10kv ac voltage insulation shielding protective cover and shielding method

Abstract

A kind of 10kV AC voltage insulation shield protective cover and shielding method, belong to 10kV system AC voltage test field.The purpose of the present application is to solve the problem of abnormal discharge phenomenon when 10kV system AC voltage is carried out in the field at present.The discharge part of the insulating cover when 10kV system AC voltage occurs, conductive foam layer is attached to the inner wall of insulating layer, conductive foam layer contacts abnormal discharge part in the process of 10kV system AC voltage test, a wire hole is formed in the insulating cover, one end of the grounding wire is connected with the conductive foam layer, the other end of the grounding wire passes through the wire hole and is connected with the wire clamp outside the insulating cover;Fastening rope is arranged at the sealing portion of the insulating cover, for tightening the sealing portion of the insulating cover.It is used for preventing abnormal discharge in the process of 10kV system AC voltage test.

Description

TECHNICAL FIELD

[0001] The present application relates to shielding devices, belonging to the field of 10kV system AC voltage withstand test. BACKGROUND

[0002] AC voltage withstand test conforms to the actual situation of the insulation of the tested product operating under AC voltage, and is the most direct and effective method for identifying the insulation strength of different devices, which has decisive significance for whether the device can be put into operation. The power frequency AC voltage withstand test needs to be carried out on the devices such as bus, circuit breaker, current transformer and voltage transformer in high-voltage cabinet in the 10kV system during routine or handover test. According to Q / GDW1168-2013 "State Maintenance Test Regulations for Power Transmission and Transformation Equipment" and GB50150-2016 "Handover Test Standard for Electrical Equipment", the voltage values applied during AC voltage withstand test of different devices in 10kV system are shown in Table 1.

[0003] Table 1 AC voltage withstand test values of 10kV system equipment handover and routine test

[0004]

[0005] However, abnormal discharge often occurs at the connection joint of the cable outgoing line side of the current transformer wiring panel in the high-voltage switch cabinet (three-phase outgoing line cable grounding joint), or at the connection joint of the 10kV bushing of the transformer and the 10kV bus, during the AC voltage withstand test on site. The reason is that according to the relationship between the effective value of the power frequency breakdown voltage of the rod gap in the extremely uneven electric field and the air gap length, the discharge distance under the power frequency withstand voltage can be calculated. Since the dispersion of the power frequency breakdown voltage of various air gaps is not large, generally 2% to 3%, it can be considered that the discharge distance under 33kV AC voltage is about 82.5mm, and the discharge distance under 42kV AC voltage is about 105mm. During actual on-site test, due to the problems such as fixed installation of equipment and cable outgoing line in the switch cabinet, the safe discharge distance between devices cannot be reached, resulting in abnormal discharge. The occurrence of this phenomenon will cause the following four problems: first, it will cause the test to be forced to stop, and the test can only continue after the discharge point is processed, which will greatly prolong the working time and cannot guarantee the completion of the test and power supply task within the specified time; second, the test cannot be carried out due to the failure to meet the safety distance, thereby increasing the risk of power failure; third, the insulation of the equipment in the interlayer has a cumulative effect, and repeated AC voltage withstand test higher than the operating voltage will increase the risk of insulation breakdown and affect the stability of the power system; fourth, when the distance between the outgoing cable and the voltage application device is not enough during AC voltage withstand test, the outgoing cable needs to be manually moved to control the distance to prevent discharge, which causes the outgoing cable to loosen and sink, resulting in human damage.

[0006] Currently, when conducting 10kV AC withstand voltage tests on-site, the discharge distance is usually controlled manually to avoid abnormal discharge. However, due to limitations in the manufacturing and installation processes of power equipment, this phenomenon is sometimes unavoidable. Although there are large insulating baffles on-site, they are generally not suitable for the actual working conditions and cannot achieve the desired insulation effect. Summary of the Invention

[0007] The purpose of this invention is to solve the problem of abnormal discharge that easily occurs when performing AC withstand voltage tests on 10kV systems in the field, and to propose a 10kV AC withstand voltage insulating shielding cover.

