Siemens Low Voltage's Surge Protection Devices Line of TPS301 as part of the Internal (Integral Mounted) Group. Type 2 SPD. Dimensions (L x W x H): 11.5 x 7.2 x 4.5. 3-Phase 4-Wire Rated: 277/480 V surge current: 150 kA per phase. Special features: mounts internal to P1, P2, P3 panels, TIASTAR motor control centers with standard 6 IN bucket