RU2550337C2 - Method for determining residual life of automatic circuit breakers - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: method for determining residual life of automatic circuit breakers in electrical installations provides for measurement and storage of current value i_j that caused actuation of the circuit breaker at each j deactivation, where j=1, …, n, and calculation of coefficient k₁(i_j) characterising allowable number of actuations depending on the switched current i_j, and additionally, it provides for continuous measurement of current i passing through the automatic circuit breaker. And residual life of the automatic circuit breaker is determined by the formula: $$T(t)=T_0-{\displaystyle \sum _{j=1}^n{k}_1(i_j)-k_2{\displaystyle \underset{0}{\overset{t}{\int }}{i}^{2}dt}},$$

where T₀ - service life of an automatic circuit breaker; k₂ - weight coefficient equal to design coefficient of life wear of the automatic circuit breaker, n - total number of actuations of the automatic circuit breaker from the beginning of operation, t - full time of operation of the automatic circuit breaker.

EFFECT: providing high-accuracy continuous assessment of residual life of a circuit breaker considering its reduction due to passage of operating currents.

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Description

The present invention relates to electrical engineering and is intended to control the residual life of circuit breakers in electrical installations.

Known methods for determining the residual life of circuit breakers, which measure the current flowing through the circuit breaker, consider the number of trips of the circuit breaker during overloads, and then calculate its residual life (GOST R 52565-2006. AC circuit breakers for voltage from 3 to 750 kV. General technical conditions. - M., Standartinform, 2007. - P.17, Table 13; Guidelines for determining the consumption of switching resource of circuit breakers during operation. - M., ORGRES, 1992. - 19 p.).

In accordance with known methods, the residual life of circuit breakers is determined based on the control of the number of trips taking into account the switched current. This does not take into account the decrease in resource due to the flow of working currents that cause heating, vibration, etc.

Of the known technical solutions, the closest to the proposed one according to the achieved result is a method for determining the residual life of circuit breakers, in which the current i _{j is} measured, which triggers at each j-th trip, j = 1, ..., n, and the coefficient k _x (i _j ), which characterizes the permissible number of operations depending on the switched current i _j , and calculates the residual resource as the difference between the total resource T ₀ and the sum of the values of the coefficients k ₁ (i _j ) for all operations (Neklepaev B.N., Vostrosablin A.A. Met Odika estimates the residual life of circuit breakers during operation // Industrial Energy, 1992, No. 10, pp. 31-32).

When implementing the known method, the residual resource is determined based on the switching component of the exhaustion of the resource at various currents. In this case, the influence of the current flowing through the circuit breaker is not taken into account in normal conditions and during overloads that affect the wear of the electrical apparatus.

Therefore, a disadvantage of the known method for determining the residual life of a circuit breaker is its low accuracy.

The purpose of the invention is to increase the accuracy of determining the residual life of circuit breakers.

This goal is achieved by the fact that in the known method for determining the residual life of circuit breakers, in which measure the current that causes a trip at each j-th trip, j = 1, ..., n, determine the coefficient k ₁ (i _j ) characterizing the allowable number of trips depending on the switched current, additionally continuously measure the current i flowing through the circuit breaker, and determine the residual life by the formula

where T ₀ is the total resource of the circuit breaker; k ₂ is the weight coefficient equal to the calculated coefficient of the resource wear of the circuit breaker, n is the total number of trips of the circuit breaker from the start of operation, t is the time.

Compared with the closest similar solution, the proposed technical solution has the following new features:

- measure the current i flowing through the circuit breaker;

- measure the time of continuous operation t;

- determine the residual life by the formula

Therefore, the claimed technical solution meets the requirement of "novelty."

For each distinguishing feature, a search is made for well-known technical solutions in the field of mechanical engineering, electrical engineering, computer modeling and programming.

The operation of measuring the current i flowing through the circuit breaker, measuring the time t of continuous operation and determining the residual life by the formula

where k ₂ is the weight coefficient equal to the estimated coefficient of resource wear of the circuit breaker, in the known methods of similar purpose are not found.

Thus, these features provide the claimed technical solution according to the requirement of "significant differences".

In the present invention, when determining the residual life of a circuit breaker, not only mechanical factors (the number of trips at various currents) causing wear, but also electrical factors, namely, changing currents flowing in normal conditions causing heating and aging of insulation and switching elements, are taken into account.

Therefore, the claimed technical solution meets the requirement of "positive effect".

