Woodward 9907-164 505 Digital Governor

The Woodward 505 Digital Governor is an advanced control system designed specifically for steam turbines, suitable for governing steam turbines with single or split-range actuators. The 9907-164 is a specific model within this series, designed for Low Voltage DC (LVDC) power supply environments, and is widely used in various industrial, power generation, and mechanical drive applications. This controller integrates control functionality with an operator panel into a single unit. It boasts powerful programmability through intuitive menu-driven software, allowing users to flexibly configure control parameters for precise and stable turbine control.

As a classic product from Woodward, the 505 Governor is renowned for its high reliability, strong adaptability, and user-friendly operation, making it a preferred choice in control systems for steam turbines worldwide. It not only meets basic speed control requirements but also offers advanced features such as cascade control, auxiliary control, remote setpoint, and load sharing, making it suitable for complex operating conditions including power generation, cogeneration, compressor drives, and pump drives.

2. Key Features & Advantages

1. High Integration & User-Friendliness: The 9907-164 505 integrates the controller and operator control panel (OCP). The front panel features a two-line (24 characters each) LCD display and 30 keys. All programming, monitoring, and operation can be performed via the panel, eliminating the need for additional control consoles.

2. Powerful Programmability: Utilizes menu-driven programming software, allowing users to flexibly configure control logic, I/O functions, PID parameters, start/stop sequences, etc., based on the specific application (e.g., generator set or mechanical drive), enabling a high degree of customization.

3. Multi-Layer Control & Limiting Functions:

• Speed/Load Control: The core control channel with Proportional, Integral, Derivative (PID) regulation.

• Auxiliary Control: Can function as an independent control channel or a limiting channel for controlling or limiting process parameters such as power, pressure, or temperature.

• Cascade Control: Can be cascaded into the speed controller to control a process parameter related to speed/load (e.g., inlet pressure, exhaust pressure).

• Valve Limiter: An independent channel for limiting valve position, aiding in start-up/shutdown and troubleshooting.

• Low Signal Select (LSS) Bus: Automatically selects the signal demanding the lowest valve position from among the Speed, Auxiliary, and Valve Limiter outputs, ensuring safety.

4. Advanced Start-up & Protection Features:

• Supports Manual, Semi-automatic, and Automatic start modes.

• Programmable Idle/Rated function for rapid speed changes.

• Auto Start Sequence, automatically adjusting warm-up times and acceleration rates based on downtime (Hot/Cold start).

• Critical Speed Avoidance, with configurable avoidance bands to automatically pass through quickly and avoid resonance.

• Comprehensive shutdown logic: including Emergency Shutdown, Controlled Shutdown, Overspeed Test Shutdown, etc.

5. Extensive Communication & Interfaces:

• Two independent Modbus communication ports (supporting RS-232/422/485, ASCII/RTU protocols) for direct integration with plant DCS or SCADA systems.

• One dedicated PC port for uploading/downloading program configurations.

• Rich analog I/O, digital I/O, and relay outputs to meet various signal interface requirements.

6. High Reliability & Safety:

• Watchdog timer and CPU fault monitoring circuit ensure safe shutdown in case of processor failure.

• Comprehensive sensor failure detection (e.g., speed sensor loss, analog input signal loss).

• Suitable for use in Class I, Division 2 / Zone 2 hazardous locations (specific certified models).

• Circuit boards feature a sulfur-resistant polyacrylate conformal coating for improved reliability in corrosive environments.

3. Detailed Core Functional Modules

1. Speed Control: The core function of the 9907-164. It senses turbine speed via one or two speed sensors, compares it with an internal setpoint, and outputs a control signal after PID calculation. In generator applications, it intelligently switches between three modes based on the status of the Generator and Utility Tie breaker contacts: Speed Control (breaker open), Frequency Control (Gen breaker closed, Tie open), and Load Control (both breakers closed, using Droop control or isochronous load sharing).

2. Auxiliary Control: An independent PID controller. Its input can be any 4-20 mA process signal (e.g., pressure, temperature, flow). It can be configured in two modes:

• Limiter Mode: Continuously monitors a process parameter. When the parameter exceeds the set limit, it reduces the valve demand to limit that parameter, preventing equipment overload.

• Controller Mode: When "enabled", it takes full control of the valve. The Speed controller tracks it, allowing bumpless transfer. Used for precise control of parameters like generator MW output, inlet pressure, etc.

3. Cascade Control: Another independent PID controller whose output directly becomes the setpoint for the Speed controller. It is used to control an "upstream" process parameter strongly related to speed/load (e.g., adjusting turbine speed/load to maintain constant exhaust pressure). It also supports setpoint tracking for bumpless engagement.

