For Sepam 20, 40, 60, and 80 relays, every protection function and stage has an associated Remote Indication Bit (TS or tele-signalisation bit) that indicates if the function has operated or not.

Sometimes, a Modbus client reading information from the Sepam can use these TS bits to determine whether or not a trip has occurred.

After a Protection Trip, the behaviour of the remote indication bit associated with a given protection stage is as follows:
- if the "Latching Mode" (Latched Trip) has been set for that protection stage, then the Remote Indication bit for that stage will stay in the TRUE (high) state until a RESET has been performed on the Sepam
- if the "Latching Mode" has not been enabled, then the Remote Indication bit status will go to FALSE as soon as the "Start" or Pick-Up for that protection stage has reset to zero.  Since we are interested in the behaviour following a trip, generally the circuit breaker will have opened, meaning that the Remote Indication bit will return a FALSE status very soon after the fault has been cleared.

For this reason, it is strongly recommended not to read the Remote Indication bits as way of capturing all the trip events that have occurred.

The most reliable way to be sure that you are capturing all the events that have been logged by the Sepam is to use the Time-Tagged Events feature.  This means that your Modbus device driver for SEPAM devices needs to be modified so that it can read the onboard event tables, as described in the user manual.

Reading the TS bits is not reliable, as you may miss events if a trip occurs during a communication link failure (and you do not have Latched Trips enabled, for example).

AEDL3

Publié pour: Schneider Electric Belgium