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Examoogle • User • info@examoogle.com • EE-2024-8821
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Mostly the timing of voltage surge represent in
Second
Micro second
Mili second
Minute
Second
Quick Summary: Voltage surges, often caused by lightning strikes or switching operations, are characterized by extremely fast rise times. Due to their transient nature, the duration of these surges is measured in microseconds (\mu s) rather than larger units like milliseconds or seconds.
Voltage surges, often caused by lightning strikes or switching operations, are characterized by extremely fast rise times. Due to their transient nature, the duration of these surges is measured in microseconds (μs)rather than larger units like milliseconds or seconds.
Tfront≈1.67×(t90−t30) — Formula for virtual front time of a surge
Ttail≈50μs — Standard duration for surge voltage decay
A voltage surge or lightning impulse is defined by the standard wave shape 1.2/50μs. The first value (1.2μs) represents the virtual front time (time to reach peak voltage), and the second value (50μs) represents the virtual time to half-value on the tail. These transients occur almost instantaneously, requiring high-speed protection devices like surge arresters.
Surge voltages are rapid transients with steep wavefronts.
The standard impulse test voltage wave is defined as 1.2/50μs.
Lightning impulses are significantly faster than switching surges, which are typically measured in hundreds of microseconds.
Protection coordination relies on these specific time scales to ensure arresters operate before equipment insulation fails.
Allows for precise testing of insulation withstand levels
Enables coordination between insulation levels (BIL) and protection devices
Extremely difficult to measure without high-bandwidth oscilloscopes
Can cause destructive breakdown in dielectric materials due to high dv/dt
Transformer insulation testing
Surge Arrester (LA) discharge performance analysis
Power system transient stability simulation
The surge duration is defined by the interval between the instant the voltage rises to 10% and 90% of its peak value.
Milliseconds are usually associated with relay operating times or circuit breaker opening times, not the primary surge event itself.
B is correct — Voltage surges exhibit extremely fast rise times and short durations, necessitated by the transient nature of electromagnetic disturbances, which are measured in microseconds (10°−6 seconds).
Always remember that lightning surges are faster (1.2/50μs) than switching surges (usually 250/2500μs); distinguishing these helps in selecting proper insulation levels for transmission equipment.