Testing dielectric



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What is dielectric test

Dielectric test to verify the insulation and continuity of electrical equipment used in the testing and insulation resistance testing frequency power or by foot (HiPot) It is known that the word stands for High Potential high voltage potential or indeed the two words are used interchangeably in the industry. Electric strength equipment to assess them for 1 minute power frequency voltage, the voltage test test voltage level of work expected to be put to work during the years of service of the likely pressures to simulate Knd.drmvrd indoor installations, testing is done only in dry conditions, if necessary, in terms of rain Astandardkh outer .vsayl described in the relevant standards will be tested

What is HiPot

The test by applying a high voltage to the main circuit and conductors made their facilities and in general, to determine the strength of the insulation between current and non-current-carrying parts of the vehicle used to check the condition of the insulation and the pressures for (accidental and unintended) is far higher than the normal operating voltage switchgear, devices or equipment occurs. HiPot test and high voltage test, measurement procedure is not in fact a process that determines the resistance of insulation against high voltage. As you know, this kind of system voltage increase for various reasons, such as switching and lightning and normal working conditions arise. and the panels can be said that the test is satisfied when the insulation boards insulator failures, such as fracture, insulation breakdown or spark on equipment not happen. Then test equipment in normal working conditions is no problem setting up .zmna This test unfolding mistakes made by members of the production line, design problems as well as inadequate space between parts is ideal

Applications

The tests on low-voltage and medium-sized panels, transformers, cables, production, repair and maintenance sector, research centers and laboratories, equipments inspection sites .... is done. It should be noted that in some circumstances it can also flow from the insulation pass. Sometimes a small amount of leakage current by applying a voltage lower than the nominal voltage is present. The leakage current may be due to factors such as insulation capacitance, insulation resistance, electrochemical phenomena and effects of the corona.But if the board or the cable or total conductor test, injury or damage, the amount of leakage current will be very high and this could be someone nearby was damaged, the damage. If in the process of making boards or in other stages such as installation equipment such as bus bars, switches, insulators and wiring and terminals and transport, and damage to the insulation board and its equipment or pipes, or not Net items are present, the possibility of damage to those parts of the equipment in a manner that is in service, due to current leakage there is irreparable damage to the facility. And thus HiPot test is the best way to detect these cases. The test can be a little insulation, are low and cracking equipment, the holes of the wire and cable, wire wrapping inadequate (conductor cable), crushing the wire and cable and detect.

How to use HiPot

By applying voltage to low-voltage switchboard referred to in the following based on the new standard IEC 61439 are done. 1) 2.5 kv -50 Hz for 1 sec for switchgear rated insulation level 0.69 kv2) 3.5 kv -50 Hz for 1 sec for switchgear rated insulation level 1 kv These tests as well as testing insulation connection must be made in 5 states Note that the new standard with regard to the injection of high-voltage equipment insulation damage in a long time. This time is reduced to 1 to 5 seconds necessary to point out that the power supply must be powerful enough to During the test, the test voltage can be fixed. Sine wave voltage should be between 45 and 62 Hz frequency and voltage of the test for a second time should be a maximum of 85% of the initial value The medium voltage switchgear with voltage mentioned in the following based on the new standard IEC 62271-200 for 1 minute (the old standard IEC 60298) are done. 1) 10 kv -50 Hz for 60 sec for switchgear rated insulation level 3.6 kv 2) 20 kv -50 Hz for 60 sec for switchgear rated insulation level 7.2 kv 3) 28 kv -50 Hz for 60 sec for switchgear rated insulation level 12 kv 4) 32 kv -50 Hz for 60 sec for switchgear rated insulation level 17.5 kv 5) 50 kv -50 Hz for 60 sec for switchgear rated insulation level 24 kv 6) 70 kv -50 Hz for 60 sec for switchgear rated insulation level 36 kv In addition, this test should be performed following the 4-position connector 1) L1 with L2, L3, PE 2) L2 with L1, L3, PE 3) L3 with L1, L2, PE 4) PE with L1, L2, L3

How to use HiPot, Megger

1-all keys except the command keys and relay circuits in the Contact Set. 2. All the conductors, bus bars and keys are missing fuse must be connected by an extension cord is necessary (the cells that are separately).3. All buses Earth must be connected. 4-circuit voltage transformers (Pt) and lightning are (Surge Arresters) and should be discontinued. 5. Enter the range of tests to isolate and exposure to body board at the time of the tests Jdda be avoided.

The advantages of DC test

1. This test flow with a very small level, lower power consumption and a lower risk for the operator. 2. The leakage current is measured, more realistic picture of the actual flow.3. In order to test some of the circuits that use diodes, capacitors, etc., only this method can be used.

Advantages of AC test

1. Due to shift polarity of the waveform applied, there is no need to increase the voltage slowly. 2. After completing the test does not test electrical discharge.3. testing in both polarity is applied to the insulation stress. The difference between AC and DC waveforms we have to apply different methods to perform the test. Testing with the same methods and principles above just the operator of the relationship between DC and AC waveform to calculate the AC wave Knd.shkl often effective value (RMS: Root Mean Squared) is expressed. By the effective value of AC, energy DC at a voltage of similar waveform similar waveform provides the example of a source of energy 25 V DC and an AC voltage source with a voltage of 25 volts is similar. A small amount of AC power waveform at the Peak RMS sine wave is higher. In fact, the measured peak voltage and RMS value are as follows: Vpeak = 2√ * Vrms Since this test is always dangerous, it is necessary to test for safety, the equipment and implemented. And for testing specific device operates according to the manufacturer's instructions.