TWI737309B - On-line measuring system for partial discharges signals of cable joints - Google Patents

Abstract

An on-line measuring system for partial discharges signals of cable joints includes two high-frequency current transformers with the same polarity, at least one ground ring and a monitoring unit. The two high-frequency current transformers respectively surround the outer surface of two shoulder portions of the cable joint. The ground ring conductively contacts an outer semiconductive layer of the cable joint. The cable shielding layers of two cables connected to the two ends of the cable joint are crossed from the outside of the two high-frequency current transformers, and are electrically connected to the ground ring. The exposed inner wires of the two cables after removing the cable shielding layer are respectively inserted into the two ends of the cable joint, and pass through the insides of the two high-frequency current transformers simultaneously. Two sensing signals generated by the two high-frequency current transformers are transferred to the monitoring unit for signal processing. The invention can eliminate the external noise of the cable joint when measuring the partial discharges inside the cable joint; and eliminate the internal noise of the cable joint when measuring the partial discharges outside the cable joint.

Description

On-line measurement system for partial discharge signals of cable joints

The present invention relates to an on-line measurement system for partial discharge signals of cable joints, in particular to an on-line measurement system for measuring the internal discharge signals of linear joints in the environment of underground cable ducts.

Under the long-term load of the underground power distribution system, the cable insulation material may deteriorate or even malfunction. Generally speaking, underground cable accidents can be divided into cable body and cable joints according to the location of occurrence. According to statistics, underground cable accidents mostly occur at cable joints, such as straight joints and terminal joints. Therefore, the research on the insulation status of the cable joints of underground cables, and the use of online detection and diagnosis to provide maintenance of the insulation status have become an important project for the maintenance and development of high-voltage power equipment.

At present, for the assessment of the insulation status of underground cables, partial discharge data is used internationally as the main indicator. If the partial discharge data can be monitored in real time, it can provide a predictable maintenance basis for the initial damage of high-voltage power equipment, and then repair it in a timely manner according to its insulation state to avoid unexpected power outages.

Common detection methods for underground cable joints can be divided into non-electrical detection and electrical detection. Non-electrical detection methods such as manual detection of the surface temperature of the cable joint with an infrared searcher, or the use of ultrasonic detection. Electrical testing usually uses high-frequency sensors for on-site online measurement, which is easy to perform quantitative testing and has good sensitivity.

However, the use of infrared searchers for manual detection cannot know the partial discharge value of the cable joint, and cannot achieve the purpose of real-time online monitoring. Generally, ultrasonic detection needs to use a sound collector to collect ultrasonic waves, and its sensitivity is very low for the detection of deep partial discharge of insulating materials. It is more suitable for gas-sealed switchgear (Gas Insulated Switchgear), which is used in the amount of cables and cable joints. The test results are limited.

When traditionally using High Frequency Current Transformer (HFCT) to measure the partial discharge of the cable connector, it can only be installed on the grounding wire or the cable body, and the captured signal will be accompanied by many external Noise, thus increasing the difficulty of spectrum identification, and will cause the problem of partial discharge signal attenuation.

An object of the present invention is to provide an online measurement system for partial discharge signals of cable joints, which can eliminate noise generated by external currents and enhance the partial discharge signals.

In order to achieve the above objective, the present invention provides an online measurement system for partial discharge signals of cable joints, which is suitable for measuring the partial discharges that occur inside and outside the linear joints. Among them, the linear joint covers the crimping part of the two cables. The basic composition of this system includes two current sensors, at least one ground ring and a monitoring unit. The two current sensors have the same polarity and are respectively installed on the two shoulders of the linear joint. When a partial discharge occurs in the linear joint, the two current sensors generate two sensing signals. The grounding ring is arranged between the two current sensors, and conductively contacts the outer semi-conductive layer of the linear joint. The respective cable shielding layers of the two cables connected at the two ends of the straight connector span from the outside of the two current sensors and are electrically connected to the grounding ring. After removing the cable shielding layer of the two cables, the exposed inner cable is inserted into the straight connector and passes through the inner side of one of the two current sensors at the same time. The monitoring unit is electrically connected to the two current sensors for performing a signal processing procedure on the two sensing signals, thereby generating a partial discharge data.

