| 摘要 |
The invention relates to systems for protection of electrical circuit with long lines from distant short-circuits with power electric engines being in such circuits. The protection system for branched three-phase electrical circuit from short-circuits includes a protection device (for example a switch) with current sensor and with semiconductive disconnecting switch, which has a device for comparison of current flowing through the protective device with value of a current insert according to current of short-circuit Iand made with possibility setting of low level of inserts Iwithin the limits of (1,53) of protection device working current І, a long main line connected to corresponding leading –off clamps of the protection device. To main line it is connected feeder lines having different type of loads including electric engines. Short-circuit current at the end of the main line Ik3 is equal or less than starting current of electric engine I, connected to the main line in the beginning or in the middle, but being more or equal value of insert current Isd - (IIk3I) . The disconnecting switch of protective device includes also a unit for control of sum of squares of all thee phases currents { Si(t)} and its minimal value {Si(t)} in the first period, when current more than insert Iis appears and also a logical section, which providing that expression presented as Ks={Si(t)}/{Si(t)} being equal or more 1,4 (Kl,4) automatically increases value of insert current Iup to I, which is equal to (1,11,5) of electrical engine starting current. |
