Megger MPQSIM, Руководство пользователя

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ADDENDUM C - SAMPLE POWER QUALITY TRAINING
AVTMMPQSIM Rev 1 May 2017
49
Transients are caused by lightning or almost any switching event on the power
system.
Transients can be categorized into several categories.
Oscillatory transients: These are typically low frequency transients in the few
hundred Hz range. They are caused by capacitor bank
switching.
Impulse transients: These are typically high frequency transients in the few hundred
KHz range. They are caused by lightning or equipment
switching operations. They can be either uni-directional or bi-
directional.
Impulsive transients can pass through transformers and appear on the low side of the
transformer. They are not reduced by the turns ratio. This can cause damage on
equipment connected to the low side of the transformer.
Extremely Fast Transients (EFT): These typically have rise times in the nano-
seconds. The EFT has limited energy and is
typically dampened out by just a few meters of
wire.
These only become an issue in locations with short cable runs, such as off shore
platforms or mines.