LVSP Varistor Protection Fuses Littelfuse LVSP Varistor Protection Fuses are designed to protect transient voltage surge suppression (TVSS) products and can survive 8 x 20µs lightning surges without opening. Littelfuse LVSP fuses can be used to facilitate TVSS module compliance to UL 1449 in permanently connected applications. The series offers a 600VAC voltage rating, 200kA interrupting rating, and 5kA to 100kA 8 x 20µs surge withstand.