4. Valve Limiter: An independent manual/automatic valve position limiting channel. Used to slowly open the valve during start-up; to manually set a maximum opening limit during operation; or for manual valve operation during system commissioning and troubleshooting.

5. Start-up & Shutdown Management:

• Start Modes: User can select Manual (operator manually opens trip-throttle valve), Semi-automatic (operator manually raises valve limiter), or Automatic (controller automatically raises valve limiter) based on site practice.

• Idle/Rated: Allows operator to quickly toggle between preset Idle and Rated speeds.

• Auto Start Sequence: Ideal for turbines requiring strict warm-up. Automatically calculates and executes the entire sequence—"low idle warm-up, high idle warm-up, accelerate to rated"—based on downtime, with pause/continue capability.

• Shutdown: Differentiated into Emergency Shutdown (instantaneous valve closure) and Controlled Shutdown (ramps speed down to zero at a preset rate before closing the valve), the latter being less stressful on equipment.

6. Synchronizing & Load Sharing:

• Synchronizing: Receives fine-tuning signals via a dedicated synchronizing input (typically connected to a Woodward DSLC Digital Synchronizer) to automatically match generator frequency and phase with the bus for smooth breaker closure.

• Load Sharing: When used with a DSLC, enables automatic, proportional real power load sharing among multiple generator units operating in parallel.

7. Communication: Two Modbus ports allow easy integration into modern industrial networks. Virtually all operating parameters, setpoints, alarm statuses, and control commands can be read from and written to via the Modbus protocol, facilitating remote monitoring and centralized management.

4. Application Areas

The Woodward 9907-164 Digital Governor, is widely applied in the following fields:

• Industrial Power Generation: Control of steam turbines driving generator sets, suitable for captive power plants, small thermal plants, biomass plants, etc.

• Combined Heat & Power (CHP): For applications requiring both electrical power and thermal energy (process steam or heating), providing precise control of turbine extraction or back-pressure.

• Mechanical Drive: Control of steam turbines driving large rotating equipment like compressors, pumps, and fans, enabling stabilization of process parameters (e.g., pressure, flow).

• Oil & Gas: For controlling compressor-drive turbines in pipeline transmission, gas processing, and refining operations.

• Pulp & Paper / Chemical: For turbines driving process air compressors or pumps, where high reliability and process control precision are required.

5. Installation & Configuration Summary

1. Installation: Must be performed according to manual instructions for mechanical mounting and electrical wiring. Pay special attention to shielding and grounding of speed sensor and analog signal wires, and separation of high-current lines (power, relay outputs) from low-signal lines to minimize EMI. For hazardous area installation, relevant electrical codes must be followed.

2. Configuration (Programming):

• Turbine Start: Select start mode, set Idle/Rated parameters or Auto Start Sequence parameters.

• Speed Control: Set gear teeth, ratio, Off-line/On-line PID parameters.

• Speed Setpoint Values: Set Min/Max Governor speed, Overspeed Trip level, Critical Speed Avoidance bands.

• Operating Parameters: Select if a generator application, set Droop percentage, Rated Speed, etc.

• Driver Configuration: Set actuator type (4-20mA or 20-160mA), use of second actuator, dither settings, etc.

• Analog Inputs / Contact Inputs / Relays / Readouts: Assign specific functions to each I/O point.

• Auxiliary Control / Cascade Control: Configure relevant parameters and PID if needed.

• Communications: Set Modbus port parameters.

• Enter "Program Mode" via the front panel (password required) with the turbine shutdown.

• Follow the clear menu structure to configure key blocks sequentially:

• Upon completing all configurations, the system performs an automatic logic check. If no errors are found, the program can be saved and exited.

3. Calibration & Testing: After configuration, perform a valve/actuator calibration and stroke test to ensure accurate correspondence between the control signal and the actual valve position.

6. Operation & Run Mode

In "Run Mode", the operator can use the front panel to:

• Monitor: Press corresponding keys (e.g., SPEED, AUX, CAS, KW) to view real-time values and setpoints for speed, auxiliary parameters, cascade parameters, load, etc.

• Adjust: Use raise/lower keys or direct numeric entry (ENTER key) to adjust Speed, Auxiliary, Cascade, etc., setpoints.

• Start/Stop Control: Use RUN, STOP, RESET keys to control the turbine.

• Function Enable/Disable: Use F3/F4 function keys or on-screen menus to enable/disable functions like Remote Setpoint, Auxiliary Control, Cascade Control.

• View Alarms & Trips: Use the ALARM key and CONT key to view current and historical alarm/trip causes.