4C1: The Lost Language of Governing
July 14, 2022
Equipment and Technology
Every industry has its own language, methods, and culture. This is especially true for the hydro turbine governor which has a history of over 150 years and users have equipment that may have been operating since the early 1900’s. The “language and knowledge” of hydro turbine governors was mainly transferred from person to person and much of the knowledge is not documented. As a result there has been a large loss of knowledge due to experienced personnel retiring or leaving the industry. The knowledge gap that is currently in the industry is contributing to old problems that were previously understood, becoming the new problems that end users are facing. Many of these “new” problems could be avoided if end users and vendors both understood the same language of governors. As an example existing hydro turbine governors were designed as a system that was made of concepts such as dither, valve lap, pressure tank dead oil volume, governor water column compensation, distributing valve, reverse power and many other terms that referenced requirements that were all considered during the design of the original governor system. In addition to the original “language” the conversion to digital controls results in additional concepts such as sample rate, bandwidth, deadtime, deadband, and other concepts which reflect the modern governor system. Many of the observed problems with refurbished or retrofitted governors can be attributed to the retrofit changing a specific subsystem without considering how the complete system was designed. These issues show up as unstable valve control, excessive valve movement, governor oil heating problems, reduced pump cycle times, large reverse power effects, noise generation / amplification, and reduced governor response to grid events. This paper is intended to be a nonvendor specific approach to providing a reference for an end user to use when they are considering a turbine governor retrofit or refurbishment project. This paper will provide a basis for an end user to understand the “language” of governor systems by documenting the key concepts used in the design of their existing governor systems, how these concepts are assembled together to make the governor system, and how these concepts can be maintained or replaced while undertaking a governor retrofit or refurbishment project. The paper will be organized to ground the reader in the “language” of the governor system using block diagrams for a typical mechanical governor system and digital governor systems. In addition the paper will include short case studies related to lessons learned with respect to problems that have resulted during a governor system retrofit. Finally the paper will include a short discussion of the available standards from IEEE, IEC, and other industry references that can also be used by the reader to understand the language of governors.