· TREA: Turbine Emergency Trip Terminal Board

An alternate arrangement puts three PPRO I/O packs directly on TREA for a single-board TMR protection systemm.

IS220PPROS1B  also has an Ethernet connection for IONet communications with the control modules.

Mark* Vle is designed with a primary and backup trip system that interacts at the trip terminal board level. Primary protection is provided with the Turbine Primary I/O pack, PTUR, operating a primary trip board (TRPG, TRPL, TRPS, TRPA). Backup protection is provided with the PPRO IO pack operating a backup trip board(TREG, TREL, TRES, TREA).

PPRO accepts three speed signals, including basic overspeed, acceleration, deceleration, and a hardware implemented overspeed. The pack monitors the operation of the primary control and can monitor the primary speed as a sign of normal operation. PPRO monitors the status and operation of the selected trip board through a comprehensive set of feedback signals. If a problem is detected, PPRO will trip the backup trip relays on the trip board and activate a trip on the primary control. The pack is fully independent of and unaffected by the primary control operation.

A maximum of three trip solenoids can be connected between the primary and emergency trip terminal boards. Connecting a solenoid between the boards isolates the power on both sides of the solenoid as well as visibility of solenoid voltage as a system feedback. The primary/emergency trip boards TRPG/TREG, TRPL/TREL, and TRPS/TRES are designed to operate as a pair and use cabling between the boards for system connections. TRPA and TREA are designed with no pairingrequired and can be used independently of each other. When TRPA and TREA are paired,thev function the same as other board pairs.

The PPRO mounts directly to a Mark Vle SPRO or TREA terminal board. When mounted on a SPRO board, cables with DC-37 pin connectors on both ends are required between the SPRO board and the selected trip terminal board.