Portable and Mobile HV Impulse Test Systems for On-Site Applications

While traditional impulse generators reside in large high-voltage halls, there is a growing demand for portable and mobile solutions to perform critical dielectric tests on location. Testing equipment like power transformers, GIS, or long cables directly in the field or at substations avoids the immense cost and risk of transportation and provides valuable diagnostic data on aged or repaired assets. Modern portable systems make this feasible.

Design Innovations for Mobility and Compactness

The core challenge is achieving high voltage and energy output in a drastically reduced footprint and weight. This is addressed through several design innovations. Advanced capacitor technology using high-energy-density film or composite dielectrics provides the required energy storage in a smaller, lighter package. The Marx generator circuit is often housed in an insulated, SF6-filled vessel or a compact, encapsulated module, which minimizes the physical clearance needed between stages. Many systems are modular, allowing multiple units to be connected in series or parallel to scale voltage and energy for different applications, and are mounted on a trailer or within a custom-built service van for true mobility.

Key Applications in Field Testing and Maintenance

The primary application is the on-site lightning impulse test for power transformers. This is often performed after repair, transportation, or a specified service period to confirm winding insulation integrity before re-energization. Portable systems are also used for testing Gas-Insulated Switchgear (GIS) sections, high-voltage cable terminations and joints, and the lightning withstand capability of wind turbine blades. For utilities, a mobile system becomes a powerful diagnostic tool that can be deployed across a network, enabling condition-based maintenance strategies for critical assets.

Operational Considerations and Field Setup

Field testing introduces unique challenges. A robust, low-impedance temporary grounding system using driven ground rods is essential for safety and waveform stability. The test setup must carefully manage electromagnetic interference (EMI) in an electrically noisy substation environment, often requiring fiber-optic links for control and data. Weather protection for the equipment and operators is crucial. Despite these factors, modern portable systems are designed with simplified connections and automated control software, enabling a small crew to set up and execute complex test sequences efficiently.

Advantages and Limitations Compared to Lab Systems

The clear advantage is testing in situ, providing the most relevant assessment of an asset's condition within its actual operating environment. It eliminates the need for costly dismantling and transport. However, trade-offs exist. Portable systems typically have lower maximum energy ratings than large laboratory generators, which may limit their use on very high-capacitance objects. The achievable test voltage is also generally lower, though systems up to 1 MV or more are available. Ultimately, they are a specialized tool that expands testing capability beyond the fixed laboratory.

Conclusion: Extending Testing Capability to the Field

The development of reliable, high-performance portable impulse test systems represents a significant advancement in high-voltage engineering practice. It empowers asset owners to perform rigorous type and diagnostic tests directly in the field, leading to more informed maintenance decisions, reduced downtime, and enhanced grid reliability. As technology continues to miniaturize components and improve energy density, the scope and ease of on-site impulse testing will only increase.