ReliaGrid™ Load-Shedding Engineered Solution

Ensuring continuity of power supply to critical loads and preventing blackouts

The load-shedding solution ensures a swift disconnection of low-priority loads after detection of a power network disturbance.  It is designed to utilize the full potential of the IEC 61850 standard for communication and interoperability of substation automation devices. It is based on full integration of ABB's Relion protection and control relays, Remote I/O unit RIO600 and Human Machine Interface (HMI)-based on ZEE600 with the load-shedding controller. 

The functionality can be also extended from covering MV feeders to LV feeders by inclusion of IEC 61850 compliant devices such as Emax2 circuit breakers equipped with Ekip Up protection and IEC 61850 communication modules. 

The fast IEC 61850 GOOSE communication between the ABB devices ensures that the load-shedding signals are exchanged and distributed within milliseconds to ensure a superior performance without signal latencies.


  • For configurations with up to 8 power sources, 6 bus bars, 60 loads distributed across 19  priorities
    - PML630 load-shedding controller or AC500 PLC with load-shed libraries in combination with Relion relays, RIO600 device, third-party devices, etc.
  • For bigger configurations, AC800M to be used as load-shedding controller, in combination with other Power Management functionality, working together with Relion relays and RIO600 device
  • Following load-shedding modes are supported:
    - Contingency based fast mode
    - Overload or demand control based slow mode
    - Frequency based activation of fast mode
    - Manual (priority and power definition) based
  • A dedicated low-voltage load-shedding solution based on Emax2, Ekip Control+, motor controllers and MCBs is also possible.
  • The engineered load-shedding solution comprises of a dedicated panel based arrangement comprising of the following:
  • Fully configured and tested load-shedding controller/device (PML630/AC500/AC800M)
  • ZEE600/ZEE600C HMI
  • Networking equipment
  • GPS (if needed)

Additional equipment like transducers, auxiliary relays etc. can be included as per project requirements.


  • Required to prevent blackouts that can be very costly
  • Post-islanding event or in already islanded network, if in-plant power generation is insufficient to meet power demand
  • Maintains power balance by shedding low-priority loads to match loss of power source(s)
  • Within tens of milliseconds to ensure frequency stability
  • Ensuring power to critical loads in plant
  • Carried out at lowest possible voltage level (granularity)=> at lowest MV outgoing feeder level or LV outgoing feeder level
  • Offers increased flexibility and scalability and improved system integration and customization, fulfilling a variety of requirements
  • All load-shedding modes enabled and available for use with every device
  • Easy system integration using IEC 61850; guaranteed load-shedding command generation time of up to 20 milliseconds from disturbance detection 

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