The Supervisory Control and Data Acquisition (SCADA) systems used by electric utilities to manage the distribution of electric power are highly dependent upon the intelligent, micro-processor based devices installed throughout the electric power distribution grid.
These intelligent devices acquire in real time the critical performance measurements (e.g. current, voltage), transmitting that information back to the central SCADA control center.
The SCADA control center can issue operate commands (CONTROL actions) to the intelligent devices.
These CONTROL actions can operate a switch, operate equipment that adjusts voltage or current, operate equipment that adjusts phase shift or any number of actions necessary to manage the electric power distribution grid.
Intelligent Devices Measurements
The intelligent devices typically measure AC current based upon the secondary output of a primary current transformer, typically 0 to 5 ampere AC.
Transforming the 0 to 5 ampere AC signal to level appropriate to a micro-processor based circuit is handled by solid-core, toroidal current transformers.
The 0 to 5 ampere conductor is looped through the center opening of the current transformer. A solid core current transformer offers superior transformation accuracy at a very competitive component price.
Solid-core current transformer can be designed to perform beyond the rated primary before magnetic core saturation offering the ability to measure AC current surges.
The advent of digital signal processors (DSP) offers high signal sampling rates, enabling the measurement of the AC base frequency and the harmonics of the base frequency.
Surface Mount Technology (SMT) components offers compact designs capable of operating in harsh operating environments.
3 Phase SCADA Remote Terminal Unit
A three(3) phase SCADA Remote Terminal Unit (RTU) incorporates analog input measurement of AC current and AC voltage, digital signal processing necessary for the calculation of power, power factor, harmonics amplitudes, etc. and data transmission to the SCADA control center.