D11 Working Group Report

by IEEE PES PSRC  D11 Working Group

The IEEE Power & Energy Society’s Power System Relaying and Control Committee has been working for many years on identifying the developments in Smart Grid technologies and their impact on the protective relaying of electric power systems. One of the results of these efforts was the establishment of working group D11 in the Line Protection Subcommittee with the task to develop a report on the “Effect of Distribution Automation on Protective Relaying.”
The material in the report is arranged in five chapters and two annexes.
The first introductory chapter describes Distribution Automation (DA) as part of today's evolution of the distribution system. Many utilities already have some Distribution Automation applications (e.g., remote controlling of feeder switches and breakers, automatic reconfiguration, fault detection, fault location, voltage and reactive power control, Advanced Metering Infrastructure (AMI), etc.) and the trend is undeniable and expanding.
Modern protection technology provides capabilities that can be used to optimize network operation in coordination with DA applications. Certain DA application deployments impact the system configuration and therefore may have some impact on protective relaying.

This document expresses some thoughts on this matter by providing a brief history, describing how various schemes can affect relaying, describing the effect on relay applications and settings, and concluding with the impact on system maintenance.
It also defines that the purpose of the report is to explore the effect on protective relaying when distribution automation (DA) is applied on a primary, non-network, distribution system. For the purpose of this document, DA is defined as the sectionalization  and reconfiguration of  distribution circuits, including the  use  of  automatic or  remote-controlled  transfer switches, line  reclosers, fault interrupters, sectionalizers,  and / or automated capacitor controls. 

Line fuse operation may be impacted after reconfiguration and the consequences of a mis-operation should be considered.
However, detailed discussion on fusing is considered outside the scope of the document.
The following sections of the first chapter cover definitions of different terms and abbreviations used in the report.

The second chapter is dedicated to the history of distribution automation. The first section presents the history of Substation-based Automation, which is followed by the history of Line Distribution Automation. The last section in the chapter focuses on today's Distribution Automation applications:

  • Local intelligence
  • Distributed intelligence
  • Central intelligence

Telecommunication requirements for distribution automation applications are discussed at the end of this chapter.
Chapter 3 is the main part of the document describing the effects of distribution automation on relay applications and settings.
The first section in this chapter is focused on circuit reconfiguration, which is defined as the modification of the topology of a distribution network by operating NC (Normally Closed) and NO (Normally Open) switches or circuit reclosers. Switches located along the feeders are NC and allow isolating sections of the feeder when required.

These are also called Sectionalizing Switches. Switches connected between two feeders are NO and allow transferring loads between the feeders when they are closed. These are also called Tie Switches.              
Load sectionalizing device locations, load serving issues and looping are discussed.
One of the most important functions in DA is the service restoration in the event of a fault of a primary feeder. The main goal of automatic service restoration is the operation of the tie switches to restore the energy supply to the maximum number of possible areas having been affected by the fault. The problem has a combinatorial nature since it deals with the on/off status of the switches. Fault Location, Isolation and Service Restoration (FLISR) is one of the most commonly used distribution automation applications described in this section of the report and shown in Figures 2 and 3.

The next section of this chapter analyses the impact of distribution automation on various protection schemes.  Overcurrent protection using multiple setting groups and adaptive relaying to adapt to the changes in topology are considered.
The zones of protection and the issues of overcurrent protection coordination are later discussed.
The last section of Chapter3 concentrates on protection functional requirements after circuit reconfiguration and covers topics such as fuse saving sacrificing, fault locating, remote or alternate settings, precautions to avoid harming utility personnel.
The challenges related to the connection of distributed resources (DR) to the distribution system are analyzed at the end, addressing issues such as load (line) reconfiguration, DR and DA relay protection, as well as DR control by the DA system.

A short Chapter 4 looks at the impact of distribution automation on system maintenance and Chapter 5 contains the Bibliography.
The two annexes cover Changes of Power Flow Due to Different Topology Scenarios and One Company's History with Distribution Automation.

The report can be downloaded from



Working Group D11 Infrastructure: 
Fred Friend, Chair
Gerald Johnson, Vice-chair

Working Group Members:
Brian Mugalian, Calin Micu,
Charles Sufana, Cheong Siew,
Claire Patti, Daniel Goodrich,
Don Lukach, Don Parker,
Farajollah Soudi, Jack Jester,
Jakov Vico, Jay Sperl,
John Tengdin, Juan Gers,
Kevin Donahoe, Matt Black,
Mike Meisinger, Pat Heavey,
Patrick Carroll, Raluca Lascu,
S.S. Mani Venkata, Steven Hodder, Victor Ortiz, Wayne Hartmann

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