Supervisory Control (SCADA)

The ability to perform operations at an unattended location from an attended station or operating center and to have a definite indication that the operations have been successfully carried out can provide sig­nificant cost savings in the operation of a power system. In most sys­tems there are locations where operations, such as opening or closing circuit breakers, must be done from time to time, but the cost of provid­ing and maintaining operator attendance cannot be justified. Delays that could result from the need to send an operator to such locations may lengthen an outage and deteriorate customer service. Furthermore, the cost of providing attendance at remote stations or providing person­nel to perform switching continues to escalate. This makes operator attendance of remote stations even more uneconomical. These have been major reasons for the development of supervisory control and data acquisition (SCADA) systems. Devices to control equipment remotely have been used for many years, and the need for remote indication as well as control led to the development of equip­ment that could perform the operations, monitor them, and report back to the control center that the desired control action had been sat­isfactorily effected. At the same time it is often important to transmit such information as loads and bus voltages to an operating center.

Initially such systems depended upon wire communication circuits for both the transmission of the control signals and supervision. The performance of more than one or two operations was beyond the capa­bilities of such early systems. The development of selective calling techniques in the telephone industry were soon applied to power sys­tem supervisory control equipment, so that one communications cir­cuit could be used to perform and monitor many operations and indi­cations and also to telemeter corresponding operating information back to the operating center.

Almost all modern dispatch and operating centers of power systems are now provided with at least some SCADA system equipment. SCADA equipment has proven to be efficient and economical for power system operations. It is a very effective aid for station opera­tors, making it possible for them to maintain relatively complete knowledge of conditions on the portions of the system for which they are responsible.

Questionnaire:

• What is Supervisory control (SCADA)? Explain.