CN216054228U

CN216054228U - Large current transformer with test winding

Info

Publication number: CN216054228U
Application number: CN202122639922.5U
Authority: CN
Inventors: 吴薇; 王传川; 杨育京; 夏江涛; 王莹; 郭颂; 翟琛
Original assignee: China XD Electric Co Ltd; Xian XD High Voltage Apparatus Co Ltd
Current assignee: China XD Electric Co Ltd; Xian XD High Voltage Apparatus Co Ltd
Priority date: 2021-10-29
Filing date: 2021-10-29
Publication date: 2022-03-15
Anticipated expiration: 2031-10-29

Abstract

The utility model discloses a large-current transformer with a test winding, which comprises an iron core, a secondary winding and the test winding; the secondary winding is wound on the iron core, the test winding is wound on the secondary winding, and insulating layers are arranged among the iron core, the secondary winding and the test winding. The secondary winding of the current transformer is wound with a test winding, so that the current transformer does not need to be electrified from a primary side when a transformation ratio test is carried out, and the test winding passes a small test current, so that the current induced in the secondary winding is the same as the current induced in the secondary winding when the rated primary current passes through the primary winding. When the large-current transformer is used for on-site transformation ratio testing, a plurality of large-capacity current boosters are not needed, so that the workload of testing the transformation ratio of the current transformer is greatly reduced, manpower and material resources are saved, and the working efficiency is improved.

Description

Large current transformer with test winding

Technical Field

The utility model belongs to the field of current transformers, and relates to a large current transformer with a test winding.

Background

The current transformer is an interface element for various protection devices and measuring instruments to truly reflect the true current signals of a primary system, is widely applied to the technical fields of monitoring, protection, wave recording, distance measurement and the like of a power system, and plays a significant role in the operation of a power grid. With the increasing installed capacity of the generator set in China, the rated current on the bus is also increased. The rated primary current typically reaches tens of thousands of amperes. At present, when a product is subjected to a hand-over test on site or is subjected to regular maintenance and repair during operation of the product, the transformation ratio of the current transformer needs to be tested in order to check the correctness of a circuit and find out any error which may occur in a protection device. Then, a closed high-current test loop is formed by connecting equipment such as a high-power current booster and the like to the outer side of the outgoing casing of the generator.

In the prior art, a closed large-current test loop is formed by connecting equipment such as a high-power current booster and the like to the outer side of an outgoing line sleeve of a generator. The method is difficult to implement on the construction site of the project.

In the prior art, because a test loop is very long, the capacity requirement of a large-current booster is often greater than the capacity limit value of a current transformer, so that a test unit has a large burden on equipment investment.

In the prior art, time and labor are wasted during on-site handover test and operation, maintenance and repair, and great loss of manpower and time is caused.

SUMMERY OF THE UTILITY MODEL

The utility model aims to overcome the defects of the prior art and provide the large current transformer with the test winding, so that the workload of the current transformer for testing the transformation ratio is reduced, manpower and material resources are saved, and the working efficiency is improved.

In order to achieve the purpose, the utility model adopts the following technical scheme to realize the purpose:

a large current transformer with a test winding comprises an iron core, a secondary winding and the test winding;

the secondary winding is wound on the iron core, the test winding is wound on the secondary winding, and insulating layers are arranged among the iron core, the secondary winding and the test winding.

Preferably, the insulating layer is wrapped around the core in two layers.

Preferably, the number of winding layers of the secondary winding is more than one, and two insulating layers are wound between the secondary winding layers in a half-lap wrapping mode.

Preferably, four insulating layers are wound in a half-lap wrapping manner between the secondary winding and the test winding.

Preferably, the insulating layer is a polyester film.

Preferably, the upper half of the iron core is wrapped with two layers of cotton tapes, and the cotton tapes are positioned between the insulating layer and the iron core.

Preferably, the beginning and the end of the secondary winding and the beginning and the end of the test winding are both led out by flexible wires.

