Guardian® Overspeed Protection System

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.

Key BenefitsSpecificationsRelated Products

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

Key Specifications:

  • 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)

Agency Certifications:

(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

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