In one embodiment, the respective cable shielding layers of the two cables are stripped from the outside, and the stripped two cable shielding layers are connected to form a cable jumper shielding wire, and the cable jumper shielding wire spans from the outside of the two current sensors And it is electrically connected with the grounding ring.

In one embodiment, the number of grounding rings is one, and the grounding ring and the cable jumper shielding wire are connected by a single grounding lead.

In one embodiment, the number of grounding rings is two, and the two grounding rings are respectively installed on the two shoulders of the linear joint. The two grounding rings are respectively electrically connected to the cable jumper shielding wire by two grounding leads. Each ground ring includes two semi-circular ring-shaped conductive sheets, and each semi-circular ring-shaped conductive sheet has a ground hole. Each ground lead has a ground hole with one end tied to one of the semicircular ring-shaped conductive sheets, and the other end is crimped with the cable jumper shielding wire.

In one embodiment, the monitoring unit is used to measure the internal discharge of the linear connector, and it includes two oscillating circuits, two surge protection components, a first multiplexer, a differential, an amplifier, and an absolute value holding circuit. , A peak hold circuit, an analog-to-digital converter and a microcontroller. The two oscillating circuits are respectively electrically connected to the two current sensors, and the two surge protection elements are respectively electrically connected to the two oscillating circuits and both are electrically connected to the first multiplexer. The first multiplexer, the differential and the amplifier are electrically connected in sequence. The absolute value holding circuit is connected between the amplifier and the peak holding circuit, and the peak holding circuit is electrically connected between the absolute value holding circuit and the analog-to-digital converter.

In one embodiment, the monitoring unit further includes an adder and a second multiplexer for measuring the external discharge of the linear joint. Wherein, the adder and the differential form a parallel structure, the parallel structure is electrically connected between the first multiplexer and the second multiplexer, and the second multiplexer is electrically connected between the parallel structure and the amplifier.

In one embodiment, each current sensor is composed of two semicircular ring-shaped sensing elements, and is suitable for temporary installation on a linear joint in an existing underground cable duct by means of a clamp.

In one embodiment, each current sensor is a single complete ring-shaped sensing element, which is suitable for being installed at both ends of the linear joint during installation.

The present invention uses a non-invasive high frequency current transformer (High Frequency Current Transformer, HFCT) to measure the partial discharge pulse current on the cable connector, and is matched with a signal processing module such as a back-end differential circuit to accurately identify the local The discharge signal comes from the inside or outside of the cable connector, and separates the noise to obtain the relevant data of the partial discharge.

The foregoing and other technical content, features, and effects of the present invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the drawings. The directional terms mentioned in the following embodiments, for example: up, down, left, right, front or back, etc., are only directions for referring to the accompanying drawings. Therefore, these directional terms are only used for explanation and not for limiting the present invention.

FIG. 1 is an embodiment of the online measurement system for partial discharge signals of cable joints and its use environment of the present invention. The online measurement system 10 for partial discharge signals of cable joints (hereinafter referred to as "system 10") of this embodiment is applicable to the environment of R, S, T three-phase 25 kV distribution-level high-voltage underground cable ducts inside a manhole 20. In the underground cable duct shown in FIG. 1, each single-phase cable includes a straight line connector 30 and the cables 31L and 31R connected to the left and right ends. 25 kV distribution-level linear connectors 30 are generally used for feeder lines (600A, 500MCM) and branch lines (200A, #1 AMG) or similar structures to the two. For each linear joint 30, the system 10 provides two current sensors 11L and 11R, two grounding rings (see the grounding rings 12L and 12R in FIG. 2) arranged in the housing 122, and a partial discharge monitoring unit (Partial Discharge Monitoring Unit). , PDMU) 13, used to measure the partial discharge generated inside the linear joint 30.

