This test is performed by applying a high voltage to the main circuit and conductors and their accessories and is generally used to distinguish the insulating power between current-carrying and non-current-carrying parts and also to investigate the insulation conditions due to pressures.
(Random and unwanted) far more than the normal operating voltage of panels, devices or equipment. HiPot test or Strong pressure test, Is not really a measurement method but a process that determines the insulation resistance to high voltage.
As you know, such overvoltages of the system occur for various reasons such as switching and lightning and… under normal operating conditions.
This test determines the appropriate insulation connection of the products by determining the specified voltage and time, such as whether there is or will be a dielectric failure in the equipment or conductor set, which will be tolerated according to the standard if the arc is not visible. Regarding electrical panels, it can be said that the test result is satisfactory when there is no damage in the insulation of the panel, such as insulator breakage, insulation failure or sparking on the equipment.
The test equipment is then set up in its normal working condition without any problems. In addition, this test is ideal for revealing mistakes made by production line personnel, design problems, as well as inappropriate space between parts.
Applications and capabilities HIPOT:
This test is performed on low and medium pressure switchboards, motor transformers, cables, production line, equipment maintenance department, research centers and laboratories, equipment entry checkpoints. Takes place.
It is important to note that even the best insulators can withstand some current in some situations. Sometimes there may be a small amount of leakage current by applying a voltage lower than the rated voltage. This leakage current can be due to factors such as capacitive insulation capacity, insulation resistance, corona phenomenon and electrochemical effects.
However, if the panel or cable or assembly of the conductor under test is damaged or damaged, the amount of leakage current will be very high and this can injure a person who is near the damaged area. If in the process of making the panel or in other steps such as installing equipment such as bus loads, switches, insulators and wiring and terminal and transportation, and… damage to the panel and its equipment insulation or holes or impurities in If there are items, there is a possibility of damage to that part of the equipment while it is in service, due to current leakage and irreparable damage to the facility.
Thus, HiPot testing is the best way to diagnose the above. This test can also detect low insulation, short distance and cracking of equipment, perforation of wires and cables, insufficient twisting of wires (cable conductors), crushing of wires and cables, and so on.
Instructions for determining the amount of voltage injection Dielectric test By HiPot device in low and medium
pressure panels ü in low pressure panels by applying the voltage mentioned below according to the new standard IEC 61439.
1) 2.5 kv -50 Hz for 1 sec for switchgear rated insulation level 0.69 kv
2) 3.5 kv -50 Hz for 1 sec for switchgear rated insulation level 1 kv
• This test, like the insulation test, must be performed in 5 connection modes
Explain that the new standard reduces the time to 1 to 5 seconds due to the fact that injecting high voltage over a long period of time will damage the insulation of the equipment. It is necessary to remember that the power supply must be powerful enough. To be able to keep the test voltage constant during the test.
The voltage wave should be sinusoidal and its frequency should be between 45 and 62 Hz, and the voltage value of the test for the second time should be selected at most 85% of the initial value. 1 minute (old standard IEC 60298).
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
Also this test should be done in the following 4 connection modes
1) L1 with L2, L3, PE
2) L2 with L1, L3, PE
3) L3 with L1, L2, PE
4) PE with L1, L2, L3
General items that must be done to ensure accuracy and safety before performing the HiPot test,MeggerObserved:
We put all the switches on except the command circuit and relay switches.
All conductor paths, bus loads, and switches that do not have fuses must be connected by an interface wire (in cells that are separate).
All earth rails must be connected.
We have to cut off the circuit of voltage transformers (Pt) and surge arresters (Surge Arresters).
Isolate the test area and avoid contact with the panel body again during the tests.
Select the voltage values of Test Power Frequency Dielectric Withstand for main low voltage circuits with different voltages based on the standard (IEC61439) table below.
Insulation test voltage range (Ac) rms Insulation voltage range Ui line by line AC Or DC
1000V Ui <60
1500V 60 <ui <300 <b = ””> </ ui <300 <>
1890V 300 <ui <690 <b = ””> </ Ui <690 <>
2000V 690 <ui <800 <b = ””> </ ui <800 <>
2200V 800 <ui <1000 <b = ””> </ ui <1000 <>
3820 V 1000 <ui <1500 <b = ”” × </ui <1500 <>
× for DC voltage only
Select the voltage values of Test Power Frequency Dielectric Withstand for auxiliary and control circuits according to the standard) (IEC61439 table below).
Insulation test voltage range (Ac) rms Insulation voltage range Ui line by line
250V Ui <12
500V 12 <ui <60 <b = ””> </ui <60 <>
2 Ui + 1000 with a minimum of 1500 60 <Ui
Advantages of DC testing
1. This test is performed with a very small current level, less power consumption and less risk for the operator.
2. The measured leakage current is a more realistic picture of the actual flow.
3. Only this method can be used to test some circuits in which diodes, capacitors and شده are used.
Advantages of AC testing
Due to the constant change of polarity of the applied waveform, there is no need to increase the voltage slowly.
After the test, there is no need to electrically discharge the equipment under test.
This test applies stress insulation to both polarities.
The difference between AC and DC waveforms forces us to apply different methods of testing. The principles of testing with the above methods are the same and it is enough for the operator to calculate the relationship between the DC waveform and its AC equivalent. The AC waveform is often expressed as the effective value (RMS: Root Mean Squared). This effective amount of AC provides the same amount of effective energy as the DC waveform at the same voltage. For example, the amount of effective energy of a 25 volt DC source and an AC voltage source with the same effective voltage of 25 volts.
The small amount of RMS waveform in AC power at the peak point of the sine waveform is much larger. In fact, there is the
following relationship between the measured peak voltage and the RMS value:
Vpeak = 2√ * Vrms
Since this test is always associated with risk, before performing the test, it is necessary to think of measures for the safety of the person and equipment. And to perform the test according to the instructions of the manufacturer of that particular device.