CN108344927B - Power cable partial discharge monitoring device and method - Google Patents
Power cable partial discharge monitoring device and method Download PDFInfo
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- CN108344927B CN108344927B CN201710055326.8A CN201710055326A CN108344927B CN 108344927 B CN108344927 B CN 108344927B CN 201710055326 A CN201710055326 A CN 201710055326A CN 108344927 B CN108344927 B CN 108344927B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
- G01R31/1263—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation
- G01R31/1272—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation of cable, line or wire insulation, e.g. using partial discharge measurements
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/14—Circuits therefor, e.g. for generating test voltages, sensing circuits
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Abstract
The invention relates to a power cable partial discharge monitoring device and method. The device comprises: the alternating-current high-voltage generating equipment is electrically connected with the power cable; the high-voltage capacitive coupling sensor is electrically connected with the alternating-current high-voltage generating equipment; the signal coupling unit is arranged on the metal outer protective layer of the middle joint; the partial discharge tester is electrically connected with the high-voltage capacitive coupling sensor; an alternating current high voltage generating device for applying a low frequency alternating current voltage signal to the power cable to cause partial discharge of the power cable to generate a partial discharge pulse signal; a plurality of signal coupling units for coupling the partial discharge pulse signal to the entire power cable when the power cable is partially discharged; the high-voltage capacitive coupling sensor is used for acquiring a partial discharge pulse signal on the power cable; the partial discharge tester is used for calculating the partial discharge quantity of the power cable according to the partial discharge pulse signal. The invention can realize the full-line transmission of the partial discharge pulse signal in the power cable and improve the calculation precision of the partial discharge quantity.
Description
Technical Field
The invention relates to the technical field of high voltage detection, in particular to a power cable partial discharge monitoring device and method.
Background
In the operation process of the power cable, the insulation capability of the power cable is reduced due to the influence of various reasons (the effect of electric field force and current, manufacturing process defects, construction damage, water inflow, gas corrosion, external force damage and the like), and partial discharge is caused at the position which does not penetrate through the main insulation layer or the outer insulation of a cable joint. In addition, the insulation material of the existing power cable is mainly made of solid organic insulation material, partial discharge can further deteriorate the insulation capability of the power cable, and the partial discharge is easily developed into breakdown to influence the normal use of the power cable. Therefore, detecting partial discharge of a power cable is an effective way to evaluate its insulation performance.
In the prior art, a power cable manufacturer detects the partial discharge amount of a factory cable according to the regulations of relevant standards. For example, when a high-frequency pulse current method is used to detect the partial discharge amount of a power cable having a certain length, a discharge pulse in the range of 30 to 500kHz of a partial discharge spectrum is collected, and then the partial discharge amount of the power cable is calculated. The high-frequency pulse current method technology needs to be tested in a high-voltage electromagnetic shielding room, and the analyzed data is relatively credible.
However, after the power cable is laid and put into operation, high-frequency signals of 30-500kHz, such as wireless communication, power line carrier waves and corona, can exist on the site, so that the field detection result of the high-frequency pulse current method is inaccurate. In order to avoid the interference of the on-site high-frequency signals, power cable providers adopt a frequency band of more than 10MHz and even GHz for local discharge amount detection. However, the resistance of the inner and outer shielding layers of the power cable causes severe attenuation (in the frequency band of 10MHz or more and even GHz), so that the high-frequency signal frequency band can only be used for detecting and positioning partial discharge of a cable terminal or an intermediate joint. Therefore, an effective power cable on-line monitoring device and method are needed.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a power cable partial discharge monitoring device and a method, which are used for solving the problems of interruption of a partial discharge high-frequency signal of a middle joint of a single-core cable and serious attenuation of a higher-frequency-band signal in the prior art.