The essence of the invention is as follows. The physical resource of a circuit breaker during its operation is consumed as a result of wear of mechanical and electrical components when exposed to flowing currents, mechanical shock loads and electromechanical switching processes during shutdowns. The wear rate is determined by the energy of the impact on the switch and can be represented by the sum of two components: electromechanical during shutdowns and electrical when current flows in the operating mode. The electromechanical component of wear occurs during outages and depends on the amount of current breaking during switching. The exhaustion of the resource during shutdown is regulated by the manufacturers of circuit breakers (Andreev D.A., Nazarychev I.A. Analysis of methods for assessing the switching resource of high-voltage switches // Vestnik IGEU, 2008, issue 2, p. 1-16). The electrical component of wear is proportional to heat loss and, consequently, to the integral of the current squared (Kabyshev A.V., Tarasov E.V. Low-voltage circuit breakers. - Tomsk, Publishing House of the Tomsk Polytechnic University, 2011, S.15-16).

The drawing shows a functional diagram of a device that implements the proposed method for determining the residual life of circuit breakers. The diagram shows: 1 - circuit breaker; 2 - sensor operation of the switch, for example a block contact; 3 - current sensor; 4 - load; 5 - controller; 6 - data bus; 7 - operator panel; 10 - computer.

The system operates as follows. The signals from the protection actuation sensor 2 and current sensor 3 of the circuit breaker 1 connected to the load 4 are fed to the inputs of controller 5. Controller 5 performs the following functions:

- analog-to-digital conversion of the output signal of the current sensor;

- storing the value of current i _{j of the} circuit breaker, which caused its operation at each j-th trip, j = 1, ..., n, and calculating the coefficient k ₁ (i _j ) depending on the current;

- countdown of time t from the start of operation of the circuit breaker;

- calculation of the residual life of the circuit breaker according to the formula

- data transfer on the number of trips, the currents that triggered the trips, as well as the remaining resource in the computer 10 for memorization, storage and further use.

In formula (1), to calculate the residual life of a circuit breaker, the terms on the right-hand side have the following meaning:

- T ₀ - full rated service life of the circuit breaker (number of switching), corresponding to the technical conditions;

- составляющая, характеризующая электромеханическое изнашивание автоматического выключателя;-

- a component characterizing the electromechanical wear of a circuit breaker;

- составляющая, характеризующая электрическое изнашивание автоматического выключателя;-

- a component characterizing the electrical wear of a circuit breaker;

- k ₁ (i _j ) is the coefficient characterizing the mechanical wear of the circuit breaker due to the breaking of the current circuit during operation. It is determined in accordance with GOST R 52565-2006 (AC circuit breakers for voltage from 3 to 750 kV. General specifications. - M., Standartinform, 2007. - P. 17, table) and is equal to the ratio of the regulated number of switching without load to the number of commutation at current i _j

Quantitative data regarding the resource are indicated in the technical data of circuit breakers and reference books (for example: Circuit Breakers. Nomenclature Catalog. - Divnogorsk Plant of Low-Voltage Automats OJSC. - Divnogorsk, 2008. - 94 pp.);

- k ₂ - coefficient characterizing the electrical wear of the circuit breaker due to the flow of current during operation. The wear of the circuit breaker depends on the power released at the closed contacts. Approximately this coefficient is determined by the formula

where I _n is the rated current of the circuit breaker.

In accordance with formula (2), at minimum current, electrical wear is practically absent. With an increase in switching current, electrical wear increases compared to conventional mechanical wear.

The results of measurements and calculations are displayed on the monitor. Thus, in the process of operating a circuit breaker, its residual life is continuously evaluated taking into account the electromechanical and electrical components. The current rating is stored in the controller memory, displayed on the monitor and can be used for timely replacement or repair of the circuit breaker.

Therefore, the use in a known method for determining the residual life of circuit breakers, in which the current causing the trip at each jth trip, j = 1, ..., n, is measured, the coefficient k _x (i _j ) is determined, which characterizes the permissible number of trips depending on the switched current additionally continuous measurement of the current i flowing through the circuit breaker, and determining the residual life by the formula

where T ₀ is the total resource of the circuit breaker; k ₂ is the weight coefficient equal to the calculated coefficient of the resource wear of the circuit breaker, n is the total number of times the circuit breaker has been activated since the start of operation, t is the time, which improves the accuracy of determining the residual life of the circuit breaker.

Using the proposed method for determining the residual life of circuit breakers in power supply systems will improve the reliability and survivability of electrical equipment.

Claims (1)

A method for determining the residual life of circuit breakers, in which the current causing the trip at each jth trip, j = 1, ..., n, is measured, a coefficient k ₁ (i _j ) is determined that characterizes the permissible number of trips depending on the switched current i _j , characterized in that it additionally continuously measures the current i flowing through the circuit breaker, and determines the residual life by the formula

where T ₀ is the total resource of the circuit breaker; k ₂ is the weight coefficient equal to the estimated coefficient of the resource wear of the circuit breaker, n is the total number of times the circuit breaker has been activated since the start of operation, t is the total operating time of the circuit breaker.