Success through Globalization
By in

Success through Globalization

REIVAX throughout the years has managed to achieve success through its Globalization process. This process can be seen and understood as a long term commitment to generate value to customers,…

RAMP TRACKING FILTER - PSS
By in

RAMP TRACKING FILTER - PSS

HISTORY OF THE RAMP TRACKING FILTER (PSS) In the 1940s, a researcher of stability of electrical power systems suggested that the electromechanical oscillations that arise between synchronous generators of systems…

Automatic CAM optimization for Kaplan and Bulb Turbines
By in

Automatic CAM optimization for Kaplan and Bulb Turbines

Abstract:
Kaplan and Bulb turbines can operate at a high efficiency for a wide range of flow rates and heads due to their double-regulated characteristics, which allows adjusting of the positions of both wicket gates and runner blades. The maximum efficiency is achieved by determining the optimal runner blade angle to wicket gate positioning for a given head, which is called a combination (CAM) curve. These curves are initially generated from scaled model tests and are later on validated in the field by index testing. The index testing is usually costly and only provides the combination curve for a single value of the head. The automatic optimizing system demonstrated in this paper measures and calculates the optimal positioning between the wicket gate and runner blades at the various heads. Important variables are measured to determine the turbine efficiency, such as power, net head, and flow rates. The system interfaces with the governor to test the combination that maximizes the efficiency during normal operation of the machine. This system is already installed in three units operated by Enel Green Power, who economically and technically supported this research. This paper presents the efficiency gains achieved using the automatic optimizing system. The efficiency gain will either result in an increase of output power at normal operation, or can reduce the water volume used to produce the same output power, depending on the operational mode of the turbine.

Read more about Reivax’s process and learn about how easily long-term upgrades can be made to hydro stations through the link below:

Extending Static Excitation System Life
By in

Extending Static Excitation System Life

Built in 1929 and operating since 1931, this 85MW hydro plant in southern Quebec underwent it’s latest excitation system upgrade in 1994.  23 years later, the Owner determined that a failure in the excitation system could lead to a significant loss of revenue due as OEM technical support and spare parts were difficult to come by.  The existing excitation system was a UNITROL equipment with single channel controls and redundant thyristor bridges.

The existing power section was experiencing some occasional overheating issues, but was still in relatively good condition, so the owner decided to tender the replacement as an excitation front-end control upgrade and retaining the existing PPT, thyristor bridges, breaker, discharge circuit etc.  

REIVAX was awarded the upgrade project by offering a solution with the following benefits:

  • Increased system reliability
  • Better Mean Time To Repair (MTTR)
  • Extending the unit life expectancy
  • Improved NERC testing capabilities

After a few months of operation of the new system, the customer was asked to provide a performance feedback on the overall experience with REIVAX and the product performance and gave an overall Excellent rating with a recommendation to buy from REIVAX again should the need for another excitation system arise.

Reivax's solution

An increased system reliability was achieved by implementing redundant control channel in the same overall space as the existing controls.  In the event of a failure in one of the control channels, the stand-by controller automatically takes over without any interruption in operation.  See the below picture of the front-end control upgrade mounting plate installed in the existing cabinet.

The existing thyristor bridges were operated as a 1+1 system, where one active thyristor bridge assumed all the field current.  The excitation cabinets are located close to some hot air from the generator and would occasionally cause a unit trip due to over temperature.  REIVAX bridge interface allowed the bridges to operate in parallel, thus sharing the current and operating at a lower temperature, hence improving both reliability and extending the life expectancy of the power section.  To accomplish this, Hall Effect CTs were installed for current sharing purpose and PT100 sensors were added, so that temperatures could be monitored more accurately and to have the ability to pin point the exact failure location, see the below picture.

REIVAX intuitive 15” HMI interface provides an automatic tuning tool for both the AVR and PSS functions.  The built-in step response function allows the user to validate that the chosen tuning parameters provide the acceptable response.  The same function also allows the user to easily perform NERC testing.  The AVR transfer function, as per IEEE 421.5, is illustrated on the HMI screen with access to the various excitation limiter functions.  The built-in frequency response tool with the result in a Bode plot makes for a very powerful, yet simple way to tune the Power System Stabilizer (PSS), see the below picture.

Thank you - Hydro Vision 2018
By in

Thank you - Hydro Vision 2018

Hydro Vision 2018 in Charlotte, NC ended on June 28th.  On behalf of Reivax North America, I wish to thank our existing and new potential customers that stopped by our…