Design of HMI for SCADA systems must be including consideration of Human Factors Engineering (HFE). It is estimated around 50% or more of all loss of load events in mission critical facilities involves action of human. A reported scenario begins wit a single correct response and component failure by the automatic control system to isolate the failure and maintain service to the load, however resulting in an off normal system condition. Intervention of incorrect human in attempting to restore the system to normal conditions after that the result in loss service to the load. HFE consideration in the lay out of operator controls can help prevent these occurrences.
1. Labeling: all control devices must e labeled clearly that are large enough with high contrast. The primary designation should be the functional description. The labels also carry the device tag number.
2. Layout: control should be arranged and grouped in logical and intuitive manner. Some of technique to design intuitive layout as below:
• Grouping control associated with individual pieces of equipment.
• Placing control switches top to bottom or left to right in which the operators are operated during a normal shutdown or startup.
• Spacing devices are far enough apart.
• Arranging controls in the electrical or physical process order.
• Color control coding devices.
• Colored backgrounds or borders.
3. Color schemes: used for controls and for graphic screens used within the process.