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Abstract

Contents

Introduction

For the first time in the world, the notion of survivability has been formulated Osipovich Russian Admiral Stepan Makarov - the ability of the vessel to continue the fight, with damage in a variety of combat units [1].

In the energy sector under the survivability is the property of the object to resist perturbations, not allowing them to cascade of massive malnutrition consumers [4].

1. Theme urgency

The impetus for the development of methods for evaluating and predicting failures in the power chain (ES) has served as the accident, which occurred November 9, 1965 in the United States, which has led to the fact that in a territory with a population of about 30 million people in more than 10 hours of electricity supply has been discontinued. The damage from the accident was more than $ 100 million. Followed after a dozen small (in economic terms), but similar accidents in the country ended July 13, 1977 accident in New York City. Within 25 hours was paralyzed life in New York. The damage from the impact of the accident was more than $ 1 billion [4].

After 26 years, 14 August 2003 in 16 hours and 11 minutes local time due to injuries on the line Niagara - Mohawk without electricity has remained almost the entire eastern part of North America, t.e.50 million people [5].

On each of these failures may say that the grid has lost viability. Vitality Power System (EPS) depends on its structure, configuration, reliability, electrical equipment, relay protection and automation, as well as the qualifications of staff, the safety factor, active power reserve, etc [6].

When operating EPS seen the emergence of the so-called chain-of accidents, short-circuit in one of the consumers of electricity and because of the consistent refusal triggered a circuit through which a current is passed through the emergency and set in motion their relays [7].

Location of this accident were observed in 25 of EPS and two ECO former Soviet Union. For 5 years there had been 75 accidents in chain. In 81% of cases Location of this accident occurred due to network faults and failures to check the safety of switching devices [8]. On the chain-failure accounts for 90% of the national economic damage [9].

Under the chain-depth accident disorder refers to the level of functioning energy system installations in case of accidents and irregularities in the work [7,8,10].

An indication of the power system survivability can serve as the frequency of occurrence of accidents in chain system with different depth of a power failure [8]. Therefore, the work related to the improvement of methods of determining the survivability of power systems and substations are highly relevant tasks.

2. Purpose of work

Get a new vitality actual dependency unit load on the frequency and duration of the occurrence of faults in the protected network element reliability of relay protection, through which the through-fault current and time of their diagnosis. To achieve this goal it is necessary to solve the following problem:

  1. Improved mathematical model for determining the survivability of the load node 110/6-10 kV substation (SS-I and SS-II).
  2. Getting engineering formulas with which to assess the vitality of the load node.
  3. Example of calculation of reliability and survivability 110/6-10 kV substation.

3. The scientific value of the work

A new analytical dependence, which allows you to evaluate the survivability of the substation, which depends on the frequency of occurrence of faults in the lines extending from the bus section (SS-I and SS-II), safety shutdown systems associated protective switching devices and the timing of their diagnosis.

4. The practical value of the work

Resulting in the dependence predicts the persistence of the substation, to compare the result with the normalized level of industry documents and if the resulting level of survivability unit load will be more normalized 1/year, it is possible to develop such organizational and technical arrangements under which the level will be normalized, ie, 1/year.

5. Basic material

As an indicator of vitality load node in the chain-the frequency of occurrence of the accident, ie the frequency of the load off site in the event of faults in the protected network element and denial triggered a range of protective switching devices (CAD) through which passed through fault current and powered their "current" protection.

                   (1)

6. The research results

The persistence of the load node is defined in the dynamic mode, that is, when in the off sections of the tire lines or accidentally consuming a short circuit (SC).

Characterize the vitality of the load node will flow parameter his tripping for faults in the area of the current protection - i-order switching device connected to the corresponding SS-I and SS-II.

For example, if the line receives power from the switching device under number 9 which in turn receives power from the I N (Fig. 1), whereas school-I will lose vitality at the coincidence in time and space of two random events: - fault has occurred in the line and - there was a failure in the switch trips at number 9. In this case, the broken line L1 off with a time delay of 0.5 seconds. "Overcurrent protection" switching apparatus, number 18, and all consumers who receive power from the SS-I will falsely disabled.

Figure 1 - Schematic diagram of the substation
Figure 2 - Equivalent circuit of the substation to calculate its reliability

We denote vitality bus section I, that is, the flow parameter outages section tires, short-circuit in the lines, consumers who receive electricity from the lines , using the formula (1) we get:

                   (2)

In the case where: , then (1) becomes:

                   (3)
where                    (4)
- parameter flow of short-circuit occurred in the i-th line off from NL-I; - the number of reported faults occurring in the i-th line of the observation time t.