In a first aspect, the present invention provides a power cable partial discharge monitoring device, which is suitable for a long-distance single-core power cable with an intermediate joint metal outer sheath cross-interconnected, and comprises: the device comprises alternating current high voltage generating equipment, a high voltage capacitive coupling sensor and/or a high frequency current transformer, a plurality of signal coupling units and a partial discharge tester; wherein the alternating current high voltage generating device is electrically connected with the power cable; the high-voltage capacitive coupling sensor is electrically connected with the alternating-current high-voltage generating equipment; the high-frequency current transformer is arranged between the alternating-current high-voltage generating equipment and the power cable sectional metal outer protective layer and is electrically connected with the alternating-current high-voltage generating equipment and the power cable sectional metal outer protective layer; the signal coupling unit is arranged on the metal outer protective layer of the intermediate joint; the partial discharge tester is electrically connected with the high-voltage capacitive coupling sensor;
the alternating-current high-voltage generating equipment is used for applying a low-frequency alternating-current voltage signal to a power cable to enable the power cable to be partially discharged to generate a partial discharge pulse signal;
a plurality of signal coupling units for coupling a partial discharge pulse signal to the entire power cable when the power cable is partially discharged;
the high-voltage capacitive coupling sensor and/or the high-frequency current transformer are/is used for acquiring a partial discharge pulse signal on the power cable;
the partial discharge tester is used for calculating the partial discharge amount of the power cable according to the partial discharge pulse signal.
Optionally, the signal coupling unit is divided into three phases, and the three phases are respectively connected with the metal outer protective layer of the middle joint.
Alternatively, the three phases of the signal coupling units can be connected in a star-shaped neutral point grounding mode, a star-shaped neutral point non-grounding mode or a triangular mode.
Alternatively, the signal coupling unit may be integrated with the intermediate splice enclosure cross-connect box.
Optionally, the high voltage capacitive coupling sensor comprises a coupling capacitor and a matching resistor; the first pole of the coupling capacitor is connected with the output end of the alternating-current high-voltage generating equipment, and the second pole of the coupling capacitor is connected with the first end of the matching resistor; and the second end of the matching resistor is connected with the common end.
In a second aspect, an embodiment of the present invention further provides a power cable partial discharge monitoring method, which is implemented based on the power cable partial discharge monitoring device in the first aspect, and the method includes:
the high-voltage alternating current generating device generates a low-frequency alternating current voltage signal which is applied to the power cable to enable the power cable to be partially discharged to generate a partial discharge pulse signal;
a plurality of signal coupling units couple the partial discharge pulse signals to the power cable full line;
a high-voltage capacitive coupling sensor and/or a high-frequency current transformer acquire a partial discharge pulse signal on the power cable and send the partial discharge pulse signal to the partial discharge tester;
and the partial discharge tester calculates the partial discharge quantity of the power cable according to the partial discharge pulse signal.
Optionally, the step of generating by the ac high voltage generating device a low frequency ac voltage signal to be applied to the power cable to cause the power cable to be partially discharged to generate a partial discharge pulse signal is preceded by the step of:
the power cable is characterized in that a signal coupling unit is arranged between any two adjacent sections of the power cable, the metal outer protective layers of any two sections are in cross connection, and a first input end, a second input end and a third input end of the signal coupling unit are respectively connected to the ABC phase metal outer protective layers of the sections.
Optionally, the three phases of the signal coupling unit are connected in a star-neutral-point grounding manner, a star-neutral-point non-grounding manner or a triangular manner.
According to the technical scheme, the power cable is provided with the alternating-current high-voltage generating equipment, the high-voltage capacitive coupling sensor and/or the high-frequency current transformer, the plurality of signal coupling units and the partial discharge tester; applying a low-frequency alternating voltage signal to a power cable by using alternating-current high-voltage generating equipment to enable the power cable to be partially discharged to generate a partial discharge pulse signal; coupling a partial discharge pulse signal to the power cable full line when the power cable is partially discharged using a plurality of signal coupling units; acquiring a partial discharge pulse signal on the power cable by using a high-voltage capacitive coupling sensor and/or the high-frequency current transformer; and calculating the partial discharge amount of the power cable according to the partial discharge pulse signal by using a partial discharge tester. Compared with the prior art, the method is suitable for the long-distance high-voltage ultrahigh-voltage power cable, and realizes the full-line partial discharge detection of the power cable; and a high-frequency pulse current method can be adopted, so that the phenomenon that a higher-frequency pulse signal is refracted and reflected in the power cable and is quickly attenuated is avoided, and the calculation precision of the local discharge capacity is improved. In addition, since the partial discharge pulse signal can be transmitted over the entire power cable, the capacity of the ac high voltage generator can be reduced in the case of the same length of power cable, or the length of the detection power cable can be increased in the case of the same capacity of ac high voltage generator.
