High Voltage Testing Solutions
High Voltage Testing of electrical equipment covers a wide range of techniques depending on the nature of the equipment and the type of test required. High Voltage testing is usually performed to qualify the device to operate safely during rated electrical conditions, a way to check the effectiveness of its insulation. The objective sought during the high voltage testing will determine the type and amount of voltage applied and the acceptable current flow. If the high voltage testing target is getting the value of the insulation, we are speaking about Insulation Resistance Tests. When we are looking for the breakdown voltage, the point where the dielectric fails allowing much current to flow, it is a Dielectric Breakdown Test, and this high voltage testing is usually a destructive test. When the test checks that the leakage current is below a preset safety limit for an established voltage value (below the breakdown voltage), we are speaking about a Dielectric Withstand Test, which is a non destructive high voltage testing, and through which we are also verifying the insulation integrity of the equipment. All this high voltage testing is sometimes referred to as hipot (high potential) testing, but related testers differs much according to the test objective and whether they are on factory or on site.
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High Voltage Testing in Transformers
It is typical the use of high voltage testing on transformers to confirm performance. The main high voltage tests are included in type and routine tests made by the manufacturer in the factory to meet the required standards, quality and reliability. Some of them are insulation resistance tests, dielectric type tests, lightning and switching impulse tests, partial discharge measurement, etc. This high voltage testing checks the insulation between primary to earth, secondary to earth and between primary & secondary, using generators of up to 100 KV range and higher, while the on-field testers for maintenance purposes are much lower range.
Other high voltage testing is carried out at site, during commissioning tests and/or periodic maintenance. One of the most typical is the withstand voltage test, to check if the transformer dielectric strength is in suitable condition for the service, or during maintenance programs to demonstrate the equipment keeps capable of withstanding overvoltages during operation. The overvoltage is usually applied during 60 seconds, between primary and secondary of the transformer, or between secondary and ground. This high voltage testing is successful if the measured current does not cause the insulation to break, being lower than the maximum leakage current allowed, so that the product will be safe to use under normal operating conditions. Now, this kind of testing is available in the SMC Raptor System.
The Raptor System upgraded with the high voltage testing functionality
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The Raptor HV, a high voltage testing slave, complements the Raptor System, extending the Raptor applications for testing transformers, among others. The Raptor is an innovative and advanced substation test system that replaces the need for multiple test sets, now enhanced with the high voltage testing capability. The HV works in combination with the Master unit, and provides the same outstanding Raptor style portability, being easily moved around with little effort. The Raptor HV kit goes up to 2,000 volts and the current kits goes up to 15,000 amps, providing a world-wide unique system which combines both high current and high voltage testing with the required power for the main maintenance and commissioning test applications in substations and switchgear. The unit also complies with international safety requirements indicating high voltage activity and emergency stop button.
The main high voltage testing applications of the Raptor HV are as follows:
- CT, VT and PT withstand voltage tests
- CT and VT excitation curve /knee point.
- VT and PT ratio measurement.
- Polarity test in VT’s secondary winding.
- Step & touch voltage measurements.
- Testing voltage sensors and converters.
For more information, please check the related SMC products.
For additional Information about high voltage testing solutions, see the following contents
- High voltage test: Range of EuroSMC products suitable for high voltage test applications in transformers, motors and generators; overview of Raptor.
- HV test equipment: Extended applications in the Raptor System with a HV test equipment, the Raptor HV slave. A unique high current and high voltage substation test system.
- HV test: Range of EuroSMC products suitable for HV test applications in transformers; overview of Raptor CV-05.