Preface

Hydro generators in different plants are rarely identical, and it is not uncommon for small, medium, or large utilities to have a significant variety of unit sizes, origins, and vintage in their fleet of generators. Among these generators, there might be units 60 or more years old with all original components including stator windings due to the robust nature of this class of machinery. Some might still have a pilot and main rotating exciter or a static pilot with a main rotating exciter, or have full static excitation. Additionally, there may be units operating over a wide range of rotating speeds in 50 and 60?Hz power grids with a few still operating at 25?Hz or other frequencies. All are designed and built by a long list of manufacturers from around the globe using a variety of materials and methods governed by different standards. These generators are still owned by traditional utilities and also owned by new deregulated independent power producers (IPPs) that acquire traditional utilities from all over the world. There are new large hydro plants still being built for traditional utilities and IPPs to the most modern design standards and manufacturing methods. The owners of all types are called upon to operate and maintain an incredibly wide variety of machines.

The reasons why one may find so many "old" units still in operation is not difficult to determine. First of all, historically generators have been designed and manufactured with the intent to be robust enough to last typically 50?years or more. Second, replacing operating units is very capital-intensive and done only when a catastrophic failure has occurred or some significant economic benefit is possible only with complete replacement. Third, although typically designed to last many years, large hydro generators are known to be capable of having their lives extended far beyond 50?years if well maintained and operated. There are some generators in operation today that were placed in service in 1896, an example is the Dominion Power and Transmission Company's units in Decew Falls, Ontario, Canada, now operated by Ontario Power Generation. To continue to operate reliably older generators require replacement of at least some major components, such as the armature winding, rotor winding insulation, or replacing the entire stator frame and core or rotor spider. Managing the scope and timing of major maintenance is always a challenge.

There are copious amounts of information about the operation, maintenance, and troubleshooting of large hydro generators in many publications and online communities. All vendors at one stage or another have produced and published interesting literature about the operation of their generators. Institutions such as EPRI, CIGRE, IEC, IEEE, CEATI, and other organizations cover various aspects of the operation and maintenance of generators in general, but often have difficulty providing specific information that may help troubleshoot a particular generator design or operating problem. It is no wonder then that with so many dissimilar units in operation having different operating conditions, we are often forced to call the "experts," who tend to be folks almost as old as the oldest units in operation. These are individuals who have crawled around, inspected, tested, and maintained many diverse generators over the years. In doing so, they have retained knowledge about the different designs, materials, and manufacturing characteristics, typical problems, and workable solutions. This type of expertise cannot easily be learned in a classroom.

Unfortunately, not every company retains an individual with the breadth and depth of expertise required for troubleshooting the generators. In fact, with the advent of deregulation, many small nonutility (third-party) power producers operate small fleets of generators without the benefit of in-house expertise. In lieu of that, they depend heavily on OEMs and independent consultants. Large utilities in many places have also seen their expertise dissipate, not to a small extent because of a refocusing of management priorities. All these developments are occurring at the same time that these aging units are called to operate in a deregulated or semideregulated world which typically results in an increase in load-cycling.

Some effort has been made over the years to capture the experts' knowledge and make it readily available to any operator as a computer-based expert system. However, difficulty with adaptation of the associated computer programs to the many different types of generators and related equipment in existence has proved to be the Achilles heel of this technology. There is just no substitute for someone who understands machine design and has the required experience to recognize the significance of visual indications while crawling through a machine on a regular basis.

This book is designed to partially fill the gap by offering a comprehensive view of many issues related to the operation, inspection, maintenance, and troubleshooting of large hydro generators. All of the information in the book is the result of many years of combined hands-on experience of the authors, which at the time of this writing, amounts to 157?years. It was written with the machine's operator and inspector in mind, as well as providing a guide to uprating and life enhancement of large hydro generators. Although not designed to provide a step-by-step guide for the troubleshooting of large hydro generators, it serves as a valuable source of information that may prove to be useful during troubleshooting activities. The topics covered are also cross-referenced to other sources. Many such references are included to facilitate those readers interested in enlarging their knowledge of a specific issue under discussion. For the most part, theoretical equations have been left out, as there are several exceptionally good books on the theory of operation of synchronous machines. Those readers who so desire can readily access those books, several references are cited. This book, however, is about the practical aspects that characterize the design, operation, and maintenance of large hydro generators, and a number of practical calculations used commonly in maintenance and testing situations have been added.

Chapter 1 (Principles of Operation of Synchronous Machines) provides a basis of theory for electricity and electromagnetism upon which the machines covered in this book are based. As well, the fundamentals of synchronous machine construction and operation are also discussed. This is for the benefit of generator operators who have a mechanics background and are inclined to attain a modicum of proficiency in understanding the basic principles of operation of the generator. It also comes in handy for those professors who would like to adopt this book as a reference for a course on large rotating electric machinery.

Chapters 2 and 3 (Generator Design and Construction and Generator Auxiliary Systems) contain a very detailed and informative description of all the components found in a typical generator and its associated auxiliary systems. Described therein are the functions that the components perform, as well as all relevant design and operational constrains. Some additional insight into design methods and calculations are also provided.

Chapter 4 (Operation and Control) introduces the layperson to the many operational variables that describe a generator. Most generator-grid interaction issues and their effect on machine components and operation are covered in great detail.

Chapter 5 (Monitoring and Diagnostics) and Chapter 6 (Generator Protection) serve to introduce all aspects related to the online and offline monitoring and protection of a large hydro generator. Although not intended to serve as a guideline for designing and setting up the protection systems of a generator, they provide a wealth of background information and pointers to additional literature.

Chapters 7 (Inspection Practices and Methodology), leads off the second part of the book with a look at preparing for a hands-on inspection of large hydro generators. The chapter discusses the issues of concern for both safety of personnel and the equipment as well as the types of tools and approaches used in inspecting large hydro generators. This chapter also contains a collection of inspection forms that can be used for inspecting large hydro generators. These forms are very useful and can be readily adapted to any machine and plant.

Chapter 8 (Stator Inspection), Chapter 9 (Rotor Inspection), and Chapter 10 (Auxilliaries Inspection) constitute the core of this book. They describe all components presented in Chapters 2 and 3, but within the context of their behavior under real operational constraints, modes of failure, and typical troubleshooting activities. These chapters provide detailed information on what to look for, and how to recognize problems in the machine during inspection. Chapters 8 and 9 also contain hundreds of pictures to assist in the inspection process in a methodical step-by-step crawl through of the machine.

Chapter 11 (Maintenance and Testing) contains a comprehensive summary of the many techniques used to test the many components and systems comprising a generator. The purpose of the descriptions is not to serve as a guide to performing the tests as there are well established guides and standards for this purpose. Rather, they are intended to...