Protection Relay monitors 2-winding transformers.

Press Release Summary:

SEL-387A monitors and protects transformers and other 2-port electrical apparatus. Protection includes differential and overcurrent protection for 3-phase current inputs, and optional Restricted Earth Fault function. Four serial communications ports enable remote metering and control of system functions and settings via PC. Sequential-events recorder logs all changes of state within relay logic elements, providing data regarding events and conditions leading up to events.

Original Press Release:

Economical SEL-387A Relay Offers Protection, Communications, and Automation Enhancements for Two-Winding Transformers

The new SEL-387A Relay not only saves on purchase price but also eliminates the need for auxiliary equipment that adds significant costs to protection schemes as well as design complexities requiring added engineering time.

Schweitzer Engineering Laboratories, Inc. (SEL), the leading manufacturer of power system protection, control, and monitoring equipment, announces the SEL-387A Relay, an economical and feature-rich current differential and overcurrent protection relay for two-winding transformers and other two-port electrical apparatus. The SEL-387A Relay provides owners and operators of two-winding power transformers with advanced monitoring, communications, and protection functions that were previously available only in more expensive relays designed for more complex transformer configurations.

The additional inputs, outputs, built-in logic, and other features and options of the new SEL-387A Relay eliminate the need for interposing relays and auxiliary equipment that add significant cost to protection and control schemes as well as design complexities that require extensive engineering drawings.

Protection elements include single- or dual-slope percentage differential characteristic, overcurrent protection for both sets of three-phase current inputs, and optional Restricted Earth Fault (REF) function. The SEL-387A Relay provides security against conditions that may result in relay misoperation, resulting from both system and transformer events. The fifth-harmonic element prevents relay misoperation during allowable overexcitation conditions. This SEL innovative technology assures owners and operators of no false trips during transformer energization.

The SEL-387A Relay includes flexible integration functions that allow this relay to be applied to larger substation integration and automation projects. Four serial communications ports enable remote metering and control of system functions and settings via PC for added efficiency and security. A Sequential Events Recorder (SER) logs all changes of state within the relay logic elements, providing system engineers with valuable data regarding events and conditions leading up to the events. The SEL-387A event reports provide an oscillographic record of abnormal events, enabling engineers to quickly see what happened.

Temperature metering functions provide system operators with important transformer operating data from ambient and transformer-mounted RTD sensors. An intelligent breaker monitor keeps track of the number of breaker operations for each terminal, together with total interrupted current and contact wear by pole, allowing users to schedule timely breaker maintenance based on estimated breaker wear. The SEL-387A has an operating temperature range from -40°C to +85°C and is covered by a ten-year warranty.

Schweitzer Engineering Laboratories (SEL) has made electric power safer, more reliable, and more economical since 1984. This ISO 9001-certified company serves the electric power industry worldwide through the design, manufacture, supply, and support of products and services for power system protection, control, and monitoring. For more information, contact SEL by phone (509) 332-1890; fax (509) 332-7990; or mail to 2350 NE Hopkins Court, Pullman, WA 99163-5603. SEL is on-line at

More from Agricultural & Farming Products

All Topics

COVID-19 Response Suppliers COVID-19 Response:
Can Your Company Help Provide Critical Supplies?

We are using the power of our platform to aid in the mass shortage of critical supplies. If your company can help provide supplies, capabilities, or materials for products such as N-95 Masks and Tyvek SuitsPlease let us know.

COVID-19 Response Suppliers