[0008] A 10kV AC withstand voltage insulating shielding cover, the cover comprising an insulating cover, a conductive foam layer, a fastening rope, a grounding wire, and a wire clamp;

[0009] An insulating cover is placed over the abnormal discharge location of the AC withstand voltage test of the 10kV system. A conductive foam layer is attached to the inner wall of the insulating layer. The conductive foam layer is in contact with the abnormal discharge location of the withstand voltage test of the 10kV system. A wire outlet hole is opened on the insulating cover. One end of the grounding wire is connected to the conductive foam layer, and the other end of the grounding wire passes through the wire outlet hole and is connected to the wire clamp outside the insulating cover.

[0010] The fastening rope is placed at the seal of the insulating cover to tighten the seal.

[0011] Preferably, the insulating cover is made of soft ethylene propylene insulating rubber material and is pear-shaped.

[0012] Preferably, the conductive foam layer is bonded together using YH-T806 special adhesive.

[0013] Preferably, the fastening rope is made of nylon.

[0014] Preferably, the abnormal discharge location in the AC withstand voltage test of the 10kV system is the grounding joint of the three-phase outgoing cable or the 10kV bushing joint of the transformer.

[0015] Preferably, there is one insulating cover.

[0016] Use an insulating cover to enclose the grounding joint of the three-phase outgoing cable or the 10kV bushing joint of the transformer.

[0017] Preferably, there are 3 insulating covers.

[0018] Each three-phase outgoing cable grounding joint or each phase 10kV bushing joint of the transformer should be enclosed by an insulating cover.

[0019] A shielding method based on a 10kV AC withstand voltage insulating shielding cover, the method comprising the following steps:

[0020] Place the insulating cover over the three-phase outgoing cable grounding joint or the 10kV busbar bushing joint, ensuring that the conductive foam layer is in contact with the three-phase outgoing cable grounding joint or the 10kV busbar bushing joint. Tighten the securing rope to completely enclose the three-phase cable grounding outgoing joint or the transformer 10kV bushing joint within the insulating cover, and then ground the clamp.

[0021] The beneficial effects of this invention are:

[0022] The existing switchgear contains circuit breakers, current transformers, etc. The current transformer terminal block is connected to the outgoing cable connector. The switchgear supplies power to users through the outgoing cables. When performing AC withstand voltage tests on site, we need to disconnect the current transformer terminal block from the outgoing cable connector. Figure 1 The outgoing cable joint (three-phase cable grounding joint) is covered with the insulating cover of this application. Voltage is applied to the circuit breaker and current transformer in the switchgear for a withstand voltage test. If the current transformer terminal block and the outgoing cable joint are not disconnected, the outgoing cable will be energized during the withstand voltage test, and the voltage may be fed back to the other side through the cable. If the current transformer terminal block is disconnected from the outgoing cable joint, but the outgoing cable joint (three-phase outgoing cable grounding joint) is not covered, there may be induced current in the outgoing cable joint, which may cause an electric shock accident at the other end of the outgoing cable. Therefore, when conducting the withstand voltage test, the current transformer terminal block and the outgoing cable joint must be disconnected, the outgoing cable joint must be covered with an insulating cover and grounded. The insulating cover contains conductive sponge, which is connected to ground to insulate and shield the outgoing cable joint, and also to make the electric field inside the insulating cover uniform.

[0023] Figure 2 The process involves disconnecting the 10kV bushing connector from the 10kV busbar, then covering the 10kV bushing connector with an insulating cover, applying voltage to the 10kV busbar, and conducting a withstand voltage test.

