Quality  |   Introduction  |   Solutions  |   Products  |  Resources  |   Technical Library  |   Links  |   Contact Us  |   Home

2C139 Shaft Overcurrent Protection Relay

If the bearing insulation on rotating machines breaks down, the voltage induced between the shaft ends, due to machine dissymmetries, creates a shaft current that can damage the bearings. The level of damage depends on the magnitude & duration of the shaft current.

It is therefore desirable to provide sensitive protection that can detect shaft currents of 1A or less. The shaft current measurement principle enables more sensitive protection than shaft voltage measurements or vibration monitoring. Vibration monitors only operate after bearing damage has occurred. By applying the shaft overcurrent protection relay type 2C139 together with a special current transformer, the machine can be tripped & the cause of the bearing insulation breakdown determined before the bearing is damaged.

Rejection of the 50Hz component is important where the shaft current transformer is exposed to large fundamental leakage flux from the machine. The 2C139 relay may be employed to overcome this problem by monitoring the 150Hz component of the shaft overcurrent & is available with a minimum setting sensitivity of 0.1% of In.

Where the 50Hz fundamental frequency is to be monitored the 2C138 model should be specified.


  • High sensitivity (0.1% of Is)
  • 50Hz & HF noise suppression
  • Tuned to 150 Hz
  • Optional reset functions: Instantaneous (Fast), definite time, count down
  • 40-300V DC aux. supply
  • 20-70V DC aux. optional
  • Low CT burden & high thermal rating
  • Optional 1A or 5A CT input
  • Instantaneous pick up LED
  • Configurable output contacts
  • 0-31s time delay (125ms steps)
  • Push button / electrical flag reset
  • Non-volatile trip indication
  • Multi voltage inhibit / enable input
  • Multi voltage flag reset input
  • Auxiliary supply fail alarm
  • Flush or rack mount draw out case
  • Made in Australia

For RMS Direct Sales & Product Support Click Here

©1998-2012 Relay Monitoring Systems Pty. Ltd.      ACN 052 484 483     ABN 76 052 484 483

Quality  |   Introduction  |   Solutions  |   Products  |  Resources  |   Technical Library  |   Links  |   Contact Us  |   Home