R.5.12
SEL-421 Relay Reference Manual Date Code 20111215
SEL Communications Protocols
Virtual File Interface
Consider the following examples for converting a list of fields to comma-
delimited text. Consider the following list of fields:
Stri,ng 1
Stri"ng 2
String 3
String4
The translation to comma-delimited text is as follows:
"Stri,ng 1","Stri""ng 2","String 3","String4"
Root Directory
The root directory contains three subdirectories and one file, CFG.TXT.
CFG.TXT File (Read-Only)
The CFG.TXT file contains general configuration information about the relay
and each setting class. External support software retrieves the CFG.TXT file
to interact automatically with the connected relay.
Settings Directory
You can access the relay settings through files in the SETTINGS directory. We
recommend that you use support software to access the settings files, rather
than directly accessing the text files. External settings support software
functions by reading settings from all of these files. The relay only allows you
to write to the individual SET_cn files, where c is the settings class code and n
is the settings instance. Changing settings with external support software
involves the following steps:
Step 1. The PC software reads the CFG.TXT and SET_ALL.TXT files
from the relay.
Step 2. You modify the settings at the PC.
For each settings class that you modify, the software sends a
SET_cn.TXT file to the SEL-421.
Step 3. The PC software reads the ERR.TXT file.
If it is not empty, the relay detects errors in the SET_cn.TXT file.
Step 4. For any detected errors, modify the settings and send the
settings until the relay accepts your settings.
Step 5. Repeat steps 2–4 for each settings class that you want to
modify.
Step 6. Test and commission the relay.
SET_ALL.TXT File (Read-Only)
The SET_ALL.TXT file contains all of the settings for all of the settings
classes in the relay.
SET_cn.TXT Files (Read and Write)
There is a file for each instance of each setting class. Table 5.10 summarizes
the settings files. The settings class is designated by c, and the settings
instance number is n.
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