Design and manufacturing problems can cause premature equipment failure. To minimize that risk, Doble&#;s high-voltage laboratory offers a wide range of qualification and acceptance tests for medium-voltage and high-voltage rotating machines up to AC kV, DC 400 kV and Impulse kV.
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Doble&#;s team has more than 100 years combined experience with testing and evaluating generator and motor insulation systems, including large rotating machine stator bars and coils. Serving satisfied customers for over 80 years, our laboratories can perform over 200 laboratory tests on both solid and liquid insulation.
In addition to laboratory testing, Doble specialists have extensive field testing experience in power factor, partial discharge, electromagnetic signature analysis, EL CID and AC/DC Hi-Pot testing as well as visual inspection, condition assessment and failure investigation of generators, motors, transformers, cables and other power apparatus.
The voltage endurance test is performed according to IEEE- and IEEE-. An AC high voltage is applied to the coils for 400 hours. The heaters are set to 90°C &#; 120°C and thermocouples are placed in the heater plates to monitor temperature. Several diagnostic tests, such as polarization index, Hi-Pot, partial discharge, dissipation factor and tip-up, are carried out.
To pass the test, the coils should not fail in less than 400 hours (time length depending on voltage). Failing the voltage endurance test can indicate a manufacturing quality issue even if similar coils have previously passed the voltage endurance test.
An impulse test can be performed per IEEE 522- to evaluate turn-to-turn insulation in multi-turn coils.
Doble can perform insulation breakdown tests on stator coils and bars. The failure site can be dissected.
Dissection locations are chosen by an experienced generator insulation specialist to discover the weakest insulation spots. If a coil fails voltage endurance testing, a dissection is required at the failure location. A Doble specialist will determine the cause of failure based on knowledge and experience of the generator insulation system. Microscopic examination on dissected samples can be conducted to check any manufacturing quality issues.
The primary purpose of high-potential testing is to evaluate the dielectric strength of electrical components. Dielectric strength refers to the ability of an insulating material to withstand high voltages without breaking down. The test determines whether the insulation in a device or system can handle voltage levels higher than its standard operating voltage, ensuring a safety margin. During the dielectric strength test, the current limit is carefully monitored to ensure normal operation in compliance with the established test standards, validating correct operation for each production unit at one point.
High-potential test standards help identify weaknesses in insulation, such as cracks, pinholes, or other defects that could compromise the safety and reliability of the equipment. It is crucial in preventing electrical failures that could lead to malfunctions, downtime, or even safety hazards.
High-potential testing ensures that electrical equipment complies with safety protocols and regulations, providing a measure of confidence in the product&#;s safety and reliability. Adhering to established safety protocols is essential for both manufacturers and end-users to mitigate the risks associated with electrical systems.
Integrating high-potential testing into the manufacturing procedure helps verify the quality of the production units, ensuring that each device meets the specified safety and performance criteria. Ensuring consistency and reliability throughout the entire production line makes this step essential.
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The key elements encompass various facets crucial to its effectiveness. These include the following:
Test Voltage: The applied voltage during high-potential testing surpasses standard operating levels to stress-test the insulation.
Insulation Resistance and Leakage Current: Measures the resistance of insulation and identifies leakage current, indicating potential insulation problems.
Safety Test Equipment: Advanced dielectric strength tests are equipped with safety mechanisms, current limits, and negative peak voltage detection to enhance consumer protection.
Proper Insulation for Client Protection: High voltage testing ensures that electrical equipment has proper insulation, reducing the risk of electric shocks and other safety hazards for end-users.
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Protective Circuits: Hipot tester are equipped with productive circuits to limit the current and prevent sudden and uncontrolled flows, enhancing overall client safety during testing.
Client Safety Standards: Adherence to safety protocols is a critical aspect of hi-pot testing. Manufacturers must follow established safety guidelines to ensure the safety of both testing personnel and end-users.
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Circuit Phase Conductors and Stray Wire Strands: High-potential testing assesses the insulation integrity of conductors, identifying potential hazards from uncontrolled wire strands.
Circuit integrity testing and Tolerance Errors: Ensures Circuit integrity and identifies Marginal errors in the manufacturing procedure.
Sudden and Uncontrolled Flow and Test Setup: Detects issues related to sudden and uncontrolled current flows, optimizing the experimental setup for accuracy.
Earth Ground and AC Test Voltage: Addresses concerns related to earth ground and assesses the device&#;s response to AC voltages.
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DC voltage and AC High-potential Testing: AC test voltage strains the insulation when it reaches its peak, whether positive or negative. The DC hi-pot test, on the other hand, can only test one polarity.
Voltage Transient and Safety Circuits: Advanced dielectric strength hipot tester accounts for test voltage transients and incorporates security circuits for enhanced client safety.
Maximum Allowable Current and Open Circuit Breakers: Monitors the maximum allowable current and detects issues with open circuit breakers.
Transient Over voltages and Enlarged Solder Footprint: Identifies transient over-voltages and assesses potential concerns like enlarged solder footprints on circuit boards.
Hipot testing is a vital step in the production process of electrical equipment, contributing to the safety and reliability of electrical systems. It helps identify potential issues with insulation, ensures compliance with safety protocols, and verifies the quality of production units, ultimately minimizing the risk of electrical failures and enhancing user welfare.
It ensures that the equipment can withstand higher-than-normal voltages, reducing the risk of electrical failures.
AC Hipot testing involves applying an alternating current, while DC Hipot testing uses a direct current. The choice between AC and DC testing relies on the specific needs of the tested device.
Hipot testing ensures that electrical equipment has solid insulation, reducing the risk of electric motors and other safety hazards for end-users.
Following established safety guidelines helps mitigate the risks associated with electrical systems and ensures that the tested equipment meets the required safety and performance criteria.
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