Uninterruptible Primary Power- Trayer Primary Loop Protection The most reliable distribution system is one that provides uninterruptible power. Trayer has developed many relay and switchgear options to provide that level of reliability. Trayer uses time-proven technology from the transmission side of the industry and adapts it to a distribution system. This design uses two sources of power, like an ATS, but during a fault condition on the primary cable, the voltage outage to the customer is eliminated. Primary Loop Protection achieves true zero-cycle interruption. This is a field-proven system design that features Trayer’s vacuum fault interrupter switchgear and our own specialized relaying designs. The Trayer PLP system is the industry’s least expensive and most reliable solution for uninterruptible primary power.