Electro-Magnetic Interference Monitoring

The EMI Monitoring system offers visualization of the spectrum bands and total power bands through National Instruments InSightCM tool.


The EMI system monitors abnormalities from energized, high voltage assets. It looks for patterns/signatures in RF spectrum from 30 kHz to 100 MHz to indicate potential failures along the generator and out to the IsoPhase Bus. For generators, the EMI Monitoring system is typically configured to monitoring five (5) RF bands that are indicative of components. Alarm levels are set when Power levels within a band exceed a threshold; the thresholds may be configured by the user.

The intent is to maximize the detection of EM emissions as a power in spectrum and in total power in band function. The conditions associated with EM emissions detected by the system include:

  • Arcing
  • Coronal Discharges
  • Gap Discharges
  • Partial Discharges
  • Sparking

Current Transformers are typically coupled around the Generator to Neutral Ground connection, although it alternatively could be coupled around a frame ground.

The System is easy to install and does not require an outage, or insertion of any probes or couplers into the generator or transformer. An RFCT (Radio Frequency




The EMI Monitoring system usually scans five unique RF spectra, although more can be added by the user. Different metrics are used for generators and transformers.


  • Band 1: Exciter and Collector
    (typically set 30kHz to 500kHz)

  • Band 2: Stator Core and Slots area
    (typically set 500kHz to 5 MHz

  • Band 3: End Windings
    (typically set 5 MHz to 30 MHz)

  • Band 4: Isophase Bus or other connections
    (typically set 30 MHz to 100 MHz)

  • Band 5: Total Power Band to compare generator noise to overall system noise


  • Single Total Power Band: Compares total power of the Transformer with the total power of the Generator

Thresholds are User Defined and set in Microvolts (uV). Typically, 3 levels are used.

  • Below 1000 uV—no issues present
  • Between 1000 uV and 10,000 uV — growing issue that demands observation
  • Above 10,000 uV—remedial action required



  • Multiple RFCT (Radio Frequency Current Transformer)
  • All Components necessary to install
  • Supports Coaxial runs up to 200 feet
  • One National Instruments InSightCMTM license
  • Support from Subject Matter Experts

The EMI Monitoring system offers a cost-effective alternative to traditional methods of failure detection. When compared with traditional methods, Cutsforth™ EMI Monitoring offers the following benefits:

  • Lower Costs
  • Multiple Component Measurements within a single system, for example, measure stator and end-windings and Isophase Bus with a single system rather than multiple systems using invasive couplers and probes
  • Holistic view of the generator and auxiliary equipment health in one application
  • Non-invasive installation, no outage required.
  • Installation does not require an outage