The current meter on the pts series also has a megohmmeter scale to allow for easy resistance measurements while the hipot is in operation. Follow the hazard analysis hipot testing for beam tube ion pump power. I had no ac hipot to perform vacuum bottle integrity and withstand test. If the test cable has a defect severe enough at the withstand test voltage, an electrical tree will initiate and grow in the insulation. Mats can detect the presence of a person in the test area. First, to test a cable with 60 hz power requires a very high power supply. Hilo programmable during test time lo can be set to off during hipot test hi can be set to off during ir test indication. Connect the high voltage test cable to the ac out u post and the ground test cable is connected to ground g post as shown in illustration b.
It is the data behind the hipot test that can help manufacturers ensure the product is safe and consistent. Performed by stressing the insulation of the product far beyond what it would encounter during normal use. In the boost or voltage withstand test process, as a result of short circuit, flashover, breakdown, such as over current, the current trip of relay protection, automatic voltage regulator power that test materials are not up to standard, at this time regulator should be back to zero, cutting off power supply, inspect the test products. In some ways a hipot test is the opposite of a continuity test. The pilot should refer to the manual wiring of figure 1 or the relevant test transformer. In most cases hipot testing is applied as a passfail or gonogo test. Very low frequency vlf withstand testing the basics. Vlf cable test voltage ieee standard high voltage inc. This type of system works for fast hipot tests but can be impractical for long duration hipot tests. The indicator lamp within the button will light when test expires with pass condition. After login, press the hv enable button center to enable the system for high voltage hipot testing. This is to test if the insulator can withstand the operating voltage and not breakdown. Warning the 955i is intended to be powered from a power. There are four approaches that are used for testing insulation with ac.
These are intended to detect defects in the insulation of the cable system in. Why is a vlf hipot used instead of a regular 60 hz model. Prior to pulling the cable, after pulling the cable, after splicing and final terminating the cable, as a final system test prior to turning it over to the end user. Shari richardson is a director of engineering and the lead engineer on all medical applications at quadtech. Hipot testing involves applying an overvoltage to the cable system for a short duration to verify the dielectric integrity of the system cable, splices, and terminations. Thus, the instruments have a 100ma trip current rating and 200ma short. Hipot test is the most common type of electrical safety test. The hv test lead outside shield conductor is connected to the concentric neutral ground point of the cable under test. Connection setup for a vlf cable connecting a vlf test instrument to a cable refer to ieee 400. Very low frequency vlf withstand testing is the application of an ac sinusoidal waveform, generally at 0. If the conditions are not met then they can cause false failures and possibly damage the power supply.
Periodically test the memory to ensure consistent testing and that the parameters are not altered. Test button this is a momentary contact switch used to start a test. If a vlf test is too low in voltage andor too short in duration, more harm than good may result. Dielectric withstand or hipot test the dielectric voltagewithstand test, or hipot high potential test, is designed to stress the insulation of your. It is similar to an ac hipot test but the test voltage is at 0. Sentry plus series hipot testers instruction manual. That is, with the same test connections and with the same test voltage applied for the same length of time. The operators manual for the particular test set being used should be read and well understood. Guidelines for high potential hipot dc testing of medium. Aug 12, 2014 this application note illustrates how to effectively perform electrical safety testing of imds with feedthroughs. The hipot test the dielectric voltagewithstand test is commonly known as the hipot test. Ensure the tester and test station uses all the builtin safety features and functions of the hipot tester.
Designed to verify that the insulation of a product is adequate enough to withstand high voltage. Many manufacturers specify that ac be used to test their equipment, and the ac hipot testing has a large following. Due to the nature of a dc withstand test, setting high and low leakage limits can prove difficult. Then, either learn a cable attached to the tester, or load a previously stored cable from the database, and press the test button to initiate a test. Dc hipots can be used for the following testing applications. Nov 26, 2018 at the completion of a test, observe that the hv light is out. Hipot test is short name of high potential high voltage teat and it also known as dielectric withstand test. Low voltage and high voltage cable testing electrical. The vlf test instrument should be solidly grounded before connecting up any cables. For the test to be completed, certain conditions must be met so the product will pass. Safety, operation, and procedure instructions for the pts. As a result of a hipot test, at the point of an insulation defect an electrical tree will start to progress, create the insulation breakdown and.
