IEEE Power & Energy Magazine - May/June 2017 - 53

CLASS: The World's Largest
Voltage-Led Load-Management Project

numerous load-management (LM) schemes have been investigated (and some even implemented, particularly those focused on reducing or shifting demand), this source of flexibility still remains largely unexploited due to practicality and scalability issues. Typical LM schemes require engaging directly with
customers (providing price signals, remotely controlling specific appliances, and so forth), and this,
in itself, is a major barrier when millions of customers and devices are needed to provide meaningful
volumes of flexibility to the TSO: the cost and complexity involved in the communication and control
infrastructure may well be prohibitive.
One way to unlock this source of flexibility, without directly involving thousands or millions of customers, is to exploit the positive correlation between supplied voltage and demand. Permanent energy
efficiency measures reduce voltages as much as possible-commonly known as conservation voltage
reduction (CVR). DNOs, however, could provide a
new source of flexibility by controlling existing voltage regulation devices only when and to the extent
required by the TSO-an active, flexibility-driven
approach able to support the electricity system.
One such large-scale smart grid project is the
Customer Load Active System Services (CLASS)
operated by the U.K. DNO Electricity North West
Limited (ENWL) from 2014 to 2016 and funded
by the Low Carbon Networks Fund. CLASS proposed and implemented an innovative voltage-led
LM scheme that was demonstrated to be both
practical and scalable and that saw, among other
stakeholders, National Grid (the U.K. TSO) and
ENWL joining forces to deploy and test this innovative approach. In this article, we first introduce
the basic concepts of the project, followed by a
description of the main infrastructure adopted for
its implementation. Then, we present the potential
benefits arising from the regional- and nationalscale deployment of the scheme. Finally, we discuss regulatory aspects that might enable DNOs
to play a more active role in providing flexibility
to future low-carbon electricity systems.

©istockphoto.com/maxkabakov

The CLASS Project: Managing
Demand, Not Customers

may/june 2017

The CLASS project proposes an innovative LM
scheme in which DNOs, by controlling the supplied voltage using the on-load tap changer (OLTC)
of primary substation transformers, can reduce
customer demand for short periods (e.g., 15, 30,
or 60 min) when and to the extent required by the
TSO. This so called voltage-led LM scheme has
as key advantages 1) its practicality, as it relies
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Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - May/June 2017

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