Tech Essentials

What is Intelligent Electronic Device? A Complete Guide

Intelligent Electronic Devices (IEDs) are becoming increasingly popular in the electric power industry. But what exactly are they and what purpose do they serve? This comprehensive guide provides an in-depth look at Intelligent Electronic Devices, their functions, applications and role in power system automation.

What is an Intelligent Electronic Device?

An Intelligent Electronic Device (IED) refers to a microprocessor-based controller used to monitor, protect and control equipment in power systems like substations and distributed generation sites.

IEDs are integrated devices that combine multiple functions like:

  • Protection
  • Control
  • Monitoring
  • Metering
  • Communication

into one intelligent electronic device.

Unlike traditional electromechanical relays, IEDs utilize microprocessors and software programming to implement advanced power system functions. Their versatility, intelligence and communication capabilities make them a core component of smart grid and automation applications.

Key Functions of Intelligent Electronic Devices

Some of the major functions performed by IEDs include:

1. Protection

IEDs provide advanced protection functions to detect abnormal conditions and trigger actions like tripping circuit breakers. Common protection functions include:

  • Overcurrent protection
  • Earth fault/ground fault protection
  • Under/over voltage protection
  • Frequency protection
  • Differential protection
  • Motor, transformer, generator protection

By combining multiple protection elements, the IED can provide comprehensive protection for any power system equipment.

2. Control

IEDs can perform automatic local or remote control of connected equipment like:

  • Circuit breakers
  • Reclosers
  • Load tap changers
  • Capacitor banks
  • Smart meters

Control functions include open/close operations, interlocking logic, sequence coordination, etc. This enables intelligent automation and control.

3. Monitoring

IEDs provide equipment condition and performance monitoring like:

  • Current and voltage levels
  • Power quality parameters
  • Fault event records
  • Equipment operating statistics
  • Maintenance indicators

This data can be analyzed to optimize asset management.

4. Metering

Advanced metering capabilities of IEDs include:

  • Watt, VAR, VA, power factor, frequency metering
  • Demand and energy metering
  • Power quality metering
  • Fault record analysis
  • Harmonics measurement

Metering data can be used for billing, analytics, system studies etc.

5. Communication

IEDs have communication ports and protocols to enable integration with automation systems like:

  • Distributed control systems
  • PLCs
  • Other IEDs

This allows interoperability, remote monitoring and networked control.

Applications of Intelligent Electronic Devices

Some major applications where IEDs play a critical role include:

Substation Automation

IEDs are central components of modern smart substations. They monitor, protect and control substation equipment like transformers, breakers, reactors. Advanced automation is achieved by networking IEDs using protocols like IEC 61850.

Distributed Energy Resource Management

In distributed generation sites with renewable energy resources like solar, wind, IEDs provide automated grid integration, protection and control capabilities.

Distribution Automation

IEDs enable remote monitoring, fault location, self-healing and Volt-VAR optimization in smart distribution grids.

Power System Protection

IEDs provide intelligent, networked protection for critical equipment like generators, motors, transmission lines, etc. They implement key schemes like differential protection.

Power Quality Monitoring

IEDs provide continuous power quality monitoring and diagnostics. Issues like transients, harmonics, unbalance can be detected and mitigated.

Motor Control and Protection

For large industrial motors and drives, IEDs provide coordinated control, protection, condition monitoring and analytics.

Railway Electrification

IEDs are used for protection, control and monitoring of railway AC and DC traction power systems.

Smart Metering

Advanced metering IEDs enable automated reading, outage reporting, tamper detection, pre-paid billing for smart meters and AMI systems.

Evolution of Intelligent Electronic Devices

The first microprocessor based IEDs emerged in the 1970s and were mostly used for protection and control. Early IEDs replaced electro-mechanical protective relays.

Over the years, IED technology has rapidly evolved with:

  • More powerful microprocessors
  • Improved signal processing and analytics
  • Advanced communication protocols
  • Interoperability standards like IEC 61850
  • Integration of multiple functions into one device

Modern feature-rich IEDs bear little resemblance to their primitive ancestors. IEDs have enabled smarter, self-healing power grids using automation and real-time data.

IED Standards

Some key standards related to Intelligent Electronic Devices include:

  • IEC 61850: Communication networks and systems for power utility automation
  • IEC 60870-5: Telecontrol protocols like DNP3 and IEC 60870-5-101/104
  • IEC 60255: Measuring relays and protection equipment
  • IEEE C37.2: Standard for electrical power system device function numbers

Benefits of Intelligent Electronic Devices

Some major benefits offered by IEDs over conventional protection and control devices:

  • All-in-one integrated solution combining multiple functions
  • Intelligent protection, automation and control
  • Improved reliability and accuracy
  • Interoperability with open standard protocols
  • Advanced communication and cybersecurity
  • Compact hardware, saving space and costs
  • Detailed event, fault and disturbance recording
  • Remote access for monitoring and control
  • Platform for developing smart grid applications
  • Enable smarter, self-healing power grids

The unique capabilities of IEDs make them indispensable components of modern electrical grids and industrial automation systems.

