If the system is not properly grounded, the SPD cannot operate normally.

At this time, all communication systems must be grounded to the same ground electrode as the power system. This is because if the grounds are different, flash over may occur due to the potential difference between the grounds.

When a lightning strike occurs, the potential difference between two grounds can reach thousands of volts. As a result, damage to the interface chip is a common sight for service engineers.

Ground potential difference due to lightning current

Potential differences can develop between different grounding systems within a facility or between grounds in separate buildings, in which case a current flows between the two grounds.

If two computers, each with different grounds, are connected by data lines, damage can occur due to the potential difference between the two grounds. This situation is common when data lines connect two different buildings.

For example, if two computers are connected with a 0.05Ω shielded coaxial cable and the potential difference between the two computer grounds is 2V, a current of 40A will flow between them. Additionally, these large currents can act as false signals or data pulses.

Ground potential difference and Loop

Additionally, if equipment receives power from different transformers, this problem can occur even within the same building.

Normally, the open state is maintained between two different grounds, but when a large potential difference occurs between the two grounds due to lightning, etc., it is necessary to install an SPD to lower this potential difference to protect the system.