[0024] To improve the breakdown voltage of the air gap, two main approaches are employed: first, improving the electric field distribution within the air gap to make it as uniform as possible; and second, weakening or suppressing the ionization process in the gaseous medium. This application, based on these two approaches, designs a 10kV AC withstand voltage insulation shielding protection device. The insulation layer uses soft ethylene propylene rubber material with a thickness of 0.5cm and a pear-shaped design. This utilizes the principle of a barrier to hinder the generation and movement of charged particles in the air gap space during the discharge process. This material possesses excellent electrical insulation, impact elasticity, low density, and water resistance, and its low-temperature resistance is highly suitable for low-temperature conditions in winter. During AC withstand voltage testing, it ensures that no abnormal discharge occurs.

[0025] The shielding cover contains conductive foam material, 0.25cm thick, bonded to the inside of an EPDM rubber insulation layer. It is adhered using YH-T806 special adhesive to ensure flexibility and elasticity after bonding. This conductive foam is connected to ground via a grounding wire and clamp, with the grounding wire and clamp connected by a riveting structure. The grounding wire is a standard 25mm². 2 The bare copper flexible wire uses a 300A chrome-plated grounding clamp. This design serves three purposes: First, it provides protection by using conductive foam to prevent the metal wire tip from damaging the EPDM rubber insulation, thus affecting the insulation effect. Second, it provides shielding by effectively increasing the radius of curvature of the electrodes, homogenizing the electric field at the tip, reducing the maximum field strength, and increasing the initiation voltage of corona discharge in a highly non-uniform electric field, thereby increasing the breakdown voltage. Furthermore, grounding the conductive foam provides double grounding protection, improving safety during testing and ensuring the safety of personnel working at the cable end.

[0026] The fastening rope is made of nylon material. After the insulating cover is put on, it can be tightened to ensure that the metal part of the cable joint is completely enclosed in the insulating cover and completely avoids abnormal discharge.

[0027] When using it in the field, first disconnect the connection between the three-phase cable grounding joint and the CT (current transformer), then put the insulating protective cover on the first end of the three-phase outgoing cable grounding joint, such as... Figure 1 As shown, tighten the securing rope. If the distance between the three phases of the cable is too far during on-site use, a separate protective cover can be used for each phase cable grounding joint. Finally, ground the clamp.

[0028] This 10kV AC withstand voltage insulating shield has the following advantages:

[0029] 1. The average time for withstand voltage testing of the 10kV high-voltage chamber was shortened by 20 minutes before and after using the shielding cover.

[0030] 2. A dual protective grounding system was designed to improve safety during the test.

[0031] 3. It can be easily fitted onto the grounding joint of the three-phase outgoing cable or the 10kV bushing joint of the transformer, which is close to the pressurization equipment, to avoid abnormal discharge during AC withstand voltage testing and reduce the cumulative effect on insulation damage.

[0032] 4. Reduce human-caused damage to outgoing cables. Attached Figure Description

[0033] Figure 1 A device for conducting withstand voltage tests on circuit breakers and current transformers inside switchgear to cover the grounding joints of three-phase outgoing cables;

[0034] Figure 2A device for conducting withstand voltage tests on 10kV busbars by covering the bushing joint on the 10kV side of the transformer. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0038] Specific implementation method one: Combining Figure 1 and Figure 2 This embodiment describes a 10kV AC withstand voltage insulating shielding protective cover, which includes an insulating cover 1, a conductive foam layer 2, a fastening rope 3, a grounding wire 4, and a wire clamp 5.

[0039] An insulating cover 1 covers the abnormal discharge location of the AC withstand voltage test of the 10kV system. A conductive foam layer 2 is attached to the inner wall of the insulating layer 1. The conductive foam layer 2 is in contact with the abnormal discharge location of the withstand voltage test of the 10kV system. A wire outlet hole is opened on the insulating cover 1. One end of the grounding wire 4 is connected to the conductive foam layer 2, and the other end of the grounding wire 4 passes through the wire outlet hole and is connected to the wire clamp 5 outside the insulating cover 1.

[0040] The fastening rope 3 is set at the seal of the insulating cover 1 to tighten the seal of the insulating cover 1.