Preferably, when the current transformer normally operates, the secondary winding is an output winding, the starting head and the tail end of the secondary winding are connected with loads, and the test winding is in an open circuit state, namely the starting head and the tail end of the test winding are free from wiring; when the current transformer transformation ratio test is carried out, the test winding is used as a primary winding.

Compared with the prior art, the utility model has the following beneficial effects:

the utility model winds the test winding outside the secondary winding of the current transformer, so that the current transformer does not need to be electrified from the primary side when the transformation ratio test is carried out, and the test winding passes a small test current, so that the current induced in the secondary winding is the same as the current induced in the secondary winding when the primary winding passes the rated primary current. When the large-current transformer is subjected to on-site transformation ratio testing, a plurality of large-capacity current boosters are not needed, so that the workload of the current transformer for testing the transformation ratio is greatly reduced, manpower and material resources are saved, and the working efficiency is improved; the purpose of reducing current is achieved by increasing the number of turns by utilizing the equal ampere-turn principle, and a large-current transformation ratio test is converted into a low-current test; the large-current transformer can be used in a field connection test of the large-current transformer and can also be used for product operation, maintenance and overhaul.

Drawings

FIG. 1 is a front view of a current transformer of the present invention;

FIG. 2 is a top view of the current transformer of the present invention;

FIG. 3 is a circuit diagram of a current transformer of the present invention;

fig. 4 is a diagram of a transformation ratio test circuit of the current transformer of the present invention.

Wherein: 1-an iron core; 2-a flexible wire; 3-testing winding; 4-secondary winding; 5-primary winding.

Detailed Description

The utility model is described in further detail below with reference to the accompanying drawings:

referring to fig. 1 and fig. 2, the large current transformer with the test winding according to the present invention includes a secondary winding 4 and a test winding 3. The secondary winding 4 comprises an iron core 1, a thin cotton tape, a polyester film and an enameled wire. And a thin cotton tape, a polyester film and an enameled wire are arranged outside the iron core 1. The test winding 3 and the secondary winding 4 are wound on the same iron core 1. The test winding 3 is wound outside the secondary winding 4 and is separated by an insulating layer. The insulating layer is made of polyester film.

The iron core 1 is firstly half-folded and wrapped by two layers of cotton tapes, the cotton tapes are thin cotton tapes, and then the two layers of polyester films are half-folded and wrapped to form a first polyester film layer. And the enameled wire is used for winding, and the winding is ensured to be uniform during winding. If the number of winding layers exceeds one, half-folding and wrapping two layers of polyester films between the layers, and half-folding and wrapping four layers of polyester films after winding to form a second polyester film layer. And finishing the winding of the secondary winding 4, and leading out the starting end and the tail end of the secondary winding 4 by using flexible wires 2 respectively, wherein the labels are S1 and S2, and the flexible wires 2 adopt high-temperature-resistant flexible wires.

And winding a certain number of enameled wires on the wound secondary winding 4 to form a test winding 3. The number of turns of the test winding 3 depends on how many turns of the secondary winding 4 are. Proportional to the number of turns of the secondary winding 4. And after the winding is finished, half-overlapping and wrapping four layers of polyester films to finish the winding of the test winding 3, leading out the starting head and the tail head of the test winding 3 by using flexible wires 2 respectively, wherein the labels are T1 and T2, and the flexible wires 2 adopt high-temperature-resistant flexible wires.

The purpose of adding the test winding 3 in the current transformer is to enable the current transformer to carry out the transformation ratio test without passing current from the primary side, and the test winding 3 passes a small test current so that the current induced in the secondary winding 4 is the same as the current induced in the secondary winding 4 when the primary winding 5 passes the rated primary current. The number of turns of the test winding 3 multiplied by the test current is equal to the rated primary current of the current transformer to be tested.

