The project involved the supply, delivery, installation, testing and commissioning of new Digital Governor Panels at the 70 MW Middle Marsyangdi Hydropower Station, comprising two generating units of 35 MW each. The project was undertaken for Nepal Electricity Authority to replace the existing Digital Governor Panels with new microprocessor-based governing systems capable of controlling turbine speed and generator output under grid-connected and isolated operating conditions.

The technical scope covered two sets of turbine governor digital control panels with redundant controllers, analog and digital I/O cards, redundant power supplies and communication modules. The new governor systems were required to integrate with the existing Unit Control System through hardwired signals and operate the existing distribution/proportional valves without modification to the hydraulic system. The scope also included dismantling the existing governor panels, integration of compatible field instrumentation, mandatory spare parts and the accessories required for safe and continuous operation.

MSI executed the replacement and integration of the Digital Governor Panels while retaining compatibility with the existing turbine control environment. This required coordination between the new digital control hardware, existing hydraulic control equipment, field instrumentation and Unit Control System. Nepal Electricity Authority confirmed that the Digital Governor Panel installation, testing and commissioning works were successfully completed on 5 December 2024.

Objectives

The project was designed to achieve the following goals:

• To replace the existing Digital Governor Panels for both generating units with new microprocessor-based Digital Governor systems
• To provide stable turbine speed and generator output control under grid-connected and isolated operating conditions
• To integrate the new governor systems with the existing Unit Control System through hardwired analog and digital signals
• To integrate the new Governor Controllers with the existing distribution/proportional valves without modification to the hydraulic system
• To provide redundant control architecture for improved continuity and reliability of governor functions
• To complete installation, testing, tuning and commissioning of the new Digital Governor systems in accordance with the specified requirements

Key Deliverables

The following systems, instruments, and tools were supplied, installed, and commissioned as part of the project:

Digital Governor Control Systems

• Two sets of Digital Governor Cabinets for the two generating units, incorporating redundant CPUs, analog and digital I/O cards, redundant power supplies and communication modules
• Microprocessor-based PID governor systems designed for turbine speed, active power load and wicket gate opening control
• Control capability for Speed Control, Load Control and Opening Control, with provisions for grid-connected and isolated operation
• Integration of the Digital Governor systems with the existing Unit Control System through hardwired analog and digital signals
• Integration and tuning of the new Governor Controllers with the existing distribution/proportional valves without modification to the hydraulic system

Integration and Field Systems 

• Integration of existing speed sensors, position transducers and other compatible field instrumentation with the new Governor Controllers
• Integration with the existing electro-hydraulic turbine control arrangement for the Francis turbine units
• Provision of required instrumentation, control and signal cables, piping materials, safety devices and associated accessories
• Dismantling and transportation of the existing Governor Panels and essential accessories to the Owner's designated stores
• Installation, adjustment, testing and commissioning of the new governing systems for both generating units

Spares, Software and Operational Support

• Two sets of mandatory spare parts, including complete PLC sets with controllers, communication modules, power supply modules and I/O cards
• Fully configured HMI Touch Screens and associated system spares
• One laptop with software for the Digital Governor system
• Mandatory spares specified to support fifteen years of system operation
• Supporting devices and accessories required for safe and continuous operation of the governing systems

Challenges

The project involved several technical, execution, and coordination challenges associated with implementing a substation augmentation through an integrated project scope:

• Replacing the existing Digital Governor Panels while maintaining compatibility with the existing Francis turbine control and hydraulic systems
• Integrating the new microprocessor-based Governor Controllers with the existing distribution/proportional valves without modifying the hydraulic system
• Coordinating new redundant digital control hardware with the existing Unit Control System through hardwired analog and digital interfaces
• Integrating existing field instruments and speed sensing arrangements with the new governor architecture while maintaining the required governing functions
• Tuning and validating the new governor systems to support speed, load and wicket gate control under grid-connected and isolated operating conditions

Solution

MSI adopted a structured execution and coordination approach to address the technical and implementation requirements of the project:

• Existing Governor Panels were dismantled and replaced with two new microprocessor-based Digital Governor Cabinets incorporating redundant control, I/O and power supply architecture
• The new Governor Controllers were integrated with the existing distribution/proportional valves and tuned to operate with the existing hydraulic system without requiring hydraulic modification
• Hardwired analog and digital interfaces were established between the new Digital Governors and the existing Unit Control System
• Existing compatible speed sensors, position transducers and other field instrumentation were incorporated into the new governing system
• Installation was followed by system adjustment, functional testing and commissioning to verify operation of the new Digital Governor Panels for both generating units

Impact

The implementation of the project established a modernized digital governing system for the two generating units at Middle Marsyangdi Hydropower Station. 

• Replaced the existing Digital Governor Panels with new microprocessor-based governor systems incorporating redundant control architecture
• Maintained integration with the existing turbine hydraulic system and distribution/proportional valves without hydraulic modification
• Established coordinated control of turbine speed, active power load and wicket gate opening through the new governing systems
• Supported grid-connected and isolated operating requirements through the specified governor control functions
• Successfully completed installation, testing and commissioning of the Digital Governor Panels on 5 December 2024, as confirmed by Nepal Electricity Authority

Conclusion

The Middle Marsyangdi Hydropower Station project involved the replacement and modernization of Digital Governor Panels for two 35 MW generating units within the 70 MW hydropower facility. The scope combined new redundant digital governor technology with the station's existing turbine hydraulic system, Unit Control System, distribution/proportional valves and field instrumentation, requiring careful integration and system tuning.

MSI's execution covered supply, delivery, dismantling, installation, integration, testing and commissioning of the new Digital Governor systems. The successful completion of installation, testing and commissioning on 5 December 2024 demonstrates MSI's capability to undertake turbine control modernization projects where new digital systems must be integrated with existing hydropower equipment and operational infrastructure.