A Pragma Group Company

Tan delta and capacitance monitor

BHM Bushing Health Monitor

BHM Bushing Health Monitor

Installed Bushing Sensor

Installed Bushing Sensor


Bushing Health Monitor

Problem Situations

Bushing Failures represent one of the top three failure modes of large power transformers. Up to 40% of transformer failures are caused by bushings. 52% of bushing failures are violent. This may pose a safety hazard to personnel and may cause collateral damage to other equipment in the immediate area.

Another significant problem is the mechanical stability of the winding and the ability to withstand tremendous mechanical forces due to short circuit currents. If a winding mechanical support system is loose, the next high peak current associated with a short circuit somewhere in the system may cause mechanical winding deformation resulting in a major insulation failure. Timely detection of a deformed winding may avoid a catastrophic failure.


The BHWM is designed to monitor both the C1 Capacitance and Tan Delta (Power Factor) of each individual bushing and winding distortion. The BHWM has unique features unlike any other bushing monitor that is available today. Measurement of the power factor and capacitance is based on the common “Sum of Currents Method” algorithms. Winding distortion is monitored by estimating the change in transformer leakage reactance.


• Continuously monitors the bushing power factor and capacitance

• Continuously monitors for winding distortion using leakage reactance

• Stores up to 5 years of data

• Up to two sets of Bushings (6 bushing total)

• RS 485 ModBus RTU communications interface

• OEM and End User versions available

• Uses Standard Bushing Sensors

For more information contact Martec or visit the EDI website.