HIPOT testing is one of the best ways of determining how your electrical assets are performing. Basically, HIPOT is the name of a broad category of safety testing instruments that you can use to check the strength (or deterioration) of electrical insulators or insulation materials.
Most electrical devices produce leakage, even at minimal amounts. A HIPOT Test is designed to test for “good insulation”. This means that it is effectively the opposite of a continuity test. Continuity tests are designed to check how well electrical current flows from one point to another— HIPOT tests are designed to check that electrical current does NOT flow from one point to another. To ensure that a current is not actually flowing, very high voltages are applied.
Why is HIPOT testing so important?
HIPOT testing essentially tests whether the electrical insulation is adequate. The test is non-destructive to good insulation. HIPOT tests are very effective in trying to find points or places in the insulating material that have been nicked or crushed, and therefore produce a leakage. Other issues that a proper HIPOT test can identify are stray wire strands, braided shielding, and conductive or corrosive contaminants around the conductors.
In addition, HIPOT tests can also identify cases where there is insufficient creepage or clearance distances relating to the manufacturing process, which would need to be addressed.
Can you use HIPOT tests during manufacturing?
HIPOT tests are particularly useful during the manufacturing process. This can ensure that there are no issues or anomalies in construction and that units are produced of uniform quality. If production-line tests reveal any inconsistencies—that is, the results differ from those obtained when type testing—it can indicate that there is a process failure that has been introduced in construction.
The causes of such process failures could be as simple as a new operator working in the winding department, or a supplier changing materials.
What voltage are HIPOT tests conducted at?
The formula for a HIPOT test is double the operating voltage, plus 1,000V. The reason for the additional 1,000V is that insulation can be subjected to various surges in day-to-day usage, and experiments have provided clear indications that these overvoltages can be as high as 1,000V.
How are HIPOT tests conducted?
HIPOT testers should earth one side of the supply and connect the other side to the conductor. Then, a high voltage is applied and the difference between the conductors, separated by the insulator, results in a very small current. Small currents are permissible and don’t necessarily indicate a defect, but the key point is that there is no breakdown or deterioration of the insulating material.
How long are HIPOT tests conducted for?
The standard formula for a HIPOT test is one minute, but this can depend on the safety standard being adhered to. It is recommended to initially test the equipment for 1 sec and then test it for 1 min to verify the design parameters. A typical rule of thumb is 120% of 2U + 1,000V.
What current is used for HIPOT tests?
Most modern HIPOT testing devices allow the current to be set manually. Additionally, if the leakage levels of an insulating material are already known, then you can predict the HIPOT test current.
If you are trying to work out the trip level, we recommend testing several product samples to determine the average HIPOT current. Then, the current leakage trip level should simply be set a little higher than the average value you’ve calculated.
There are various alternative methods for selecting an appropriate current—the critical factor is that the trip level should be set sufficiently high to avoid failure caused by leakage current and low enough to determine whether there is a breakdown in the insulation.
What voltage are HIPOT tests conducted with?
Most safety standard regulations have provisions for either AC or DC voltages. With AC, the insulation material is under stress at the peaks of its alternating sine waves. To achieve an equivalent stress with DC voltages, therefore, you need to test with a voltage of root 2 times the ac test voltage.
For example, if testing at 1000V-ac, the corresponding DC voltage would be 1000 x root 2 (or, 1.4142). This would be 1414V-dc.
What do you need to be careful of during a HIPOT test?
As with all electrical testing, there are a number of safety measures to ensure no mishaps occur.
1. The total charge one can receive in a shock must not be more than 45 uC.
2. Total HIPOT energy must be limited to 350mJ.
3. The total current must not be more than 5 mA peak.
4. Fault current should be limited to 10ms.
For the cable, all the standard operating procedures that one would expect should be followed (wear insulating gloves, make sure the test is complete before removing the cable, etc.).