Dijital ters güç koruma rolesi yazılım tasarımı
Başlık çevirisi mevcut değil.
- Tez No: 75113
- Danışmanlar: DOÇ. DR. ÖMER USTA
- Tez Türü: Yüksek Lisans
- Konular: Elektrik ve Elektronik Mühendisliği, Electrical and Electronics Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1998
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Elektrik Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 60
Özet
ÖZET Güç sistemlerinde, çeşitli nedenlerden dolayı generatörün şebekeden güç çekmesi yani motor olarak çalışması tahrik sisteminin zarar görmesine yolaçar. Ters güç röleleri, güç sistemlerini ters güç akışına karşı korumada kullanılmaktadır. Ters güç koruması, gücün büyüklüğünün ölçülmesi ve yönünün belirlenmesi ile yapılır, ölçülen güç değeri generatörün motor olarak çalışması için yeterli olan güç değerinden büyükse ve bu güç akışı birkaç saniyeden daha uzun bir süre devam ediyorsa ters güç rölesi açma işareti verir. Bu çalışmada ilk olarak ters güç röleleri tanıtılmıştır. Güç ölçüm yöntemleri incelenmiştir. Dijital ters güç korumasında kullanılan yeni bir algoritma geliştirilmiştir. Bu yeni algoritmanın performansı, senkron generatörün çeşitli çalışma koşullan altında değerlendirilmiştir. Simülasyon çalışmasında kullanılan veriler (üç fazın akım ve gerilimi) EMTP programı yardımıyla elde edilmiştir. ıx
Özet (Çeviri)
SUMMARY This study examines reverse power relay. Reverse power relays are mainly used to protect parallel operating generators from absorbing power in case of any fault in their drive systems. Reverse power flows cause generator motoring. Generator motoring would cause damage to the prime mover such as turbine over heating in steam turbines and cavitation due to low flow in hydrauturbines. If power flows to the generator from the bus, reverse power relay will trip turbine and generator circuit breaker circuit. To limit overspeed, tripping of turbine followed by tripping of the generator is recommended. To prevent operation for system disturbances, it necessary to use a time delay as part of the relay, a delay of a few seconds will normally adequate. Reverse power flows result from a low prime mover input to the ac generator. When this input can not satisfy all losses, the deficiency is supplied by the generator absorbing real power from the system. Also reverse power flows would occur if the turbine is tripped but the generator breaker is not. Gas turbines have a motoring power use that can reach 50-120 percent of full load power. However there are mechanical components which may be damaged by reverse power flows as 5-10 percent. A relay setting of 3-5 percent of rated power is normally adequate. For steam turbines, reverse power relays must be set a very low level due to the small amount of power drawn by motoring generator(2-3 percent). A typical setting may be one-half percent of rated power. Several different types of protection relays are used for motoring detection, with sensitivities from 1 mA to 5 A. They have adjustable operating times. When more sensitive relays are used, care should be taken in selecting a current transformer. Solid state and microprocessor technology allows high accuracy. When the mover is spun an synchronous speed with no power input, the approximate reverse power required to motor a generator, as a percentage of the nameplate rating in kW, is: Condensing steam turbine 1 to 3% Noncondensing steam turbine 3+% Diesel engine 25% Hydraulic turbine 0.2 to 2+ %However, for industrial sites with more than one generator, reverse power relays are used. Reverse power relay settings can be critical in the case of separation from the utility. The ability of the plant to remain the service following islanding condition depends on the response of the turbine governors, the amount of connected load, and the initial loading of the turbines. In figure 1, there are two generator which have different initial operating points. They will not share load changes equally when large load occurs. Therefore generator^) supplies generator^ ) in load line. LOAD UNE SHOWING MOTORING (LOAD * P,“ P2 : P, NEGATIVE) P, 0.0 P, r1 r2 INITIAL INITIAL POWER Figure 1 Two unit with same drop but different initial operating points will not share load changes equally when large load occurs Digital relay technology may be used in reverse power protection. Digital technology make it possible to integrate several protection functions into a single digital relay. Digital technology provides an economically viable alternative for the protection of the intertie. Digital technology provides advantages which are improved performance, greater flexibility, reduced panel space and wiring, metering of various parameters, event reporting fault data recording, remote communication, continuous self checking and self calibration. A block diagram of a multifunction protective relay is shown in Figure 2. »VTı t CT» v.->-[^niE}- R0M1 log») DSP P»P»«W ur EE PR?tf PDwr S.'OD'» ][ hftjtr. it i WdB. I TCP* ”W w«> ; Kw. P*aoe»5a* Figure 2 Block diagram of a multifunction protective relay There are basically two approaches in the design of digital relays. In first approach, the microprocessor simply replaces the relay logic but does not process the voltage and current signals and hence uses many analog components. The performance at these relays depend on the accuracy of analog components. In the second approach, microprocessor both processes the signals and performs the logic offering simpler designs and performance advantage. The instantaneous power p(t) transferred through the supply terminals has a periodicity determined by the periodicity of the voltage and current and is given by h />(*) = v(0'(0 (1) Power can be calculated viably in dc power systems above equations for dc power systems. The ac power systems voltage v(/)and current /(/) signals can be represented as follows v(t) = V smwt (2) i(t) = I sin(M'/-ç>) (3) xiiIf eqn.(2) and eqn.(3) substitute in eqn.(l), instantaneous power will be given by p = P(l - cos 2wt) - Q sin 2wt (4) P active power equals the average value of instantaneous power. Q reactive power is maximum value of second term of eqn(4). Average value of Q is zero. The techniques used for power measurements are discussed in chapter 3. Several algorithms can be used in digital reverse power protection. The algorithms process current and voltage signals then calculate the active and reactive power. Then, the algorithms determine direction of power flow. If reverse power flow occurs, they will trip the generator tie breaker. The algorithm proposed in this study is based on the fastest and simplest power measurement techniques. This method uses sampled value of current and voltage signals and calculate the instantaneous active and reactive power using eqn.(5) and eqn.(6) PI*] = v [*]/ [k] +v [k}i [k] + v [k\i [k] (5) 3 a a b b c c e,ı*ı=^(*'j4',[*ı-y*])+,'1ı*ı('J*ı-M*ı)+vJ*ı(',w-/J*ı)) Then the instantaneous power is integrated over a period of time to obtain the active (average) power. Whenever the average reverse power is greater than a pre-defined value, the algorithm starts to count. If the reverse power is greater than trip value and also stays in that level for a period of time, the generator tie-breaker will be tripped. In chapters, computer simulation studies of the algorithm are made. Performance of the proposed algorithm is examined under several fault conditions of the synchronous generator. Extensive computer simulation studies are under taken in chapter 5 to analyze the proposed algorithm performances under a normal, faulted and abnormal power system operating conditions. The data representing power system operating condition are produced using EMTP power system simulation program. These data, three phase voltages and currents are applied to the proposed algorithm as inputs. XUlThe proposed reverse power protection algorithm stays stable for normal power system operating conditions, balanced conditions and unbalanced faulted conditions as it is expected, and trips the generator tie-breaker whenever the power flow reverse and exceeds a pre-defined value. XIV
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