| 摘要 |
<p>The invention relates to an overload protection method for energetic equipments, by using the thermal image analysis, destined to be used for energetical equipments needing overload protection, such as for example power cables, power transformers, engines and electrical generators etc. The method consists in monitoring the temperature of the critical thermal points of the equipment to be protected, determined by computation, comparing it to the limit value and taking the decision to disconnect the equipment when the limit value is surpassed, according to the invention, the method comprising the following stages corresponding to the operating flow of the protection system used: a) reading the current value in the primary circuit of the energetic equipment to be protected; b) comparing the read current value to a preset short-circuit value; c) signalling the fault condition and activating the protection, in case the preset short-circuit value is surpassed; d) calculating the temperature by using the thermal image recurrence formula: teta^(K)^ = teta^(k-1) ^ +deltat [A teta ^(K-1) ^ +B [l^(K) ^]^2^], where: A, B are coeficients, teta^(k) ^ - the temperature at the current pace, the temperature to be calculated, respectively, teta^(k - 1) ^ - the temperature calculated at the earlier pace, delta t - the time interval between two measurements, l^(K) ^ - the current value which circulates through the equipment at the actual pace; d) comparing the calculated temperature value to a preset critical value; e) signalling the overload status and activating the protection, when the preset critical value is surpassed.</p> |
