Repeated grounding means that in a system where the neutral point is directly grounded, a metal wire is used to connect the grounding device at one or more places on the neutral main line. In the low-voltage three-phase four-wire neutral point directly grounded line, the construction unit should ground the neutral main line and the terminal of the branch line of the distribution line during installation, and ground the zero main line every 1 km. For power distribution lines with a grounding point of more than 50 meters, the neutral line connected to the user should still be grounded repeatedly, and the repeated grounding resistance should not be greater than 10 ohms.
If the grounding is not repeated, the voltage of the leakage device to ground is the voltage drop generated by the single-phase short-circuit current in the neutral part; and with repeated grounding, the voltage of the leakage device shell to ground is only the voltage generated by the ground short-circuit current on the repeated grounding resistance. drop. Obviously, at this time, the ground voltage of the equipment shell only accounts for a part of the neutral voltage drop, so the risk is relatively reduced.
(2) Shorten the duration of shell-touch or ground short-circuit faultSince repeated grounding and working grounding constitute the parallel branch of the neutral line, once a short circuit occurs, the short-circuit current can be increased, and the longer the line, the greater the short-circuit current, which accelerates the action of the line protection device and shortens the duration of the fault .
(3) Reduce the risk of electric shock when the neutral line is brokenIf several electrical equipment are connected to the zero line that is not repeatedly grounded, after a zero line breaks between the equipment, when a shell short-circuit occurs in a certain electrical equipment, all the equipment connected to the right of the zero line break point Electrical equipment enclosures all carry voltages close to the phase voltage, and the equipment enclosure to the left of the breaking point has a ground voltage approximately equal to zero. If there is a break during repeated grounding, after a zero line breaks between the devices, the sum of the ground voltages of the device shells on the left and right sides of the break is the grid phase voltage. Because the voltage of the equipment casing to ground is less than the phase voltage, the risk of electric shock is reduced.
(4) Improve the lightning protection performance of overhead linesThe repeated grounding on the zero line of the overhead line has a shunting effect on the lightning current, which is conducive to limiting the lightning overvoltage, thereby improving the lightning protection performance.
Microsoft Surface charger have 4 types. For Surface Pro 1/2/3/4.
Surface Pro 1/2: 12V 3.6A
Surface Pro 3: 12V 2.58A
Surface Pro 4: 15V 1.6A
Microsoft charger has different connector with other Laptop Adapter. Its connector is magnetic tip.
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