Leading IED Manufacturers

Some top IED manufacturers include:

  • ABB
  • Siemens
  • Schneider Electric
  • General Electric
  • Eaton
  • Mitsubishi Electric
  • Fanox
  • ERLPhase
  • Basler Electric
  • NR Electric

Various types of IEDs like protection relays, RTUs, bay controllers, reclosers, meters etc. are offered by these companies. They provide hardware, software tools and integration services for IED based solutions.

IED Market Growth

According to MarketsandMarkets, the global IED market size is projected to grow from USD 16.36 billion in 2022 to USD 25.37 billion by 2027, at a CAGR of 9.0% during the forecast period.

Key growth drivers include:

  • Modernization of aging power infrastructure
  • Integration of renewable energy
  • Advancements in digital substations
  • Investments in smart grid technologies
  • Integration of IEDs with IoT platforms
  • Infrastructural developments in emerging economies

The IED market is witnessing strong growth as grids get smarter, distribution systems more automated and end-to-end digitalization increases.

IEDs in Smart Grids and IIoT

IEDs play an integral role in enabling key smart grid capabilities like:

  • Automated fault location, isolation and service restoration
  • Self-healing distribution grids
  • Advanced distribution automation
  • Renewable integration through Microgrids
  • WAMS, synchrophasors for wide-area monitoring
  • Volt/VAR optimization
  • Smart metering and AMI

By providing an open, interconnected platform, IEDs facilitate secure data exchange and interoperability between grid components.

Integration of IEDs with Industrial IoT allows unified data collection, predictive analytics and higher visibility into grid operations. This creates opportunities for machine learning applications, predictive maintenance, distributed control etc.


Intelligent Electronic Devices provide technologically advanced, multifunctional solutions for power system automation. With inbuilt intelligence, seamless interoperability and data-driven capabilities, IEDs serve as key enablers of smarter, resilient and sustainable grid infrastructure worldwide. Continued innovation in IED technology will unlock further grid modernization use cases as the grids of tomorrow take shape.

Frequently Asked Questions

What is an Intelligent Electronic Device?

An Intelligent Electronic Device (IED) is a microprocessor-based controller that combines multiple capabilities like protection, control, monitoring, metering and communication for power system equipment automation and control.

What are the key functions of IEDs?

Main functions of IEDs include:

  • Protection (overcurrent, differential, voltage, frequency etc.)
  • Control (breaker, tap changers etc.)
  • Monitoring (alarms, events, equipment status)
  • Metering (power quality, harmonics, demand, energy)
  • Communication (tocols like DNP3, IEC 61850)

Where are IEDs used?

Major applications include substation automation, distribution automation, generator protection, railway electrification, smart metering, power quality monitoring etc.

What benefits do IEDs provide over traditional devices?

Benefits include integrated solution, improved reliability, interoperability, cybersecurity, compact hardware, detailed event recording, remote access and advanced automation.

What communication protocols do IEDs use?

Common communication protocols supported by IEDs include:

  • IEC 61850: Standard for substation communication and interoperability
  • DNP3: Popular protocol for SCADA integration
  • IEC 60870-5-104: Used for telecontrol in distribution grids
  • Modbus: Serial communication protocol for industrial devices
  • IEC 60870-5-101: Used for telecontrol equipment and systems
  • IEC 61850-9-2: Communication standard for IED to IED interface

How are IEDs connected in substations?

In substations, IEDs are networked over an Ethernet switch using IEC 61850 to enable station-wide interoperability. Bay-level IEDs connect to switchgear, while station IEDs integrate bay data.

What impact have IEDs made on power system protection?

IEDs have revolutionized protection by providing intelligent, interconnected, communicable, multi-function digital relays for protection, control, and monitoring.

How do IEDs help in smart grid implementation?

IEDs facilitate key smart grid capabilities like automation, integration of renewables, microgrids, wide-area monitoring, analytics, and smart metering through advanced protection, control, and connectivity.

What is the future outlook of the IED market?

The IED market is poised for strong growth driven by investments in digital substations, distribution automation, smart grids and Industrial IoT. Global IED market revenue is forecast to reach $25.37 billion by 2027.

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