Optimal transmission and distribution investment decisions under increasing energy scenario

Introduction

The CIGRE C1/C6.37 CIRED Joint Working Group (JWG) was created in 2017 and then membership recruiting started, with the first meeting (virtual) in December 2017. The first in person meeting was at CIGRE Session 2018 in Paris, with around 30 members and observers attending. The JWG had got 30 members from 15 countries that participated in different ways, like attending online meetings, answering the survey, and contributing to the research and writing of the different chapters of this report. Additionally, the JWG released three publications with the results of its work at the events as follows:

• CIRED 25th International Conference on Electricity Distribution, Madrid, Spain, in June 2019
• CIGRE Symposium, Chengdu, China, in September 2019
• CIGRE Session 48 (e-session 2020), SC C1 Tutorial “Optimal Power System Planning and Investment Decisions under Growing Uncertainty”, jointly presented by WG C1.39 and JWG C1/C6.37 CIRED, in August 2020

The main objectives of the CIGRE C1/C6.37 CIRED Joint Working Group (JWG) were to investigates how transmission and distribution planning scenarios are consistently used to ensure holistic investment decisions are made by both TSOs and DSOs. In this context, the scope were focused on the specific activities as follows:

1. Survey and description of recommended methodological practices to build robust, resilient transmission and distribution investment plans, in developed and developing countries. It will include the analysis of current practices on considering and modelling uncertainties, and risk management in generation, transmission, distribution and demand sides.

   How are potential paradigm shifts in electricity demand taken into account, e.g. in electric vehicle charging, sector coupling for heating, or appliance-specific demand response?

   To what extent are scenarios used as transmission and distribution planning inputs, consistent with each other and also with other sector planning assumptions as for gas or combined heat and power networks or transport infrastructure. What would be best practice for such consistency?

    

2. Survey on transmission and distribution planning under uncertainty and distributors’ evaluation of recommendations on planning under uncertainty (e.g. process-driven, standardized solutions that can be implemented quickly once uncertainties resolve themselves).

   How can optimal transmission and distribution networks which correspond to different scenarios, be reconciled into good short-term investment decisions, as the future evolves? What would be best practice for this?

    

3. Review the investment decision making processes, for transmission and distribution, in different jurisdictions and how coordination among them is done (if it is done).

   How are the plans for transmission and for the underlying distribution grids made consistent with each other, especially if the operators are different?

    

4. Derive joint learnings and recommendations associated to optimal investment decisions under uncertainties – from distribution to transmission and vice versa.

The scope is covered starting with a review of previous CIGRE Working Groups (WG) that focused on planning decisions, methodologies and implications derived from the growing integration of distributed energy resources, such as WG C1.22 “Investment decisions in a changing and uncertain environment”, WG C6.19 “Planning and optimization methods for active distribution systems” and Joint Working Group (JWG) CIGRE/CIRED JWG C1.29 “Planning criteria for future transmission networks in the presence of a greater variability of power exchange with distribution systems”.

Scope

A review of the regulatory framework for investments in transmission and distribution is provided for various regions and countries around the world. The regulatory frameworks tended to share and be structured around similar traditional planning processes and reporting objectives, with limited requirements regarding risk-based metrics or practices using probabilistic risk assessments methods, with most specifying requirements on scenario and contingency centric approaches. Widest variations are observed at the distribution level, most likely due to variations in regional governments, utility business structures, and system designs.

A survey was developed by the JWG that collected information on the way ISOs, TSOs and DSOs integrate uncertainties into their planning process, in transmission and distribution, and how they interact especially at their interface. The survey investigated the current planning practices of operators through 39 questions, whose main topics were the information about the company, planning scope, scenarios, uncertainties, and decisions, regulatory regime of network investment remuneration, and the barriers and tools for the information exchange.

There were 43 responses received, 63% DSO and 37% TSO/ISO, from operators of Oceania (5), North America (4), South America (5), Europe (21) and Asia (8). Main results mean that due to their historical design and regulations, ISO, TSO and DSO can have ways of planning in terms of drivers, uncertainties and decision-making process which can complicate their coordination especially for projects at their interface. The two main sources of...