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Aşırı yüklere bağlı bozulmalar sonucunda dağıtım sistemlerinin restorasyonu

Restoration of ditribution systems during excessive loads

  1. Tez No: 46312
  2. Yazar: BERRİN ÇELİK
  3. Danışmanlar: PROF.DR. NESRİN TARKAN
  4. Tez Türü: Yüksek Lisans
  5. Konular: Elektrik ve Elektronik Mühendisliği, Electrical and Electronics Engineering
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 1995
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Belirtilmemiş.
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 76

Özet

ÖZET Enerji sistemlerinin yoğun elektrik kesintileri ile karşı karşıya kalmalarındaki artış, son zamanlardaki endüstri yapısındaki devrimsel değişikliğin ve gittikçe artan sistem yüklenmesinin bir sonucudur. Uzun süreli kesintilerin yerleşim alanlarında, ekonomide ve güç sistemlerinin kendisinde oluşturduğu zararlar, hızlı ve efektif bir restorasyonun çok önemli olduğunu kanıtlar. İyi bir restorasyon planı, bu alanlardaki etkileri azaltacaktır. Tezin amacı, uzun süreli kesintiler sonunda oluşan aşın yüklerin maksimum transformatör kapasitesini aştığı durumlar için nasıl bir restorasyon planının uygulanacağının tespit edilmesidir. Dağıtım sisteminde bütün bölümlere enerji vermek için yeterli kapasite olmadığından, bölümlere adım-adım restorasyon uygulanır. Uzun süren kesintiler sonucunda“soğuk yük karşılama cold load pick up”durumunda toplam yük karakteristiğini temsil etmek için gecikmeli üstel model kullanılır. Bu analitik modelden yararlanılarak toplam restorasyon zamanını, ortalama müşteri kesinti süresini ve müşteriye satılan enerjiyi optimize etmek için bir restorasyon işlemi bulunur. Adım-adım restorasyonda bölümlerin restorasyon sırasının, toplam restorasyon süresinde ve sistem güvenilirliğinde önemli bir rol oynadığı gösterilmiş ve dağıtım sisteminin değişik bölümlerinin optimal restorasyon sırası, minimum toplam restorasyon süresi ve minimum müşteri kesinti süresi içine saptanmaşıtır. Isıl limitler düşünüldüğünde, dağıtım sistemlerinin karşılaştığı en kötü durumlardan biri, soğuk yük karşılama problemi olduğu için, mümkün olan en hızlı şekilde sistemin normal işletime döndürülmesi ve sistemin daha küçük yedek transformatör kapasitesi ile işletilmesi, kuruluşların finansal tasarruflarını arttırmalarım sağlayacaktır. vii

Özet (Çeviri)

