Composite insulator power frequency and lightning impulse tests
Composite insulators are core components in power systems, used in transmission lines and substations to isolate high-voltage conductors and support mechanical loads. Compared with traditional ceramic or porcelain insulators, their composite materials (such as silicone rubber sheds and fiber glass core rods) provide better anti-aging and anti-pollution flashover performance. However, they need to withstand power frequency voltage (normal working conditions) and lightning impulse (abnormal working conditions) during operation, so these two tests are the core of certification and quality control. The tests are designed to simulate the real environment to ensure that the insulators does not flash over, breakdown or mechanical failure, thereby preventing grid failures, power outages and even safety accidents. From a macro perspective, these tests are not only technical means, but also the cornerstone of power system reliability engineering, reflecting the idea of preventive maintenance and risk management (for example, optimizing design life through test data and reducing life cycle costs).
1. Detailed explanation of power frequency test
The power frequency test is a basic test that focuses on verifying the behavior of insulators under steady-state voltage. The power frequency test is based on the principle of AC high
voltage, applying a continuous power frequency voltage (rated value is usually 1.5-2.2 times the system voltage) for 1-5 minutes (according to IEC 61109). The core is to detect dielectric loss and leakage current: the current of intact insulators is stable; if there are internal defects (such as core rod cracks), the current surge causes temperature rise and triggers thermal breakdown. Standard requirements include dry tests (clean surface) and wet tests (simulating rain and fog, such as spray systems to create uniform water droplets). For example, IEC 61109 stipulates that 110kV insulators must withstand 265kV (dry) and 230kV (wet) power frequency voltages. The depth of thought is that it reveals how microscopic defects in materials (such as silicone rubber oxidation) evolve into macroscopic faults-this has promoted the development of nano-filler composite materials (improving dielectric strength).
2. Lightning impulse test
The lightning impulse test focuses on transient high voltage and simulates the extreme conditions of lightning strikes. The lightning impulse test applies a standard waveform (typically 1.2/50μs: wavefront time 1.2μs, half-peak time 50μs), and the voltage amplitude can be as high as hundreds of kV (such as a 550kV system requires a 1250kV impulse). The principle is to detect the response of the insulators under a μs-level pulse: intact parts disperse energy; defective parts concentrate the electric field to cause flashover. Standards (such as IEC 60060-1) require multiple positive and negative polarity impulses (15 times each), and the passing standard is no flashover or damage. The depth of thought lies in simulating the randomness of natural lightning strikes (such as waveform variation), which promotes the application of statistical methods in test design (such as using Weibull distribution to analyze the probability of failure). Compared with power frequency tests, lightning tests pay more attention to “survivability” and embody the concept of system resilience.The lightning impulse test applies a standard waveform (typically 1.2/50 μs: wavefront time 1.2μs, half-peak time 50μs), and the voltage amplitude can be as high as hundreds of kV (for example, a 550kV system requires a 1250kV impulse). The principle is to detect the response of the insulators under a μs-level pulse: intact parts disperse energy; defective parts concentrate the electric field to cause flashover. Standards (such as IEC 60060-1) require multiple positive and negative polarity impulses (15 times each), and the passing standard is no flashover or damage. The depth of thought lies in simulating the randomness of natural lightning strikes (such as waveform variation), which promotes the application of statistical methods in test design (such as using Weibull distribution to analyze the probability of failure). Compared with power frequency tests, lightning tests pay more attention to “survivability” and embody the concept of system resilience.
Power frequency and lightning impulse tests are the “double insurance” for the safe operation of composite insulators: power frequency tests protect steady-state reliability, and lightning impulse tests ensure transient resilience. The collaboration between the two not only verifies technical performance, but also contains system thinking – from micro materials to macro grids, it embodies the risk management philosophy of prevention first. With the rise of smart grids and green energy, these tests will evolve towards digitalization and customization (such as AI-driven adaptive testing).