Drawings
The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and not to be construed as limiting the invention in any way, and in which:
fig. 1 is a structural diagram of a partial discharge monitoring device for a power cable according to an embodiment of the present invention;
fig. 2 is a structural diagram of another power cable partial discharge monitoring device provided in the embodiment of the present invention;
fig. 3 is a schematic flow chart of a method for monitoring partial discharge of a power cable according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In a first aspect, the present invention provides a power cable partial discharge monitoring device, as shown in fig. 1, adapted to a long-distance single-core power cable 1 with a metal outer sheath of an intermediate joint cross-interconnected, the device comprising: the device comprises an alternating current high voltage generating device 0, a plurality of signal coupling units 2, a high voltage capacitive coupling sensor 3 and a partial discharge tester 4. Wherein, the alternating current high voltage generating equipment 0 is electrically connected with the power cable 1; the high-voltage capacitive coupling sensor 3 is electrically connected with the alternating-current high-voltage generating equipment 0; the signal coupling unit 2 is arranged on a metal outer protective layer of a middle joint of the power cable 1; the partial discharge tester 4 is electrically connected with the high-voltage capacitive coupling sensor 3;
an ac high voltage generating device 0 for applying a low frequency ac voltage signal to the power cable 1 to partially discharge the power cable 1 to generate a partial discharge pulse signal;
a plurality of signal coupling units 2 for coupling the partial discharge pulse signal to the entire line of the power cable 1 when the power cable 1 is partially discharged;
the high-voltage capacitive coupling sensor 3 is used for acquiring a partial discharge pulse signal on the power cable 1;
and the partial discharge tester 4 is used for calculating the partial discharge amount of the power cable 1 according to the partial discharge pulse signal.
In the embodiment of the present invention, the frequency of the low-frequency ac voltage signal is power frequency (50Hz), and the amplitude of the low-frequency ac voltage signal is a pulse signal exceeding 66 kV. Of course, the person skilled in the art can set the frequency of the low-frequency alternating voltage signal according to the specific scenario, for example, 30Hz to 300 Hz; the amplitude may be 60kV to 110kV, and the invention is not limited.
It should be noted that the power cable 1 in the embodiment of the present invention includes a plurality of segments, a segment 11, a segment 12, and a segment 13 (only 3 segments are shown in the figure) shown in fig. 1. For example, the segment 11 includes a segment a phase 111, a segment B phase 112, and a segment C phase 113 (only the segment 11 is illustrated), and the tail end of the metal outer sheath of the segment a phase 111 (the right end of the segment a phase 111 in fig. 1) is connected to the head end of the metal outer sheath of the segment B phase 121 in the segment 12 (the left end of the segment B phase 121 in fig. 1); the tail end of the metal outer sheath of the segment B phase 112 (the right end of the segment B phase 112 in fig. 1) is connected with the head end of the segment C phase 123 in the segment 12 (the left end of the segment C phase 123 in fig. 1); the tail end of the metal outer sheath of the segment C phase 113 (the right end of the segment C phase 113 in fig. 1) is connected to the head end of the metal outer sheath of the segment a phase 121 in the segment 12 (the left end of the segment a phase 121 in fig. 1). The metal outer protective layers of any two other adjacent sections of the power cable are connected in the cross-connection mode. Of course, other cross-connection modes can be adopted between two adjacent segments, and the invention is not limited.
As shown in fig. 1, the ac high voltage generating apparatus 0 according to the embodiment of the present invention includes a controller 10, a frequency converter 11, an exciting transformer 12, a series resonant inductor 13, and a capacitive voltage divider 14. The input end of the controller 10 is connected to the output end of the capacitive voltage divider 14, and the output end thereof is connected to the control end of the frequency converter 11. The input end of the frequency converter is connected with a power frequency (50Hz) alternating current power supply, and the output end of the frequency converter is connected with the input end of an excitation transformer 12. The first output end of the excitation transformer 12 is connected to the input end of the series resonant inductor 13, and the second output end thereof is connected to the ABC phase metal outer sheath of the corresponding segment 11 at one end of the power cable 1. The output terminal of the series resonant inductor 13 is connected to the a phase of the power cable 1, and BC of the power cable 1 is connected to the common terminal GND. The first end of the capacitive voltage divider 14 is connected to the output end of the series resonant inductor 13, and the second end thereof is connected to the second output end of the excitation transformer 12.
It should be noted that, in the embodiment of the present invention, the series resonant inductor 13 and the capacitive voltage divider 14 form a resonant circuit, a resonant frequency of the resonant circuit may be set at 30 to 300Hz, for example, 50Hz or 60Hz, and a person skilled in the art may adjust the resonant frequency of the resonant circuit according to a specific scenario, which is not limited by the present invention.