The current sensors 11L and 11R of this embodiment adopt high-frequency current sensors, which are also called high-frequency current sensors. Two current sensors 11L and 11R are installed on the left and right ends of the linear connector 30 to sense the partial discharge pulse current inside the linear connector 30 to generate two sensing signals, and transmit the measured two sensing signals The partial discharge monitoring unit 13 performs a differential signal processing procedure, thereby generating a partial discharge data. The grounding rings 12L and 12R inside the two shells 122 are installed on the shoulders of the two ends of the linear connector 30, and can electrically contact the outer semi-conductive layer of the shoulders to avoid the measurement by the two current sensors 11L and 11R The partial discharge signal is interfered by noise. The partial discharge monitoring unit 13 can perform subsequent signal processing on the partial discharge signals from the two current sensors 11L and 11R, and transmit the processed data to a computer through the network 14 for insulation diagnosis analysis.

FIG. 2 illustrates an embodiment of the wiring structure between the system 10 and the linear joint 30 for a single-phase cable. The linear joint 30 has two shoulders 30L and 30R at its two ends, and an outer semi-conductive layer 30S on its surface. The two ports of the straight connector 30 are respectively connected to the inner cables 311L and 311R of the two cables 31L and 31R. When the system 10 is connected to the linear connector 30, the two current sensors 11L and 11R are respectively installed on the shoulders 30L and 30R of the linear connector 30, and are electrically connected to the partial discharge monitoring unit 13. In this embodiment, the two current sensors 11L and 11R need to have the same polarity.

The ground ring 12L or 12R of this embodiment is essentially a conductive sheet, which is installed on the inner side wall of the housing 122, surrounds the shoulders 30L and 30R of the linear joint 30 and contacts the outer semiconductive layer 30S. In addition to accommodating the ground ring 12L or 12R, the housing 122 can also accommodate two current sensors 11L and 11R. It should be noted that the positions of the two ground rings 12L or 12R need to be between the two current sensors 11L and 11R.

2A, each cable 31L (or 31R) has a central conductor 313, and the outer side of the central conductor 313 is sequentially covered with an inner semiconducting layer 314, an insulating layer 315, an outer semiconducting layer 316, and a cable shield. Layer 32L (or 32R) and a skin 312L (or 312R). It is worth noting that in order to avoid the interference of external noise, part of the cable shielding layers 32L and 32R of the two cables 31L and 31R together with the outer skins 312L and 312R are stripped, and then the two stripped cable shielding layers 32L and 32R are connected to each other. Synthesize a cable to jumper the shielding wire 32. The cable jumper shielding wire 32 is crossed from the outside of the two current sensors 11L and 11R, and then the two grounding leads 15L and 15R are electrically connected to the two grounding rings 12L and 12R, respectively. In one embodiment, the two ground leads 15L and 15R each have one end connected to a ground hole 124 of the ground rings 12L and 12R, and the other end connected to a crimping terminal 33, and the shielding wire is connected to the cable through the crimping terminal 33. 32 crimped together. In this way, the current flowing through the cable shielding layers 32L and 32R will not pass through the inner sides of the two current sensors 11L and 11R, thereby eliminating noise caused by the current flowing through the cable shielding layers 32L and 32R.

In the cable 31L or 31R, an inner cable 311L, 311R is exposed after the cable shielding layer 32L, 32R and the outer skin 312L, 312R are stripped. The inner cables 311L and 311R include various layers such as a central conductor 313, an inner semiconductive layer 314, an insulating layer 315, and an outer semiconductive layer 316. When wiring, the inner cables 311L and 311R are inserted into the straight connector 30 and pass through the inner side of the two current sensors 11L and 11R at the same time.

