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Sepam - trip in case of loss of communication. Using S-LAN Monitoring on Series 20, 40, and 80 relays.

This FAQ explains about S-LAN (SLAN) Communication Monitoring function on Sepam Series 20, 40, and 80 relays.

By default, Series 20 and 40 relays provide S-LAN Monitoring as a built-in function that is disabled by default.  For certain applications, the user may wish to implement logic to ensure that the relay will trip the CB in case of a communication failure.  For example, for a feeder that is typically controlled from a SCADA, it may be dangerous to keep the feeder energized if the SCADA has lost communication with the protection relay.  The solution proposed by Sepam is to adopt a system where the SCADA master must periodically send a command over Modbus (or IEC61850) to the relay to show that the communications link is functional.  If the Sepam does not receive this signal within a user-defined period (e.g., 20 seconds), then the relay trips the Circuit Breaker.  For Series 20 and 40 relays, the function is controlled with the 2 remote commands TC15 and TC16.

The basic principle of this function is illustrated in the image below.

For the Sepam Series 80 relays, this function is not yet provided as part of the default standard control logic (as of firmware version V8.01).  However, it can be implemented using Logic Equations or the Logipam Ladder Diagram function.  The basic principle is as follows:

a) configure settable bits to enable and disable the custom function (optional)

b) use a TC (remote) command and connect it to a TOF timer to extend the impulse signal and ensure that the ladder diagram will work as designed

c) use a separate TON timer to monitor the time between signals received from the SCADA.  If the user-defined duration is exceeded, then use the V_TRIPCB function to trip the CB.

Important notes:

1) as with all customized Logipam programs, a corresponding customized SFT2841 settings file is also required.  Before the relay is put into service, the values of any timers or clocks programmed in the ladder diagram must be checked using SFT2841 in Connected Mode.

2) the solution described here is only a sample approach.  The user assumes all responsibility for the final solution implemented, and Schneider Electric accepts no responsibility or liability for any damages or loss that may be incurred due to the use of this function.

The screen captures below show the essential parts of the Logipam program, as well as the SFT2841 screen which allows the user to check the status of the Logipam timers.  There are also sample files attached to this FAQ for a Sepam M87 motor relay - these files are provided as a sample only, and are not intended for use in an actual installation.


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