Design issues:

While designing an element in a power transmission system or a machine, there are a number of issues or problems that one has to overcome. These include:

• The size of the system with regard to the number of input points or output points.
• Throughput of the system, which is governed by factors such as
  • Magnitude of the field input or the field output
  • The time required for the capture of data. This time is dictated by the time constraints of the monitored process and the time taken to respond to any event.
  • The use of sophisticate schemes for data compression
  • The level of integrity expected of the data communication
  • If a deterministic protocol requires guaranteed response in specific time
  • The physical media acceptable in a particular application
• Certain key plant input or output and operations associated to it may be deemed as being of high integrity. The redundancy needs to be considered in one or many areas to reduce the effects of failure. This redundancy may include:
  • Dual links for plant input or output to many PLC or  RTU
  • Dual communication links that handle dialogues with primary supervisory processors
  • Redundancy in the main supervising processor that is provided by either employing a fault tolerant processor or by having multiple processors to provide a shadowing function.
• As the loading with regard to the number of plant input or output increases, the processing power requirement also increases. A typical partitioning would include:
  • Frontend processors that are devoted to handling acquisition of data from field PLC and RTU equipment.
  • Graphics workstations, wherein a number of operators positions are needed. A distributed client-server based architecture spreading the load between a main processor and a many graphic workstations should be provided for.
  • One or more Main Supervisory processors provide centralized control and the representation of the field input or output by one or more databases.

Questions:

• What factors do the throughput of the system depend on?
• How does the number of plant input or output affect the processing power needed?