Kevin Clark, Vitrek Inc. Hipot testing has long been a standard procedure for assuring the electrical safety compliance of electronic equipment. Early commercial hipot testers were actually not much more than a variac-driven step-up transformer used to ramp up the test voltage and then dwell at the specified voltage for the prescribed time period — all the while monitoring. The Vitrek V7X Hipot Tester is well-suited to the requirements of electrical safety production testing.
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Hipot Test is short name of high potential high voltage Test and it is also known as Dielectric Withstand Test. Hipot test makes surety of no current will flow from one point to another point. Continuity Test checks surety of current flows easily from one point to another point while Hipot Test checks surety of current would not flow from one point to another point and turn up the voltage really high just to make sure no current will flow.
The hipot test is a nondestructive test that determines the adequacy of electrical insulation for the normally occurring over voltage transient. This is a high-voltage test that is applied to all devices for a specific time in order to ensure that the insulation is not marginal. Hipot tests are helpful in finding nicked or crushed insulation, stray wire strands or braided shielding, conductive or corrosive contaminants around the conductors, terminal spacing problems, and tolerance errors in cables.
Inadequate creepage and clearance distances introduced during the manufacturing process. The production-line hipot test, however, is a test of the manufacturing process to determine whether the construction of a production unit is about the same as the construction of the unit that was subjected to type testing. Some of the process failures that can be detected by a production-line hipot test include, for example, a transformer wound in such a way that creepage and clearance have been reduced.
Other examples include identifying a pinhole defect in insulation or finding an enlarged solder footprint. Hipot testers usually connect one side of the supply to safety ground Earth ground. The other side of the supply is connected to the conductor being tested. With the supply connected like this there are two places a given conductor can be connected: high voltage or ground. When you have more than two contacts to be hipot tested you connect one contact to high voltage and connect all other contacts to ground.
Testing a contact in this fashion makes sure it is isolated from all other contacts. If the insulation between the two is adequate, then the application of a large voltage difference between the two conductors separated by the insulator would result in the flow of a very small current.
Although this small current is acceptable, no breakdown of either the air insulation or the solid insulation should take place. Therefore, the current of interest is the current that is the result of a partial discharge or breakdown, rather than the current due to capacitive coupling. The test duration must be in accordance with the safety standard being used. The test time for most standards, including products covered under IEC , is 1 minute.
Most modern hipot testers allow the user to set the current limit. However, if the actual leakage current of the product is known, then the hipot test current can be predicted. The best way to identify the trip level is to test some product samples and establish an average hipot current. Once this has been achieved, then the leakage current trip level should be set to a slightly higher value than the average figure.
The hipot tester current trip level should be set high enough to avoid nuisance failure related to leakage current and, at the same time, low enough not to overlook a true breakdown in insulation. When using ac test voltage, the insulation in question is being stressed most when the voltage is at its peak, i. For example, for a V-ac voltage, the equivalent dc voltage to produce the same amount of stress on the insulation would be x 1.
One of the advantages of using a dc test voltage is that the leakage current trip can be set to a much lower value than that of an ac test voltage. This would allow a manufacturer to filter those products that have marginal insulation, which would have been passed by an ac tester. When using a dc hipot tester, the capacitors in the circuit could be highly charged and, therefore, a safe-discharge device or setup is needed.
However, it is a good practice to always ensure that a product is discharged, regardless of the test voltage or its nature, before it is handled. It applies the voltage gradually. By monitoring the current flow as voltages increase, an operator can detect a potential insulation breakdown before it occurs.
A minor disadvantage of the dc hipot tester is that because dc test voltages are more difficult to generate, the cost of a dc tester may be slightly higher than that of an ac tester. It can be applied at higher levels without risk or injuring good insulation.
Since the dc is free of capacitive division, it is more effective in picking out mechanical damage as well as inclusions or areas in the dielectric which have lower resistance.
One of the advantages of an ac hipot test is that it can check both voltage polarities, whereas a dc test charges the insulation in only one polarity. This may become a concern for products that actually use ac voltage for their normal operation. The test setup and procedures are identical for both ac and dc hipot tests. A minor disadvantage of the ac hipot tester is that if the circuit under test has large values of Y capacitors, then, depending on the current trip setting of the hipot tester, the ac tester could indicate a failure.
Most safety standards allow the user to disconnect the Y capacitors prior to testing or, alternatively, to use a dc hipot tester.
