Scope:  This guide provides engineering principles, practices, and guidelines for the selection and application of fast response systems of customer-side loads in modern power grids. It considers the impact of increasing the penetration of renewable energy sources in power systems. The definitions, classification and characteristics of rapid load response resources are elaborated in this guide, such as active response loads, interruptible loads and energy storage. It provides complementary approaches for mitigating frequency stability issues of bulk power systems and microgrids, as well as absorbing renewable power. Function architecture, control strategy, and system implementation for quick response systems of customer-side loads are explored in this guide.

Purpose: In modern power grids, quick response resources of customer-side loads should be measured, controlled, and applied to realize power balance between supply and demand sides. This guide aims to provide practice procedure and criteria on quick and flexible customer-side load control and response system for interactivity and coordination of energy source-grid-load. The purpose of this guide is to provide the knowledge base, shared experience, and opportunities for greater utilization of quick response resources of customer-side loads, such as maintaining frequency stability and improving the ability to absorb renewable energy in modern power grids.