Application of open type current transformer with switching

Abstract：Introduces the application of open type currenttransformer in the renovation project, as well as the role of open type currenttransformer with switching quantity, and the advantages of comparison withconventional open type current transformer, and analyzes with engineeringexamples.

Keywords: low voltage distribution system, switching, opentype current transformer, anti-theft, working principle

With the transformation of urban and agriculturalnetworks in China's power industry and the increasing automation of low-voltagedistribution systems, open type current transformers, as an importantelectrical component in low-voltage distribution systems, have become more andmore obvious in the transformation of power grids and have been widely used inmeasurement, metering, relay protection, system monitoring, groundingprotection and various power system analysis.

However, the open type low-voltage transformers on themarket at present may be installed with snaps that are not tightened to causethe core to be not completely closed; or during operation, the transformershell is subjected to great stress and the shell hinge breaks, resulting in theupper and lower cores not being closed, affecting the accuracy of thetransformer or no current output. The open type current transformer with switchcan effectively feedback the above situation to the instrument or thebackground, and has a broad application prospect in power monitoring projects.

The working principle ofthe open-ended low-voltage current transformer is shown in Figure 1. Theprimary winding of the open-ended current transformer is connected in serieswith the line under test, I1 is the line current, that is, the primary currentof the current transformer, and N1 is the primary turns of the currenttransformer. I2 is the secondary current of the current transformer, N2 is thesecondary turns of the current transformer, and Z2e is the impedance of thesecondary circuit equipment and connecting wires. When the primary currentflows in from the P1 end of the current transformer, and the P2 end goes out,in the case that the secondary Z2e is turned on, according to the principle ofelectromagnetic induction, the secondary winding of the current transformer hasa current I2 flowing from S1, through Z2e to S2, form a closed loop. It can beobtained that the current is I1×N1=I2×N2 in the ideal state, so there isI1/I2=N1/N2=K, and K is the transformation ratio of the current transformer.However, after the iron core of the open current transformer is cut, theperformance of the iron core will be worse, so the cross-sectional area of theiron core of the transformer must be increased, and the number of ampere turnsmust be increased, and I1×N1=I2 ×N2≥100AN.

In addition, thetransformer on the switch, when the transformer snap did not card or thetransformer aging caused by the rupture of the shell, the switch button popsup, normally closed to normally open, the signal termination transmission, thetransformer no signal output; when the transformer snap is normal, the switchstate is normally closed, the transformer works normally.

Open type current transformers are mainly used inindustrial city network and agricultural network renovation projects. Featuresare easy to install, no need to remove the primary busbar, and can also beoperated with electricity. However, the current low-voltage open typetransformers on the market have the following drawbacks.

(1) Open type current transformeron the market may not be installed when the clasp is not tight or the core isnot closed, the risk of the transformer falling off or disconnected duringoperation.

(2) Open type currenttransformer will have no signal and other problems if it is artificially openedtwice after installation.

AKH-0.66/K-SW series currenttransformer can solve the above problems. This transformer has a beautifulappearance and is easy and simple to install and maintain. As shown in Figure2, the transformer has the following advantages.

(2) AKH-0.66/K-SW series current transformer, there arefour leads in the module, two to transmit the current signal, two to transmitthe switching signal.

(3) AKH-0.66/K-SW seriescurrent transformers, when the buckle is not locked or the transformer isaging, the casing is broken, the upper and lower casings pop open, the ironcore is in poor contact, and the switch stuck on the lower casing of thetransformer protrudes The button will pop up, the switch will be disconnected,and the switching signal will terminate the transmission, which will prompt theopen-type low-voltage transformer to stop working.

(4) AKH-0.66/K-SW series current transformer, the upper and lower shells withlead seal holes, once the installation is completed immediately lead seal.

5. Conclusion

The emergence ofAKH-0.66/K-SW series current transformer, with abnormal open alarm, stop on thepower event reporting and other functions, but also for the enterprise toreduce the cost of human and material resources, due to the huge market, oncethe formation of production capacity, but also can drive the rapid developmentof other industries.