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This FAQ shows a simple equivalence between a Logic Equation expression and the corresponding Logipam Ladder Diagram on Sepam 80. As explained in other FAQ documents, Logipam and Logic Equations cannot be active simultaneously on a given Sepam Series 80 relay. For users who are not familiar with Sepam Logipam diagrams, this example shows that any logic condition realized with Logic Equations can also be realized using Ladder Diagrams.
To build Sepam Series 80 Logipam programs, the SFT2885 software is required. Once the program has been validated for export, the SFT2841 software is used to load the Logipam file to the Sepam relay itself.
For this example, suppose you wish to have a settable bit in the relay that is memorized even in case of an auxiliary power loss. By writing a Modbus command to the relay, you can either set the bit to 1 or 0, then use this value to control other protection functions on the relay. The following equation gives one possible way to represent the desired logic:
VL1=SR(TC63,TC64) // TC63 set inhibition, TC64 reset inhibit
Assuming the variable "VL1" has been defined, it could then be used to control other expressions defined in the equations for that relay. For example, we could use "AND" logic with this variable to either enable or inhibit a given protection unit. The "TC" elements can be accessed by a Modbus Master writing commands via Modbus communications to the Sepam relay. The Modbus addresses and procedure to write commands to the Sepam relay are given in the Sepam Series 80 Modbus manual.
The following screenshot shows how the same logic could be implemented using Logipam with the SFT2885 software. There is also a sample SFT2885 file attached to this FAQ document.
To summarize, we have used a "Memorized Bit" to store the state of the controllable bit. Modbus Remote Controls #63 and #64 have been added to the program to set and reset this bit, respectively. The lines further below show how the memorized bit could be used in combination with other elements in the ladder diagram.
As shown in this simple example, logic that has been implemented with Logic Equations can always be converted to equivalent Logipam (Ladder Diagram) representations.
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