Is Partial Discharge (PD) accurate? What standard does it conforms to?

PD Testing is an internationally recognized testing technique used in more than 28 countries for detecting insulation defects. According to IEEE 400, the only proven and effective way to establish an electrical preventative/ predictive maintenance program is using Partial Discharge Testing.

Many grids are turning to this test as a first line test to check for early insulation defects as it is totally non destructive in nature compared to the usual hipot test.

If Partial Discharge testing is so good and highly rated, why is it not many people are adopting  this testing method?

There are three reasons behind this:

•    PD testing is a fairly new technology compared to the usual Hipot (Megger) test. PD testing has matured over the years and today it has already been proven to be much more powerful indicator for insulation defects compared to offline test (like hipot, Megger etc).  

•    PD testing may be the most powerful indicator for detecting insulation defect but it is also the most sophisticated test to be carried out. The interpretations of the results are extremely challenging and require very well trained personnel to do the analysis. Once results are correctly interpreted, PD testing will give the best detailed diagnosis of the insulation condition of equipment compared to any Hipot. Megger test etc.

•    As PD testing is sophisticated, the cost of inspection is generally much higher than usual Hipot testing. However, the cost of PD testing is much lower nowadays.

Is partial discharge carried our on live High Voltage equipment and do you need to open the panel covers?

Partial Discharge is carried out live on High Voltage equipment without having to opening the covers.  Being an Airborne System, measurements can still be taken with or without the covers.

Is noise a problem when measuring Partial Discharge? 

Yes, it is a problem especially when it is an airborne system.  However with extensive site experience built up over the years, we have developed  powerful softwares with  unique algorthms to eliminate most of the broadband noise picked up during inspections.

What are the equipment that can be tested with the PD PAC Partial Discharge ?

Most High Voltage equipment from 3KV and above can be tested, of types such as GIS, Vacuum or oil breakers, motor, transformer and tap changers etc.Depending on the design of the electrical equipment and the strength of the electric field,even low voltage equipment can generate Partial Discharges such as LV busbars,LV motors etc.Also, the higher the voltage the higher is the likelihood of  occurrence of Partial Discharge.

Is it important to identify the type of discharge?

Yes, it is important as insulation problems can be serious leading to flashovers if it is not detected early. Also, insulation problems cannot be easily seen until it is too late.

Do you need to monitor for more than 2 days any high voltage equipment suspected of having partial discharge activity?

Contrary to popular beliefs, Partial Discharge is present in all High Voltage equipment in small quantities and low magnitudes.  It is when problems start to develop that the partial discharge activity increases.  With a highly sensitive sensor, you can detect the increased in partial discharge activity almost instantly. From our wide experience,only 2% of the equipment inspected would require 2 days or more in  on-line monitoring to capture PD information accurately.There is no need for a shut down in doing this test.

 
Should Partial Discharge Testing be done before or after a service shutdown?

How is the PD PAC compares with the rest of the partial discharge testing systems in the market?