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Sepam 80 - can the Nominal Frequency be set using Modbus communication (without SFT2841) with the protection relay online?

For the Sepam Series 80 relays, generally most of the important setting parameters should be set using SFT2841 in Connected Mode.  In other words, the user should have a PC connected directly to the port on the front face of the relay and either modify settings one by one, or upload a SFT2841 settings file that has been prepared beforehand.

For certain users, there may be a need to modify parameter settings remotely using Modbus communication, and even without the SFT2841 software.  For the Sepam Series 20 and 40 relays, there is a relatively larger set of parameters that can be directly modified by a Modbus Master connected to the Sepam, provided that the "Remote Setting" parameter is enabled on the relay.

As described in the Sepam 80 user documentation (Modbus Manual), parameters such as the Nominal Frequency and Working Language of the Sepam 80 are "read only," and cannot be set remotely by Modbus.

Schneider Electric has received requests from a number of users wishing to modify the Nominal Frequency of the Sepam 80 remotely by communication.  Firstly, it should be noted that even if this parameter is properly modified by using the SFT2841 software in Connected Mode, that it should generally be done with the relay offline and the protected feeder de-energized.  During the time when the Nominal Frequency setting is being modified, the protection functions of the relay are not operational, and the user's installation is not being protected.

Secondly, specifically as it concerns the Nominal Frequency setting on the relay, this parameter has intentionally been made "read only," and Schneider will not provide any procedure to allow the user to set it using Modbus communication.

However, there are certain applications where a customized solution developed by Schneider Electric can be used.  Specifically, for Shore Connection projects involving oil platforms, it is necessary for protection relays to operate at either 50Hz or 60Hz depending on the requirements of the offshore power system. For this type of application only, the Schneider Electric Shore Connection Team has developed a customized solution where a PLC can be programmed to set the Sepam 80 Nominal Frequency to the required value.  The solution can only be delivered and implemented by the Schneider Shore Connection Team, and the low-level technical details cannot be published.

To summarize, the Sepam 80 Nominal Frequency should only be modified using SFT2841 in Connected Mode for the vast majority of cases.  If you have a specific need that is related to an offshore application, please contact your local Schneider Electric Representative and ask them to raise a request with the Shore Connection Team.


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