HI-POD Test Short Notes

Hi-Pod test is high voltage test/ Dielectric with-stand test.

We perform it to check the system capability to with-stand high voltage at transient time, which might occur during a sudden load released or high load switching, a high transient voltage wave might be produced in this time. Also, during fault conditions. To ensure as well the dielectric medium between two conductors.

Why we use DC HI POD in cable testing ?

ANS: For the cables, the distance between the cables are very LESS , when you use AC high pod test it will produce high Capacitance  due to this capacitance the leakage current will be high so, you will get low INSULATION value.

Second reason, Due to this capacitance it will produce a ferranti effect on the other end of the cable (the voltage will be high at the other end which might damage the cable).

Voltage supply value at Hi-Pod.   (SAT)

Bus bar:

80% (2Vn+1000).  AC Hi-Pod test.

Or 

80% Vpeak.

Cables: 

80% (2Vn+1000)*1.414.   DC Hi-Pod test.

Or

80% Vpeak*1.414

Vn: system nominal voltage

Vpeak: system voltage with-stand

SAT: site acceptance test (first time you do the test in you site)

Why we should reduce the percentage of the hipod test for more than the 3rd time we perform the test?

ANS: For the 1st time (FAT) they do 100% of the test (2Vn+1000) V2

    For the 2nd time (SAT) they do 80% of the test (2Vn+1000) V2

    For the 3rd time (Maintenance/ Inspection/ Troubleshooting) we do 60% of the test (2Vn+1000) V2

Because if we maintain at 100% the property of the insulating material will change and the dielectric strength of the cable will be reduced!

What are procedures to do hipod test? 

ANS:1- we have to disconnect all connect equipment to the cable/ busbar, etc..

Ex; BusBar, we have to disconnect all connected P.T. ,Out going, earthing switch

2- if we are going to hipodtest PHASE (R)

 **The other 2 PHASES (Y&B) shall be shorted and connected to earth.

  “That’s to ensure the dielectric strength between the tested phase and the others”.

3- It’s highly recommended to check the humidity of the test environment.

4- Select/ set the leakage current measurement on the test kit.

5- Increase the injected voltage gradually (SBS).

6- Check and record the leakage current value in your testing sheet.

7- If you finished the test, you need to discharge the injected phase using earth rod to your earthing system to avoid sparks,…etc.

8- After hi-pod test it’s highly recommended to perform insulation resistance test (Megger test) for all phases, to ensure that the component insulation is not damaged.

*** During hi-pod test if you get a high leakage current value specially during (SAT);

 1. The surface of the material might not cleaned properly.

 2. The test environment humidity is high.

 3. For cables might be bad insulation/ insulation damage during laying.