Bushing type current transformer for 35kV and below grade oil immersed transformer

Abstract

The invention discloses a bushing type current transformer for a 35kV and below grade oil immersed transformer, which comprises a secondary winding and a grounding assembly, the grounding assembly comprises a metal shielding layer and a grounding lead, the metal shielding layer is of an annular structure, the metal shielding layer is attached to the inner diameter circumference of the secondary winding, and the grounding lead is connected with the secondary winding. A grounding lead is welded on the outer side surface of the metal shielding layer, the metal shielding layer is bound and fixed on the inner side of the secondary winding through an insulating material, and the grounding lead is connected with the transformer shell and is grounded. The metal shielding layer is additionally arranged in the inner diameter direction of the current transformer, namely the position between the current transformer and the high-voltage bushing, the metal shielding layer is provided with the grounding lead, and the grounding lead is led out to be fixedly connected with the transformer shell, so that reliable grounding is realized. When the transformer bushing has an insulation fault and main insulation breakdown, the leakage current can be timely led to the ground through the grounding wire provided by the mutual inductor, so that the safety of a person and a secondary circuit device is protected.

Description

Technical Field

[0001] The invention relates to the technical field of bushing type current transformers, and in particular to a bushing type current transformer for oil immersed transformers suitable for voltage levels of 35 kV and below and a processing method thereof. Background Art

[0002] During the operation of the transformer, leakage or grounding faults may occur, which will pose a threat to personal safety. Grounding the transformer bushing end screen is one of the important measures to ensure the safe and stable operation of the power system. Generally, by grounding the transformer bushing end screen, the leakage current can be promptly introduced to the earth to prevent electric shock, and the reliability and stability of the equipment can be guaranteed. At the same time, in severe weather conditions such as lightning, grounding the transformer bushing end screen can also prevent lightning damage to the equipment.

[0003] However, some of the bushings used in oil-immersed transformers of 35kV and below are pure porcelain bushings. This type of bushing has no ground screen and cannot be directly grounded from the bushing, which poses a safety hazard during operation. Summary of the invention

[0004] The present invention is an improvement made to at least one defect of the prior art. It provides a bushing-type current transformer for oil-immersed transformers of 35 kV and below. The grounding wire is led out of the current transformer and then grounded through the box, thereby protecting the current transformer and the secondary circuit safety, solving the grounding problem, and ensuring the safety of people and secondary side equipment.

[0005] The technical solution adopted by the present invention is a bushing-type current transformer for oil-immersed transformers of 35kV and below, including a secondary winding and a grounding assembly, wherein the secondary winding is an annular iron core, and a secondary conductor evenly wound on the annular iron core according to the number of turns required by the design and a secondary lead connected to one end of the secondary conductor, and the secondary conductor is wrapped with insulating material on the outside; the grounding assembly includes a metal shielding layer and a grounding lead, the metal shielding layer is an annular structure, the metal shielding layer is attached to the inner diameter circumference of the secondary winding, a grounding lead is welded on the outer surface of the metal shielding layer, the metal shielding layer is fixed to the inner side of the secondary winding by wrapping with insulating material, and the grounding lead is connected to the transformer housing and grounded.

[0006] Preferably, insulating material is wrapped between the secondary conductor and the iron core.

[0007] Preferably, the number of the secondary leads is at least two.

[0008] Preferably, the grounding lead and the secondary lead are positioned correspondingly and extend from the same side, and the grounding lead and the secondary lead are led out in the same manner for installation.

[0009] Preferably, the metal shielding layer is made of copper foil and is in a circular shape with arc-shaped curling edges on the upper and lower sides, which fit the upper and lower end surfaces of the secondary winding just right, so that the metal shielding layer completely covers the inner diameter side of the secondary winding from top to bottom.

[0010] The beneficial effect of the present invention is that the present invention adds a metal shielding layer in the inner diameter direction of the current transformer, that is, the position between the current transformer and the high-voltage bushing. The metal shielding layer has a grounding lead, and the grounding lead is led out and fixedly connected to the transformer housing to achieve reliable grounding. When the transformer bushing has an insulation failure and the main insulation is broken down, the leakage current can be timely introduced into the earth through the grounding wire provided by the transformer to protect the safety of people and secondary circuit devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic diagram of the cross-sectional structure of a bushing-type current transformer.

[0012] Figure 2 Schematic diagram of the grounding component structure.

[0013] Figure 3 It is a schematic diagram of the three-dimensional structure of the bushing type current transformer.

[0014] Markings in the figure: 1- ground lead, 2- secondary lead, 3- secondary conductor, 4- insulation material, 5- iron core, 6- metal shielding layer. DETAILED DESCRIPTION

[0015] In order to make the purpose, 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 in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. The "inside" mentioned in the text refers to the axial side of the secondary winding, and the corresponding "outside" refers to the circumferential side of the secondary winding.