FIG. 2B shows the structure in which the inner cables 311L and 311R are inserted into the linear joint 30. In FIG. 2B, the two shoulders 30L and 30R of the linear connector 30 have not been installed with the current sensors 11L, 11R and the grounding rings 12L, 12R, and the shoulder 30R has a hole called the grounding eye 124A to provide the grounding lead 15R binding. The linear joint 30 includes an outer semiconducting layer 30S, an insulating layer 301, an inner semiconducting layer 302, and a conductor connecting sleeve 303 from the outside to the inside. After the two inner cables 311L and 311R are inserted into the straight joint 30, the central conductor 313 of the two inner cables 311L and 311R is electrically connected through the conductor connection sleeve 303. The inner semiconductive layer 314, insulating layer 315, and outer semiconductive layer 316 of the two inner cables 311L and 311R are electrically connected to the inner semiconductive layer 302, insulating layer 301, and outer semiconductive layer 30S of the linear joint 30, respectively. . It is worth mentioning that the experiment has proved that if the current sensors 11L and 11R are installed in the structure of Figure 2B but the grounding rings 12L and 12R are not installed, the noise elimination effect is far inferior to that after the installation of the grounding rings 12L and 12R. Effect. Therefore, adding grounding rings 12L and 12R can greatly improve the measurement accuracy, which is an effect that is difficult for those skilled in the art to predict.

In the embodiment of FIG. 2, the direction of the external current flowing through the central conductor 313 of the inner cables 311L and 311R is all to the left, and the direction of the pulse current of the internal discharge of the linear joint 30 is one left and one right. The sensing signal generated by the two current sensors 11L and 11R induced by the external current and the pulse current of the internal discharge is subtracted by a differential 134, and the external current is the same on the two current sensors 11L and 11R. The sensed signal of polarity and magnitude is subtracted to zero after passing through the differential 134, thereby eliminating the interference caused by the external current flowing through the central conductor 313 to the internal partial discharge signal of the linear joint 30. On the contrary, the internally discharged pulse current will generate sensing signals of the same magnitude but opposite polarity on the two current sensors 11L and 11R, and the subtracted signal after passing through the differential 134 will be doubled, thereby enhancing the linear joint 30 The internal partial discharge signal.

3A to 3C are schematic diagrams of the combined structure of the left shoulder 30L of the linear connector 30, the current sensor 11L, the ground ring 12L, and the housing 122 of the embodiment shown in FIG. 2, wherein FIG. 3A is an exploded view, and FIG. 3B is a combined view. Figure 3C is a side view. The inside of the housing 122 shown in FIGS. 3A to 3C all includes a ground ring 12L surrounding the shoulder 30L.

The current sensor 11L of FIG. 3A is a single ring-shaped sensing element, which has a complete ring-shaped structure and includes a coil for inducing a pulse current signal and connected to the partial discharge monitoring unit 13, suitable for installation and construction of the linear joint 30 Installed at its two ends. The left end of the linear joint 30 in FIG. 3A passes through the inner side of the high-frequency current sensor 11L. The ground ring 12L of this embodiment includes two semi-circular ring-shaped conductive sheets, and each semi-circular ring-shaped conductive sheet is, for example, the conductive copper foil 125 in FIG. 3A. The left side of the housing 122 is used for accommodating the current sensor 11L; the right side is designed according to the shape of the conductive copper foil 125 and is used for accommodating the conductive copper foil 125. The right side of the housing 122 has a hole 124B. The semicircular ring-shaped conductive copper foil 125 is attached to the inner side wall of the semicircular ring-shaped casing 122, the conductive copper foil 125 is in close contact with the outer semiconductive layer 30S of the shoulder 30L of the linear connector 30, and the ground hole 124 is connected to the hole 124B on the casing 122 and After the grounding eye 124A on the shoulder 30L is aligned and combined, its appearance structure is shown in Fig. 3B.

Fig. 3C shows that the semi-circular annular housing 122 provides a plurality of screw holes 123 for aligning with another semi-circular annular housing 122 to be combined and fixed as shown in Fig. 3B. After the combination, the grounding hole 124, the grounding eye 124A, and the hole 124B are overlapped for binding one end of the grounding lead 15L, and crimping the other end of the grounding lead 15L with the left end of the cable jumper shielding wire 32.

FIG. 3D and FIG. 3E show a second type of current sensor 110R, which is installed at the right end of the linear connector 30. The current sensor 110R is a combination of two semi-circular ring-shaped sensing elements 112R and 114R, and is suitable for temporary installation on the linear joint 30 in the existing underground cable duct in a clamping manner.