[0041] In this embodiment, the abnormal discharge location in the 10kV system AC withstand voltage test refers to: the connection between the current transformer terminal block and the outgoing cable joint, or the connection between the transformer 10kV bushing joint and the 10kV busbar. During the withstand voltage test, [the following is likely a separate, unrelated instruction:] Figure 1 The outgoing cable joints (three-phase outgoing cable grounding joints) are covered with the insulating cover of this application. Voltage is applied to the circuit breakers and current transformers inside the switchgear to conduct a withstand voltage test. Figure 2 The 10kV bushing connector of the transformer is separated from the 10kV busbar by a small gap. Then, an insulating cover is placed over the 10kV bushing connector of the transformer, and voltage is applied to the 10kV busbar to conduct a withstand voltage test.

[0042] In order to avoid abnormal discharge during 10kV AC withstand voltage tests, reduce test time and number of tests, prevent equipment damage, and improve work efficiency, this application designs a 10kV AC withstand voltage insulation shielding cover, which can be placed on the cable outlet joint inside the high-voltage switchgear or on the terminal block at the top of the low-voltage bushing on the 10kV side of the transformer, thereby reducing abnormal discharge during the test.

[0043] Specific Implementation Method Two: This implementation method further defines the 10kV AC withstand voltage insulating shielding protection cover described in Specific Implementation Method One. In this implementation method, the insulating cover 1 is made of soft ethylene propylene insulating rubber material and is pear-shaped.

[0044] In this embodiment, the insulating cover 1 utilizes the principle of a barrier to prevent the generation and movement of charged particles in the air gap space during the discharge process. This material has excellent electrical insulation, impact elasticity, low density, and water resistance.

[0045] Specific Implementation Method 3: This implementation method further defines the 10kV AC withstand voltage insulating shielding protective cover described in Specific Implementation Method 1. In this implementation method, the conductive foam layer 2 is bonded together with YH-T806 special adhesive.

[0046] Specific Implementation Method Four: This implementation method further defines the 10kV AC withstand voltage insulating shielding protective cover described in Specific Implementation Method One. In this implementation method, the fastening rope 3 is made of nylon material.

[0047] Specific Implementation Method 5: This implementation method further defines the 10kV AC withstand voltage insulation shielding protection cover described in Specific Implementation Method 1. In this implementation method, the abnormal discharge location of the 10kV system AC withstand voltage test is the grounding joint of the three-phase outgoing cable or the 10kV bushing joint of the transformer.

[0048] Specific Implementation Method Six: This implementation method further defines the 10kV AC withstand voltage insulating shielding protective cover described in Specific Implementation Method Five. In this implementation method, the insulating cover 1 is one unit.

[0049] Use an insulating cover to enclose the grounding joint of the three-phase outgoing cable or the 10kV bushing joint of the transformer.

[0050] Specific Implementation Method Seven: This implementation method further defines the 10kV AC withstand voltage insulating shielding protective cover described in Specific Implementation Method Five. In this implementation method, there are three insulating covers 1.

[0051] Each three-phase outgoing cable grounding joint or each phase 10kV bushing joint of the transformer should be enclosed by an insulating cover.

[0052] In this embodiment, if the distance between the grounding joints of the three-phase outgoing cables or the distance between the three-phase 10kV bushing joints of the transformer is too far when used on site, a protective cover can be used on each phase, and finally the clamp can be grounded.

[0053] Specific Implementation Method Eight: Based on the shielding method implemented by the 10kV AC withstand voltage insulating shielding protective cover described in Specific Implementation Method Five, in this embodiment, the method includes the following steps:

[0054] Place the insulating cover 1 over the three-phase outgoing cable grounding joint or the 10kV busbar sleeve joint, so that the conductive foam layer 2 is in contact with the three-phase outgoing cable grounding joint or the 10kV busbar sleeve joint. Tighten the fastening rope 3 to completely enclose the three-phase outgoing cable grounding joint or the transformer 10kV sleeve joint inside the insulating cover 1, and ground the clamp 5.