Fig. 3 provides a circuit diagram of a high current transformer with a simplified test ratio function. N1 is the primary winding 5, N2 is the secondary winding 4, and Nt is the test winding 3. When the current transformer normally operates, N2 is an output winding, the ends S1 and S2 are connected to a load, and Nt is in an open circuit state, namely the ends T1 and T2 are left unconnected. When the current transformer transformation ratio test is carried out, Nt is used as a primary winding, N2 is used as a secondary winding 4, and a temporary current transformer is formed to participate in the transformation ratio test. The transformation ratio test circuit is shown in fig. 4, wherein T1 and T2 of the test winding 3 are connected to a low-power current source, and S1 and S2 of the secondary winding 4 are connected to an ammeter.

The large-current transformer with the test winding adopts the equal ampere-turn principle, and takes an 10000/1A bus type current transformer as an example to explain the test principle. The primary current of the large-current transformer with the simplified transformation ratio test function is 10000A, the number of turns is 1 turn, the secondary current is 1A, the number of ampere turns is 10000 ampere turns, and the number of turns of the secondary winding 4 is 10000 turns. And (3) setting the test winding 3Nt to be 1000 turns, wherein the rated current passing through the test winding 3 is 10A, and the test winding is uniformly wound on the outer side of the secondary winding 4N2 in an enameled wire flat winding manner. When the current transformer works normally, the N2 winding is a secondary output winding, the ampere turn number of the secondary output winding is 10000 ampere turns, the primary winding 5 is a through 1 turn, and 10000A current is supplied; when the transformation ratio test is carried out, the N2 winding is still a secondary output winding, the passing rated current is 1A, the ampere turn number is 10000 ampere turns, the Nt winding is used as a primary winding 5, the passing rated current is 10A, and the ampere turn number is 10000 ampere turns. According to the design, under the normal working and the variable ratio test state, the first and second times are 10000 ampere-turns and are unchanged, namely, the aim of reducing the current value is achieved by increasing the number of turns by adopting the equal ampere-turn principle.

When the large-current transformer is used for a transformation ratio test, a large-capacity current booster with the power of 100kW is at least needed. When the method of adding the test winding 3 is adopted to reduce the primary current to 10A, the transformation ratio test work of the current transformer can be completed by adopting a small current booster with the power of 200W. Therefore, when the large-current transformer with the test winding is used for the transformation ratio test, only a small 200W current booster is externally connected, and the field transformation ratio test work of the large-current transformer is greatly reduced.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A large current transformer with a test winding is characterized by comprising an iron core (1), a secondary winding (4) and a test winding (3);

the secondary winding (4) is wound on the iron core (1), the test winding (3) is wound on the secondary winding (4), and a first insulating layer is arranged between the iron core (1) and the secondary winding (4); and a second insulating layer is arranged between the secondary winding (4) and the test winding (3).

2. A high current transformer with test winding according to claim 1, characterized in that the first insulating layer is wound two layers on the core (1) in a half-lap wrapping manner.

3. The large current transformer with the test winding according to claim 1, wherein the secondary winding (4) is wound with more than one layer, and two insulating layers are half-lap-wound between the layers of the secondary winding (4).

4. A high current transformer with test winding according to claim 1, characterized in that four insulating layers are half-lap wound between the secondary winding (4) and the test winding (3) to form a second insulating layer.

5. The high current transformer with test winding as claimed in claim 1, wherein the insulating layer is made of polyester film.

6. A high current transformer with test winding according to claim 1, characterized in that the core (1) is wound with two layers of cotton tape in a half-lap wrapping manner, the cotton tape being located between the first insulating layer and the core (1).

7. A large current transformer with test winding according to claim 1, characterized in that the beginning and end of the secondary winding (4) and the beginning and end of the test winding (3) are led out by using the flexible wire (2).

8. A large current transformer with test winding according to claim 1, characterized in that when the current transformer is in normal operation, the secondary winding (4) is an output winding, the start and end of the secondary winding (4) are connected with a load, and the test winding (3) is in an open circuit state.

9. A high current transformer with test winding according to claim 1, characterized in that the test winding (3) is used as the primary winding (5) when conducting a current transformer transformation ratio test; the secondary winding (4) is an output winding, and the start and the end of the secondary winding (4) are connected with loads.