JWG B5/C4.61 Impact of Low Inertia Network on Protection and Control

The increased use of power electronic components in electrical networks leads to new and increasing challenges. For example, the characteristics of fault current and residual voltage may change significantly both in the transient and in the stable phase of short circuit. Besides, high penetration of power electronic components will also reduce the inertia of the power network significantly, which is threatening power system stability. In these conditions, the schemes adopted by traditional protection may not be suitable for certain faults (fault location or fault type). The components connected via power electronic with low inertia may include:

  • FACTS components
  • New non-synchronous generation sources
  • Battery storage and other new type of loads
  • HVDC Interconnectors.

The WG shall consider the challenges of protecting electrical networks with reduced system inertia and changed fault characteristics. The following items will be discussed:

  1. The analysis of fault characteristic (fault level, harmonic, non-linear parameter, variable parameter etc.) and how they affect traditional protection schemes, including site experience and simulation methods
  2. How the reduced inertia affects the system stability margin and the protection mechanism of detecting the loss of stability under disturbance
  3. Ideas or methods of mathematics modelling for power electronic components (may be different for protection and stability control) to simulate transient fault phenomena for protection studies and tests.
  4. Countermeasures or new schemes for protection and automation to adapt to this evolution of electric networks
  5. Control methods and tactics to facilitate operation of protection systems (e.g injection of negative or zero sequence currents in normal operation or in emergency) including control tactics of the power electronic component itself.

A survey of operators worldwide is to be conducted to establish the scale of the problem, related to the above topics. The study will focus on how the reduced inertia/changed fault characteristics will affect the existing power system protection and control (philosophy, methodology and equipment/systems etc.), and possible mitigations. The WG shall investigate impacts upon fault clearance times, system stability and possible deficiencies in existing protection and control techniques as well as emerging techniques which may be better suited. This shall include how technologies such as FACTS or HVDC may assist stability control and protection. 

The WG shall liaise with and refer to the work of WG B5.48 (Detecting Faults on Networks with Low Fault Levels and System Inertia due to Application of new Technologies) to avoid duplication of effort.


  • Technical Brochure
  • Summary in Electra
  • Abstract for Electra
  • Tutorial Proposal Forms and Power Point slides

Time Schedule: start: January 2017 Final report: December 2020

Convener: Ray Zhang (UK)