High-Impedance Differential Protection
Provide high-speed, economical bus protection with a three-phase, high-impedance differential bus zone. High-impedance differential protection offers immunity against relay misoperation resulting from CT saturation. The SEL-587Z Relay uses internal 2000-ohm resistors to provide security against the effects of CT saturation for through faults. Internally mounted metal-oxide varistors (MOVs) are connected in parallel with the high-impedance element to clamp secondary peak voltage to less than 2 kV. Make use of simple settings and dedicated same-ratio CTs to create a cost-effective and easily expandable bus protection solution.

Overcurrent Protection
The SEL-587Z features separate phase, neutral, and negative-sequence overcurrent elements, including instantaneous, definite-time, and inverse time-overcurrent elements, for backup overcurrent protection.

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

Protection and Control Logic
SELogic control equations with SELogic variables and timers facilitate traditional or advanced protection schemes.

Monitoring and Reporting
Oscillographic event reports (up to ten 15-cycle reports) and metering functions eliminate or reduce external recorder and metering requirements. The SER stores the latest 512 entries in nonvolatile memory.

Serial Data Communications
Use the front and rear serial ports for communicating with ASCII terminals, a local human-machine interface (HMI), SCADA, or distributed control systems (DCSs). As an ordering option, select an EIA-232 or EIA-485 rear serial port. Through settings, select and configure the ports for SEL ASCII and interleaved SEL Fast Binary messages or for the Modbus RTU outstation protocol.