Explore High Potential Cable Testing
What is High Potential Testing?
High potential called hi-pot test system can be performed with DC, AC, or VLF AC (also known as Very Low Frequency ) test voltage. Hipot testing can be conducted as an acceptance test for new installations or as a maintenance test for existing installation of cables.
Hipot testing is applying an overvoltage to the cable system for a short duration to verify the dielectric strength of the system including cable, splices, and terminations. In most cases, hi-pot testing is applied as a pass/fail or go/no-go test. If the cable system does not fail during the test, it is considered to have passed the test and can be placed into or back into service.
DC Hipot Testing for cable
The DC hipot testing of cables was developed in the early 1900s, it is mainly for testing laminated cable such as paper insulated lead covered cable types. The DC hipot tester is easy to operate and displays an accurate leakage current value. It is small light-weight, and portable. The current standards provided from DC hipot tester for acceptance testing of cable with extruded (e.g. cross-linked polyethylene [XLP] or ethylene propylene rubber [EPR] insulation or laminated construction (such as paper insulated lead covered [PILC]). However, some standards like IEEE400 don’t suggest DC hipot testing for maintenance testing of field-aged XLP or EPR cables anymore. Because this method will cause damage and it is not meaningful to maintenance.
Cases of DC hipot testing on site
HUAYI brand DC hipot tester has the characteristics of large output power and small volume, reliable overvoltage, overcurrent, and zero closing protection function, with 0.75 times voltage switching function. With new technology, new materials, and new devices, with large output power, small size, lightweight, reliable overvoltage, overcurrent, and zero closing protection function, with 0.75 times voltage latch function, and equipped with time relay, which can set timing sound alarm in the test.
1. Conductance current test of valve type arrester.
2, power transformer DC withstand voltage test and leakage current measurement.
3, high voltage cable (35 ~ 500kV and below) DC withstand voltage test and leakage current measurement.
4, zinc oxide arrester U1mA DC reference voltage test and 0.75U1mA leakage current test.
VLF Hipot Testing
In fact, the VLF hipot testing s an alternative to the power frequency withstand voltage test. In the power frequency withstand voltage test of large and medium-sized generators, motors, power cables and other test objects, due to their large capacitance in the insulation layer, a large capacity test transformer or resonance transformer is required. VLF hipot test has the same advantages as DC hipot testers – they are relatively small and lightweight. The capacity is about one-fifth of the power frequency, and the operation is simple. This is the main reason why this method is widely used in developed countries. The latest national regulations on preventive tests of cable have expressly stipulated that DC high voltage is no longer used for voltage withstand the test of electrical equipment, and AC voltage withstands test is recommended.
Cases of VLF hipot testing on site
The new generation of 0.1Hz ultra-low frequency high voltage generator developed by our company adopts the latest power electronic components and the latest ARM7 single-chip technology, further reducing the volume and weight of the equipment, fool operation, and more stable performance. It adopts 7-inch touch screen, the latest arm7 single chip microcomputer, high-speed ad acquisition circuit, and is equipped with background management software overcoming the shortcomings of the first generation of a mechanical booster, such as short service life, high failure rate and large volume. Large test range: 0.1Hz, 0.05Hz, and 0.02hz multi-frequency selection, large test range. Through years of practice, a large number of user feedback shows that: - 80kV ultra-low frequency high voltage technology is leading in the country, with the highest cost performance!
AC Hipot Testing
The AC hipot testing test can be divided into power frequency, frequency conversion, and 0.1hz ultra-low frequency test technology. For high voltage cables above 35KV, the ac hipot testing is mainly used with the frequency conversion test method(variable frequency AC resonant test system). The test system is composed of a High Voltage Reactor, a High Voltage Divider, an Exciting transformer, Variable Frequency Power Supply.
How to choose the suitable AC resonant test system for Cables?
There are main factors which will affect the capacity and voltage of AC hipoting test system.
1. The Voltage level of the cable.
2. The maximum test length of the cable
3. The cross section area of cable
4. The reactor size and capacity.
Cases of AC hipot testing on site
Huayi brand AC resonant test system has overvoltage, overcurrent, zero start, system mismatch (flashover) and other protection functions, overvoltage and overcurrent protection value can be adjusted according to user needs, flashover protection action when the test product flashover to protect the type product. It has three working modes, which are convenient for users to flexibly choose according to the field situation and improve the test speed. The working modes are: automatic mode, manual mode, automatic tuning manual boost mode.
The AC testing system can store and print data in different places, and the data number stored is a number, convenient to help users identify and find.The starting point of the frequency can be set arbitrarily within the specified range, and the LCD large screen displays the scanning curve, which is convenient for users to intuitively understand whether to find the resonance point. Using DSP platform technology, it can easily increase or decrease functions and upgrade according to user needs, and also make the human-machine exchange interface more humanized.The reactor with the same voltage grade and capacity is smaller in volume and lighter in weight. Low temperature rise at rated load; Dry casting, high mechanical strength, good electrical insulation performance, beautiful and reliable.
Frequently Asked Questions
What is the IEC standard for the cable hipot test?
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IEC 60950 Hipot Test. Applied Technical Services performs IEC 60950 Hipot Test services to help clients verify the safety and reliability of electrical systems. The Applied Technical Services Family of Companies conducts High Potential testing in accordance with IEC 60950 Hipot test standards.
What is the difference between AC and DC high voltage testing?
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High-voltage AC hipot testing applies an alternating voltage to the cable. On the other hand, the high voltage DC hipot testing applies a direct voltage to the cable.
Is VLF testing AC or DC?
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VLF testing utilizes ac signals at frequencies in the range of 0.01 Hz to 1 Hz. The most commonly used, commercially available VLF ac voltage test frequency is 0.1 Hz. It is AC hipot testing.
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Wuhan Huayi Electric Power Technology Co.,Ltd
HUAYI is a professional manufacturer in China that researches and manufactures electric testing equipment. Established in 2005, the company is one of the earliest high-voltage testers manufacturers in China. HUAYI insists on developing and marketing independently and makes efforts to improve the products' quality, reduce cost, and improve efficiency.
HUAYI is committed to preventative, maintenance, troubleshooting, and commissioning. With ISO certification, professional engineering support, and satisfactory customer service, our brand has been recognized and supported by many users.
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