SCADA in Power Systems

SCADA in Power Systems

This article examines SCADA in power systems, local and central structure, telecommunication networks, and the role of RTU, HVI, and the control center.

The application of remote information acquisition and control systems began in the late 19th century and, with technological advancements, evolved into its modern form known as SCADA. In power systems, SCADA plays a vital role in monitoring, control, load management, increasing reliability, and reducing risks caused by faults. This article examines the structure of SCADA in power networks in three main sections: the local system, the communication system, and the central system.

History of SCADA Application in Power Systems

• The first telemetry systems were used in the 1880s for transmitting simple information.

• In the 1920s–۱۹۳۰s, two-way systems were designed, but they were electromechanical and lacked the ability to transmit analog quantities.

• The real development of telemetry occurred in the aviation industry and meteorological stations.

• From the 1960s, with the advent of computers, modern monitoring and control systems took shape.

• Today, SCADA is used in power grids, oil, gas, water, transportation, and even metro and bus systems.

The main goal of SCADA in power systems: optimizing performance, increasing reliability, reducing risks, and ensuring sustainable energy supply.

SCADA in Power Systems

In power networks—generation, transmission, and distribution of electricity—SCADA acts as the supervisory and control brain. This system enables real-time monitoring and control of equipment spread over a wide area, from high-voltage substations to distribution feeders. SCADA collects analog and digital data from field equipment such as RTUs, IEDs, protection relays, switches, current and voltage transformers, and sends it to the control center. Based on this data, the operator at the center can make decisions or issue control commands such as switching breakers on/off, changing tap changer positions, load regulation, network management, and fault response.

Why is SCADA Critical in Power Systems?

• Real-time network monitoring: Voltage, current, power, frequency, switch status, and line load.

• Reduced outage time: Fast fault detection and remote maneuvering capability.

• Increased network reliability: Prevention of overload, voltage fluctuation, and network collapse.

• Substation and feeder automation: Eliminating the need for constant operator presence at the site.

• Intelligent analysis and decision-making: SCADA data serves as input for advanced systems like DMS, EMS, and load forecasting systems.

• Energy management and economic optimization: Production control, load management, and loss reduction.

Main Components of SCADA in Power Networks

• Field Devices: RTU, IED, PLC, protection relays, sensors, power switches.

• Telecommunication Networks: Fiber optics, radio, PLC, microwave.

• Communication Protocols: IEC 60870-5-104, DNP3, IEC 61850.

• Control Center: Servers, HMI, event logging systems, database, analysis software.

Key Applications of SCADA in Power Systems

• Control and monitoring of high-voltage substations

• Distribution feeder management (Distribution Automation)

• Fault location, isolation, and service restoration (FLISR)

• Load management and demand response

• Coordination with protection systems

• Management of distributed generation and renewable energy

SCADA Structure in Power Systems

For centralized control of the power network, accurate information on equipment status, alarms, voltage, current, and power must be available at the control center. The SCADA structure consists of three parts:

• Local System

• Communication System

• Central System

Local System

The local system includes equipment installed in substations and power plants, responsible for data collection and command execution. This system acts as the eyes, ears, and hands of SCADA.

Components of the Local System

• HVI (High Voltage Interface)

• MR (Marshalling Rack)

• RTU (Remote Terminal Unit)

MR Equipment The MR panel contains terminals where all alarms, statuses, and measurement outputs are connected.

HVI Equipment The HVI is responsible for converting high-voltage signals (CT/PT) to levels acceptable for the RTU. Transducers measure active power, reactive power, voltage, and current, and convert them to DC signals.

DHVI System A simpler version of HVI where transducers are installed in protection panels, and signals are directly fed into the MR.

RTU The RTU collects digital and analog data and sends it to the control center.

Types of RTU Data:

• Status (Digital): Breaker status, alarms

• Measurand (Analog): Voltage, current, power

• Received Commands: Changing breaker, disconnector, and tap changer status

Modern RTUs feature capabilities such as remote diagnostics, multi-protocol support, and data collection from subordinate RTUs.

Communication System

The communication system acts as the neural network of SCADA, transmitting information between the local system and the control center.

Communication Media

• Telephone

• Radio

• Microwave

• Coaxial cable

• Fiber optics

• PLC (Power Line Carrier)

• Satellite

Types of Telecommunication Configurations

• Point to Point (Type 1): Each terminal has a dedicated channel.

• Point to Point (Type 2): Multiple terminals connect to a single CIU.

• Party-Line: Multiple terminals share a common channel and are differentiated by addressing.

Central System (Control Center)

The control center is the heart of SCADA and includes:

• MMI equipment

• Main computers

• FEP (Front-End Processor)

• CIU (Communication Interface Unit)

• Redundant systems

Control Center Functions

• Data collection

• Information analysis and processing

• Network status display

• Sending commands to terminals

• Load and energy management

• Short-term and long-term planning

Hardware Structure of the Control Center

• CIU: Telecommunication interface

• FEP: Front-end processor to reduce the load on the main computer

• HOST: Main computer of the center

• Redundant System: To increase reliability

Software Structure of the Control Center Includes four sections:

• Operating System (OS)

• Data Acquisition and Control Software

• Application Software (PAS)

• MMI Software

Data Acquisition Software

• Poller (MPP)

• SAP

• FEP

Database Management

• Database Manager

• Database Editor

• Database Builder

Conclusion

SCADA in power systems is a complex and vital structure consisting of three main parts: the local system, the communication system, and the central system. This system enables precise monitoring, fast control, load management, increased reliability, and risk reduction, and is recognized as the backbone of modern power network management.