WO2019029638A1

WO2019029638A1 - Partial discharge built-in sensor structure of capacitance high-voltage cable joint

Info

Publication number: WO2019029638A1
Application number: PCT/CN2018/099698
Authority: WO
Inventors: 席菲菲; 李高峰; 夏荣; 周峰; 任志刚; 刘弘景
Original assignee: 重庆泰山电缆有限公司; 国网北京市电力公司; 山东电工电气集团有限公司; 国家电网有限公司
Priority date: 2017-08-10
Filing date: 2018-08-09
Publication date: 2019-02-14
Also published as: CN107402343B; CN107402343A

Abstract

Disclosed by the present invention is a partial discharge built-in sensor structure of a capacitance high-voltage cable joint, comprising a sensor and a high-voltage cable; the sensor is cylindrical and is provided in sequence from inside to outside with: a dielectric thin film, a copper foil electrode, and a buffer layer, the copper foil electrode and the dielectric thin film adhering tightly to form a sensor electrode; the sensor is provided thereon with a radio frequency wire joint. The high-voltage cable is provided in sequence from inside to outside with a conductive cable core, an inner semi-conductive layer, an insulating layer, an outer semi-conductive layer, a semi-conductive water-resistant strip, a corrugated aluminum sheath, an anti-corrosion layer, and an outer sheath; the periphery of the inner semi-conductive layer is connected to the dielectric thin film; an end of the sensor is connected to a connector in which an inner portion is a spiral structure, the inner portion spiral structure of the connector fitting with the corrugated aluminum sheath of the high voltage cable; the periphery of the corrugated aluminum sheath is connected to the inner portion spiral structure of the connector. The present invention increases the sensitivity in monitoring partial discharge of high-voltage cables and is long-lasting and durable, while assembly and disassembly are extremely convenient.

Description

Capacitive high voltage cable joint partial discharge built-in sensor structure

Technical field

The invention relates to the field of partial discharge detecting instruments for electrical equipment, in particular to a built-in sensor structure for partial discharge of a capacitive high-voltage cable joint.

Background technique

With the development of the economy, the stable operation of electric power has been concerned by the state, and partial discharge monitoring has been a non-destructive project to test cable insulation. The partial discharge monitoring is used to judge the aging degree of the cable.

The cable intermediate joint is a high-incidence part of the insulation accident. It can be seen that the cable accessory has become a weak link of the high-voltage cable line insulation and a typical part of the operation failure. The electrical insulation performance of the cable accessory itself, as well as the quality of the cable and the impact of the cable laying, installation process, environmental impact, etc., can cause cable operation failure. In the event of a failure, it will cause a certain economic loss.

At present, partial discharge monitoring is mainly performed by sensing devices such as capacitive sensors, inductive sensors, and antenna sensors, but there are certain problems, and the detection accuracy is not high. The external sensor cannot be used for online monitoring for a long time because it is interfered by external electromagnetic signals, has low detection sensitivity and poor anti-interference ability.

Therefore, those skilled in the art are working to develop a partial discharge built-in sensor structure of a capacitive high-voltage cable joint which has high monitoring precision and can be used for long-term monitoring of the aging degree of a high-voltage cable.

Summary of the invention

In view of the above-mentioned drawbacks of the prior art, the technical problem to be solved by the present invention is to provide a capacitive high-voltage cable joint partial discharge built-in sensor structure.

To achieve the above object, the present invention provides a capacitive high voltage cable joint partial discharge built-in sensor structure, including a sensor and a high voltage cable;

The sensor has a cylindrical shape, and is disposed in order from the inside to the outside: a dielectric film, a copper foil electrode, a buffer layer, and a metal casing, and the copper foil electrode is closely adhered to the dielectric film to form a sensor electrode; Provided with a radio frequency cable connector;

The high-voltage cable is provided with a conductive core, an inner semi-conductive layer, an insulating layer, an outer semi-conductive layer, a semi-conductive electric water belt, a corrugated aluminum sheath, an anti-corrosion layer and an outer sheath from the inside to the outside; the inner half The outer periphery of the conductive layer is connected to the dielectric film;

One end of the sensor is connected with a connector having a spiral structure inside, and the internal spiral structure of the connector is matched with the corrugated aluminum sheath of the high-voltage cable; the outer circumference of the corrugated aluminum sheath is connected with the inner spiral structure of the connector.

