The term Exception refers to the system situation which is not in the scope of normal operation.

Exception types

• Expected exceptions, resulting from exceptional events ( triggers ), such as component fault or operator's errors.
• Unexpected exceptions, due to operational complexity, such as inter-unit or human-machine mismatch.

Sources of exceptions

Exceptions may be by design, defining the response to a triggers. Exceptional situations may also be due to design mistakes or bugs.

Examples

Examples of exception by design are:

• When operating a backup unit following a fault of a primary unit.
• When the value of a system variable ( parameter) does not match the situation

  Exceptional situations are risky, because in regular system development, the support for these situations is often lousy.

Operating in exceptional conditions

Basic training of the system operation is about recognizing the system situation and acting in normal conditions. An operator trained only to operate in normal conditions cannot respond effectively to events specific to exceptional conditions.

Updated on 03 Jun 2017.