Penta-PD ,Partial Discharge Detector

Partial Discharge (PD) is a localised dielectric breakdown of a small portion of a solid or fluid electrical insulation system under high voltage stress, which does not bridge the space between two conductors. When the Voltage stress exceeds the breakdown strength of that portion of the insulating material, a Partial Discharge begins and continues to deteriorate that insulation.

Partial Discharge Detector Penta-PD is an ideal partner for condition-based maintenance programs. Partial Discharge Detector Penta-PD incorporates all 5 types of online PD sensor technology. Information from multiple sensors gives Partial Discharge Detector Penta-PD the versatility to detect various type PD in variety of substation apparatus.

 Electromagnetic (EM)

  1. TEV – Transient Earth Voltage  (Inbuilt) 1MHz – 60MHz
  2. UHF – Ultra High Frequency  – 300MHz – 2GHz
  3. HFCT – High Frequency Current Transformer 500kHz – 20MHz

Acoustic Sensors (AE)

  1. Acoustic Contact – 20kHz- 300kHz
  2. Airborne Acoustic (Inbuilt) – 40kHz

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Partial Discharge Detector

PANTA PD

Why we need 5 PD sensing technology?
Partial Discharge is a complex phenomenon . To understand the need of  multiple type of sensors we have to go through the type  of Partial discharges which are as below  -:

  1. Corona – discharge to air
  2. Floating Electrode – metal to metal
  3. Particle discharge – conductive particles contaminate insulation medium
  4. Voids – gaps in solid insulation or gas bubbles in oil
  5. Surface discharge – tracking over outside of insulators/bushings

Each one of above type of PD Activity is have different characteristics hence creating a need to use different type of PD Sensors .

Explanation -: 

Void Discharge:

Partial Discharge DetectorManufacturer’s defects in solid insulation. Found in Cables, Bushings, GIS Junction insulation. Highly destructive to insulation. Voids typically continue to grow until failure. If a void PD is discovered, the insulator should be replaced.
Sensors:

  • UHF
  • HFCT
  • AE Contact Probe
  • TEV

Corona Discharge:

Partial Discharge DetectorCorona is a discharge to air from the sharp surface of a conductor. Corona is typically not a problem besides the sound and the radio frequency emission. Fortunately the corona signal has a many characterises that are much different from other forms of PD. Corona disturbances do not interfere with other PD measurements.
Sensors:

  • AE
  • Ultrasonic
  • HFCT

Surface Discharge:

Partial Discharge Detector

Discharge along the surface of insulation can be very destructive.  Also known as “surface tracking”. Usually cause by contamination or weathering of insulator surface. It is different from corona because it tends to track to grounded metal. Corona discharges to air. Corona conditions can evolve into surface PD as they become more severe. This can happen on any MV and HV equipment. Happens when strength of insulation breaks down in high humidity environments. or poor maintenance of equipment can lead to this phenomenon.  Moistures Intrusion is also common cause of surface PD.
Sensors:

  • Airborne Acoustic
  • Acoustic Contact
  • UHF
  • TEV

Floating Discharge:

Occurs when exposed load carrying conductor is exposed to another conductive surface of different potential not connected to said conductor. Types: Metal to Insulation OR Metal to Metal. Caused by manf. defect, non-grounded price of metal within the field. Floating Discharge is the most common type of PD. Often caused by human interaction. IE conductors not positioned properly. Foreign or loose object inside of insulation.
Sensors:

  • UHF
  • Airborne Acoustic
  • Acoustic Contact
  • TEV
  • HFCT

Particle Discharge:

Occurs in GIS (SF6 gas)  and oil insulated transformers. Caused when conductive particles are left inside system. Allows PD to jump from particle to particle.  Purifying and processing the oil or SF6 is  recommended.
Sensors:

  • UHF
  • AE (Airborne Acoustic)
  • Acoustic Contact
  • HFCT
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