Gas generator services for your power plant

The main driver for generator issues is thermal effects from load shifting.  When you need to start and stop the equipment often and you’re operating in partial load, the resulting load shift changes the thermal profile within the stator and the rotating field—which in turn causes the components to shift.  Here’s a look at some typical cyclic rotation issues on the rotating field.

The life expectancy differences between a base-loaded unit and a heavily cycled unit is represented in the curve below.  The upper bound limit shows a unit with more of a base-loaded operating profile, while the lower bound limit represents a unit that has a heavier load cycle (daily stops/starts, greater than average running hours, part load operation, load shifting, etc).

Standard insulation and blocking schemes often struggle with the thermal transients of frequent cycling, which can result in thermal sensitivity or insulation failure. By implementing Flex Pack technology on the rotor and stator, we enable the rotor components to better handle the increased relative motion caused by thermal variations, while allowing the stator connection rings and stator end windings to move independently during these start-stop cycles. This isolates mechanical stress and helps ensure that your generator is robust enough to handle these changes in operational profile without a forced outage.

One of the main sources of service problems on the generator rotor is the collectors. Having a Collector Brush Monitoring system will aid operators in knowing if there is a potential problem before it happens. GE Vernova offers a monitoring system to go along with our Enhanced Brush Holder Rigging system.

On the generator stator side, the insulated copper winding is the number one reason for service issues. A Partial Discharge Analysis (PDA) is a great way to track and trend the health of your winding over its lifetime. PDA tests can be done periodically, or on a real-time basis, depending on system options. GE Vernova offers this option, along with others (like shorted turns monitoring and vibration detection) as part of the Generator Health Monitoring System.

The main reasons for rotor rewinds are grounds, shorts, main terminal stud failures, high vibrations, thermal sensitivity, insulation migration and damage, and amortisseur migration and damage. If you unit is experiencing any of these issues, it’s probably time for a rotor rewind.

The top reasons for stator rewinds are ground, shorts, operating the unit outside of GE Vernova’s operations protocol, bar armor and/or insulation damage and degradation, collateral damage/FOD, and bar abrasion. If any of these things are happening with your equipment, contact us.

GE Vernova’s Generator Health Monitoring (GHM) offering can help avoid unplanned downtime by allowing you to make informed decisions based on accurate operational and inspection data. GHM is a fully integrated and modular remote monitoring suite available for any type of air-cooled, water-cooled, or hydrogen-cooled power plant generator that provides continuous inspection and condition assessment, as well as early identification of any issues. One of the most important things to monitor and test, which is part of our GHM offering, is the flux probe, so even if you aren’t taking advantage of GE Vernova’s Generator Health Monitoring, we would recommend doing periodic flux probe testing on your generator.

In the early 2000s, the power producing industry had a significant number of power-producing machines installed to account for the substantial increase in energy demand.  As such, these machines are coming up to and passing the 20 years in active service milestone.  Predictive models are estimating the servicing of many of these machine’s generators in the near future with many at the same time. 

In order to prepare for this maintenance “bubble”, we are increasing our capacity in our shops as well as increasing the ready-to-serve inventory.  We are currently experiencing increased volume and over capacity at peak times.  If you wait to plan your maintenance, there’s a good chance for delays in order to provide the services you need.

Incremental repairs on aging insulation and original blocking schemes eventually lead to shorter inspection intervals and an increased risk of forced outages. A technology reset, such as a stator rewind paired with a rotor rewind with Flex Pack options, installs the latest technology within your existing footprint. This modernization “resets the clock” for up to another 25-year lifecycle and helps ensure that your generator is robust enough to handle the thermal and mechanical stresses of today’s high-cycling grid environment.

Yes. GE Vernova can evaluate your generator through a detailed uprate study, unlocking the potential of the rotor and stator components. Items such as uprated stator bars, connection rings, hydrogen pressure increases, high-voltage bushing modifications, and additional cooler flow rates can often match your generator’s output to your turbine’s new capacity without requiring walls or foundations to be moved. Other BOP items, such as the generator excitation system and step-up transformers, may also need modification or replacement, which would be flagged in a detailed generator study.