waveforms, where peak value of the voltage or the current is adjustable as required. Mathematical representation of these waveforms are available in relevant standards, and Table 2 provides the details of standard test waveforms used in different location categories. Effect of external transients in 'A' location is negligible due to the protection provided by the inductance of the building wiring. Category B location is exposed to both internally created and lightning created transients and hence both ring wave and combination wave test parameters are defined. Category C has the highest exposure for lightning and utility switching transients. Combination waveform with high current and voltage, 3-10 kA and 6-20 kV waveform parameters are specified for category C locations. AB C Category A: Branch and Receptacle Locations Category B: Load Side of the Main Overcurrent Protection Device to Distribution Panels Category C: Secondary Side of the Service Transformer Drop to the Line Side of the Main Overcurrent Device (a) UL1449-Type 1 UL1449-Type 2 UL1449-Type 3 Line Side Meter Main Secondary Side Service Transformer Service Disconnect Distribution Panel Branch Conductors Load Side Branch and Receptacle Locations Type 1: Permanently Connected Device Installed Before or After the Service Disconnect Overcurrent Device and Intended to be Installed With no External Overcurrent Protective Device Type 2: Permanently Connected Device Installed After the Service Disconnect Overcurrent Device Type 3: Point of Use SPDs That Are Installed With a Minimum of 30 Feet of Conductor Length From the Service Panel (b) FIG 4 Locations and categories of surge protectors in a building and associated standards. June 2022 z IEEE POWER ELECTRONICS MAGAZINE 51