Author Archives: Zakaria El Intissar

The Applied Voltage Test (AV) is a fundamental dielectric test performed on power transformers to verify the integrity of insulation between windings and earth. Unlike impulse tests that simulate lightning or switching surges, the Applied Voltage Test checks the transformer’s ability to withstand power-frequency overvoltages under controlled conditions. Defined in IEC 60076-3, the Applied Voltage Test is a… Read More »

The Switching Impulse Test (SI) is a critical dielectric test used to verify the insulation strength of high-voltage and extra-high-voltage power transformers under slow-front overvoltage conditions. Unlike lightning impulse tests, which simulate very fast surges, the switching impulse test represents overvoltages caused by system switching operations, such as line energization, fault clearing, or circuit-breaker reclosing. IEC 60076-3 defines… Read More »

The Neutral Terminal Lightning Impulse Test (LIN) is a specific dielectric test defined in IEC 60076-3 for power transformers. Unlike the standard lightning impulse test applied to line terminals, the LIN test is applied directly to the neutral terminal of a winding to verify the adequacy of its insulation under lightning-type overvoltages. Although the LIN test is not… Read More »

The Chopped Wave Lightning Impulse Test is one of the most severe dielectric tests performed on high-voltage power transformers. While a normal lightning impulse test checks how a transformer handles a standard 1.2/50 μs surge, the chopped wave represents a much sharper, more dangerous type of overvoltage that can happen in real power systems. IEC 60076-3 requires the… Read More »

Lightning Impulse (LI) testing is one of the most important dielectric tests used in transformer manufacturing. It ensures a transformer can survive the types of electrical stresses created by lightning strikes on overhead power lines. Even if a substation has surge protection, a transformer may still experience fast and intense voltage surges. For this reason, every medium- and… Read More »

When engineers design a power transformer, one of the most important decisions they make is how strong the insulation needs to be. Proper insulation ensures that the transformer can survive real-world electrical stresses such as lightning, switching operations, and temporary overvoltages. IEC 60076-3 is the international standard that governs how these insulation levels are defined and how they… Read More »