The "Single-Point Grounding" Principle for Security System Safety Design

1.Basic Concept of “Single-Point Grounding”

Single-point grounding refers to a configuration in which the main system host is connected to earth at one single point, while all remote devices—including cameras and other equipment—must remain electrically insulated from earth. Specifically, “single-point grounding” means that for any “system” where components are directly electrically connected, the central aggregation point (i.e., the main system host or subsystem host) must be grounded at one point only.

For example, in an optical fiber transmission system: the front-end multi-channel optical transmitters act as subsystem hosts. Their enclosures are grounded at a single point to earth, while all cameras connected via cables to these optical transmitters must remain insulated from earth. This constitutes “single-point grounding” for a system with direct electrical connectivity. The grounding of the back-end main system host cannot substitute for this, because the optical fiber provides electrical isolation between the two ends.

2. Engineering Requirements for “Single-Point Grounding”

The main host must be grounded at a single point, and all remote equipment in the system must remain floating relative to earth. Electrostatic charges generated within the system are discharged through the host’s grounding point, maintaining static equipotentiality with earth to ensure operational safety.

After implementing single-point grounding, the system’s “ground potential” refers to the potential of the system relative to earth’s zero potential—specifically, the potential at the system’s grounding point.

In security industry forums, some so-called “professional lightning protection” advocates have described lightning-induced electromotive forces (EMF) on cables using terms like “overvoltage” or “high potential,” claiming that “grounding surge protectors at both ends of the cable can clamp both ends to the same potential.”

However, high-frequency analysis shows that for alternating induced EMF on cables, even if the grounding resistance of the surge protector is zero and the ground potentials at both ends are equal, the clamping voltages of voltage-limiting surge protectors at both ends will always be “equal in magnitude but opposite in polarity.” There is no true equipotential condition whatsoever. Moreover, the “discharge path to ground” includes the total AC/DC impedance of the cable and grounding conductors, as well as the grounding resistance itself. The notion of “effectively diverting lightning current” in such configurations is merely an illusion.

Lightning-induced EMF is unrelated to earth; there is no issue of discharging current into the ground. “Single-point grounding” is intended solely for dissipating electrostatic charges within the system, so it does not require low grounding resistance or a dedicated grounding grid. It fundamentally differs from traditional lightning rod grounding, power system grounding, or surge protector grounding designed to handle large currents. A simple connection using ordinary wire to building rebar or a water pipe is sufficient.

3. Rationality Analysis of “Single-Point Grounding”

“Single-point grounding” eliminates all ground loops, effectively blocking intrusion paths for “lightning-induced ground potential” and “power grid ground potential” into low-voltage electronic systems. This is the most effective foundational technique for lightning protection, surge suppression, and interference prevention.

In contrast, multi-point grounding introduces ground potential interference, power grid surges, and lightning反击 (back-flash) voltages. Numerous real-world cases in security engineering have confirmed that multi-point grounding has led to the destruction of both security equipment and lightning protection devices.

“Single-point grounding” in security systems is not only compatible with protection against induced lightning—it is, in fact, a fundamental principle and essential prerequisite for proper lightning protection design in such systems.

Direct lightning strikes do not—and should not—rely on any part of the system being grounded for discharge. Protection against induced lightning only requires protective circuits to suppress the induced voltage at equipment ports to a level below the equipment’s “maximum safe voltage.” Such protective circuits do not need to be connected to earth.

With “single-point grounding,” the entire system floats at the same potential as the grounding point. Artificially creating multi-point grounding while attempting to achieve “equipotential bonding” is theoretically and practically unattainable for wide-area information systems.

Adhering to the “single-point grounding” safety design principle helps avoid being misled by the myth of “grounding-based lightning protection” and prevents unnecessary investment in overly complex grounding systems.