                   (5)
where - parameter flow of failures in the system operation off of i-switching device ; - number identified as a result of damage diagnostics system outages of the j-switching device, which could lead to a denial it is triggered by short circuit within range of its current protection; - time between the diagnostic test of the circuit breaker; t- time monitoring of electrical substation.

Similarly, we define and vitality NL-II

                   (6)

Formulas (2) and (6) are valid under the following conditions:

                   (7)

In the derivation of these formulas have the following assumptions:

  1. The interval of time between the fault and the time interval between failures, identifying the system off switching devices as a result of their diagnosis, are independent random variables, which are not inconsistent with the exponential probability distribution function with parameters and respectively;
  2. The duration of finding the system off switching devices in the failed state of undiscovered does not contradict the exponential probability distribution function;
  3. The relay (RE) can fail only when they are in standby mode;
  4. If at the time of occurrence of faults in the line, which must respond RP, she was in good condition, it is unlikely its failure in the alarm mode [8];
  5. Failures in the scheme of RE systems and drive the circuit breaker identified and eliminated only by an absolutely reliable diagnostic tests that take place with a time interval .

Refusal to an item of protective switching device (CAD) is understood one which leads to the failure to disconnect the damaged item for faults in the network coverage area of its relay protection [6].

Probability of tripping bus section at time t can be defined as follows:

                   (8)
where – flow parameter outages bus sections with fault lines.

Figure 3 - Survivability lost of load units section I (animation: 7 frames, 5 loops, 183 kilobytes)
Figure 3 - Survivability lost of load units section I (animation: 7 frames, 5 loops, 183 kilobytes)

At writing of this abstract master's degree work is not yet completed. Final completion: December, 2013. Complete text of work and materials on a theme can be got at an author or his leader after the indicated date.

Findings

  1. To determine the most accurate assessment of survivability load units of 110/6 - 10 kV electrical monitoring should be carried out not for the groups of the same elements, and specifically for each of its identity. The more time monitoring of substation equipment, the more we get the value of the load node survivability.
  2. Monitoring the operation of electrical substations should begin from the moment of its start-up until the moment of disposal.
  3. Observed for T = 12 years for electrical substation 110/6 kV, which supplies electricity to the coal mine, it was found that the persistence of bus sections: , аnd .
  4. It is shown that changing the term diagnostic system shutdown APC 6 kV with =1 year to =0,5 years can increase the survivability of the sections I and II 4 times.
  5. The probability that for t = 10 years sections I and II substation lose viability: .

List literatyry

  1. Макаров С.О. Разбор элементов, составляющих боевую силу судов.// Морской сборник, 1894,№6, с.1– 106.
  2. Prevention of power failures Vol. 3. Studies of the task groups on the northeast power interruption. A report to the federal power commission. June, 1967, 142 p.
  3. Гук Ю.Б. Теория надежности в электроэнергетике. – Л.: Энергоатомиздат. Ленинградское отд-ние, 1990. – 208 с.
  4. Надежность систем энергетики. Терминология. – М.: Наука, 1980,вып. 95. – 42 с.
  5. Ковалев А.П., Якимишина В.В. О живучести объектов энергетики//Промышленная энергетика, №1, 2006. – с. 20-26.
  6. Ковалев А.П, Якимишина В.В, Нагорный М.А. Оценка надежности узлов нагрузки подстанции 110/10 кВ//Промышленная энергетика, № 11, 2010. – c. 24-28.
  7. Фабрикант В.П. О применении теории надежности к оценке устройств релейной защиты///Электричество, № 9, 1965. – с. 6– 9.
  8. Эндрени Дж. Моделирование при расчётах надёжности в электроэнергетических системах. Пер. с англ./Под ред. Ю.И. Руденко. – М.: Энергоатомиздат, 1983. – 336 с.
  9. Диллон Б., Сингх Ч. Инженерные методы обеспечения надежности систем: Пер. с англ. – М.: Мир, 1984. – 318 с.
  10. Руденко Б.Н., Ушаков И.Н. Надежность систем энергетики. -М.: Наука, 1986. – 252 с.
  11. Китушин В. Г. Определение характеристик отказов системы при цепочечном развитии аварий. – Энергетика и транспорт, 1977, №3.
  12. Ковалев А.П., Чурсинов В. И., Якимишина В. В. Оценка вероятности появления цепочечных аварий в энергосистемах. – Вестник Кременчугского гос.политехн. ун-та, 2004, вып. 3/2004(26).