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Examoogle • User • info@examoogle.com • EE-2024-8821
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If voltage surge represented by 5/50 µs then at 5 µs value of voltage will be
Zero
Peak
Half of the Peak
None of above
Peak
Quick Summary: A standard lightning impulse voltage waveform is denoted as $T_1/T_2$ µs, where $T_1$ represents the front time (rise time) and $T_2$ represents the tail time. In the notation $5/50$ µs, the value $5$ µs corresponds to the time taken to reach the peak amplitude of the surge.
A standard lightning impulse voltage waveform is denoted as T1/T2 µs, where T1 represents the front time (rise time) and T2 represents the tail time. In the notation 5/50 µs, the value 5 µs corresponds to the time taken to reach the peak amplitude of the surge.
Tfront=1.25×(t90%−t10%) — Calculation of virtual front time
Ttail — Time to reach half peak value on the tail
The surge waveform starts from zero, rises to its peak value at T1, and decays to half of its peak value at T2. The front time T1 is defined as 1.25 times the interval between the points where the wave is 10% and 90% of its peak value, effectively representing the peak reaching time.
The notation T1/T2 is specified by IS 2071 standards for impulse testing.
The wave shape is vital for dielectric testing of transformers and circuit breakers.
The 5 µs point marks the crest of the surge in this specific waveform.
The tail time (50 µs) is measured to the point where voltage drops to 50% of its peak.
Simulates real-world lightning strikes on power lines
Essential for insulation coordination studies
High equipment cost for impulse generators
Strict safety protocols required during testing
Testing transformer insulation
Testing high-voltage circuit breaker BIL (Basic Insulation Level)
Commonly used standard impulse wave is 1.2/50 µs, though 5/50 µs is used in specific research or older standards.
Option A is incorrect as voltage is zero at t=0.
Option C is incorrect as 50% of peak value is reached at 50 µs.
B is correct — In the standard notation T1/T2 µs, T1 represents the front time, which is the time taken to reach the peak value of the surge.
Always remember that the first number in T1/T2 is the rise time to peak, and the second number is the duration to decay to half-peak on the tail.