In practical application, the power cable partial discharge monitoring device provided by the embodiment of the invention further comprises a wave choke inductor 5. The input end of the wave-blocking inductor 5 is connected with the output end of the series-resonance inductor 13, and the output end of the wave-blocking inductor is connected with the phase a of the power cable 1 and the first end of the high-voltage capacitive coupling sensor 14, so as to prevent the high-frequency signal from being transmitted to the power cable 1 to cause interference.
The wave choke inductor 5 can be implemented by an inductor in the prior art, and the parameter value of the wave choke inductor 5 can be adjusted according to the parameters such as the frequency and the amplitude of the signal to be filtered, which is not limited in the invention.
In the embodiment of the present invention, a plurality of signal coupling units 2 are provided. Each signal coupling unit 2 comprises a first input terminal 211, a second input terminal 212, a third input terminal 213 and an output terminal 214. The first input end 211 of the signal coupling unit 2 is connected to the tail end of the metal outer sheath of the segment a-phase 111 in the segment 11, the second input end 212 thereof is connected to the tail end of the metal outer sheath of the segment B-phase 112, the third input end 213 thereof is connected to the tail end of the metal outer sheath of the segment C-phase 113, and the output end 214 thereof is connected to the common terminal GND. It can be seen that, no matter where the power cable is in partial discharge, the partial discharge pulse signal is transmitted on the whole power cable line through the signal coupling unit 2, for example, when partial discharge occurs in the segment B phase in the segment 13, the partial discharge pulse signal is transmitted to the segment C phase in the segment 12 and the segment a phase in the segment 11 through the signal coupling unit 2, and the whole line transmission is realized at the final end.
The signal coupling unit 2 in the embodiment of the present invention may be provided in various structures. As shown in fig. 1 and 2, the three phases of the signal coupling units can be connected in a star-neutral-point grounding manner, a star-neutral-point non-grounding manner or a triangular manner. As shown in fig. 1, the high voltage capacitive coupling sensor 3 in the embodiment of the present invention includes a coupling capacitor 31 and a matching resistor 32. A first pole of the coupling capacitor 31 is connected to the output terminal of the ac high voltage generator 0, and a second pole thereof is connected to a first terminal of the matching resistor 32; a second terminal of the matching resistor 32 is connected to the common terminal GND. The high-voltage capacitive coupling sensor 3 can obtain a partial discharge pulse signal generated when the power cable 1 is partially discharged from the output end of the wave-blocking inductor 5, and then the partial discharge pulse signal is divided by the matching resistor 32.
In the embodiment of the present invention, the frequency converter 11 converts the power frequency ac power into a low frequency ac voltage signal (30 to 300Hz, for example, 50Hz or 60Hz), and after the amplitude of the low frequency ac voltage signal is adjusted by the exciting transformer 12, the low frequency ac voltage signal with the resonant frequency is screened by the resonant circuit formed by the series resonant inductor 13 and the capacitive voltage divider 14. The low-frequency alternating voltage signal is filtered by the wave-blocking inductor 5 and then transmitted to the power cable 1. When the power cable 1 is partially discharged, the partial discharge pulse signal generated by the power cable 1 is transmitted all the way through the signal coupling unit 2 to one end (the left end of the power cable 1 in fig. 1) of the power cable 1, and then transmitted to the common terminal GND through the high-voltage capacitive coupling sensor 3. When the partial discharge pulse signal passes through the high-voltage capacitive coupling sensor 3, the partial discharge tester 4 acquires the partial discharge pulse signal in real time through the detection end arranged at the matching resistor 32, and calculates the partial discharge amount according to the partial discharge pulse signal.
It should be noted that, in the embodiment of the present invention, an electrical connection relationship of the high-voltage capacitive coupling sensor 3 is introduced, and a person skilled in the art may calculate parameters of the matching resistor 32 and the coupling capacitor 31 in the high-voltage capacitive coupling sensor 3 according to an actual application scenario of the power cable, where the specific calculation method may be implemented by using an existing method. In addition, those skilled in the art may select other circuits to implement the high-voltage capacitive coupling sensor 3 according to actual needs, and the embodiments of the present invention also fall into the protection scope.
