Advanced on-line monitors are now available for most components of a hydrogenerator. These include stator windings, bearings, air gap, and most recently rotor windings. This paper will describe continuous on-line monitors available for these components, as well as a system which can integrate their output with conventional operating data to provide complete asset management.
Partial discharge (PD) testing has become the most pervasive tool for assessing the condition of the stator winding insulation during normal operation of a hydrogenerator. In the past, the testing was done with a portable measuring instrument. More recently, cost-effective continuous PD monitoring systems have been developed and will be described.
Shaft vibration protection systems have long been standard on large critical power generation assets outside of hydro. Because of the increased need for availability of hydro assets this measurement has now become a standard part of most specifications in hydro plants for both new unit and refurbishment projects for medium and large turbines. A system has been developed which leverages the years of experience in monitoring critical power generation equipment for the specific monitoring requirements of low speed hydraulic machinery.
While many hydrogenerators do not experience alignment issues within the generator, in large diameter generators the size of the components and the forces involved during operation lead to an increased likelihood of variations in air gap due to relative flexibility of the stator and susceptibility to temperature expansion. The development on an online air gap monitoring system, rotor and stator mounted, combined with other monitoring systems is key to early identification and repair of issues in order to extend unit life.
Although salient pole field windings tend to be very reliable, in each major outage plant personnel spend a considerable amount of time doing the ‘pole drop’ test, to assure themselves that there are no shorted turns on the field poles. A new continuous on-line monitor for rotor flux has been developed and proven effective in detected shorted rotor poles in salient pole machines and will be described.
These technological advances in sensors and monitors can greatly benefit from integration into higher level diagnostics. Combining the results of these on-line monitoring systems leads to a much more comprehensive diagnostic. HydroX™ (for Hydro Expert) is a knowledge-based expert system program for on-line monitoring of hydro-generators. Working with the New York Power Authority, the system was developed over five years and a prototype sytem will be decribed which has been in operation for 2 years on two 55MVA generators at NYPA’s St. Lawrence Power Project.