FIG. 4 is another embodiment of the wiring structure of the system 10 and the linear joint 30. The difference from the embodiment in FIG. 2 is that the number of the ground ring 12 in this embodiment is only one, which surrounds the middle part of the linear joint 30 and is located between the two current sensors 11L and 11R, and can be compared with the outer semiconductive layer 30S. Conductive close contact. In addition, the ground ring 12 and the cable jumper shield wire 32 are connected by a single ground lead 15. Although the structure of FIG. 4 is relatively simplified, it can also eliminate the noise interference caused by the current flowing through the cable shielding layers 32L and 32R and the center conductor 313 from the outside of the linear connector 30, and strengthen the internal part of the linear connector 30 Discharge signal and other functions.

FIG. 5 is a functional block diagram of a partial discharge monitoring unit (PDMU) according to an embodiment of the present invention. For the combined structure of two current sensors 11L and 11R and two grounding rings 12L and 12R installed on each linear joint 30, the partial discharge monitoring unit 13 provides two oscillation circuits 131, two surge protection elements 132, and a multiplexer. 133, a differential 134, an amplifier 135, an absolute value hold circuit 136, a peak hold circuit 137, an analog-to-digital converter (ADC) 138, and a microcontroller (Microcontroller Unit) , MCU) 139. The two oscillating circuits 131 are electrically connected to the two current sensors 11L and 11R, respectively. The two surge protection elements 132 are respectively electrically connected to the two oscillating circuits 131 and both are electrically connected to the multiplexer 133. Subsequently, the multiplexer 133, the differential 134, and the amplifier 135 are electrically connected in sequence. In particular, in this embodiment, the absolute value holding circuit 136 is connected between the amplifier 135 and the peak holding circuit 137, and the peak holding circuit 137 is electrically connected between the absolute value holding circuit 136 and the analog-to-digital converter 138.

In underground cable ducts, the linear joints 30 of the R, S, T three-phase cables each generate two sets of sensing signals through two current sensors 11L and 11R, and the two sensing signals are respectively extended by two oscillating circuits 131 to extend their partial discharge pulses. The identification time is used by the two surge protection elements 132 to prevent voltage surges from damaging the signal processing module at the back end. Next, the measurement phase is selected through the multiplexer 133, the differential 134 identifies whether it is the internal signal of the linear connector 30, and the amplifier 135 amplifies the signal. The absolute value holding circuit 136 converts the signal to a positive value, and then the peak holding circuit 137 takes the maximum value of the signal, which is sampled and transmitted to the microcontroller 139 through the analog-to-digital converter 138. Finally, the microcontroller 139 transmits the data to the computer 16 for insulation diagnosis and analysis.

FIG. 6 is a functional block diagram of a partial discharge monitoring unit according to another embodiment of the present invention. The difference from FIG. 5 is that the partial discharge monitoring unit 13A has an adder 134A and a second multiplexer 133A. The adder 134A and the differential 134 form a parallel structure, the parallel structure is electrically connected between the first multiplexer 133 and the second multiplexer 133A, and the second multiplexer 133A is electrically connected to the parallel structure and the amplifier 135 between. Both the first multiplexer 133 and the second multiplexer 133A are electrically connected to the microcontroller 139.

The sensing signals generated by the partial discharges generated outside the two current sensors 11L and 11R induction linear joint 30 are added by the adder 134A, and the external discharges generate the same polarity on the two current sensors 11L and 11R The sense signal of sum size will be doubled after passing through the adder 134, thereby enhancing the external discharge signal of the linear connector 30. On the contrary, the internal current will generate sensing signals of the same magnitude but opposite polarity on the two current sensors 11L and 11R, which are subtracted to zero after passing through the adder 134A. When measuring the external discharge of the linear connector 30, the noise interference caused by its internal current can be eliminated.

