MOSFET technology and offer an improved trip-time performance.

A software logic enables the input and output channels to be assigned to the various functions.

A time stamp is attached to all the data such as currents, voltages, binary inputs, events and diagnostic information acquired by a bay unit.

Where more analog and binary inputs are needed, several bay units can be combined to form a feeder/bus coupler

bay (e.g. a bus coupler bay with CTs on both sides of the bus-tie breaker requires two bay units).

The bay unit is provided with local intelligence and performs local protection (e.g. breaker failure, end fault,

breaker pole discrepancy) as well as the event and disturbance recording.

In the event that the central unit is out of operation or the optical fiber communication is disrupted an alarm is generated. 

The bay unit will continue to operate and all local protection as well as the recorders (event and disturbance) will remain fully functional (stand-alone operation).

The hardware structure is based on a closed, monolithic casing and presented in two mounting solutions:

· Without LHMI: ideal solution if convenient access to all information via the central unit or by an existing

substation automation system is sufficient.

· With LHMI and 15 programmable LEDs (Figure 7): ideal solution for distributed and kiosk mounting (AIS), since

all information is available in the bay.

For this option it is possible to have the LHMI either built in or connected via a flexible cable to a fixed mounting position.