| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to reduce the maintenance cost by setting the minimum value of a healthy semiconductor so that it has a specific relation with a protection level of a surge arrestor, a coefficient of voltage unbalance between semiconductor elements, a coefficient of allowance, and breakdown voltages of the semiconductor elements. SOLUTION: While an allowance left for the protection level UA of a surge arrestor is KMG, the minimum necessary number of series NRQ for continuous operation is determined by a formula NRQ=(UA×KIB×KMG)/UTH. At that time, a coefficient of allowance KMG itself depends on the design of a thyristor valve, however, design values at the time of designing the thyristor valve are used for the values of a coefficient of voltage unbalance KIB and the protection level of the arrestor UA. Since the design values generally include a certain measure of allowance, actual values of KIB and UA are smaller than the design values. Therefore, if the minimum necessary number of series NRQ is determined using measured values of KIB and UA, the value of NRQ is smaller than the one with the design values. As a result, an inspection interval can be made longer and thereby the maintenance cost can be lessened. |
