A molded case circuit breaker having a trip unit with one or more integrally formed dielectric protrusions that are configured to slidably interconnect with corresponding dielectric members of the base when the trip unit is secured to the base. The dielectric protrusions extend from dielectric walls located between adjacent enclosure chambers that house the current transformers and are configured to remain in contact with the dielectric members of the base as the trip unit is being moved with respect with the base. By remaining in contact to one another while the trip unit is moved with respect to the base, the dielectric protrusions, along with the dielectric members, maintain a strong dielectric barrier within the exterior spaces between the CT enclosure chambers, thereby preventing debris from traveling between and accumulating on the trip unit and the base.