Power plant control – Integrating process and substation automation into one system

Power plant electrical system

This paper deals mainly with thermal plants such as steam power units, gas-fired combined-cycle power plants and waste incineration plants in terms of integrating both process and electrical control into one consistent system.

Depending on the specific plant type some other components, such as a static starter system in GT-plants or emergency / black start diesel generators, are not shown in this example.

For the integration of electrical systems it is important to identify the typical elements of the single line diagram. The requirements regarding integration have to be identified for each element and an integration concept has to be defined.

Only those devices typically coming from medium or high voltage substations are supporting IEC 61850.

Figure 1 shows a single line diagram of a power plant.

Electrical control system requirements

For the integration of the electrical systems as described in the chapter above the control system has to be designed to fulfill some important requirements:

Monitoring

Monitoring of the electrical system has to be possible at workplaces of the control room, workplaces dedicated to control of the electrical system and workplaces for maintenance planning. Graphic displays have to be available presenting the status of the overall or parts of the electrical system.

To be able to take immediate action in case of disturbances, it is also important to be aware of all alarms and have a quick overview in which part / area alarms are active.

Manual (remote) operation

The manual (remote) operations of electrical devices have to be supported by consistent means; e.g., faceplates in the control room or locally at the device cubicle using push-buttons or control panels.

Automatic operation

From a power plant control system point-of-view, automatic operation means that electrical devices are part of automatic control sequences executed in an automation controller. This requirement applies only for those devices that interact with process control.

For this interaction, the automation controller and those electrical devices have to communicate using a common interface.

Recording

For purposes of disturbance analysis, documentation, reporting and optimization, the plant control system has to be capable of recording electrical system status signals, alarms, events and measured values.

Plant-wide sequence-of-events (SOE)

Fatal failures of the electrical system have an impact on the overall plant operation; e.g., may lead to a plant trip. For analysis of such failures a plant-wide chronological sequence-of-events is needed.

To cover every type of failure, a time stamp accuracy with 1 ms time accuracy is needed.