Operating Modes

This chapter describes the different operating modes of the Datalogging and their behavior.

• Mode 0/1: Buffer and disposal in chronologic order
  • Mode 0: Limited storage (keeps oldest, but stops if full)
  • Mode 1: Endless (ring buffer) operation modes (deletes oldest)
• Mode 2: Buffer and disposal via FTP, Log file(s) copied to ftp server area for further use
• Mode 3: Events Recorder, logs data before and after an event.

Mode 0/1: Buffer and disposal in chronologic order

Overview Mode 0/1

Mode 0/1 is for buffering the values from the AC500 application in case of a broken or intentionally interrupted connection between AC500 and telecontrol. In the normal state 1 the values are directly sent from the FIFOin (input values from application) to FIFOout (telecontrol connection). As soon as the connection is interrupted, the Datalogger changes to working state 2. The values are sent to the File FIFO instead. When the File FIFO is full, the Datalogging is stopped (Mode 0) or the oldest data will be overwritten (Mode 1 = ringbuffer). When the connection is established again and the RELEASE_HISTORY pin is triggered, the Datalogger changes to working state 3. It cares for disposal of the values in chronological order. The buffered values are written to FIFOout (working state 3a). This may take some time during which new values are coming from the application and stored into FIFOin. Before the FIFOin overflows the Datalogger switches to working state 3b and buffers the new values. After that it can continue with working state 3a. Only if the File FIFO is empty (all files deleted) the Datalogger changes back to normal state 1.

The advantage of Mode 0/1 is that all values (directly and buffered) are sent to telecontrol in strictly chronological order which is expected by most control stations (SCADA systems/historians).

As it takes up to 30 seconds before a communication break is detected (e.g. with TCP/IP protocols by the AC500 hardware/firmware), the data rate at which data should be logged in case of a communication break has to be calculated and limited.

Mode 2: Buffer and disposal via FTP

Overview Mode 2

Mode 2 is also used for buffering the values from AC500 application in case of a broken connection between AC500 and telecontrol. State 1 and state 2 are similar to Mode 0/1. The difference is the disposal. When the connection is established again the Datalogger changes directly back to state 1 and the input values in FIFOin are directly sent to FIFOout (telecontrol connection). The buffered values in File FIFO are internally moved from disk 1 to disk 2 which can then be accessed or used by FTP (client or server). This move action can also be triggered by the command MOVE_FILES, or when file 1 is full. The advantage of Mode 2 is the immediate availability of the latest and all current values after an outage.

Mode 3: Events Recorder

Overview Mode 3

Mode 3 is used to record data values around an event, before and after the event x, e.g. outage of a part of the plant. The values are continuously recorded into the File FIFO file system independent of the connection status to telecontrol. If the File FIFO is full the oldest values are overwritten (ring buffer). Thus the File FIFO always contains the values from the past period n, which is depending on the amount of values per second and on the size of the File FIFO. When a certain event x occurs, the command MOVE_FILES can be given directly or after the period m. With the command MOVE_FILES the values in File FIFO are internally moved from disk1 to disk 2 and can be read out by an FTP action (client or server) when required.

The buffered values represent the time before the event (n-m) and after the event (m).

The advantage of mode 3 is that the values from the time period before the event (n-m) and after the event (m) are recorded and can help to reconstruct the cause and effect of the event.