The basic principle of security design of the security system is "single point earthing"
2. The "single point earthing" project requires the host to "single point earthing". All equipment at the far end of the system is suspended to the ground. The electrostatic charge generated by the system is discharged through the host earthing point, and the static potential is maintained with the earth to ensure the safety of operation. . The (ground) potential of the system after single-point earthing refers to the “ground potential†of the system with respect to the zero potential of the earth, ie, the potential of the system earthing point; the “Professional Lightning Protection†in the Security Forum once received the cable. Lightning induced electromotive force is described by "overvoltage" and "high potential", claiming that "cables at both ends can be clamped to equipotential at both ends with a grounded lightning protector at both ends." The high-frequency analysis shows that for the alternating induced electromotive force on the cable, even if the grounding resistance of the lightning arrester is 0 and the ground potential at both ends is equal, the “clamping voltage†of the lightning arrester at both ends is always “clamping voltage†Equal in size, opposite in polarity, where is there any potential equalization? In addition, the grounding "discharge circuit" includes the AC and DC impedance sum of the cable and the grounding wire as well as the grounding resistance. The so-called "effective discharge of the lightning current" is merely an illusion. Lightning induced electromotive force has nothing to do with the earth. There is no problem of discharge of current to the earth; "single point earthing" is used to discharge the static charge of the system, and there is no high requirement for grounding resistance, and no special grounding net is required; "single point "Grounding" and the traditional lightning rod grounding, power grid grounding, anti-surge protection device ground leakage current is essentially different from the requirements of the difference, using ordinary wire to connect the building steel, water pipes can be connected.
3. The rationality analysis of “single point earthing†“single point earthing†cuts off all ground loops and effectively blocks the path of “lightning ground potential†and “grid ground potential†invading the weak current system. This is lightning protection, Anti-surge, anti-interference is the most effective basic technical means; multi-point grounding introduces ground potential interference and grid surge, the introduction of lightning counter-attack voltage, burning of security equipment and lightning protection equipment case has been more and more security engineering injury cases Confirmed.
The "single point earthing" of the security system is not only not inconsistent with the anti-induction mine, but also the basic concept that the lightning protection design of the security system should follow and the basic conditions for the lightning protection design; because the anti-radar does not need, it cannot be connected to the earth through any part of the system. Discharge; Anti-Induction Lightning Only need to pass the protection circuit to suppress the voltage value when the lightning-induced electromotive force reaches the equipment port to ensure that it is lower than the “highest safety voltage†of the equipment, and the protection circuit used does not need to connect to earth.
The system "single point grounding" causes the entire system to float with ground potentials. Artificially created multi-point grounding and attempted to achieve "equipotential bonding", this is theoretically and practically impossible for the "wide area information system."
Adhering to the "single point earthing" safety design principle can avoid being misled by "grounding and lightning protection", and can avoid the investment in the complex grounding system.
"Single point earthing" is the "touchstone and watershed" for testing and judging the safety design and hidden danger design of the security system.
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