In order to create a variable to read the SOE values you need to use the IECioa.DBF file. For example, for a Digital Tag with IOA address 100 you have to use the IECioa.DBF and set the column SOEENABL value to 1.

After setting the SOEENABL to 1 you can create a variable tag with Tag address SD100. Now this variable tag reads the SOE data. You can also trend this variable if you like to keep the track of the SOE value changes.
 

Please make sure you have the following settings in ini file

[IEC870IP]

IOAConfigFileName = C:\\Citect\\V7\\Data\\Iecioa.dbf (this has to path where you have placed your IECioa.dbf file)

UseIOAConfigFile = 1