Hi sir I have a doubt Now I am injecting Dc voltage at diode How to calculate half wave and full wave Proper reason you have 1. What is the permissible leakage current value for a 11kv cable. If there any formula for calculating leakage current. Therefore, if we use dc test voltage, we ensure that the dc test voltage is under root 2 or 1. Does anyone have information on how medium voltage shielded cables new installation installed outdoors can build capacitance charge in open air?
The cables run underground; one end comes up parallel feed the steel structure of a switch-yard, and the other end to a utility wooden pole and are braced to a cross-arm — The 15kv terminations are installed and left to be tested on both ends. The rule of thumb for duration of hipot testing seconds. Is that descripted in a standard like IEC ? I wanted to notify you that Shrikant Kajale Kajale Projects has copied and pasted your article and posted on LinkedIn pretending he wrote it.
DC or AC? PS: I have 5 Electrolytic Caps connected in parallel to the input terminals. If a1. In the section regarding current setting for the HIPOT test, the current trip level is set as 2x the scaled up value of the rated leakage. It appears that the 2x is just to reduce trips since the real part of the test is arcing and breakdown.
Is that correct? Can we measure Partial discharge while doing AC Hipot test. What is the difference in measuring leakage current and partial discharge while performing Dielectric tests. Is there any Standard for the amount of allowable leakage current during the High-Pot testing of Switchgears?.
For Eg. Considering high-pot testing is somewhat distractive specially for old and existing electrical equipment, what do you recommend as an alternative test for high-pot testing? Approximate cost. Any special care required for operators while handling this test?
This can be done on both types of cables? Approximate what will be the total time required to conduct 2 sec HIPOT test for cable having approximate length of 2 M and connector at both ends? Siva Your question is not very clear. Hipot test are very simple depending what you are testing.
Hossein It is easy, go on spread sheet, design your sheet. Vinod The test voltage always depend on what your testing. What settings do you set the Fluke Multimeter to?
Any help would be appreciated! Usual problem, but still I am not cleared…If there is any acceptable leakage current value is there during Hi-pot test, please share with us.. In modern day test kit, we could find many options, 25mA, 50mA, 75mA… I heard, insulation should not get breakdown or kit should not trip. I kept in 25mA option and it is tripped, but same way I kept it in mA, and it is not tripped. I am sure it is less than mA.
But I need to know what is the acceptable range of leakage current. Dear Jignesh, If I need to test Hipot test with the product. Do we need to test Hipot test before Functional test or after Functional test? Dear Mr. My question: Is there a table of all different voltages of transformer and the voltages to apply to hipot transformer. Surge absorber, CT, and busbar still connecting to cable. I gave 13,5 kV for 10 mins and the leakage current is ms. JP, excellent! I had an Indian EE friend in America.
S in EE. I know how the hi-pot test works and the setup. Please include the test equipment diagram in your paper. Why is that? It has to be all in digits, not? Shaukat Ali : 6 x Three types questions are to block spam programs imitating humans and flooding the website. Normally a spam is not supposed to recognize such thing, and will not be able to proceed further. I want an insulation for instrumentation purpose from readily available insulation polymers that can be molded which has very low leakage in the range of femtoamps, I am basicaly interested in measuring current in that range, Operating voltage is in the range of Vdc to v DC.
Im curious to how you came up with the rule of thumb for the test voltage. I looked at the IEC spec and couldnt quite figure it out. Your article of hipot is very good and easy to digest, I would like to contact you to ask some direction to solve an issue. We are seeing VSWR large spikes in coaxial at 2.
Based in our calculation we can correlate the periodicity in inches of the spikes. If we use core balance current transformer for earth fault protection then do we need to connect S2 terminal of CBCT to the ground terminal. If possiblethat, then can me provied circuit daigrame or components name also.
Safety guidelines for hipot testing and setting up a safe testing area
December 1, 37 Comments. Filed under Uncategorized. About Jignesh. Parmar B. Tech Power System Control , B. E Electrical.
Dielectric withstand test
A dielectric withstand test or high potential or hipot test is an electrical test performed on a component or product to determine the effectiveness of its insulation. The test may be between mutually insulated sections of a part or energized parts and electrical ground. The test is a means to qualify a device's ability to operate safely during rated electrical conditions. A dielectric withstand test may be done as a factory test on new equipment, or may be done on apparatus already in service as a routine maintenance test. Voltage withstand testing is done with a high voltage source and voltage and current meters. A single instrument called a "hipot tester" is often used to perform this test.