Design and application of the hottest low voltage

2022-08-09
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Design and application of low-voltage double winding current transformer

Abstract: for low-voltage distribution lines with many feeders, there are mainly the following methods to realize system monitoring: 1 Multi channel system monitoring is realized by using current transformer connected to multi-function power monitor and 485 communication meter; 2. Connect the current transformer with the transmitter to realize Using the above two schemes has high cost and large investment. This paper introduces a low-voltage double winding current transformer, which can be used with artu-m32 to realize the intelligent distribution scheme of telemetering many terminal distribution lines. This scheme has the advantages of low cost, less investment, simple installation and wiring, and is conducive to the further promotion and application of low-voltage intelligent distribution

key words: low voltage double winding current transformer working principle application

1 introduction

low voltage current transformer has the characteristics of small volume, light weight, high accuracy, large capacity, convenient installation, etc., and the measurement range is relatively large, with secondary output signals of 5A or 1a, but there is no way to realize information transmission for long-range transmission and system monitoring and acquisition, and it must be through transmitters or power instruments. According to the market demand, our company has developed akh-0.66s series double winding current transformer. The primary current measurement range is a, and the secondary has two groups of outputs, one group outputs 5A or 1a, and the other group outputs ma. The primary current can be overloaded times, which can be directly used for system acquisition and remote transmission. It can be used together with artu-m32, which can simplify the system structure, reduce costs, and improve system reliability

2 product design

2.1 structural features

this product has novel structure, beautiful appearance, transparent flip design, anti-theft device, and convenient wiring. The shell material of the transformer adopts pc/abs alloy, which has the characteristics of high temperature resistance, high mechanical strength, environmental protection and so on; As shown in Figure 1 (b) and Figure 2 (b), the iron core of the main winding (6) adopts oriented cold rolled silicon steel sheet, as shown in Figure 1 (b) and Figure 2 (b), and the iron core of the auxiliary winding (5) adopts permalloy, which has the characteristics of stable performance, high mechanical strength and extremely high permeability; Enameled wire adopts high-strength enameled wire, which has the characteristics of high insulation strength and strong temperature resistance

the double winding current transformer is developed on the basis of the traditional low-voltage bus type current transformer, which is compatible with the installation of cables and copper bars. According to the measurement range of primary current, 5a-1250a adopts one-piece (3) electrical control cabinet: install the strong current control system and the operation control switch of the experimental platform; Type design scheme, with main specifications of s-30i, s-40i and s-50ii; 1250a-6300a adopts split structure design, and its main specifications include s-60ii, s-80ii, s-100ii, s-120ii and s-200ii, which are split types, as shown in Figure 1 (a) and Figure 2 (a)

1- terminal 1S1; 2-terminal 2S1; 3-terminal 1S2; 4-terminal 1S2; 5-secondary winding; 6-main winding

2.2 working principle

the working principle of double winding current transformer is the same as that of current transformer. The basic working principle is shown in Figure 1 (b), figure 2 (b) and figure 3. The primary current I1 of double winding current transformer flows in from P1 end of main winding (6) to P2, the number of turns of primary winding of main winding (6) is N1, and the secondary current I2 of main winding (6) flows out from terminal 1S1 (1) and through ammeter to terminal 1S2 (3), The number of turns of the secondary winding of the secondary winding (5) is N2, and the output terminals 2S1 (2) and 2s2 (4) of the secondary winding (5) output AC Ma small current signals, which are supplied to the measurement and control device to adopt 3 After equipment installation and commissioning. So there are:

i1 × N1+ I2 × N2= I0 × N1 (1)

I2 × N2+I3 × N3 = I0′ × N2 (2)

can be obtained from formula (1):

i2 × N2= I0 × N1- I1 × N1

can be obtained from formula (2):

i2 × N2= I0′ × N2 - I3 × N3,

so you can get:

i0 × N1- I1 × N1= I0′ × N2 - I3 × N3,

i.e.

i0 × N1+ I3 × N3= I0 × N1+ I0′ × N2

that is, in the above formula, I0 is the excitation current of the main winding (6), and I0 'is the excitation current of the auxiliary winding (5). Therefore, the output error of the main winding (6) can be adjusted by increasing the core section or improving the core performance or by error compensation, while the error compensation of the secondary winding (5) is achieved by jointly improving the performance of the two windings; The electromotive force of double winding current transformer is also similar to the principle of current transformer, which will not be introduced in detail here

figure 3

4. Application

double winding current transformer can not only output 5A or 1A for ammeter measurement, but also output AC Ma small current signal. It can be applied to telemetry system to collect and upload directly, realizing the remote measurement of current signal; Because the double winding current transformer has strong overload capacity, it can also be applied to various motor protection circuits

dual winding current transformer and artu-m32 telemetry unit can form a low-cost intelligent low-voltage distribution multi loop monitoring system. It is another efficient and low-cost solution for low-voltage intelligent distribution system, which is conducive to the further promotion and application of low-voltage intelligent distribution

4.1 application example

take monitoring 32 low-voltage feeders in parallel as an example, and each feeder needs to measure three-phase current. The A-phase and c-phase currents of each feeder are collected by akh-0.66s double winding current transformer, and the 32 feeders are measured remotely by two artu-m32 telemetry units. The B-phase current is the vector sum of A-phase and c-phase by default, as shown in Figure 4 (a) and Figure 4 (b)

figure 4

4.2 scheme price comparison

scheme 1. the hardware cost of using akh-0.66/s double winding current transformer is as follows: 64 akh-0.66/s double winding current transformers, the cost increase is about 10560 yuan, 64 pointer ammeters, the cost increase is about 1600 yuan, 2 artu-m32 telemetry units, the cost is 7200 yuan, and the total cost is 19360 yuan. Its characteristic is that there is a pointer meter to display the current locally, the remote output is a digital signal, and the background acquisition does not need to be a/d converted again, with high accuracy

scheme 2. The hardware cost of using bd-ai is as follows: 64 akh-0.66 current transformers increase the cost by about 2560 yuan, 64 bd-ai transmitters increase the cost by about 43520 yuan, and the total cost is 46080 yuan. Its characteristic is that the remote output is an analog signal without local display. The background acquisition needs to be a/d converted again, which will respond to the secondary error

scheme 3. The hardware cost of using pz72-ai3/c is as follows: 64 akh-0.66 current transformers increase the cost by about 2560 yuan, 32 pz72-ai3/c transmitters increase the cost by about 37120 yuan, and the total cost is 39680 yuan. Its features are the same as the first item (the display mode is changed to digital)

in conclusion, the combination of dual winding current transformer and artu-m32 has the highest cost performance ratio, which can realize the intelligent and low-cost multi loop monitoring of low-voltage distribution, which is conducive to the further promotion and application of low-voltage intelligent distribution

5 conclusion

the double winding current transformer has been applied in the engineering power distribution monitoring system of industrial and mining enterprises in Shanghai, Shenzhen, Hangzhou, Jinan, Inner Mongolia and other places, which has reduced the investment cost and produced better social and economic benefits

references

[1] Jiangsu ankerui Electric Appliance Co., Ltd. has a small production capacity, output and market share of domestic special engineering plastics Electric quantity sensor selection manual double winding current transformer operation manual, version 200809

[2] Ren Zhiyuan, Zhou Zhong Principle and Application guide of electric power measurement digital instruments, China Electric Power Press, 2007 (end)

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