Cold pressure connection method for high-voltage outgoing line and tap switch of transformer

Abstract

The application discloses a cold-pressing connection method for high-voltage outgoing lines and tap switches of a transformer, which comprises the following steps: firstly, determining the wire specifications and the wire quantity to be connected, and determining the tinned copper sleeve specifications; calculating the filling rate according to the wire cross-sectional area and the effective internal area of the tinned copper sleeve, so as to determine the wire quantity to be crimped and the filling wire; performing paint removal treatment on the wire end part to be cold-pressing connected, and the filling wire should be subjected to the paint removal treatment; and cold-pressing the wire by using a cold-pressing tool. The method replaces the existing traditional welding connection mode, the whole operation process is simple, different specifications of the high-voltage outgoing lines and the tap switches of the transformer can be quickly connected, the unique filling mode can ensure the tensile strength and the current-carrying performance of the wire, improves the wiring quality, and greatly improves the production efficiency.

Description

Technical Field

[0001] This invention relates to the field of transformer technology, specifically to a method for cold-pressing connection between a transformer's high-voltage output line and a tap changer. Background Technology

[0002] Currently, the high-voltage coils of traditional oil-immersed transformers of 35kV and below are typically made of enameled round copper wire. After the coil is wound, a high-voltage lead is led out from the top of the coil and connected to the tap changer. Because the specifications of the enameled round copper wire in the high-voltage coil are different from those of the copper wire at the tap changer interface, it is usually necessary to weld the different specifications and quantities of enameled round copper wire together for a transition. The traditional welding process is as follows:

[0003] 1. Remove all the paint from the wires that need to be soldered, with the paint-removed area 10mm away from the soldering point;

[0004] 2. Spiral the wire on one side of the tap changer that needs to be welded around the high-voltage coil lead wire, with at least 3 turns.

[0005] 3. Heat the winding part with a flame in a rotating manner, and stop when the temperature rises to between 1000℃ and 1100℃ and the two copper wires melt into one piece evenly;

[0006] 4. After the copper material has cooled down, polish the surface oxide layer.

[0007] 5. After sanding, wrap the welded area evenly with a half-layer of insulating paper, ensuring that the wrapped area extends 30-40mm beyond the paint peeling area at both ends.

[0008] Traditional welding methods have many problems and hidden dangers: the entire operation takes a long time, about 20 minutes, and requires a certain level of professional skill from the operator; there are obvious protrusions at the welded parts; the welding quality is unstable, and welding defects such as excessive melting, shrinkage porosity, and gas pores caused during welding are not easily detected; the mechanical properties after welding are reduced, which can lead to wire breakage or reduced current carrying capacity. Therefore, a more efficient, stable, and high-quality process for connecting high-voltage outgoing lines to tap changers is needed. Summary of the Invention

[0009] This invention provides a cold-pressing connection method for high-voltage output lines of transformers and tap changers to solve the technical problems existing in the prior art, replacing the existing welding method. It adopts a rapid cold-pressing method to connect two copper wires of different specifications. The whole process is short, easy to operate, greatly improves production efficiency, and ensures product quality.

[0010] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0011] A method for cold-pressing connection between a transformer's high-voltage output line and a tap changer, comprising the following specific steps:

[0012] Step 1: Determine the specifications and quantity of the wires to be connected, and determine the specifications of the tinned copper sleeve.

[0013] The copper wire diameter d1 of the high-voltage output line of an oil-immersed transformer is 0.9mm-2.5mm; the tin-plated copper bushing length L is 15mm-20mm, the inner diameter d is 4mm-7mm, the outer diameter D is 5mm-8mm, and the wall thickness is 1mm. Figure 1 As shown.

[0014] Step 2: Calculate the fill rate based on the cross-sectional area of ​​the conductor and the effective area inside the tinned copper sleeve, thereby determining the number of conductors that need to be crimped. The fill rate calculation formula is: A=(N1*π*R12+N2*π*R22) / π*R32;

[0015] A*100%: Fill rate; N1: Number of high-voltage leads; R1: Radius of high-voltage leads; N2: Number of tap changer connecting wires; R2: Radius of connecting wires; R3: Inner radius of tinned copper sleeve. The calculated result of A should satisfy 50% < A ≤ 60%. When A < 50%, a high-voltage lead wire gauge should be used as a filler wire gauge for filling. When A > 60%, a larger specification tinned copper sleeve should be used to ensure that the number of crimped wires is 2-4.

[0016] Step 3: Remove the varnish from the ends of the wires that need to be cold-pressed. The length of the varnish removed from the high-voltage lead wire and the connecting wire should exceed the length of the tin-plated copper sleeve by 10mm-15mm, ensuring that the varnish removed part extends 5mm-7.5mm beyond the two ends of the tin-plated copper sleeve when it is inserted.

[0017] All filler wires should be stripped of paint, and the length of the filler wires should extend 5mm-10mm beyond both ends of the tin-plated copper sleeve.

[0018] Step 4: Use a cold pressing tool to cold press the wires. There are 2-3 crimping surfaces for each tinned copper sleeve, with a spacing of 5mm between the crimping surfaces, and the crimping direction is consistent.

