Definition

The system time stamping provides a consistent SOE (sequence of events), time stamped at the source, in order to allow the user to analyze the source of abnormal behavior in a distributed automation system.

The SOE is displayed in an alarm summary or SOE page of a client (such as a SCADA).

Each source of time stamped event of the SOE is a discrete I/O value change (transition) detected by a time stamping module or an internal variable value change detected by a PLC.

The following graphic shows an example of AVEVA Plant SCADA SOE page display:

Benefits

The system time stamping benefits are:

• No need for PLC programming.

• Direct communication between the time stamping modules and the client. If the time stamping modules are in a Modicon Quantum or M580 Ethernet I/O drop, the PLC communication bandwidth is not used.

• Consistency in the I/O values between the process (time stamping modules) and the client (SCADA).

• Advanced diagnostic functions:

  • Signalization of uncertain SOE (sequence during which some events may be lost) to the client.

  • Time quality information associated with each time stamped event.

• No loss of events in normal operating conditions:

  • A buffer is available to store the events in each time stamping module. The event storage is stopped when the buffer is full.

  • Rising and falling edges transitions are stored for each discrete I/O and PLC internal variables.

• Hot Standby configurations on the PLC and/or redundant SCADA are managed.