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A dielectric withstand test (or pressure test, high potential or hipot test) is an electrical test performed on a component or product to determine the effectiveness of its 
insulation
Insulation may refer to:
Thermal
* Thermal insulation, use of materials to reduce rates of heat transfer
** List of insulation materials
** Building insulation, thermal insulation added to buildings for comfort and energy efficiency
*** Insulated ...
. 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. If the current through a device under test is less than a specified limit at the required test potential and time duration, the device meets the dielectric
In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the mate ...
withstand requirement. 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.Paul Gill (2009), ''Electrical Power Equipment Maintenance and Testing'', Second Edition, CRC Press, 1574446568, page 459
Voltage
Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...
withstand testing is done with a high voltage source and voltage and current meters. A single instrument called a "pressure test set" or "hipot tester" is often used to perform this test. It applies the necessary voltages to a device and monitors leakage current. The current can trip a fault indicator. The tester has output overload protection. The test voltage may be either direct current
Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or even ...
or alternating current
Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in whic ...
at power frequency or other frequency, like resonant frequency (30 to 300 Hz determined by load) or VLF (0.01 Hz to 0.1 Hz), when convenient. The maximum voltage is given in the test standard for the particular product. The application rate may also be adjusted to manage leakage currents resulting from inherent capacitive effects of the test object. The duration of the test is dependent on the test requirements of the asset owner but is normally up to 5 minutes. The applied voltage, rate of application and test duration depend on the specification requirements of the equipment. Different test standards apply for consumer electronics, military electrical devices, high voltage cables, switchgear and other apparatus.
Typical hipot equipment leakage current trip limit settings range between 0.1 and 20 mACondor Application Note 5/00, pg. 2 and are set by the user according to test object characteristics and rate of voltage application. The objective is to choose a current setting that will not cause the tester to falsely trip during voltage application, while at the same time, selecting a value that minimizes possible damage to the device under test should an inadvertent discharge or breakdown occur.
See also
*Dielectric loss
Dielectric loss quantifies a dielectric material's inherent dissipation of electromagnetic energy (e.g. heat). It can be parameterized in terms of either the loss angle ''δ'' or the corresponding loss tangent tan ''δ''. Both refer to the ...
* Electrical breakdown
* Electrical isolation test
In electrical engineering, an electrical isolation test is a direct current (DC) or alternating current (AC) resistance test that is performed on sub-systems of an electronic system to verify that a specified level of isolation resistance is me ...
* Impulse generator
* VLF cable testing
VLF cable testing (Very Low Frequency) is a technique for testing of medium and high voltage (MV and HV) cables. VLF systems are advantageous in that they can be manufactured to be small and lightweight; making them useful – especially for field ...
* Burn-in
Burn-in is the process by which components of a system are exercised before being placed in service (and often, before the system being completely assembled from those components). This testing process will force certain failures to occur under ...
References
Electrical tests {{engineering-stub