Background

The failed Basler SSE 250-50kW static excitation system was at the end of its life and spare parts were difficult to acquire. With the unit losing operating revenue every week, the customer was in desperate need to quickly procure and install a new excitation system for the 4.3MVA hydro plant.  They approached various excitation suppliers to inquire about expedited delivery options.

During the COVID-19 pandemic, the world experienced supply issues in home electronics, food, drinks, toilette paper, alcohol wipes, material for home renovation etc. as people panicked to stock up on supplies and to spend more time at home.  Today the world is experiencing material shortages in other areas, such as, microchips, steel, copper, wood, packaging material etc. and these items are impacting manufacturers of electrical goods, including excitation systems.

Given that the customer wanted to be fully operational by December 1^st, 2021 and run the unit continuously until August 1^st, 2022, there was no time to design, source material and manufacture a new excitation system, therefore, other options were explored. As a leading supplier of excitation systems and governor systems, REIVAX designs and manufactures many systems in a given year and in some cases our customers experience changes in their outage schedules, which may delay the installation of a system.

After examining the excitation current/voltage requirements and the available footprint, REIVAX reached out to one of our customers to whom we had delivered an exciter for a 12.5MVA hydro generator, but the installation had been delayed to later in 2022.  While the unit could deliver more field current and had more redundancy options than what was required for the 4.3MVA unit, it was determined that this was the best option for the customer considering the $15kUSD in lost revenue per week.

4.3MVA plant with Francis turbine

Scope of work

The new excitation system that was delivered with the following features:

• •  Fully redundant control channels, each one with AUTO/Manual
• •  One (1) six pulse SCR bridge rated 400Adc field current with redundant fans
• •  15” local HMI panel for operation, testing and diagnostics
• •  Limiters and protection features
• •  Power system stabilizer
• •  Ethernet Modbus communication and IRIG-B time sync
• •  AC breaker
• •  Field overvoltage and discharge circuit
• •  SEL-2664 field ground coupler
• •  Two (2) SEL-501 overcurrent relays

REVAX RTX POWER excitation line-up

Installation and Commissioning

The customer contracted directly with a local company to remove the old static excitation system and to install the new REIVAX static excitation system.  REIVAX was hired to supervise the installation and to perform the commissioning of the system.  Once the old system was removed, the new REIXAX system was bolted in place and all field wiring was re-used and connected to terminal blocks in the new exciter.

Some challenges occurred during the install as the plant had undergone various work over the years and some of the changes had not been reflected in the plant drawings.  REIVAX field engineer and the installation company quickly identified and corrected the related wiring issues.

During the commissioning, base values and limiters were adjusted to the 4.3MVA generator and tuning of the control loops, limiters and Power System Stabilizer (PSS) was performed using the REIVAX built-in step response tool and frequency response tool.  Changes to the tuning parameters were made directly via the 15” HMI mounted on the cabinet door using the graphical representation of the IEEE421.5 transfer function.

The removal, installation and commissioning of the new REIVAX static excitation system was completed in 7 days, more than 3 weeks earlier than the customer’s Dec 1^st, 2021 deadline.

REIVAX will be re-manufacturing a new identical unit for our generous customer that was willing to support a fellow utility in a difficult situation.

Exciter HMI screen – 3.3MVA operation  (low water condition).