[0016] Usually the main grounding of transformers are: 1. Winding neutral point grounding: This is for working grounding and constitutes a high current grounding system.

[0017] 2. Shell grounding: This is for protective grounding to prevent the induced voltage on the shell from being too high and endangering personal safety.

[0018] 3. Core grounding: This is to protect the grounding and prevent the electrostatic voltage of the core from being too high, which will damage the insulation between the transformer core and other equipment.

[0019] 4. Other grounding: grounding of bushing end and screen, grounding of transformer secondary terminal, etc.

[0020] The pure porcelain bushing involved in the present invention has no ground screen, so when an insulation failure occurs, the transformer oil will be broken down, causing damage to the transformer and its secondary circuit instruments. Therefore, a metal shielding layer is added in the inner diameter direction of the current transformer, that is, between the current transformer and the high-voltage bushing. The metal shielding layer has a grounding lead, which is led out and fixedly connected to the transformer housing to achieve reliable grounding.

[0021] like Figure 1 As shown, a bushing-type current transformer for oil-immersed transformers of 35 kV and below is a bushing-type structure installed in the oil-immersed transformer riser. The current transformer includes a secondary winding and a grounding assembly. The secondary winding is a ring-shaped iron core 5, and a secondary wire 3 uniformly wound on the ring-shaped iron core 5 according to the number of turns required by the design, and a secondary lead 2 connected to one end of the secondary wire 3, and an insulating material 4 is wrapped around the outside of the secondary wire 3; an insulating material 4 is also wrapped between the secondary wire 3 and the iron core 5, and the number of secondary leads 2 is determined to be at least two according to customer requirements.

[0022] like Figure 2 and Figure 3 As shown, the grounding assembly includes a metal shielding layer 6 and a grounding lead 1. The metal shielding layer 6 is an annular structure. The metal shielding layer 6 is attached to the inner diameter circumference of the secondary winding. The grounding lead 1 is welded on the outer side of the metal shielding layer 6 (i.e., the surface attached to the secondary winding). The metal shielding layer 6 is wrapped and fixed on the inner wall of the secondary winding by an insulating material 4. The grounding lead 1 is connected to the transformer housing and grounded. The grounding lead 1 and the secondary lead 2 are corresponding to the position and extend on the same side. The grounding lead 1 and the secondary lead 2 are led out in the same way for installation. The metal shielding layer 6 is made of copper foil, and the whole is a circular ring with arc-shaped curling on both sides. The curling just fits the upper and lower end faces of the secondary winding, so that the metal shielding layer 6 completely covers the inner diameter side of the secondary winding from top to bottom. The metal shielding layer 6 is used as a grounding pole and is placed in the inner ring of the current transformer, corresponding to the primary conductor. When the main insulation between the primary conductor and the secondary winding is broken down, the large current is grounded through the metal shielding layer 6 to protect the safety of the current transformer and the secondary circuit.

[0023] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A bushing type current transformer for oil-immersed transformers of 35 kV and below, characterized in that: It includes a secondary winding and a grounding component. The secondary winding is an annular iron core, a secondary wire evenly wound on the annular iron core according to the number of turns required by the design, and a secondary lead connected to one end of the secondary wire, and the secondary wire is wrapped with insulating material on the outside; the grounding component includes a metal shielding layer and a grounding lead. The metal shielding layer is an annular structure, and the metal shielding layer is attached to the inner diameter circumference of the secondary winding. The grounding lead is welded on the outer surface of the metal shielding layer. The metal shielding layer is fixed to the inner side of the secondary winding by wrapping with insulating material, and the grounding lead is connected to the transformer housing and grounded.

2. The bushing-type current transformer for oil-immersed transformers of 35 kV and below according to claim 1 is characterized in that: Insulating material is wrapped between the secondary conductor and the iron core.

3. The bushing-type current transformer for oil-immersed transformers of 35 kV and below according to claim 1 is characterized in that: The number of the secondary leads is at least two.

4. The bushing-type current transformer for oil-immersed transformers of 35 kV and below according to claim 1, characterized in that: The grounding lead and the secondary lead are positioned correspondingly and extend from the same side, and the grounding lead and the secondary lead are led out in the same manner for installation.

5. The bushing-type current transformer for oil-immersed transformers of 35 kV and below according to claim 1, characterized in that: The metal shielding layer is made of copper foil and is in a circular shape with arc-shaped curling edges on the upper and lower sides. The curling edges fit the upper and lower end surfaces of the secondary winding just right, so that the metal shielding layer completely covers the inner diameter side of the secondary winding from top to bottom.

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