Low-voltage neutral point lead structure of distribution transformer

Abstract

The utility model relates to a low-voltage neutral point lead structure of a distribution transformer, which is characterized in that the head ends a, b and c of a three-phase coil of the transformer are respectively connected with an a-phase low-voltage bushing, a b-phase low-voltage bushing and a c-phase low-voltage bushing through a three-phase head end copper bar and a three-phase wiring sheet, the tail ends x, y and z of the three-phase coil are connected with a tail end copper bar, and the tail ends x, y and z of the tail end copper bar are connected with the tail end copper bar. The midpoint between the y is connected with the 0-phase sleeve through a 0-phase cable I. The midpoint between the y and z of the tail end copper bar is connected with the 0-phase sleeve through a 0-phase cable II. According to the utility model, the low-voltage three-phase resistance unbalance rate of the transformer is changed from the original greater than 2% to less than 0.2%, and meanwhile, the use amount of the copper bars at the tail end is greatly reduced, so that the manufacturing cost of the transformer is saved.

Description

TECHNICAL FIELD

[0001] The utility model belongs to transformer technical field, especially relate to a low voltage neutral point lead structure of distribution transformer. BACKGROUND

[0002] At present, the distribution transformer stipulates the sleeve arrangement mode as c, b, a, 0, and the neutral point leading position is 1 point, and the neutral point lead structure leads to inconsistent three-phase low voltage resistance.

[0003] The three-phase resistance imbalance rate should not be greater than 2% according to the national standard, if the standard requirement is not met, then the amount of tail end copper bar must be increased to reduce the resistance imbalance rate, and the amount of tail end copper bar is usually 2-3 times of the theoretical amount. SUMMARY

[0004] The utility model discloses a low voltage neutral point lead structure of distribution transformer, which solves the problem of excessive three-phase low voltage resistance imbalance rate of the distribution transformer.

[0005] To achieve the above object, the utility model adopts the following technical scheme:

[0006] A low voltage neutral point lead structure of distribution transformer, the three-phase coil first end a, b, c of the transformer is connected with a-phase low voltage sleeve, b-phase low voltage sleeve, c-phase low voltage sleeve through three-phase first end copper bar, three-phase terminal, the three-phase coil tail end x, y, z is connected with tail end copper bar, and the midpoint between x and y of tail end copper bar is connected with 0-phase sleeve through 0-phase cable one, and the midpoint between y and z of tail end copper bar is connected with 0-phase sleeve through 0-phase cable two.

[0007] The 0-phase cable one and 0-phase cable two end connection terminal, and the terminal is connected with tail end copper bar through bolt.

[0008] Compared with the prior art, the utility model has the advantages that:

[0009] The utility model changes the three-phase resistance imbalance rate of the transformer from originally greater than 2% to less than 0.2%, and at the same time, the amount of tail end copper bar is greatly reduced, thereby saving the manufacturing cost of the transformer. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 It is the structural diagram of the utility model.

[0011] Figure 2 It is the side view of the utility model.

[0012] Figure 3 The circuit schematic diagram of the utility model.

[0013] Figure 4 The circuit resistance calculation schematic diagram of the utility model. DETAILED DESCRIPTION

[0014] In the description of the utility model, it is understood that the terms "first", "second" and the like are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" and the like can be explicitly or implicitly included one or more features. In the description of the utility model, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0015] Unless otherwise specified and limited, the terms "mounting", "connection" and "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected, it can be mechanical connection, or electrical connection, it can be directly connected, or indirectly connected through intermediate medium, it can be the communication inside two elements. For ordinary skilled in the art, the specific meaning of the above terms in the utility model can be understood through specific circumstances.

[0016] A low-voltage neutral point lead structure of a distribution transformer, the three-phase coil 3 of the transformer is connected with a-phase low-voltage bushing 4, b-phase low-voltage bushing 5 and c-phase low-voltage bushing 6 through three-phase head copper bar 2 and three-phase terminal 1, the tail end x, y and z of the three-phase coil 3 is connected with tail end copper bar 8, the midpoint between x and y of the tail end copper bar 8 is connected with 0-phase bushing through 0-phase cable one 9, and the midpoint between y and z of the tail end copper bar 8 is connected with 0-phase bushing 7 through 0-phase cable two 10.

[0017] The end of 0-phase cable one 9 and 0-phase cable two 10 is connected with terminal, and the terminal is connected with tail end copper bar 8 through bolt.

[0018] Resistance calculation:

[0019] R1= three-phase terminal resistance;

[0020] R2a, R2b, R2c= three-phase head copper bar resistance;

[0021] R3a, R3b, R3c= three-phase coil resistance;

[0022] R4= tail end copper bar resistance;

[0023] R7= 0-phase cable one resistance;

[0024] R8= 0-phase cable two resistance;

[0025] Then: A phase low voltage DC resistance: Ra=R1+R2a+R3a+R4 / 4+Rxa;

[0026] Where: Rxa = R7 × (R8 + R4 / 2) / (R7 + R8 + R4 / 2);

[0027] Phase B low voltage DC resistance: Rb=R1+R2b+R3b+Rxb

[0028] Where: Rxb = (R7 + R4 / 4) × (R8 + R4 / 4) / (R7 + R8 + R4 / 2)

[0029] Phase C low voltage DC resistance: Rc=R1+R2c+R3c+R4 / 2+Rxc;

[0030] Where: Rxc = R8 × (R7 + R4 / 2) / (R7 + R8 + R4 / 2);

[0031] Since the current flowing through the tail copper busbar 8 is the rated current of the transformer, while the current flowing through the 0-phase cable 9 and the 0-phase cable 10 is only 30% of the rated current at most, the tail copper busbar can be selected with normal specifications without increasing the size. The three-phase resistance balance on the low-voltage side of the transformer can be achieved by adjusting the resistance of the 0-phase cable 9 and the 0-phase cable 10.

[0032] The utility model can reduce the low-voltage three-phase resistance unbalance rate of the transformer from more than 2% to less than 0.2%, and at the same time greatly reduces the amount of tail copper busbars, thereby saving the manufacturing cost of the transformer.

[0033] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and basic spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A low voltage neutral point lead structure of a distribution transformer, characterized by, The first ends a, b and c of three-phase coils of the transformer are connected with a-phase, b-phase and c-phase low-voltage bushings through three-phase first-end copper bars and three-phase connection pieces, respectively; the tail ends x, y and z of the three-phase coils are connected with a tail-end copper bar; the midpoint between x and y of the tail-end copper bar is connected with a 0-phase bushing through a 0-phase cable I; the midpoint between y and z of the tail-end copper bar is connected with the 0-phase bushing through a 0-phase cable II.

2. A low voltage neutral point lead structure for a distribution transformer as defined in claim 1, wherein, The 0-phase cable I and the 0-phase cable II are connected with connection terminals at their ends, and the connection terminals are connected with the tail-end copper bar through bolts.

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