High-Impedance Differential Relay

The SEL-587Z High-Impedance Differential Relay is an economical and flexible relay that combines time-proven, high-impedance analog technology with the advantages of microprocessor technology. Use event reports and the Sequential Events Recorder (SER) for quick postevent analysis.

Applications

High-Impedance Bus Differential Protection—Provide high-speed, economical bus protection with a single three-phase differential bus zone. Two voltage-based setting levels are available. A high-value setting can be used for a standard trip, while a low-value setting can be used as an open-circuited CT alarm. The differential element’s internal 2000 ohm resistor allows high security to be maintained during heavy through faults or during CT saturation issues.

Simple Implementation—Apply simple settings and dedicated same-ratio CTs to create a cost-effective and easily expandable bus protection solution.

Overcurrent Protection—Provide backup overcurrent protection with the separate phase, neutral, and negative-sequence overcurrent elements, including instantaneous, definite-time, and inverse-time overcurrent elements.

Breaker Failure/Fault-Cleared Detection—Detect breaker failure and bus fault status with an overcurrent element in series with the high-impedance element.