At what electrical rating are surge protective devices not needed according to engineering supervision?

Surge protective devices (SPDs) are designed to protect electrical equipment from voltage spikes caused by events such as lightning strikes or utility switching. The correct consideration for determining when SPDs are not needed involves both the assessment of the surge threat and ensuring that safety is not compromised.

When the surge threat is negligible, it implies that the potential for damaging voltage spikes is very low. This could be due to a variety of factors, including the geographical location of the installation, the nature of the electrical systems in use, and existing protective measures already in place. In such a scenario, the necessity for surge protection diminishes significantly.

Additionally, ensuring that safety is not compromised contributes to the rationale for the lack of need for surge protective devices. It is essential that any decision made regarding the exclusion of SPDs does not place users or the equipment at risk.

Combining these two factors—assessing a negligible surge threat and confirming that safety remains intact—leads to the conclusion that surge protective devices may not be required in certain situations. This comprehensive approach highlights the engineering judgment involved in deciding on the necessity for SPDs. Therefore, recognizing that both of these conditions (A and B) work together justifies the choice.