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Kiloamp 2018-10-31 429
We understand that with the continuous development of the economy and the continuous improvement of the living standards of the people, the role of PDUs in the electronics industry is becoming more and more important. Next, let's talk about the related content of PDU control cable technical standards and functional indicators.
With the increase of power system capacity and the continuous improvement of automation level, the secondary equipment of power system has been widely used in integrated circuit type or micro type protection device. The application of these protection devices is very useful for improving the stable operation of the system. But correspondingly, some new questions have also been raised.
Therefore, in the high-voltage substation, all the current, voltage and DC trips used to connect the control room to the control room relay protection device may introduce the interference voltage from the switching field to the secondary circuit of the microelectronic device-based relay protection. A control cable with a shield should be used. In the high-voltage substation, shielded control cables are used to suppress electromagnetic interference. How to properly ground the shielding layer plays an important role in reducing the interference level of external electromagnetic fields on the microcomputer-based secondary equipment.
The interference source of the shield control cable of the cabinet PDU and the magnetic flux generated by the current in the outer conductor are indicated by dotted concentric circles, a part of which surrounds the control cable core and its shielding layer. It induces a potential in the cable core and the shield to create a shield current Is.
The magnetic flux generated by the shield current of the cabinet power supply surrounds the shielding layer and also surrounds the cable core. The magnetic flux and the external conductor generate opposite interference magnetic fluxes, so called reverse magnetic flux, in Figure 1 (a ) is expressed by concentric circles in solid lines. According to the principle of electromagnetic induction, in the ideal case, if the shielding layer resistance is zero, the reverse magnetic flux can completely cancel the interference magnetic flux, that is, the mutual inductance electromotive force Er (.) generated by the reverse magnetic flux in the cable core. The electromotive force Es (.) induced by the interference flux in the cable core is equal in magnitude and opposite in direction. It is assumed that the mutual inductance of the shielding layer to the cable core is Xm.
The shield of the cabinet power supply is unlikely to have no resistance, so the part of the interference that the electromagnetic potential induced in the cable core cannot be cancelled is proportional to the resistance of the shield. Therefore, in order to effectively eliminate the interference of electromagnetic coupling, it is necessary to use a material having a small resistivity such as copper, aluminum or the like as a shielding layer.
In short, we talk about the PDU control cable technical standards and functional indicators have all of the above, we must give full play to their subjective initiative, and constantly promote the development of the industry.
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