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Abstract

Сontent

• Introduction
• 1. Urgency of the issue
• 2. Objective
• 3 Scientific novelty
• 4. The practical value
• Conclusions
• BIBLIOGRAPHY

Introduction

This abstract is a summary to the master's thesis on the theme " Evaluation of fire safety 0.4 kV electric wiring". An issue describes fire electrified space analytical interdependence of three random events based on Markov processes and continuous time. An example of calculation is attached.

1. Urgency of the issue

In Ukraine, due to the short-circuit (SC), overload, current leakage in the ground and due to appearance of weak power contact connections in the networks of 0.4 / 0.22 kV occurs about 20% of the combustible material ignitions in the electrified areas over the total number of existing causes. Annual damage from electrical sources fires averages 150 mln. UAH[1]. At the moment there is no clear answer how and in what extent electrified room fire safety is influenced by the frequency of short circuits occurrence in the controlled network, duration of the circuit breaker tripping reliability of the switching device and the timing of its diagnostics, as well as the fuel material occurrence frequency on the unacceptably close distance from the possible ignition sources occurrence place.

2. Objective

Justify the diagnosis time of the circuit breaker, timing checks of the combustible material presence near the possible network damage occurrence, so that the probability of combustible material ignition in the electrified room during the time was at the level of existing regulations. State of the problem: according to MEM SD in 2011 in Ukraine there was recorded n1 = 11408 fires in the electrified areas from ignition sources of electrical origin, in the same year in Ukraine there were N1 = 19327000 electrified areas. The frequency of fires occurrence in these areas can be estimated as follows:

Using the Moivre - Laplace formula with a confidence level of 0.95 get an interval [2]:

In accordance with the regulationsм[3], the fire risk in the electrified the room during the year should not exceed the value of:

A value of 1 means that statistically 1 fire per year is allowed in 1,000,000 electrified rooms. In Ukraine, the risk of fires in the electrified areas during 2011 for electrical reasons in 590 times higher than the rated values. In order to achieve this goal in this work it is necessary to obtain analytical dependence: the combustible material ignition probability for a time t over the short circuit currents occurrence frequency in the network, reliable, automatic protection, and the terms of its diagnosis, the combustible material occurrence frequency (rags, fibers, dust, sawdust wood, etc.) and the length of stay close to the possible network damage location.

3. Scientific novelty

Scientific novelty of the work focuses on the development and maintenance of 0.4 kV network fire safety which is very important. Getting a new analytical dependence shall consist of the combustible material ignition probability for a time t over the short circuit currents occurrence frequency in the network, reliable, automatic protection, and the terms of its diagnosis, the combustible material occurrence frequency in the vicinity of possible network damage location. Build a "tree" of events, which explains the appearance of fire insulation in low voltage networks due to their various injuries:

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