REX640 includes two autoreclosing functions, each with up to

five programmable autoreclosing shots of desired type and

duration. A load-shedding function performs load shedding

based on underfrequency and the rate of change of the

frequency.

To validate correct closing conditions for a circuit breaker,

REX640 contains a synchrocheck function. For installations

including synchronous generators, REX640 introduces a

synchronizer that actively controls the generator’s voltage and

frequency in order to reach a synchronous situation across the

circuit breaker. The synchronizer functionality is available for a

generator circuit breaker as well as for a non-generator

(network) circuit breaker. A complete installation-wide

synchronizing system can be built using the REX640 relays. The

maximum size of the synchronizing system is eight generator

breakers and 17 non-generator breakers.

Synchronization of a generator circuit breaker can be

implemented using a single REX640 relay including the

ASGCSYN function block. The relay interfaces the external

measurement and control circuitry via hardwired binary and

analog signals. The excitation and prime mover control signals

are based on pulse commands, either with fixed or variable

length. The synchronizer function block has three different

function modes: manual, semi-automatic and automatic. In

each of these modes, the LHMI acts as the local user interface.

The LHMI includes the necessary command, indication and

measurement features for each of the modes, thus rendering

the conventional dedicated synchronizing panel unnecessary.

REX640 also supports systems in which non-generator circuit

breakers are synchronized. The prerequisite is that all the

feeders within the system are equipped with REX640 relays.