RESTORATION OF DISTRIBUTION SYSTEMS DURING EXCESSIVE LOADS SUMMARY Forced and scheduled outages are commanplace in distribution feeders. Quick restoration of power distribution systems after the long outages which cause an interruption to customers is vital to electrik utulities. The restoration issues at the distribution level the majör concern is identification of the location of the faults and then restoration of power to unfaulted parts by performing switching operations. Athough the capacity of the substation transformers and the feeders to supply the required load, and maintenance of proper operating voltage must be taken into consideration, stability and maintenance of proper system frequency do not play any role at the distribution level. Distribution systems occupy the largest physical region in power systems and therefore, they are highly susceptible to environmental conditions.Bad weather, trees and animals, as well as human errors and equipment failures are responsible for most of the outages. An outage which occurs as the result of of a breakdovvn ör a planned shutdovvn for maintenance purposes may ör may not cause service interruption in a distribution system. Most of the distribution systems do not have built-in redundancy because of their radial nature. So, failure of a distribution component usually results in interruptions to the customers. More than 90 % of the interruptions are a result of failures occurring in a distribution systems. The outages that cause interruptions are important because of unsupplied customers. Thus, the main goal is to supply power to the interrupted customers in minimum time. viiiload of each section. Because all sections couldnt be restored at once, step-by-step restorations of sections is considered. When step-by-step restoration of sections is applied, the order in which the sections are restored has significant impact on the total restoration time and reliability of the system. Dependence of transformer's maximum loading capacity on the restoration order of sections is emphasized. Based on the delayed exponential model of aggregated load on sections a restoration procedure to optimize total restoration time, average customer interruption duration and energy sold to the customers is sought without violating the maximum transformer capacity. In Chapter 2, Examining of residential load behaviour, the reason of cold load pickup is explained. The importance of modeling of aggregated load is emphasized. Cold load pickup of space conditioning load, heating and cooling load, is of a practical interest because of its major contribution in the total overload. The termodynamics of individual houses during and after an outage play an important role in determining the magnitude and the duration of the overload; therefore, an efficient modeling of the termal characteristics of a large number of different houses is critically important. In Chapter 3, To find the aggregated load dynamics of termostatically controlled devices, a stochastic difference equation model is used. Based on the results of this model, an analytical load model ( delayed exponential load model ) that represents the aggregated load of each section is proposed. In Chapter 4, step-by-step restoration is studied. The restoration problem during CLPU is formulated and the restoration times of sections are derived. It is proved that the restoration order of sections play an important role in total restoration time and it is given a restoration procedure which find optimum sequence. Optimization of various objectives is studied in Chapter 5. The objectives are the minimization of the total customer interruption duration, the minimization of the total restoration time, and the maximization of energy sold to the customers. A search XIfor the optimum is achieved with a procedure called Adjacent Pairwise Interchange Method (APIM). In Appendix A, Related with APIM Algorithm, a computer program is developed. Also the results of both the APIM algoritm and the global search for a distribution system which has ten sections are given in Appendix A. A formulation for the optimum system design is given for future work in Chapter 6. The last chapter gives the conclusions and the recommendations relating to the restoration distribution systems in CLPU condition. Since cold load pickup is one of the most severe conditions that a distribution system experiences, restoration capabilities of the system and procedures to return the distribution system to normal operation as fast as possible will benefit not only the operation engineer but also the design engineers. However, a good knowledge of koad behaviour during cold load pickup is important for implementation. In the future, availability of high resolution data from the field during an actual restoration can provide validation or improvement of the cold load pickup model used. This study in conjunction with distribution automation will allow the distribution systems to be restored as fast as possible and operated with smaller spare transformer capacity. Hence, utilities will be able to accrue financial savings by deferring upgrade of existing transformers and installation of new transformers. Xllload of each section. Because all sections couldnt be restored at once, step-by-step restorations of sections is considered. When step-by-step restoration of sections is applied, the order in which the sections are restored has significant impact on the total restoration time and reliability of the system. Dependence of transformer's maximum loading capacity on the restoration order of sections is emphasized. Based on the delayed exponential model of aggregated load on sections a restoration procedure to optimize total restoration time, average customer interruption duration and energy sold to the customers is sought without violating the maximum transformer capacity. In Chapter 2, Examining of residential load behaviour, the reason of cold load pickup is explained. The importance of modeling of aggregated load is emphasized. Cold load pickup of space conditioning load, heating and cooling load, is of a practical interest because of its major contribution in the total overload. The termodynamics of individual houses during and after an outage play an important role in determining the magnitude and the duration of the overload; therefore, an efficient modeling of the termal characteristics of a large number of different houses is critically important. In Chapter 3, To find the aggregated load dynamics of termostatically controlled devices, a stochastic difference equation model is used. Based on the results of this model, an analytical load model ( delayed exponential load model ) that represents the aggregated load of each section is proposed. In Chapter 4, step-by-step restoration is studied. The restoration problem during CLPU is formulated and the restoration times of sections are derived. It is proved that the restoration order of sections play an important role in total restoration time and it is given a restoration procedure which find optimum sequence. Optimization of various objectives is studied in Chapter 5. The objectives are the minimization of the total customer interruption duration, the minimization of the total restoration time, and the maximization of energy sold to the customers. A search XIfor the optimum is achieved with a procedure called Adjacent Pairwise Interchange Method (APIM). In Appendix A, Related with APIM Algorithm, a computer program is developed. Also the results of both the APIM algoritm and the global search for a distribution system which has ten sections are given in Appendix A. A formulation for the optimum system design is given for future work in Chapter 6. The last chapter gives the conclusions and the recommendations relating to the restoration distribution systems in CLPU condition. Since cold load pickup is one of the most severe conditions that a distribution system experiences, restoration capabilities of the system and procedures to return the distribution system to normal operation as fast as possible will benefit not only the operation engineer but also the design engineers. However, a good knowledge of koad behaviour during cold load pickup is important for implementation. In the future, availability of high resolution data from the field during an actual restoration can provide validation or improvement of the cold load pickup model used. This study in conjunction with distribution automation will allow the distribution systems to be restored as fast as possible and operated with smaller spare transformer capacity. Hence, utilities will be able to accrue financial savings by deferring upgrade of existing transformers and installation of new transformers. Xll

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