Preferably, the radio frequency cable connector is provided with a shorting cap.

Preferably, the metal casing comprises a first casing and a second casing which are connected to each other in a semicircular arc shape, and the first casing has a first convex portion at one end in the longitudinal direction and a central portion at the other end. a first recessed portion is disposed on the first convex portion along the longitudinal direction of the first housing, and is disposed on both sides of the first recessed portion along the length direction of the first housing The first housing is respectively provided with a first front end screw hole and a first rear end screw hole;

a second convex portion is disposed at a central portion of one end of the second casing in the longitudinal direction, a second concave portion is disposed at a middle portion of the other end, and a second central snail is disposed on the second convex portion along the longitudinal direction of the second casing a second front end screw hole and a second rear end screw hole are respectively disposed on the second housing along the length direction of the second housing;

The first convex portion cooperates with the second concave portion, and the first central screw hole and the second front end screw hole and the second rear end screw hole form the same connecting screw hole;

The second convex portion cooperates with the first concave portion, and the second central screw hole forms a threaded same communication screw hole with the first front end screw hole and the first rear end screw hole.

Preferably, the connector is provided with an engaging groove in a circumferential direction at one end of the sensor, and the sensor is provided with an engaging portion that engages with the engaging groove at one end of the connecting head.

Preferably, the buffer layer is intimately bonded to the metal casing.

Preferably, the dielectric film is a polytetrafluoroethylene material, the buffer layer is a silicone rubber material, and the metal casing is an aluminum material.

The invention has the beneficial effects that the invention improves the sensitivity of the partial discharge monitoring of the high voltage cable, is durable, and is convenient to install and disassemble.

DRAWINGS

Figure 1 is a schematic view of the structure of the sensor.

Figure 2 is a cross-sectional view of Figure 1.

Figure 3 is a schematic enlarged view of the structure A in Figure 2;

Figure 4 is a plan view of Figure 1.

Figure 5 is a schematic view of the first housing structure.

Figure 6 is a schematic view of the structure of the second housing.

Figure 7 is a schematic diagram of an equivalent circuit of the present invention.

Figure 8 is a cross-sectional view of a high voltage cable.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

As shown in FIG. 1 to FIG. 4, a capacitive high-voltage cable joint partial discharge built-in sensor structure includes a sensor 1 and a high voltage cable 2.

The sensor 1 has a cylindrical shape, and is provided with a dielectric film 3, a copper foil electrode 4, a buffer layer 5, and a metal casing 6 from the inside to the outside. The copper foil electrode 4 is closely bonded to the dielectric film 3 to form a complete sensor. 1 electrode.

The buffer layer 5 is tightly bonded to the metal casing 6 to form a unit for easy access; the buffer layer 5 is wrapped around the outside of the electrode and is in close contact with the copper foil electrode 4 to ensure that the cable and the cable can be operated during operation and non-operation. Close contact.

The dielectric film 3 is a polytetrafluoroethylene material and has excellent properties such as high temperature resistance and corrosion resistance. The buffer layer 5 is a silicone rubber material, and has excellent performance against high temperature, and ensures that the buffer layer does not exhibit performance degradation due to high temperature during operation of the cable. The metal casing 6 is made of aluminum material, and the metal casing 6 is made of the same material as the corrugated aluminum sheath to reduce the contact resistance and loss therebetween.

The first outer casing 6a and the second outer casing 6b are connected to each other in a semi-circular cylindrical shape, and the first casing 6a is provided with a first convex portion 10 at a central portion in the longitudinal direction of the first casing 6a. The other end is provided with a first recess 11 on the first boss 10, and a first central screw hole 12 is disposed along the longitudinal direction of the first housing 6a. A first front end screw hole 13a and a first rear end screw hole 13b are respectively disposed on the first housing 6a on both sides of the first recessed portion 11 along the longitudinal direction of the first housing 6a.

The second housing 6b is provided with a second protrusion 14 in the middle of one end in the longitudinal direction, a second recess 15 in the middle of the other end, and a second central screw hole in the longitudinal direction of the second housing 6b. 16. On the two sides of the second recessed portion 15, along the longitudinal direction of the second housing 6b, a second front end screw hole 17a and a second rear end screw hole 17b are respectively formed in the second housing 6b.

