CAUSE AND PREVENTION OF HUMAN ERROR IN ELECTRIC UTILITY OPERATIONS Terry Bilke Midwest ISO ABSTRACT Trends in the electric utility industry have increased the chances and costs of errors by power system operators. Competition is dictating that more be done with available assets. There are fewer field personnel. Cost, rather than reliability and ease of operation is taking priority in new power distribution equipment. Computers, which can be used to simplify work , are installed primarily to process more information and allow the operator to do more. Although this study touches on many aspects of electric operations, it focuses on errors committed by the people running the nerve center of the industry, the power system dispatchers or operators. By the nature of the job, these people are the most visible when something goes wrong. The effects of their mistakes are immediate and potentially costly. This is in contrast with engineering or management mistakes which might never be detected even though things later goes awry because of them. Even though errors are taken seriously by the industry, little has been done to formally track and reduce their occurrence. The two cases found relied on the principle that lack of concentration was the primary cause of mishaps. In other words, the dispatcher must be "fixed" if the situation is to improve. This theory is in contrast with other process industry and manufacturing approaches to prevent errors, defects and accidents. This study started with a survey of dispatchers from 18 utilities representing nearly 2000 years of operating experience. Operators identified underlying error causes and suggested improvements. In addition, other fields were examined to find ways to track and reduce errors. Quality management and reliability engineering principles were found that apply to error reduction. The cognitive science and industrial safety professions also have concepts that prove useful in understanding and eliminating mistakes. This paper should provide a better understanding of human error. It is intended to give practical information to operating personnel. It offers suggestions, tools and a plan that any utility can use to reduce the likelihood of errors in its control centers, power plants and out in the field. ii It's been said that those who cannot remember the past are doomed to repeat it. If we learn from others, we need not commit the same mistakes. Not only must dispatchers learn from their coworkers, but companies should share information for everyone's benefit. That is why this paper also recommends the establishment of a utility error database. Terry Bilke Midwest ISO 701 City Center Drive Carmel, IN 46032 317/249-5463 [email protected] iii CAUSE AND PREVENTION OF HUMAN ERROR IN ELECTRIC UTILITY OPERATIONS TABLE OF CONTENTS INTRODUCTION .................................................................................................................................. 1 BACKGROUND ....................................................................................................................................... 1 WHAT CAN BE DONE? ........................................................................................................................... 2 INCREASED CONCERN ............................................................................................................................ 2 OBJECTIVES .......................................................................................................................................... 3 SIGNIFICANCE ....................................................................................................................................... 3 OPERATING ERROR OVERVIEW............................................................................................................... 4 TYPES OF SWITCHING OR OPERATING ..................................................................................................... 5 Scheduled Switching ......................................................................................................................... 5 Routine Switching............................................................................................................................. 6 Unscheduled Switching..................................................................................................................... 6 Emergency or Forced Switching ....................................................................................................... 7 TRENDS IN THE SYSTEM OPERATOR JOB ................................................................................................. 7 Competition and the FERC............................................................................................................... 8 Computers ........................................................................................................................................ 8 CHANGES IN THE OPERATORS................................................................................................................. 9 COGNITIVE SCIENCE AND THE THEORY OF ERROR.............................................................. 10 INTRODUCTION.................................................................................................................................... 10 Problems Defining Errors............................................................................................................... 10 Problems with Error and Safety Data ............................................................................................. 10 Difficult to Quantify Error Costs .................................................................................................... 11 Myths Associated with Errors ......................................................................................................... 11 ERRORS ARE MULTIDIMENSIONAL ........................................................................................................ 12 ERROR CLASSIFICATIONS AND DEFINITIONS.......................................................................................... 13 Two Broad Categories .................................................................................................................... 14 Definitions...................................................................................................................................... 14 Importance of Operating Error Definition ...................................................................................... 15 LEVELS OF PERFORMANCE ................................................................................................................... 15 Skill Based Performance................................................................................................................. 16 Rule Based Performance................................................................................................................. 16 Knowledge Based Performance....................................................................................................... 17 Performance Levels Applied to Operations..................................................................................... 17 MAJOR ERROR TYPES .......................................................................................................................... 18 Slips ............................................................................................................................................... 18 Lapses or Omissions ....................................................................................................................... 22 Rule Based Mistakes....................................................................................................................... 23 Knowledge Based Mistakes............................................................................................................. 24 Violations ....................................................................................................................................... 26 Latent Errors.................................................................................................................................. 27 ERROR DETECTION.............................................................................................................................. 28 Performance Level Summary .......................................................................................................... 30 HUMAN ACTION MODEL ...................................................................................................................... 31 Background .................................................................................................................................... 31 Components.................................................................................................................................... 32 Human Variability .......................................................................................................................... 36 Problems in Complex Systems......................................................................................................... 37 How People Make Observations ..................................................................................................... 38 iv Problems with Communication ....................................................................................................... 39 INDUSTRY'S PERSPECTIVE ON HUMAN