Guardian® (two-out-of-three voting) Overspeed Protection (OSP) system monitors the turbine speed and will safely initiate a trip command if an overspeed condition occurs. The OSP system consists of three identical speed modules which individually measure a frequency input signal from a passive or most active magnetic pickup sensor. A trip condition exists when two-out-of-three speed modules detect that the speed of the turbine has increased above a preconfigured overspeed value.
Guardian provides a reliable, economical solution for protecting your turbine. A supervisor module continually monitors the three speed modules for proper operation. A single failure of a magnetic pickup unit (MPU), the supervisor, a speed module, or power supply will not affect normal operation of the Guardian OSP system.
Modular System Architecture for Improved Availability
- Three Independent Speed Modules
Each speed module monitors an active or passive magnetic pickup signal and displays its currently-sensed speed or current set point. Four dedicated LEDs are provided to indicate an overspeed test, trip, MPU failure, and fault conditions.
- Supervisor Module
The supervisor module provides Modbus communication and monitors proper operation of the speed modules. A 4-line by 20-character alphanumeric display is integrated into the operator interface. A test mode provides testing of each speed module including verification of the voting relays operation. Failure of the supervisor module will not cause or prevent a shutdown. This module supports an LED for indicating an alarm condition.
- Relay Board
The relay board contains the following output relays.
- Overspeed Trip Outputs 1 and 2
- ALARM (Power Supply Failure, Pickup Failure, Speed Module or Supervisor Failure, and Communication Error)
- Redundant Power Supply Modules
Two power-supply boards provide redundant power to the relay board, speed modules, and supervisor module. Each power supply can be powered by 18 to 32 Vdc and/or 85 to 265 Vac.
Reliable, Field-Proven Electronic Overspeed Protection
- <40 ms Response Time
- IP65 (NEMA 4) Type Enclosure
- Wide Operating Temperature Range
- Hazardous Area Certifications
Simplified Maintenance and Diagnostics
- Self-Diagnostics Capabilities
- Multi-level Password Protections
- Peak Speed Capturing with Timestamps
- Alarm and History Log with Timestamps
- Hot-swappable Modules
- Modbus Interface for DCS and TrainView HMI
- Chassis Power Options: 18-32vDC or 85-265vAC
- Chassis Dimensions (HxW): 17.0in (431.8mm) x 22.0in (558.8mm)
- Communication Options:
Redundant Modbus RTU RS-422/RS-485
- Operating Temperature Range: -4 degF to +150 degF (-20 degC to +65 degC)
(Partial list – For full details please refer to Agency Certifications for the Guardian OSP System)
- Hazardous area classification:
USA: Class 1, Div 2 Groups A, B, C, D and T3
Canada: Class 1, Zone 2 Group IIC and T3
European (ATEX): Grp II,Cat. 3, G, EEx, nACL, IIC, T3