When the first housing 6a and the second housing 6b are combined, the first protrusion 10 is just embedded in the second recess 15, the first central screw hole 12 and the second front screw hole 17a and the second rear screw hole 17b. A connecting screw hole having the same thread is formed, and a screw matched with the thread is inserted into the communicating screw hole, that is, the first housing 6a and the second housing 6b are connected to one side.

At the same time, the second raised portion 14 is just embedded in the first recessed portion 11, and the second central screw hole 16 forms the same threaded connecting hole with the first front end screw hole 13a and the first rear end screw hole 13b, and will cooperate with the aforementioned thread. The screw is inserted into the communication screw hole, that is, the other side of the first housing 6a and the second housing 6b are connected. At this point, the first housing 6a and the second housing 6b are connected into a cylindrical metal housing 6 .

The sensor 1 is provided with a radio frequency cable connector 8, which in this embodiment is a TNC connector, and is connected to an external observation processing device.

A short-circuit cap 9 is provided on the TNC connector to open the short-circuit cap 9, and the TNC connector can be connected to an external observation processing device. When not in use, close the shorting cap 9 to the TNC connector to prevent the floating potential from appearing when the high voltage cable is running. At the same time, the short-circuiting cap 9 can also isolate the inside of the sensor 1 from the outside, preventing moisture from entering the sensor 1, affecting the measurement.

The high-voltage cable 2 is provided with a conductive core 21, an inner semi-conductive layer 22, an insulating layer 23, an outer semi-conductive layer 24, a semi-conductive-resistance water strip 25, a corrugated aluminum sheath 26, an anti-corrosion layer 27, and an external protection from the inside to the outside. Set of 28. The material of the high-voltage cable 2 is peeled off to the inner semi-conductive layer 22, and the sensor 1 is placed outside the inner semi-conductive layer 22 and connected to the dielectric film 3.

A connecting end 7 having a spiral structure is connected to one end of the sensor 1. The connecting head 7 is provided with an engaging groove 18 in the circumferential direction at one end of the sensor 1. The sensor 1 is provided with an engaging portion at the end of the connecting head 7 for engaging with the engaging groove 18. 19, the engaging groove 18 is engaged with the engaging portion 19, and the sensor 1 and the connecting head 7 are integrally connected.

The internal spiral structure of the connector 7 is matched with the high-voltage cable 2 corrugated aluminum sheath 26 of the high-voltage cable 2, and the high-voltage cable 2 joint is immediately stripped to the end of the inner semi-conductive layer 22 and the stripping material is applied to the corrugated aluminum sheath 26 The connector 7 is sleeved outside the corrugated aluminum sheath 26, and the outer periphery of the corrugated aluminum sheath 26 is connected to the inner spiral structure of the connector 7.

This embodiment has an equivalent circuit as shown in FIG.

Assume: the outer diameter D ₁ of the cable insulation, the inner diameter D _{0 of the} cable insulation, the vacuum dielectric constant ε ₀ , and the relative dielectric constant ε _{r of the} insulation. Then, the capacitance between the sensor electrode and the cable core can be calculated as follows:

In the formula:

ε ₀ —— vacuum dielectric constant, value 8.85×10 ^-12 F/m;

ε _r - the relative dielectric constant of the insulating material, for XLPE, the value is 2.3;

D ₁ - the outer diameter of the cable insulation;

D ₀ - the inner diameter of the cable insulation.

Hypothesis: the relative permeability μ _{r of the} insulating material of the insulating layer,

Then the inductance per unit length in the cable can be calculated as follows:

In the formula:

μ ₀ ——the permeability of the vacuum, the value is 4π×10 ^-7 H/m;

_{r r} - the relative magnetic permeability of the insulating material;

D ₁ - the outer diameter of the cable insulation;

D ₀ - the inner diameter of the cable insulation.

Therefore, the characteristic impedance of the cable can be calculated as follows:

Assume that the cable length is l and the electrical resistance of the cable insulation is ρ.

Then the insulation resistance of the cable can be calculated as follows

In the formula,

Ρ——the electrical resistivity of the cable insulation, the cross-linked polyethylene is about 10 ¹⁴ ～10 ¹⁵ Ω·m;

l - cable length;

D ₁ - the outer diameter of the cable insulation;

D ₀ - the inner diameter of the cable insulation.