Illustration b high voltage test cable ground test cable. Once the insulation is charged full test potential, the leakage current drops off to near zero ma. All tests made following cable installation and during the warranty period must be performed in accordance with the applicable specifications. It is not practical, nearly impossible, to test a cable of several thousand feet with a 60 hz supply. Low voltage and high voltage cable testing low voltage xlpe distribution cables. The instrument used for this measurement shall have a. Ieee std 400 provides additional information on dc testing and evaluation of the insulation of shielded power cable systems.
Hipot tests are helpful in finding nicked or crushed insulation, stray wire strands or braided shielding, conductive or corrosive contaminants. If the insulation is good, it will be able to withstand the high levels of current and not fail during the test. Image you are bathing in bath tube, suddenly drier in operating dropping into bath tube, the current flows from drier through your body to ground under this situation. Usually two or more times the rated insulation current will be used. The test will expose gross imperfections that are caused by improper handling, installation techniques or termination workmanship. Dc hipot test passfail analysis a dc hipot test is done at a voltage higher than the peak operating voltage of the device under test dut, where peak voltage rms voltage x 1. This white paper seeks to clarify the theory of dielectric breakdown and the objective of the dielectric voltage withstand test. Hipot test makes surety of no current will flow from one point to another point. May 02, 2018 the ac test equipment used should have adequate voltampere va capacity to supply the required cable charging current requirements of the cable under test.
Therefore, if a test of an installed motor in a plant fails above peak operating voltage, it. The mat can be used to automatically disable or abort. Why engineers prefer vlf hipot testing protec blog. Essentially, the vlf withstand test is a go or nogo test, otherwise known as a passfail test. Yes the cable may fail under test if it has a severe defect, but thats the point of the test. After checking for opens, shorts, miswires, and resistance limits, the system applies a userselectable voltage to each connection group.
When vlf withstand testing cable, the proper test voltage and time duration are critical for the success of the test. This test is also known as the dielectric withstand test, which checks for functioning insulation. Mar 03, 2016 very low frequency vlf withstand testing the basics. The purpose of a withstand test is to verify the integrity of the cable under test. Press the green button to turn on the high voltage output when in test mode. 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.
It is not a diagnostic test but rather a stress test. Inception of an electrical tree and channel growth time are functions of. Hipot test makes surety of no current will flow from one point to another point hipot test is the opposite of a continuity test. The typical highpotential hipot test is an example of a type 1 field test. Dc hipot testing of solid dielectric cables can therefore make aged cables. Hipot testing procedure for withstand testing of hv coax. Hipot test voltages high potential test electrom instruments. At the completion of a test, observe that the hv light is out.
If the test was dc, the discharge may take some time. In earlier days, an ac hipot test required a large amount of power to energize a cable. This combination of size and power makes very low frequency cable testing perfect for testing longer sections of cable and apparatus. Connect the opposite end of the test power cable to either outlet of the duplex box. Thus, a dc hipot test voltage is often derived from a typical ac hipot test voltage which is proven to work well.
The surest way to weed out bad cables and accessories is to just perform a simple ac hipot test, just like we do with vacuum bottles, arrestors, hot sticks, switchgear bus and insulators, etc. Each manufacturer is required to comply with the same set of tests according to the same test parameters. So, recently went onto a job to perform vlf testing of 2 sets of 35kv cables, when the customer threw a curve ball at me to test the 35kv breakers. Perform the test as instructed to make best use of vlf technology. Testing cables with high voltage cirris systems corp. The pts series of dc hipot test sets provide continuously adjustable output voltages for the test and measurement of leakage current in high voltage insulation. Ever wonder what kinds of tests cable manufacturers execute in order to have their products pass quality inspection.
For many years, the traditional dc high potential hipot test has been the method of choice for both maintenance. Our management does not want us to test with dc on vacuum bottles, as there is documentation that dc can damage vacuum bottles havent. Safety, operation, and procedure instructions for the pts series of dc hipotmegohmmeters. This application note illustrates how to effectively perform electrical safety testing of imds with feedthroughs. Withstand or hipot cable testing withstand or hipot testing is used to evaluate the condition of cable insulation during installation, acceptance, or maintenance testing. In this test a high voltage ac is applied to the insulation. If the cable can withstand the applied voltage for the duration of the test, it is considered a pass. The minimum insulation resistance to earth or between phases shall be 100 megohms. Vlf testing uses very low frequencies as part of an ac cable maintenance routine. One of the many quality inspection tests that is performed is the hipot test, short for high potential test. The operators manual for the particular test set being used should be read. Nicked or crushed insulation, stray wire strands or braided shielding.
