Basic question of HI POT test | HI POT test procedure | everything about HI POT test

 HI POT test basic question

1)what is hi pot test?
2)what is the need of doing hi pot test
3)whether the hi pot test is applicable for any specify device? 

4)when hi pot test should be done?

5)how much voltage should apply for hi pot test?
6)why we use dc hi pot for cable?
7)why we reduce percentage for more than 3rd time hi pot test?
8)what is the procedure to do hi pot test
9)after hi pot what we have to do?

10)How much value acceptable for leakage current

1)what is  HI POT test

A dielectric withstand test (or pressure test, high potential or hipot test) is an electrical test performed on a component or product to determine the effectiveness of its insulation.

The test is a means to qualify a device's ability to operate safely during rated electrical conditions.

2)what is the need of doing hi pot test

Dielectric tests apply a high level of alternating currents (AC) or direct currents (DC) to the insulation barrier and measure the reaction of the material

High Voltage testing is usually performed to qualify the device to operate safely during rated electrical conditions

ensuring that the insulation will not fail because of insulation degradation from aging, moisture, wear due to vibration, or other causes

a way to check the effectiveness of its insulation

 The objective sought during the high voltage testing will determine the type and amount of voltage applied and the acceptable current flow

3)weather the HI POT test is applicable for any specific device

If any specific device BI POT is applicable for specific time for ensuring the damage insulation

We can apply hi pot for all devices even we can apply communication control cable etc

Even we can apply for small electrical equipment

But our testing Engineer should think HI POT test is only applicable for power system.

4) when hi pot test should be done

Hi pot test should be done after checking specific  device for all fault condition like doing contact resistance measurement resistance IR value etc.

After all this test we will going to check hi pot test while we are doing the hi pot it is very important to check humidity

5)How much voltage should apply for hi pot test

6)why  we use  dc hi pot for cable

For the cable distance between the cable is very small because this small distance high capacitance produce since this high capacitance high leakage current will produce this high leakage current insulation value will come small

Second reason for high capacitance due to this high capacitance Ferranti  effect will occur other  side of the cable since this Ferranti effect high voltage produce this high voltage may be damage cable insulation

So this two reason we are going inject DC for the HI POT for the cable.

7) why we reduce percentage for more than 3rd time hi pot test?

In fact we are checking device for the hi pot in the site we are use 100%

Then this device will check also in site that time we will inject 80% of value

Then at the time maintenance we will inject only 60%

Because we will use 100% all time chances the damage insulation of the cable

8)what is the procedure to do hi pot test

• First specific area for hi pot cover with bari cation tap

• Disconnect all the equipment from the hi pot device

• Check the humidity of the environment

• Set the leakage current value in the kit this very important some time leakage curret will high this leakage current will be damage kit also device

• Check the R phase that time Y and B phase short and earthed same procedure follow for checking B and Y phase

• After finish R hi pot test first discharge through earth same procedure follow for remaining phase

9)After HI POT what we have to do?

Finish the hi pot it is very important to check insulation value of the all phase for ensuring the damage the insulation

Some times while we are doing hi pot that leakage current will be high for some reason like checking the device is not cleaned properly also humidity.

10) How much value acceptable for leakage current)

Looking at the 120-kΩ rule of thumb, when testing is performed at 1,000 V and the tester is adjusted so that breakdown occurs if the resistance of the product is less than 120 kΩ then the maximum allowable leakage current would be 8.333 mA (1,000 V/120,000 Ω = 8.333 mA).

THIS IS ALL QUESTION ARRIVING OUR MINE WHILE WE ARE DOING HI POT TEST

I HOPE THIS CONTENT WILL HELP FOR YOUR ENHANCING KNOWLEDGE OF HI POT TEST

THANK YOU