Standards Development

Scope

This Technical Specification (TS) focuses on the formulation of the inertia management framework, which is served as the first part of the guidelines on inertia management of renewable penetrated power system. The follow-up Technical Specifications will be developed to explicitly address the technical re -quirements regarding inertia estimation, evaluation and provision, which shall be excluded in this TS. The scope of the TS mainly covers general, design and functional specifications for the overall frame -work. It specifically includes classification of inertia sources, requirements for system modelling and as -sessment metrics to analyse inertia, critical factors and divisible obligations that need to be considered to design the framework, and overall structure to functionalise the framework.

The content of the Tech -nical Specification includes but is not limited to the following categories:

1. Scope
2. Normative references
3. Terms and definitions
4. General specifications
5. Design specifications
6. Functional specifications

Purpose

This century, the power industry has been undergoing the revolutionary transformation from coal -fired synchronous generators to power-electronics-interfaced renewable generators. In the conventional pow-er grids, synchronous generators are the promising source to provide inertia. However, for typical re-newable generators, the frequency is decoupled from the main grid due to the interface of power elec -tronics devices, thus providing zero or low inertia to the power system. As a result, the increasing de -commissioning of synchronous generators and the accelerating penetration of asynchronous generators are potentially creating inertia shortfalls for the power system, which progressively and fundamentally alters power system frequency dynamics. Accordingly, the existing power system frequency regulation framework is required to evolve by implementing a deliberate set of choices regarding specifications of power system inertia that seek to meet the challenges of the rapid uptake of renewables worldwide.

Inertia is the prominent power system capability to immediately resist frequency changes arising from an event that results in active power mismatch. Inadequate inertia level shall deteriorate system frequency dynamics especially post disturbances, which could be characterized by the rate of change of frequency (RoCoF), and frequency nadir in the event of a contingency. Several incidents have been captured worldwide related to the lack of inertia as a consequence of significant integration of renewable gene ra-tion, such as the South Australia blackout in 2016, the Great Britain power system disruption in 2019, to name just a few. Therefore, power system operators, jurisdictional planning bodies and regulatory com -missions in many countries, such as Australia, Ireland, United Kingdom, United States of America, Can -ada, etc., have already been actively investigating methodologies to evaluate system inertia and efficient solutions to address the potential inertia shortfalls, which are formulated as national -wisenationwide rules to maintain the system inertia above the prescribed level.

There have also been extensive efforts in relevant international organisations toward the standardisation of inertia management due to renewable penetration. IEC 61400 -27-2-2020 specifies technical require-ments that are applicable to validate synthetic inertia performances for wind turbines [1]. CIGRE Tech-nical Brochure 885 gives the guide for placing synchronous condensers in the power system with pre -dominance of low or zero inertia generators [2]. These documents specifically address the technical re -quirements that the inertia provider shall satisfy to promote power system performances. CIGRE has also published the technical brochure 851 by the joint working group of C2 (power system operation and control) and C4 (power system technical performance) to comprehensively identify and summarise the impact of high penetration of inverter - based generation on system inertia of networks [3]. Despite exe -cuting various strategies for emulating synchronous inertia to renewable generators, there is still a lack of relevant international publications in IEC, IEEE or CIGRE up to now that are intended to specify iner-tia response characteristics as seen from the interconnected power systems and effective methodolo -gies to manage the power system inertia. To address the aforementioned gaps, the primary purpose of the first of the TSs is to provide specifica -tions on formulating the framework to manage the power system inertia.

In addition, the TS is anticipat -ed to assist power system operators on operating the power system with satisfactory performances, original manufacturers on designing the infrastructure with compliant inertial response, and stakeholders on understanding the underlying principles thus determining the investment in the most secure and ec o-nomic power system services. The TS is also anticipated to facilitate the maintenance of frequency sta -bility throughout the power system transformation.

IEC SC 8C focuses on the network management of interconnected electric power systems, covering is -sues such as resilience, reliability, security and stability of modern power grids. In compliance with the scope of IEC SC 8C, inertia is the critical system characteristics that calls for proactive management, and is also in close relevance to system security and stability. Furthermore, the proposal for this new item was presented at the SC 8C plenary meeting held virtually on 17th October 2023. The Japanese N ational Committee (NC) expressed the interests in nominating an expert from Japanese NC midst to co -convene the working group once established.

It also needs to be noted that the working group C2.45 (entitled “Estimation, evaluation and provision of power system inertia in networks with a high share of renewable generation”) was created in CIGRE to investigate philosophies of power system inertial response in the current context, as well as innovative technologies and international practices that facilitate power system inertia management. Liaisons from the CIGRE working group will be invited to disseminate the state of the art and to share their f indings.