In summary, the present invention uses two sets of non-intrusive high-frequency current sensors of the same polarity to be arranged at both ends of the cable joint, and the high-frequency current sensor is provided with a grounding ring outside, which is fixed on the two ends of the cable joint. At the shoulder, the shielding layer of the cable is connected to the outer semiconducting layer of the cable joint by using the grounding ring across the high-frequency current sensor. Compared with the case of no grounding ring, the present invention can effectively measure the polarity of the partial discharge pulse current signal inside the cable joint, and then filter the noise from the external circuit by the back-end differential circuit; it can also be measured The polarity of the partial discharge pulse current signal outside the cable connector is then filtered by the back end adder to filter out the noise from the inside of the connector. After that, through the amplifier circuit, absolute value circuit, peak hold circuit, analog signal sampling circuit to the microcontroller, the internal or external partial discharge evolution map is obtained, including discharge capacity, voltage phase, pulse time, and finally the measurement signal integration product The networking technology is transmitted to the cloud for real-time monitoring. With the online measurement system for partial discharge signals of cable joints of the present invention, the partial discharge signals can be accurately identified from the inside or outside of the cable joints, and noises can be separated to obtain relevant data of partial discharges.

However, the above are only preferred embodiments of the present invention, and should not be used to limit the scope of implementation of the present invention, that is, simple equivalent changes and modifications made in accordance with the scope of the patent application of the present invention and the description of the invention, All are still within the scope of the invention patent. In addition, any embodiment of the present invention or the scope of the patent application does not have to achieve all the objectives or advantages or features disclosed in the present invention. In addition, the abstract part and title are only used to assist in searching for patent documents, and are not used to limit the scope of rights of the present invention.

10: On-line measurement system for partial discharge signals of cable joints

11L, 11R, 110R: current sensor

112R, 114R: semicircular ring sensing element

12, 12L, 12R: grounding ring

122: shell

123: screw hole

124: Grounding hole

124A: Ground eye

124B: Hole

125: conductive copper foil

13, 13A: Partial discharge monitoring unit

131: Oscillation Circuit

132: Surge protection component

133: Multiplexer (the first multiplexer)

133A: second multiplexer

134: Differential

134A: Adder

135: Amplifier

136: Absolute value holding circuit

137: Peak hold circuit

138: Analog-to-digital converter

139: Microcontroller

14: Internet

15, 15L, 15R: ground lead

16: computer

20: Manhole

30: Straight connector

30L, 30R: shoulder

30S: Outer semi-conductive layer

301: Insulation layer

302: inner semiconducting layer

303: Conductor connection sleeve

31L, 31R: cable

311L, 311R: inner cable

312L, 312R: outer skin

313: Center conductor

314: inner semiconducting layer

315: Insulation layer

316: Outer semi-conductive layer

32: Cable jumper shielding wire

32L, 32R: cable shielding layer

33: Crimp terminal

FIG. 1 is a schematic diagram of a partial discharge signal line measurement system architecture of an underground power cable connector according to an embodiment of the present invention.

Fig. 2 is a schematic diagram of a partial discharge signal measurement connection diagram of an underground power cable joint according to an embodiment of the present invention.

Fig. 2A is a schematic diagram of the inner layer structure of a cable according to an embodiment of the present invention.

Fig. 2B is a schematic diagram of the internal structure of a linear joint according to an embodiment of the present invention.

3A to 3C are schematic diagrams of the combined structure of a linear connector, a high-frequency current sensor, and a ground ring according to an embodiment of the present invention.

3D and 3E show schematic diagrams of another type of high-frequency current sensor structure.

Fig. 4 is a schematic diagram of a partial discharge signal measurement connection diagram of an underground power cable joint according to another embodiment of the present invention.

FIG. 5 is a functional block diagram of a partial discharge monitoring unit (PDMU) according to an embodiment of the present invention.

FIG. 6 is a functional block diagram of a partial discharge monitoring unit according to another embodiment of the present invention.

