LID-UPD ( Leaky Insulator Detector, Ultra Sound Partial Discharge Detector)
Complete Solution FOR SUBSTATION ASSET MONITORING- An early warning before failure



Introduction: PD is an electrical discharge that occurs across a localized area of the insulation between two conducting electrodes, without completely bridging the gap (see IEC 60270). It can be caused by discontinuities or imperfections in the insulation system. PD activity is an indication of an incipient medium voltage (MV) or high voltage (HV) insulation fault and is widely regarded as the best early warning indicator of electrical insulation deterioration in MV and HV electrical assets within power networks. In general, PD occurs in systems operating at voltages of 3 kV and above; however, it should be noted that in some cases PD can also occur at lower voltages (i.e., Variable Speed Drive / Variable Frequency drive motors and LV designs). Typical drivers for implementing PD programmes include supporting Condition Based Maintenance (CBM), avoiding unplanned, often costly.

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Partial Discharge: Partial Discharge testing and monitoring is particularly important when the medium or high voltage asset is critical to the operation of a network; this may be due to the asset’s age, limited network redundancy, past failures or the financial consequences of a failure. Qualification of PD criticality within the complete network can be achieved quickly and easily using HVPD technology to provide an early warning of any incipient insulation faults. Examples of MV and HV plant that can be tested/monitored include:

  • Cables and cable accessories (terminations, joints, sealing ends)
  • Switchgear (AIS, SIS & GIS)
  • Power Transformers and Bushings
  • Transformers (Oil Filled & Dry Type)
  • Rotating Machines Motors and Generators (including Direct On-Line & Variable Speed Drive or Variable Frequency Drive motors)
  • Instrument Transformers (Voltage & Current)
  • Capacitors


  • Measurement of Leakage Current provide prior Information about the healthiness of the Transformer & Other substation equipment.
  • Since no labour is required to perform the tests, continuous monitoring allows the use of limited resources to find solutions to problems instead of finding problems.
  • Reducing unnecessary maintenance because the monitor will be constantly testing and will have accurate data on which to base decisions.
  • Collecting more accurate data as tests are conducted under real operating condition
  • Requiring no outage to perform the test, therefore there is no loss of asset productivity.
  • No introduction of infant mortality failure patterns via more invasive testing procedures.
  • Reduction of forced outages and increased safety of personnel. One will always be aware of conditions and/or problems.
  • Correlation of other dynamics such as temperature, humidity and load current to PD activity, which provides additional insight for diagnostics. There will be no need to go to several sources and gather the information.
  • Provides the opportunity for remote diagnostics. The expert does not need to come out to the field for basic diagnostics. A site visit by an expert will be the exception and not the rule.
  • Evaluation of a piece of equipment is based on its own history and not by comparison to other equipment.
  • Easily monitor worsening conditions so one can defer repairs and allow time to plan an outage.

Technical Specifications

  • TEV Sensor
  • Measurement Range (Peak) 0 – 70 dBmV
  • Measurement Range
  • (Cumulative Activity) 0 – 350,000 mV/cycle
  • Frequency Response 5 – 60 MHz
  • Resolution 1 dB
  • Accuracy ±1 dB
  • HFCT Sensor
  • Measurement Range
  • (HFCT 100/50, Ztr=3.9) 200 pC/cycle – 20,000 nC/cycle
  • Frequency Response(-3 dB response) 100 kHz – 20 MHz
  • Resolution 1 dB
  • Accuracy ±1 dB
  • Flexible CT Leakage Current Tester
  • Flexible Split-Core within built shielding
  • φ200 mm
  • AC & DC Leakage/Line Current
  • Single CT with Dual Integration Mode
  • AC & DC 3A/30A/300A/3000A (AC50/60 Hz & DC)
  • ±3% of reading
  • LCD max. 3200 reading with Annunciators
  • AC leakage current, DC leakage current,
  • DC current in AC circuit
  • 1mA
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