[0019] A fill rate of 50% < A ≤ 60% allows for maximum wire compression while ensuring current flow. Too low a fill rate leads to incomplete crimping, causing overheating during operation and resulting in softening and breakage at the crimp joint. Too high a fill rate causes excessive compression of the wire during crimping, reducing its strength and leading to breakage.

[0020] The beneficial effects of this invention are as follows: This method replaces the existing traditional welding connection method, the whole operation process is simple, and transformers of different specifications can be quickly connected to the conductors of tap changers using high-voltage output lines. The unique filling method can ensure the tensile strength and current carrying capacity of the connection, improve the wiring quality, and greatly improve production efficiency. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall cross-section before wiring in the method of the present invention;

[0022] Figure 2 This is a schematic diagram of the cross-section after cold pressing, with filler lines.

[0023] 1-High voltage lead-out line, 2-Tap switch inlet line, 3-Copper sleeve. Detailed Implementation

[0024] Combined with appendix Figure 1-2 The technical solution of the present invention is described in detail below: Taking the S13-M-100 / 10 distribution transformer as an example: Step 1: The high voltage lead wire 1 of the S13-M-100 / 10 product is a double 1.33mm enameled round copper wire, the tap changer inlet wire 2 is a single 2.5mm enameled round copper wire, and the tinned copper sleeve 3 used has the following specifications: outer diameter D = 6mm, inner diameter d = 5mm, and length L = 15mm.

[0025] Step 2: Filling Rate Calculation: Filling rate A = (2*π*(1.33 / 2)² + π*(2.5 / 2)²) / π*(5 / 2)²*100% = 39.2%; A < 50%, select 1.33mm enameled round copper wire as the filler wire, with a filler quantity of 1 wire, and repeat the calculation of the filling rate: A = (3*π*(1.33 / 2)² + π*(2.5 / 2)²) / π*(5 / 2)²*100% = 46.2%; A < 50%, select 1.33mm enameled round copper wire as the filler wire, with a filler quantity of 2 wires, and repeat the calculation of the filling rate: A = (4*π*(1.33 / 2)² + π*(2.5 / 2)²) / π*(5 / 2)²*100% = 53.3%; 50% < A ≤ 60% meets the requirements.

[0026] Step 3: Remove the enamel coating from the ends of the wires requiring cold pressing. The enamel coating removal length for the high-voltage lead and connecting wires should be 25mm. The filler wires should also have all enamel coating removed, and their length should be 25mm. Place all 5 wires into the tinned copper tubing, ensuring that each wire extends 5mm beyond both ends of the tinned copper sleeve.

[0027] Step 4: Use a cold pressing tool to cold press the wires. There are 2 crimping surfaces for each tinned copper sleeve, with a spacing of 5mm between the crimping surfaces, and the crimping direction is consistent.

[0028] Compared to traditional welding processes, this invention reduces the process time to 5-10 minutes, and the crimped connection can withstand a tensile force of 650N. Under rated current, the temperature difference within 2 hours is 0.5-2.5℃, ensuring wiring quality and improving production efficiency.

[0029] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention without creative effort.

Claims

1. A method for cold-pressing connection between a high-voltage output line of a transformer and a tap changer, characterized in that: The specific steps are as follows: Step 1: Determine the specifications and quantity of the wires to be connected, and determine the specifications of the tinned copper sleeve; Step 2: Calculate the fill rate based on the cross-sectional area of ​​the conductor and the effective area inside the tinned copper sleeve, thereby determining the number of conductors that need to be crimped. The fill rate calculation formula is: A = (N1*π*R1² + N2*π*R2²) / π*R3². A*100%: Fill rate; N1: Number of high-voltage leads; R1: Radius of high-voltage leads; N2: Number of tap changer connecting wires; R2: Radius of connecting wires; R3: Inner radius of tinned copper sleeve. The calculated result of A should satisfy 50% < A ≤ 60%. When A < 50%, the high-voltage lead wire gauge should be used as the filler wire gauge for filling. When A > 60%, a larger specification tinned copper sleeve should be used to ensure that the number of crimped wires is 2-5. Step 3: Remove the varnish from the ends of the wires that need to be cold-pressed. All filler wires should be completely varnished, and the length of the filler wires should extend 5mm-10mm beyond both ends of the tin-plated copper sleeve. Step 4: Use a cold pressing tool to cold press the wires. There are 2-3 crimping surfaces for each tinned copper sleeve, with a spacing of 5mm between the crimping surfaces, and the crimping direction is consistent.

2. The method for cold-pressing connection between the high-voltage output line of a transformer and a tap changer according to claim 1, characterized in that: The diameter of the copper wire for the high-voltage output is d1: 0.9mm-2.5mm; the length of the tin-plated copper sleeve is L: 15mm-20mm, the inner diameter is d: 4mm-7mm, the outer diameter is D: 5mm-8mm, and the wall thickness is 1mm.

3. The method for cold-pressing connection between the high-voltage output line of a transformer and a tap changer according to claim 1, characterized in that: The stripped length of the high-voltage lead wire and connecting wire should exceed the length of the tin-plated copper sleeve by 10mm-15mm, ensuring that when inserted into the tin-plated copper sleeve, the stripped part extends 5mm-7.5mm beyond both ends of the tin-plated copper sleeve.

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