Helen Marinenko

Faculty: Electrical

Speciality: Electrical engineerings systems of electro-consumption

Theme of master's work: Estimation of reliability of substation 110/10 кV, taking into account restoration elements of system and also terms of diagnostics of protection frames

Scientific adviser: Aleksandr Kovalyov

Abstract

Background The basic method of assessing the reliability of structural and complex schemes are currently the methods based on compiling the scheme of minimum cross-sections [1]. This means that the concept of the substation to assess its reliability must be submitted in the form of a special scheme of substitution, which in many cases is not an easy task. Therefore, the development and use of new ways to transform the structure of complex schemes of electricity supply systems is an urgent scientific and practical tasks.

Scientific value An improved method of transformation of the "triangle - star" and "star - triangle" for restoring network elements is taken into account the timing of diagnostic equipment.

Objective: The usage of the method of transformation of the "triangle - star" and "star - triangle" and bringing the structure of complex schemes to structures consisting of serial and parallel connection of elements based on their recovery failures.

Practical value The method of calculating the reliability of complex structure of the scheme is taken into account to recover the elements which accuracy does not differ from the methods proposed in [1] for more than 5% [1].

Status issue. Nowaday to assess the reliability of complex structure of the schemes are used calculation methods based on the schemes that the minimum cross sections, ie circuits consisting of series - connected parallel groups. Each element of the group is characterized by its parameter . The failure flow parameter and restorations, respectively . For a simple equivalent circuit consisting of serial, parallel or mixed compounds of elements, the equivalent parameters of flows of failures and recoveries, respectively we find as follows [4]:

1. Serial Communication:

2. Parallel connection:

           Formula (1) and (2) are valid when the operation element of the system can be described by alternating intervals of time of work: and . Random intervals и not contradict the exponential distribution function, that is . All values и are mutually independent and the condition:

Figure 1 - Possible realization of electrical

The results of the study.

           Equivalent circuits of power supply system does not always consist of sequential, parallel or mixed compounds of elements. There are more complex schemes bridging [1]. Under the system of power supply with a complex scheme we mean such scheme, which includes at least one group of elements having the bridging scheme. For these schemes are encouraged to use way to convert a delta-star. This method differs from the known [5] that allows the conversion of complex schemes of substitution, take into account the elements of recovery and timing of their diagnosis. The essence of the proposed conversion of the "triangle - star" is that combination of elements in the form of a triangle is replaced by an equivalent connection reliable in the form of stars, ie problem reduces to determining the intensities of equivalent failures and restore "stars" through similar reliable parameters of the triangle Figure. 1 a, б shows two schemes of combining the elements - a triangle and a star. Let each element of the triangle has a failure rate and restorations Similar parameters of reliability is the star and restorations . These structures are equivalent in terms of reliability, if the intensity of failures and recoveries between nodes 1-3, 1-2, 2-3 triangle are equal intensities of the failure and restoration between the nodes of the star. Between nodes 1-3 triangle one way passes through the element 1 and the second - through the elements 2 and 3. For nodes 1-3 stars there is only one path through the elements i and k. Equivalent circuits are shown in Fig. 1.в. Similarly prepared equivalent circuit for ways to 1-2 and 2-3 of the triangle, and stars (figure. 2. д, e).
           These structures are equivalent in terms of reliability, if the intensity of failures and recoveries between nodes 1-3, 1-2, 2-3 triangle are equal intensities of the failure and restoration between the nodes of the star. Between nodes 1-3 triangle one way passes through the element 1 and the second - through the elements 2 and 3. For nodes 1-3 stars there is only one path through the elements i and k. Equivalent circuits are shown in Fig. 2. в. Similarly prepared equivalent circuit for ways to 1-2 and 2-3 of the triangle and the star (figure. 2. д, e).
           Using these equivalent circuits, using formulas (1), (2) are equivalent failure rate and rehabilitation for all the ways the success of element of the triangle and star. Equating the corresponding failure rate and the renovation of the successful functioning of the elements of the triangle and the star, we obtain a system of six linear algebraic equations:

          Expressing the intensity of failures and restorations elements of the star through the intensity of failure and restoration elements of the triangle, we obtain:

          If you want to reverse transition from star to triangle, then using the same system of equations (3) we obtain:

                              

                               Figure 2 - Plans star and triangle

                              

                               Figure 3 - Indicators of reliability of the scheme

          Calculation of reliability of complex circuits of power supply systems taking into account the recovery of elements and using the transformation of "triangle - star" less laborious than with currently used methods, requires a special equivalent circuits minimal sections.

Conclusions:

1. A new variant of the transformation of combining the elements in the form of a triangle in terms of reliablу equivalent combination of elements in the form of stars, takes into account the restoration of the elements, allowing the complex bridge circuits lead to a simple series-parallel.

2. Based on the proposed changes has been designed method of calculating the reliability of complex schemes restoring power supply systems, which differs from the existing order, that does not require the preparation of a logical scheme of substitution minimal sections. As calculated is used a concept of electricity.

3. The accuracy of the proposed method is comparable to existing being validated [1 and 2, 3].

          In writing this essay master's work was not completed. The final work you can be obtained from the author or supervisor since December 2010.