In dc voltage test and leakage current test, as long as the high voltage silicon stack is installed on the high voltage output terminal, the dc high voltage can be obtained, and its amplitude is 1. Such testing can be conducted as an acceptance test for new installations or as a maintenance test for existing installations. When performed as type tests hipot tests are helpful in finding various important defects. Cable types, design, and associated insulation faults. This function is to change the time required for the outputted test voltage from the specified value falling to zero. This means that if the cable temperature is increased due to having been subjected to substantial load, some time should be allowed for the cable to cool down. Lcd display the liquid crystal display is the main readout for the operator and programmer of the test. This white paper seeks to clarify the theory of dielectric breakdown and. As long as the buttons are held down the hipot test will happen. Below are hipot test voltages for both dc hipot and ac hipot tests. High potential hipot dc testing guidelines for medium voltage cables photo credit. Jan 16, 2014 dc hipots can be used for the following testing applications. Make sure that all protective fuses, breakers, switches, etc. Performed by stressing the insulation of the product far.
Changing the time for voltage falling this instrument contains fall function. If either switch is released, the hipot test aborts. The higher test voltage allows for weak points or predamaged areas within the cable to breakdown during the test, rather than while they are in service. Electrical safety testing reference guide touch area. High potential hipot cable system testing can be performed using dc, ac or very low frequency ac also known as vlf test voltage. Dc hipot test at test start, there will be inrush current. Test method is operating dut and under the status of all switches, link cables. Therefore, if a test of an installed motor in a plant fails above peak operating voltage, it does not mean that. Repetitive testing can be controlled entirely from this front panel without referring to the. Guidelines for high potential hipot dc testing of medium voltage. Ac hipot tests can only be conducted as gonogo test and therefore may cause extensive damage, should the cable under test fail. These features are used with a dc hipot or ir test.
It is possible to reduce the testing time by connecting all three phases together, except for a belted cable, or if the. Cables shall be tested for insulation resistance with an insulation tester i. Dec 01, 2011 what is hipot testing dielectric strength test. In 1996, the insulated conductor industry determined that dc withstand testing of the plastic xlpe insulation systems either in the cable factory as a routine production test or after installation as the higher voltage proof test was detrimental to the life of the insulation and therefore discontinued recommending dc testing. The pts series of dc hipot test sets provide continuously adjustable output voltages for the test and. I am planning on replacing cable 2, but would like some data to back up my decision. While the dielectric voltage withstand test is widely used, the real objective of the test is often misunderstood, which may lead to incomplete testing or misleading test results. A hipot test checks that no current flows between points where there should be no current. However, it provides limited knowledge of the cable condition other than whether the cable system withstood the voltage for the duration of the test or not. Most of what ive read for hipot testing is for medium or high voltage applications. During the test cables are subjected to a test voltage significantly higher than what they experience during normal operating conditions. This technical article provides general guidelines for high potential hipot dc testing of mv power cables. Connect the interconnect cable between the control and high voltage tank two piece units only.
Cable testing revision 1 june 2, 2011 page 3 of 8 procedures to be used as well as the specifics regarding the cable sample. For example, a 2000m length of cable may have 60ma of leakage. Most associated research instruments have a 5000v output. Acceptable procedures for conducting hipot testing, although varying slightly in technique, have been standardized as either a withstand test or a timeleaking current test. A 1,500vac test checks the two isolation barriers of the equipment, namely inputtooutput and inputtoground.
Vlf testers are smaller and more practical than ac testers but output the same amount of power as a 50 hz mains device. The test can be done at various times such as acceptance of new cable installation, maintenance testing to track insulation degradation and as a pre and post test for splicing existing cables to new ones. Hipot test standards dc hipot test analysis electrom. Ive read that on megger tests, the low limit is around 50100 megohm.
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