[0055] In this embodiment, when a discharge phenomenon occurs after applying voltage during AC withstand voltage testing, we place the device on the discharge location, open the fastening rope, open the opening of the insulating protective cover to an appropriate size, and place the insulating protective cover on the cable joint that is too close to the voltage application location, so that the conductive foam layer inside the insulating protective cover is in full contact with the metal part of the cable joint. Then, we tighten and tie the fastening rope to seal the cable joint inside the insulating protective cover, and finally, we reliably connect the lead wire of the conductive foam layer to the ground.

[0056] When performing AC withstand voltage testing on the 10kV busbar bridge, the fastening rope is opened, and the opening of the insulating protective cover is opened to an appropriate size. The insulating protective cover is then placed on the terminal block of the 10kV side bushing of the transformer, ensuring that the conductive foam layer inside the insulating protective cover is in full contact with the metal part of the terminal block of the 10kV side bushing of the transformer. The fastening rope is then tightened and secured, sealing the terminal block of the 10kV side bushing of the transformer inside the insulating protective cover. Finally, the lead wire of the conductive foam layer is reliably connected to the ground.

[0057] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A 10kV AC withstand voltage insulating shielding cover, characterized in that, The protective cover includes an insulating cover (1), a conductive foam layer (2), a fastening rope (3), a grounding wire (4), and a wire clamp (5); An insulating cover (1) covers the abnormal discharge part of the AC withstand voltage test of the 10kV system. The inner wall of the insulating cover (1) is covered with a conductive foam layer (2). The conductive foam layer (2) is in contact with the abnormal discharge part of the AC withstand voltage test of the 10kV system. A wire outlet hole is opened on the insulating cover (1). One end of the grounding wire (4) is connected to the conductive foam layer (2), and the other end of the grounding wire (4) passes through the wire outlet hole and is connected to the wire clamp (5) outside the insulating cover (1). The fastening rope (3) is set at the seal of the insulating cover (1) to tighten the seal of the insulating cover (1); The insulating cover (1) is made of soft ethylene propylene insulating rubber material and is pear-shaped; Tighten the fastening rope (3) to ensure that the conductive foam layer inside the insulating protective cover is in full contact with the metal part of the cable joint.

2. The 10kV AC withstand voltage insulating shielding cover according to claim 1, characterized in that, The conductive foam layer (2) is bonded together with YH-T806 special adhesive.

3. A 10kV AC withstand voltage insulating shielding cover according to claim 1, characterized in that, The fastening rope (3) is made of nylon.

4. A 10kV AC withstand voltage insulating shielding cover according to claim 1, characterized in that, The abnormal discharge location in the AC withstand voltage test of the 10kV system is the grounding joint of the three-phase outgoing cable or the 10kV bushing joint of the transformer.

5. A 10kV AC withstand voltage insulating shielding cover according to claim 4, characterized in that, The insulating cover (1) consists of one unit. Use an insulating cover (1) to cover the grounding joint of the three-phase outgoing cable or the 10kV bushing joint of the transformer.

6. A 10kV AC withstand voltage insulating shielding cover according to claim 4, characterized in that, There are 3 insulating covers (1). One insulating cover (1) is used to cover each three-phase outgoing cable grounding joint or each phase 10kV bushing joint of the transformer.

7. A shielding method based on a 10kV AC withstand voltage insulating shielding protective cover as described in claim 4, characterized in that, The method includes the following steps: Place the insulating cover (1) over the three-phase outgoing cable grounding joint or the 10kV busbar sleeve joint, so that the conductive foam layer (2) is in contact with the three-phase outgoing cable grounding joint or the 10kV busbar sleeve joint. Tighten the fastening rope (3) to completely enclose the three-phase outgoing cable grounding joint or the transformer 10kV sleeve joint inside the insulating cover (1), and ground the clamp (5).

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