scope:

This guide encompasses the application of surge protective devices (SPDs) (secondary arresters) from the secondary terminals of the distribution transformer to the line side of the service equipment.

NOTE - For reference, Figure 1 shows that the location covered by this guide is within Category C (form C62.41.1^TM).¹ The service entrance equipment includes all terminals and busses in the enclosure, and connection made to those terminals or busses with conductors other than load-carrying conductors. SPDs limit transient [surge] overvoltages by diverting surge currents. SPD coordination consider the power system characteristics, the equipment to be protected, and the location of the SPDs. This guide also provides an annex that presents information on risk factors.² 

PURPOSE

The purpose of this guide is to address many of the aspects to be considered when applying surge protective between the secondary terminal of the distribution transformer and the line side of the service equipment.