| 摘要 |
PURPOSE:To prolong the time for overload operation properly by a method wherein the degree of the deterioration of a transformer is obtained through computation using the transformer oil temperature, the load current and the highest point temperature of the winding to estimate the possible time during which the transformer at overload can be operated. CONSTITUTION:Mean load factor Px' is obtained through computation by a computer from the equation 5 on the basis of the present oil temperature theta'o and the load current (i) in a transformer. The difference theta'w between the final temperature of the winding and the oil temperature at said mean load factor is obtained from the equation 1. Moreover, the value theta'01 of the raised oil temperature and the temperature difference theta'w1 are obtained from the table when the load factor is P1. Subsequently. The value at the rated load and the other when the load factor is P1 are substituted for the equations 2, 3 to obtain the raised oil temperature theta'02 and the temperature theta'w2 at time t2. Then the values thetax1, thetax2 of the raised temperatures during operation are obtained and substituted for the equation 4 to compute the integrated value of Tk per every DELTAt, so that the possible time during which the transformer at overload is operable can be obtained. |
