Frequency of exceedance any peak exceeding is . Its complement, is the probability of exceedance, the probability that has been exceeded at least once by time . This probability can be useful to estimate whether an extreme event will occur during a specified time period, such as the lifespan of a structure or the duration of an operation. If is small, for example for the frequency of a rare event occurring in a short time period, then Under this assumption, the frequency of exceedance is equal to the probability of exceedance per unit time, , and the probability of exceedance can be computed
Per-unit system are the same. Here, the per-unit voltages of the two sides are E and E respectively. formula_28 ‘E and E are the voltages of sides 1 and 2 in volts. N is the number of turns the coil on side 1 has. N is the number of turns the coil on side 2 has. V and V are the base voltages on sides 1 and 2. formula_29 For current, we can prove that the per-unit currents of the two sides are the same below. formula_30 where I and I are the per-unit currents of sides 1 and 2 respectively. In