‘Hipot’ is short for ‘high potential,’ which interestingly again is short for the more technical term, ‘Dielectric Withstand Test‘. It’s an electric safety test, where a direct application of a high voltage is made to a unit/device to test the effectiveness of its insulation. The test voltage is usually much higher than the operating voltage to stress test the device’s dielectric properties.
Hipot testing and earth bond testing (where applicable) form the core tests for electrical safety testing on a production line. Hipot testing is used to verify if the finished appliances, transformers, circuit boards, or electric motors have proper electrical insulation.
In the context of wire harnesses and custom cable assemblies, Hipot testing is used to verify the correct operation of safety circuits.
The test is meant to detect insulation issues in the conductive parts and earth (or the product chassis) and to ensure they are sufficient. It also ensures that degradation impact on insulation, such as pinholes and cracks in insulation, have not passed through production processes and wear and tear.
For example, a live conductor should not accidentally have been crushed between the chassis parts, causing it to become live when switched on; it is one of those things that can happen during the assembly process.
Such breakdowns in the insulation will result in current flowing across the test points of the Hipot tester, and this current flow is commonly known as leakage.
If the leakage current is too high, the device under test is considered to be unsafe for use, and the test will fail.
Besides device safety, are there any regulatory requirements and standards that make hipot testing mandatory in India?
Depending on the country and geographic region for which the product is being tested, different safety compliances apply.
For instance, BIS (Bureau of Indian Standards) is the Indian safety standards organisation, CE (Conformité Européenne) certification is a regulatory standard that verifies certain products are safe for sale and use in the European Economic Area, and UL Certification or UL Mark is an international certification which is provided by Underwriters Laboratories a US-based safety certification company.
All these standards specify mandatory high-voltage testing.
How is a hipot test carried out?
Because hipot tests usually involve dangerous voltages, the test setup must be safe to operate.
Hipot testers have safety features such as overcurrent protection, and they have an interlock for signal input.
Overcurrent protection comes in the form of a ground-fault interrupt circuit, like the ones in the AC mains outlets in your home. One can use the interlock input with mechanical switches (such as handheld push buttons) to disable the high-voltage output when the switch isn’t closed.
Another safety technique is to use an infrared sensor that opens the interlock input should anything (such as a hand) break the beam.
How do you select an ideal hipot tester?
● Wide range of built-in voltage capabilities. For example, 6.5KVDC all the way up to 30KV RMS AC
● High power output – Look for up to 50mA in DC and up to 200mA AC
● Should be able to detect tera-ohm range leakage
● Solar panel testing compatible
● Operator safety features like high-speed shutdown
What are the common issues faced with hipot testing devices?
There are primarily two types of issues that are common with hipot testing devices.
First could be minor issues with switches, ports or safety locks. These can be expected due to regular use. The second and more critical issue could be the calibration of the device.
Calibration – Calibration ensures that the readings of the hipot tester fall within specifications to improve the device’s accuracy and ensure consistent measurements in testing applications.
Since hipot testers are devices that are regularly used with high voltage, so as to avoid any accidents or damage, regular calibration is critical. By conducting at least a yearly calibration, you can ensure the overall accuracy and reliability of the equipment.
At Globetek, we sell and support the Vitrek 95x and v7x series. You can read more about it here.