This paper deals with logical-and-probabilistic method in simulating to estimate the reliability of complicated power-supply systems. It gives us information about procedure of logical-and-probabilistic method in simulating, also one example of calculating the reliability of complicated power-supply system (gas compressor station “Torzhokskaya” OJSC Gazprom). Here you can find how reliability of system itself depends on reliability of its components.

Necessity of the further reliability augmentation of an electric-power supply of users of the electric power for the gas industry at reduction of growth of expenditures by decentralized power supply stipulates use of power stations of own needs of small capacity for sufficing necessities of the factories in the electric power. To these power stations the series of habits is inherent, which should be examined carefully to provide high-scale of reliability of development and a distribution of electricity.

The electrical networks of voltage 0,4 kilovolt are the most widespread ones, they are used at all industrial and agricultural enterprises, power stations and substations. Fail-safe operation of enterprises depends to a large extent on these networks. A problem of remote reservation of failures of guards and cutout switches has always been very acute in the networks of 0,4 kilovolt. Due to a very substantial reduction of values of short-circuit currents as the distance between a point of fault and power supplies increases, it was not possible to carry out this reservation by the same traditional methods as in high-voltage power networks. This problem has been found possible to be solved only in recent years when digital technology began to be used for protection of electrical networks.