11L, 11R: current sensor

12L, 12R: Grounding ring

122: shell

13: Partial discharge monitoring unit

134: Differential

15L, 15R: ground lead

30: Straight connector

30L, 30R: shoulder

30S: Outer semi-conductive layer

31L, 31R: cable

311L, 311R: inner cable

312L, 312R: outer skin

32: Cable jumper shielding wire

32L, 32R: cable shielding layer

33: Crimp terminal

Claims (11)

An online measurement system for partial discharge signals of cable joints, which is suitable for measuring the partial discharges that occur inside and outside a straight joint. The straight joint is used to cover the crimping part of two cables and has two shoulders and an outer part. Semi-conductive layer, each of the cables has a cable shielding layer and an inner cable, the inner cable includes a central conductor, the cable shielding layer covers the inner cable and is connected to the central conductor Electrically insulated, the system includes: two current sensors with the same polarity and are respectively installed on the two shoulders of the linear joint. When a partial discharge occurs in the linear joint, the two current sensors generate two senses. Measuring signal; at least one grounding ring is arranged between the two current sensors and conductively contacts the outer semi-conductive layer of the linear joint, wherein the two cable wires each have a part of the cable shielding layer is stripped Outside the inner cable, guide the stripped two-part cable shielding layer to the outside of the two current sensors, and make the two-part cable shielding layer from the outside of the two current sensors to the ground The loop forms an electrical connection, and each of the inner cables is inserted into the straight connector and passes through the inner side of one of the two current sensors; and a monitoring unit is electrically connected to the two current sensors for pairing The two sensing signals execute a signal processing procedure. The online measurement system for partial discharge signals of cable joints as described in item 1 of the scope of patent application, wherein the two parts of the cable shielding layer that have been stripped are joined to form a cable jumper shielding wire, and the cable jumper shielding wire draws from the two currents The outside of the sensor spans and is electrically connected to the ground ring. The online measurement system for partial discharge signals of cable joints as described in item 2 of the scope of patent application, wherein the number of the grounding ring is one, and includes a single grounding lead connected between the grounding ring and the cable jumper shielding wire . In the online measurement system for partial discharge signals of cable joints as described in item 2 of the scope of patent application, the number of the grounding rings is two, and the two grounding rings are respectively installed on the two shoulders of the linear joint. As described in item 4 of the scope of patent application, the online measurement system for partial discharge signals of cable joints further includes two grounding leads, wherein each of the grounding leads is connected to one of the two grounding rings and the cable jumper shielding wire. between. In the online measurement system for partial discharge signals of cable joints as described in item 4 of the scope of patent application, each of the ground rings includes two semicircular ring-shaped conductive plates, and each of the semicircular ring-shaped conductive plates has a ground hole. The online measurement system for partial discharge signals of cable joints as described in item 6 of the scope of patent application, wherein each of the grounding leads has one end of the grounding hole tied to one of the semicircular ring-shaped conductive sheets, and the other end is connected to the cable across Connect the shielding wire crimping. The online measurement system for partial discharge signals of cable joints as described in item 1 of the scope of patent application, wherein the monitoring unit includes two oscillating circuits, two surge protection components, a first multiplexer, the differential, and an amplifier , An absolute value hold circuit, a peak hold circuit, an analog-to-digital converter and a microcontroller, the two oscillating circuits are respectively electrically connected to the two current sensors, and the two surge protection elements are respectively electrically connected to The two oscillating circuits are electrically connected to the first multiplexer, and the first multiplexer, the differential and the amplifier are electrically connected in sequence, wherein the absolute value holding circuit is connected to the amplifier Between the peak holding circuit and the peak holding circuit, the peak holding circuit is electrically connected between the absolute value holding circuit and the analog-to-digital converter. The online measurement system for partial discharge signals of cable joints as described in item 8 of the scope of patent application, wherein the monitoring unit includes an adder and a second multiplexer, wherein the adder and the difference The actuators form a parallel structure, the parallel structure is electrically connected between the first multiplexer and the second multiplexer, and the second multiplexer is electrically connected between the parallel structure and the amplifier. In the online measurement system for partial discharge signals of cable joints as described in item 1 of the scope of patent application, each of the current sensors is composed of two semicircular ring-shaped sensing elements. In the online measurement system for partial discharge signals of cable joints as described in item 1 of the scope of patent application, each of the current sensors is a complete ring-shaped sensing element.

Images