SEL Mirrored Bits^® Communications

Low-Cost, Relay-To-Relay Logic Communication

SEL developed Mirrored Bits communications to provide high-speed, secure, point-to-point communication of real or virtual contact-status bits. Protection applications include directional element-based bus protection and replacement of tone-channel equipment for communications-assisted blocking, unblocking, permissive, and transfer trip schemes. Automation applications include high-speed sectionalizing, restoration and interlock schemes, and replacement of large bundles of field wiring with several small optical fibers, lowering costs and improving reliability.

Features and Benefits

Eliminates expensive external communications equipment, wiring, and maintenance.
Provides eight user-assignable "virtual" inputs and outputs.
Simplifies and consolidates pilot protection schemes.
Connects directly to serial communications channel.
Provides comprehensive channel performance data.

Technology Overview: Mirrored Bits communications is an innovative, low-cost, relay-to-relay communications technology that exchanges the status of eight internal logic points called Mirrored Bits, encoded in a digital message, from one device to another. This patented technology opens the door to numerous protection, control, and monitoring applications that would otherwise require more expensive external communications equipment wired through contacts and control inputs. Applications for Mirrored Bits communications include line protection pilot schemes, remote device control and monitoring, relay cross-tripping, and more.

Operational Overview: The received Mirrored Bits (RMBs) of one relay follow the status, or "mirror" the status, of the respective transmit Mirrored Bits (TMBs) sent from the other relay. Each of the relays in the scheme repeatedly sends and receives the digital message while continually monitoring and checking the received message integrity. An internal monitoring point asserts when a good signal is received and deasserts immediately upon detection of a bad message. Other elements are also available for channel alarming and availability.

Field-Proven Technology

Join other SEL customers who have used Mirrored Bits communications since 1996 for fast, secure, and dependable communications. For technical and application information on Mirrored Bits communications, use the following links:

Handheld SEL-4388 Mirrored Bits Tester

The SEL-4388 gives engineers and technicians the power to accelerate commissioning and bench testing, and to improve cable identification, training, and maintenance.