1. Definition and Core Purpose of Impulse Voltage Test
The Impulse Voltage Test aims to evaluate the insulation performance of electrical equipment, serving as a crucial testing method. Its core purpose is to simulate transient overvoltages (such as voltage impulses caused by lightning strikes or switching operations) that equipment may encounter during actual operation, verify whether the insulation system can withstand such instantaneous high voltages without breakdown or damage, and ensure the safety and reliability of equipment under extreme electrical conditions.
2. Test Principle and Basic Process of Impulse Voltage Test
2.1 Principle:
The test generates high-frequency, high-amplitude pulse voltages (typically standard lightning waves like 1.2/50μs or switching waves 30/600μs) through an impulse voltage generator and applies them to the insulating components of the device under test (such as transformer windings, cable insulation, insulators, etc.), observing whether the insulation can withstand the voltage without failures like breakdown, flashover, or partial discharge.
2.2 Typical Process:
Step 1: Equipment Preparation: Connect the device under test to the impulse voltage generator and ensure the grounding system is safe.
Step 2: Pre-test: Apply a low-amplitude voltage first to calibrate the waveform and confirm the normal operation of the test system.
Step 3: Test process: Apply the specified amplitude of impulse voltage as per standards (usually 3-5 times), with an interval between each test.
Step 4: Result Judgment: Monitor voltage waveforms and current changes through oscilloscopes and other equipment to check whether the insulation is damaged (e.g., sudden current increase and voltage drop during breakdown).
3. Common Application Scenarios
| Application Field | Test Objects | Purpose |
| Power System | Transformers, high-voltage cables, insulators | Verify the ability to resist lightning and switching overvoltages |
| Electrical Equipment | High-voltage switches, surge arresters | Ensure insulation reliability under transient overvoltages |
| Electronic Components | Integrated circuits, high-voltage capacitors | Evaluate the voltage withstand limit of semiconductor devices or components |
| New Energy Field | Wind turbines, photovoltaic inverters | Ensure equipment adapts to extreme conditions like grid fluctuations and lightning strikes |
4. Key Standards and Waveform Requirements
4.1 International Standards:
IEC 60060 Series: Specifies the generation, measurement, and testing methods for impulse voltages.
IEEE Std 4: Sets standards for impulse voltage tests of electrical equipment.
4.2 Typical Waveform Parameters:
Lightning Impulse Waveform: 1.2/50μs (wave front time 1.2μs, half-peak time 50μs), simulating lightning overvoltages.
Switching Impulse Waveform: 30/600μs or 250/2500μs, simulating overvoltages caused by switching operations.
5. Result Evaluation and Failure Types
5.1 Qualification Criteria:
The device under test is qualified if it shows no breakdown or flashover under the specified number of impulses, and the insulation resistance does not decrease significantly.
5.2 Common Failure Modes:
1). Breakdown: Insulation materials are damaged, forming a conductive path, leading to voltage failure.
2). Flashover: Surface discharge occurs, usually caused by contaminated or humid insulation surfaces.
3). Partial Discharge: Discharge in tiny voids inside the insulation, which may cause insulation degradation over time.
6. Extended Application: Differences from Power Frequency Withstand Voltage Test
Items | Impulse Voltage Test | Withstand Voltage Test (Power Frequency ) |
Voltage Characteristics | High-frequency pulse voltage (transient) | 50/60Hz power frequency AC voltage (steady state) |
Voltage Waveform | Standard lightning wave (e.g., 1.2/50μs) or switching wave | Sinusoidal wave |
Simulated Scenarios | Transient overvoltages, such as lightning and switching operations | Long-term operating voltage and slight overvoltages |
Test Duration | Microsecond-level (μs) for a single pulse | 1 minute duration or longer |
Insulation Assessment Focus | Insulation strength under instantaneous electric field concentration | Insulation stability under long-term electrical stress |
Main Application Scenarios | Type tests for high-voltage equipment, verification of lightning resistance | Routine testing of equipment, insulation acceptance after maintenance |
The impulse voltage test focuses on verifying the equipment’s “insulation strength under extreme conditions”. Generating non-sinusoidal pulse waves through an impulse voltage generator to simulate extreme transient overvoltages, and confirm whether the equipment can resist breakdown caused by lightning or switching operations. The withstand votlage test, however, focuses on evaluating the “insulation stability in long-term operation”. Checking for local defects such as moisture or cracks to assess aging risks during long-term operation. Combining the two can comprehensively evaluate insulation performance from both “transient impact” and “steady-state stress” dimensions, making them indispensable in quality control and safety verification of electrical equipment.
For test specifications in specific industries or equipment selection advice, please contact PEGO for professional solutions.
