The High Potential Testing method is the most dangerous of all acceptance and general electric maintenance tests performed in this industry. It is essential that this hazardous test be conducted by a qualified and experienced individual who is NETA Certified and possesses the necessary training to be able to perform this very important test. At Industrial Tests, Inc., where we have over 35 years of HiPot Testing experience, our Engineers and Electrical Technicians
Our technicians are well trained in the use of their HiPot Testing equipment and always take the necessary safety precautions before applying high voltage to the electrical equipment under test.
Industrial Tests HiPot system testing can be performed using DC, AC, Very Low Frequency (VLF) AC, Resonant AC, and Partial Discharge testing. We can implement these testing standards as an Acceptance Test for new installations or as an Electrical Maintenance Test for existing installations.
High Potential Voltage Test Broken Down:
1) Voltage is applied across the insulation of your electrical equipment at or above the DC equivalent of the 60 Hertz operating crest voltage. This test can be applied as a dielectric absorption test, or a step voltage test. When applied as a dielectric absorption test, generally the maximum voltage is applied over a period of from 60-90 seconds. This maximum voltage is then held for 5 minutes with current flow readings being measured.
When applied as a step voltage test, the maximum voltage is applied in a number of equal increments, with each voltage step being held for an equal interval of time. The time interval between steps should be long enough to allow any current flow to reach approximate stability usually one or two minutes. A current flow reading is taken at the end of each interval, before the voltage is raised to the next level. A plot of the test voltage versus insulation resistance is drawn as the test progresses. After the maximum test voltage is reached, a dielectric absorption test may be performed at that voltage.
NOTE: If this test is performed properly over a period of years, the cable deterioration will be monitored and a failing cable can be removed from service during regular maintenance periods. Our expert Engineers and Technicians at Industrial Tests, Inc. can pinpoint any faults in your company’s electrical system, and eliminate a damaged cable during a production period, saving your company lost time and unnecessary expenses.
2) The maximum permissible test voltage for acceptance tests performed on your cables are recognized and monitored to be sufficient standards within the testing guidelines established in this industry. Also, each cable manufacturer supplies its own recommendation for testing of their respected cables. Ordinarily, routine maintenance tests are conducted with a maximum test voltage at or below 75% of the maximum test voltage permitted for acceptance testing.
3) Extreme care must be taken in choosing the appropriate test voltage for routine maintenance tests on cables which have been in service for long periods. If the level selected is too low, marginal weak spots may not be revealed, if the level selected is too high, damage to the insulation may result. Further, if it is inconvenient or impossible to disconnect switchgear, instrument transformers or cutouts from the test circuit, it may be necessary to reduce the maximum voltage to the level that this equipment can withstand without damage. These possible hazards is exactly why you should choose Industrial Tests, Inc. for all of your High Potential Testing needs, where our 35 years of excellent service and industry experience has led to such a high rate of repeat and referral customers.
4) Prior to testing, lighting arresters must be removed from the test circuit and if practical, all instrument transformers, switches, cutouts and switchgear, so that if significant leakage currents are encountered during the test, it will be known that these currents represent losses in the cable, not in the associated equipment. The test voltage should be applied from phase-to-phase and phase- to-ground on each conductor with the other conductors, the shields, and the metallic jackets also connected to the ground.
5) When the step voltage type testing is used, the condition of the cable is evaluated on the basis of:
- The absolute values of insulation resistance
- The slope of the curve voltage versus insulation resistance
- Whether or not a significant downward “knee” appears in the curve at higher levels of test voltage.
High Potential Testing Services We Perform
Resonant AC Testing is especially valuable in any situation where the load is largely capacitive with low loss such as power cables, gas-insulated switchgear,generator windings, and dry testing of insulator strings. Resonant AC Testing systems by Industrial Tests, Inc. enableMore...