (r, t) is the electric field intensity generated by the potential of the inner conductor at the position of the detection clamp,
is the inner conductor potential; under the action of an electric field, inductive charges Q appear on the surface of the metal electrode of the detection clamp, a minimum area infinitesimal dS is taken on the surface of the metal electrode of the detection clamp, and the normal direction of the area infinitesimal dS is the same as the direction of the electric field E (r, t); then, according to the gaussian theorem, the induced charge amount generated on the area bin dS is shown in the formula (2):
as can be seen from the formula (2), the induced charges generated on the area micro-element dS change with the change of the electric field intensity generated by the potential of the inner conductor at the position of the detection clamp, so the induced charges are induced on the inductive resistor Z connected with the output cablecableThe resulting voltage is shown in equation (3):
the resulting current is shown in equation (4):
I＝Uout/Zcable (4)。
6. the method as claimed in claim 5, wherein the contact area S between the detection clamp and the cable is adjusted by replacing the detection clamp, as shown in formula (3), the voltage value generated on the sensing resistor is proportional to the contact area S, the current value is proportional to the contact area S, the change rate of the voltage and the current relative to S is consistent after the contact area S is changed, and when the cable is damaged, the change rate of epsilon of the damaged part is consistentrChange in voltage value by ∈rInfluence, the change rate of the measured voltage and current relative to the contact area S can be changed after the contact area S is changed; the rate of change of the measured voltage or current with respect to the contact area S occurs after the contact area S is changedAnd if the cable is changed, judging that the cable is damaged.
7. The method as claimed in claim 5, wherein the position of the cable is clamped by adjusting the detection clamp, if the cable is not damaged, according to the formula (1) to the formula (4), all parameters are not changed, so that the measured voltage value and current value are kept unchanged, the measured first non-zero voltage or non-zero current is used as a reference parameter, and the voltage and current measured after the position of the detection clamp is changed are not more than 2% of the change of the reference parameter, considering signal attenuation, inaccurate clamping of the detection clamp and other human factors, the change is considered to be small, the voltage and current are considered to be unchanged, and the change amplitude is considered to be large when the change exceeds 2%, and the detected position is judged to be damaged.
8. A device for identifying a secondary cable of a transformer substation is characterized by comprising a detection clamp, a power supply transmitter and a detection identification end; the detection clamp is connected with the detection identification end; when the cable is used, the detection clamp is connected with the outer surface of the outer insulating layer of the cable, and the power supply emitter is connected with the shielding layer in the cable.
9. The device for substation secondary cable identification of claim 8 wherein the detection fixture comprises a metal clip sheet, a metal clip insulated handle; one end of the metal clip sheet is connected with the metal clip insulating handle, and the metal clip sheet is connected with the detection identification end through a conductive connecting wire; the metal clip sheet comprises two metal fan-shaped sheets which are oppositely arranged to form a clamping jaw, and one end of each of the two metal fan-shaped sheets is fixedly connected with the metal clip insulating handle; when the cable clamp is used, the two metal fan-shaped sheets form a clamping jaw with a fan-shaped sheet, the clamping jaw with the fan-shaped sheet is clamped on the outer surface of the outer insulating layer of the cable and is in contact with the outer surface of the outer insulating layer, and the other ends of the two metal fan-shaped sheets are connected through a buckle, so that the two metal fan-shaped sheets are tightly wrapped on the outer layer of the cable; when the cable conductor needs to be detected, the power supply emitter is connected with the shielding layer in the cable conductor through the lead and injects voltage, the detection clamp and the shielding layer form a parallel capacitor structure at the moment, an electric field is arranged inside the detection clamp, the metal clamping sheets on the detection clamp can sense electric charges, and the detection device detects the electric charges on the detection clamp and records the electric charges.
10. The device for identifying the secondary cable of the transformer substation as claimed in claim 8, wherein the detection clamp is connected with an induction resistor, the induction resistor is fixedly arranged in the detection identification end, one end of the induction resistor is connected with the detection clamp, the other end of the induction resistor is grounded through an output cable, the detection clamp can generate voltage on the induction resistor, and the detection identification end judges whether the cable is good or bad by analyzing the voltage and the current; if the change degree of the voltage or the current does not exceed the threshold value, the cable wire is not damaged; if at least one of the voltage and the current has a change amplitude exceeding a threshold value, the detection position corresponding to the cable is damaged; if at least one of the voltage and the current is zero, the corresponding detection position of the cable wire is broken or seriously damaged.
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