Referring to Fig. 7, it can be found that when there is a discharge signal in the cable core, the transfer function of the sensor coupling detection signal is:

It can be seen that the main influencing factors for the power frequency voltage division at lower frequencies are the values of R and R _S , so the power frequency high voltage is mainly at R, and the detection system has only a small voltage drop.

For signals with higher frequencies such as discharge signals, the main influence on the transfer function is the ratio of C to C _S . It can be known from the sensor structure that the two capacitance values are related to the size of the electrodes in the sensor and the length of the stripped shield, so adjusting the electrode size can further optimize the performance of the sensor.

The above has described in detail the preferred embodiments of the invention. It will be appreciated that many modifications and variations can be made in the present invention without departing from the scope of the invention. Therefore, any technical solution that can be obtained by a person skilled in the art based on the prior art based on the prior art by logic analysis, reasoning or limited experimentation should be within the scope of protection determined by the claims.

Claims

Capacitive high-voltage cable joint partial discharge built-in sensor structure, characterized by: comprising a sensor (1) and a high voltage cable (2);

The sensor (1) has a cylindrical shape, and is provided with a dielectric film (3), a copper foil electrode (4), a buffer layer (5), and a metal casing (6) from the inside to the outside, and the copper foil electrode (4) closely bonding with the dielectric film (3) to form a sensor (1) electrode; the sensor (1) is provided with a radio frequency cable connector (8);

The high-voltage cable (2) is provided with a conductive core (21), an inner semi-conductive layer (22), an insulating layer (23), an outer semi-conductive layer (24), and a semi-conductive water strip (25) in order from the inside to the outside. a corrugated aluminum sheath (26), an anti-corrosion layer (27), an outer sheath (28); the outer semi-conductive layer (22) is connected to the dielectric film (3);

One end of the sensor (1) is connected with a connector (7) having a spiral structure inside, and the internal spiral structure of the connector (7) is matched with the corrugated aluminum sheath (26) of the high-voltage cable (2); the wrinkles The outer circumference of the aluminum sheath (26) is connected to the inner spiral structure of the connector (7).
The capacitive high-voltage cable joint partial discharge built-in sensor structure according to claim 1, wherein the RF cable connector (8) is provided with a short-circuit cap (9).
The capacitive high-voltage cable joint partial discharge built-in sensor structure according to claim 1, wherein said metal casing (6) comprises a first casing (6a) and a second casing which are connected to each other in a semicircular arc shape. a first protrusion (10) is disposed at a central portion of the first housing (6a) in the longitudinal direction, and a first recess (11) is disposed at a middle portion of the other end, the first protrusion (10) a first central screw hole (12) is disposed along the longitudinal direction of the first housing (6a), on both sides of the first recess (11), along the length direction of the first housing (6a), a first front end screw hole (13a) and a first rear end screw hole (13b) are respectively disposed on the first housing (6a);

a second protrusion (14) is disposed at a central portion of the second housing (6b) in the longitudinal direction, and a second recess (15) is disposed at a middle portion of the other end, and the second protrusion (14) is along the second The second housing (6b) is provided with a second central screw hole (16) in the longitudinal direction, on both sides of the second recess (15), along the length direction of the second housing (6b), in the second a second front end screw hole (17a) and a second rear end screw hole (17b) are respectively disposed on the housing (6b);

The first raised portion (10) cooperates with the second recessed portion (15), the first central screw hole (12) and the second front end screw hole (17a) and the second rear end screw hole (17b) forming a communicating screw hole having the same thread;

The second raised portion (14) cooperates with the first recessed portion (11), the second central screw hole (16) and the first front end screw hole (13a) and the first rear end screw hole (13b) A connecting screw hole having the same thread is formed.
The capacitive high-voltage cable joint partial discharge built-in sensor structure according to claim 1, wherein the connecting head (7) is provided with an engaging groove (18) in a circumferential direction at one end of the sensor (1). The sensor (1) is provided with an engaging portion (19) that engages with the engaging groove (18) at one end of the connecting head (7).
The capacitive high-voltage cable joint partial discharge built-in sensor structure according to claim 1, wherein the buffer layer (5) is tightly bonded to the metal casing (6).
The capacitive high-voltage cable joint partial discharge built-in sensor structure according to claim 1, wherein the dielectric film (3) is a polytetrafluoroethylene material, and the buffer layer (5) is a silicone rubber material, The metal casing (6) is made of aluminum.