In practical applications, as shown in fig. 2, an HFCT (high frequency current transformer) may be disposed between the excitation transformer 12 and the metal outer sheath of the power cable segment 11, and the HFCT may measure a partial discharge pulse signal and then transmit the signal to the partial discharge tester 4. The partial discharge amount is calculated by the partial discharge tester 4 based on the above-described partial discharge pulse signal. Of course, the partial discharge tester 4 may also collect partial discharge pulse signals from the HFCT and the high-voltage capacitive coupling sensor 3, respectively, then calculate the partial discharge amount, respectively, and take the average of the two as the final partial discharge amount, thereby improving the accuracy.
In a second aspect, an embodiment of the present invention further provides a power cable partial discharge monitoring method, which is implemented based on the power cable partial discharge monitoring device in the first aspect, and as shown in fig. 3, the method includes:
s1, generating a low-frequency alternating-current voltage signal by an alternating-current high-voltage generating device, applying the low-frequency alternating-current voltage signal to the power cable to enable the power cable to be partially discharged to generate a partial discharge pulse signal;
s2, coupling the partial discharge pulse signal to the whole line of the power cable by a plurality of signal coupling units;
s3, the high-voltage capacitive coupling sensor and/or the high-frequency current transformer acquire a partial discharge pulse signal on the power cable and send the partial discharge pulse signal to the partial discharge tester;
and S4, the partial discharge tester calculates the partial discharge amount of the power cable according to the partial discharge pulse signal.
In the embodiment of the present invention, an ac high voltage generator 0 is connected to one end of the power cable 1. The alternating-current high-voltage generating equipment 0 converts a power-frequency alternating-current power supply into low-frequency alternating-current voltage signals (30-300 Hz, such as 50Hz and 60Hz), and then the low-frequency alternating-current voltage signals corresponding to the resonant frequency are screened out through the resonant circuit. The low-frequency alternating voltage signal is filtered by the wave-blocking inductor 5 and then transmitted to the power cable 1. When the power cable 1 is partially discharged, the partial discharge pulse signal generated by the power cable 1 is transmitted all the way through the signal coupling unit 2 to one end (the left end of the power cable 1 in fig. 1) of the power cable 1, and then transmitted to the common terminal GND through the high-voltage capacitive coupling sensor 3. When the partial discharge pulse signal passes through the high-voltage capacitive coupling sensor 3, the high-voltage capacitive coupling sensor 3 can obtain the partial discharge pulse signal generated when the power cable 1 is partially discharged from the output end of the wave-blocking inductor 5, and then the partial discharge pulse signal is divided by the matching resistor 32. The partial discharge tester 4 acquires the partial discharge pulse signal in real time by being arranged at the detection end of the matching resistor 32; then, the partial discharge amount of the power cable 1 is calculated from the above-mentioned partial discharge pulse signal.
The method for monitoring the partial discharge of the power cable provided by the embodiment of the invention further comprises the following steps:
s5, arranging a signal coupling unit between any two adjacent sections of the power cable, wherein the metal outer protective layers of any two sections are in cross connection, and a first input end, a second input end and a third input end of the signal coupling unit are respectively connected to the ABC phase metal outer protective layers of the sections.
In the embodiment of the present invention, when monitoring partial discharge, a signal coupling unit 2 is further required to be disposed between any two adjacent segments. One ends of the first, second and third shorting wires of each signal coupling unit are shorted, or one ends of the first, second and third shorting wires are electrically connected to a common terminal in common.
In summary, the power cable partial discharge monitoring apparatus and method provided by the embodiments of the present invention are provided with an ac high voltage generating device, a high voltage capacitive coupling sensor, a plurality of signal coupling units, and a partial discharge tester; applying a low-frequency alternating voltage signal to a power cable by using alternating-current high-voltage generating equipment to enable the power cable to be partially discharged to generate a partial discharge pulse signal; the signal coupling units are arranged between any two adjacent sections of the power cable and couple partial discharge pulse signals to the whole line of the power cable; acquiring a partial discharge pulse signal on a power cable by using a high-voltage capacitive coupling sensor and/or a high-frequency current transformer; and the partial discharge tester calculates the partial discharge quantity of the power cable according to the partial discharge pulse signal. Therefore, the method is suitable for the long-distance high-voltage and ultrahigh-voltage power cable, and realizes the full-line partial discharge detection of the power cable; and a high-frequency pulse current method can be adopted, so that the phenomenon that a higher-frequency pulse signal is refracted and reflected in the power cable and is quickly attenuated is avoided, and the calculation precision of the local discharge capacity is improved.
In the present invention, the terms "first", "second", and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. The term "plurality" means two or more unless expressly limited otherwise.
Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations fall within the scope defined by the appended claims.
Claims (8)
1. A power cable partial discharge monitoring device adapted for a long distance single core power cable with cross-interconnected metallic outer jacket of an intermediate joint, the device comprising: the device comprises alternating current high voltage generating equipment, a high voltage capacitive coupling sensor and/or a high frequency current transformer, a plurality of signal coupling units and a partial discharge tester; wherein the alternating current high voltage generating device is electrically connected with the power cable; the high-voltage capacitive coupling sensor is electrically connected with the alternating-current high-voltage generating equipment; the high-frequency current transformer is arranged between the alternating-current high-voltage generating equipment and the power cable sectional metal outer protective layer and is electrically connected with the alternating-current high-voltage generating equipment and the power cable sectional metal outer protective layer; the signal coupling unit is arranged on the metal outer protective layer of the intermediate joint; the partial discharge tester is electrically connected with the high-voltage capacitive coupling sensor;
the alternating-current high-voltage generating equipment is used for applying a low-frequency alternating-current voltage signal to the power cable by converting a power-frequency alternating-current power supply into an alternating-current voltage signal with a frequency band of 30-300 Hz so as to enable the power cable to generate a partial discharge pulse signal through partial discharge;
a plurality of signal coupling units for coupling a partial discharge pulse signal to the entire power cable when the power cable is partially discharged;
the high-voltage capacitive coupling sensor and/or the high-frequency current transformer are/is used for acquiring a partial discharge pulse signal on the power cable;
the partial discharge tester is used for calculating the partial discharge amount of the power cable according to the partial discharge pulse signal.
2. The apparatus according to claim 1, wherein the signal coupling unit is divided into three phases, and is connected to the metal outer sheath of the middle connector.
3. A power cable partial discharge monitoring device according to claim 2, wherein the signal coupling unit three phases are connectable in star-neutral-grounded, star-neutral-ungrounded or delta-connected manner.
4. A power cable partial discharge monitoring device according to any of claims 1 to 3, wherein the signal coupling unit is integrated with an intermediate splice sheath cross-connect box.
5. A power cable partial discharge monitoring device according to any of claims 1 to 3, wherein the high voltage capacitive coupling sensor comprises a coupling capacitor and a matching resistor; the first pole of the coupling capacitor is connected with the output end of the alternating-current high-voltage generating equipment, and the second pole of the coupling capacitor is connected with the first end of the matching resistor; and the second end of the matching resistor is connected with the common end.
6. A power cable partial discharge monitoring method, which is implemented based on the power cable partial discharge monitoring device of any one of claims 1 to 5, and comprises the following steps:
the high-voltage alternating current generating device generates a low-frequency alternating current voltage signal which is applied to the power cable to enable the power cable to be partially discharged to generate a partial discharge pulse signal;
a plurality of signal coupling units couple the partial discharge pulse signals to the power cable full line;
a high-voltage capacitive coupling sensor and/or a high-frequency current transformer acquire a partial discharge pulse signal on the power cable and send the partial discharge pulse signal to the partial discharge tester;
and the partial discharge tester calculates the partial discharge quantity of the power cable according to the partial discharge pulse signal.
7. The power cable partial discharge monitoring method of claim 6, wherein the step of generating a low frequency ac voltage signal by the ac high voltage generating device to be applied to the power cable to cause partial discharge of the power cable to generate a partial discharge pulse signal is preceded by the steps of:
the power cable is characterized in that a signal coupling unit is arranged between any two adjacent sections of the power cable, the metal outer protective layers of any two sections are in cross connection, and a first input end, a second input end and a third input end of the signal coupling unit are respectively connected to the ABC phase metal outer protective layers of the sections.
8. A power cable partial discharge monitoring method according to claim 6 or 7, characterized in that the three phases of the signal coupling unit are connected in star-neutral-grounded, star-neutral-ungrounded or delta-connected manner.
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| CN109406974A (en) * | 2018-12-13 | 2019-03-01 | 合肥金瑞配网电气设备有限公司 | A kind of authentic partial discharge monitoring device of switchgear |
| CN115047302B (en) * | 2022-08-15 | 2022-12-30 | 国网江西省电力有限公司电力科学研究院 | Cable series resonance partial discharge detection system and method based on double transformers |
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