Pragmatic methods for optimization of low voltage distribution network in indian scenario

Abstract

One of the ser ious concer ns plaguing the wor ld is the limited energy reserves that are on the verge of extinction. In order to preserve these for futur e gener ations, it is essential to use r emaining ener gy r eser ves sparingly and to minimize the losses encountered in energy usage. A majority of losses in the electr ical ener gy sector occur in the distr ibution side; while transmission and sub-tr ansmission lines account for only about 30% of the total losses In the distr ibution networ k, ther e ar e two main distr ibution network lines namely, primary distribution lines feeding High Tension (HT) consumer s, distr ibution tr ansfor mer s and secondar y distr ibution lines (low voltage distribution network, LV network) fed by distribution transformers in India. Hence LV network is the last link connecting the consumers and needs more consideration for optimization. Alt h ou gh t h er e a r e m a n y r esea r ch p a p er s d iscu ssin g t h e reconfiguration algorithms for loss minimization of distr ibution systems hardly any work related to loss reduction in developing countries scenario is reported. Very little work has been done on LV network where the impact of unbalance is predominant due to the presence of single phase loads. It results in cur r ent in the neutr al line which in tur n causes additional line loss in the distribution lines and copper loss in the distribution transformers. To establish the r elevance of the pr oblem of unbalance and its remedy, the existence of single phase consumer s in a typical state of India is consider ed for the analysis. It has been ver ified that number of single phase consumer s is mor e than the number of thr ee phase consumer s. To fur ther augment the r esults, a study on the consumption patter n of consumer s in a typical city of India is performed for a period of five months in the year 2007. They have been segregated with reference to single phase and three phases. It is obser ved that the single phase consumption is mor e than thr ee phase consumption. It also indicates the consistent occurrence of unbalance in low voltage distr ibution networ k r esulting in line loss, over cur r ent and low voltage. Based on the extensive liter atur e sur vey, most of the wor ks in the distribution networ k ar e r elated to either pr imar y distr ibution networ k or distr ibution automation. Hence this thesis focuses on LV networ k and reconfiguration of consumers for load balancing is identified as potential area for the present work. The main objective of this thesis is to r educe ener gy losses in LV network and perform node reconfiguration cost-effectively. Taking real time data from three numbers of distribution transformers and the consumption pr ofile of all the connected consumer s as input, a technique that determines cur r ent unbalance, the time of peak unbalance in a day and cor r elates the consumers pertaining to it is developed and implemented in this thesis. Main objectives of this thesis are Development of Distribution Simulation Package (DSP) for load analysis of LV network using Lab VIEW, Implementation of Real-time On-line Monitor ing System for LV networ k, Development of Fuzzy-logic based load balancing exper t system and Heur istic method Pole-wise load balancing system. I n Real-t im e O n -lin e M on it or in g syst em , Ener gy monitor ing system study is undertaken in one sample distribution transformer with its LV network of consumers. The data is obtained from energy meter connected to secondar y of the distr ibution tr ansfor mer with its 34 consumer s ever y 30- m in u t e. R em ot e m et er in g is d on e u p t o con su m er en d in t h e sa m p le transformer to get the correct representative samples of individual consumers. Fr om the ener gy meter r eadings obtained, ener gy loss of LV networ k is computed. Load balancing algorithm is developed to predict the unbalance in the distribution network as well as correct the unbalance by reconfiguring the loads. DSP has been developed with LabVIEW as off-line distribution monitor ing system. This package is capable of displaying the distribution parameters like voltage, cur r ent and power factor in any hour of day. Also power and ener gy measur ement for ever y half-an-hour is displayed. Low voltage distr ibution networ k power quality par ameter s and issues ar e also st u d ied . DSP for m s t h e b a sis for off-lin e a n a lysis of L V n et wor k in formulating significant inferences A fuzzy logic based load balancing is implemented to balance the cur r ent in thr ee phases. The input to the fuzzy contr oller is the individual phase cur r ent. The output of the fuzzy contr oller is the load change value, negative value for load receiving and positive value for load releasing. Expert system per for ms the optimal inter changing of the load points between the r eleasing and r eceiving phases. The effect of load r econfigur ation on loss reduction is studied practically in one number urban distribution transformer (Urban DT1). CYMDIST simulation software is used to study two additional transformers (Urban DT2 and Urban DT3). Further optimization by reducing neutral current in the LV network is a t t em p t ed b y u sin g t h e h eu r ist ic m et h od ology. F or t h e d iffer en t combination of loads descr ibed, consumer s ar e shifted pole wise so that all the individual poles of the distribution transformer remains balanced after the process and the neutral current in all sections of LV distribution network gets reduced. But in fuzzy method unbalance exist pole-wise, even though total LV networ k is balanced. Two distr ibution tr ansfor mer s, Ur ban DT2 and Urban DT3 are taken for study. Based on the analysis, the result obtained in simulation softwar e by r econfigur ing the consumer s (nodes) of Ur ban DT2 and Ur ban DT3 so as to balance the system is pr esented in this wor k. . The proposed load balancing technique effectively meets the criteria to minimize energy loss which has been proved by CYMDIST simulation. The cost effectiveness and suitability of the wor k for low voltage distribution network scenario is highlighted with comparisons and possibility of energy saving in terms of few millions of rupees per month is explained. In an era of energy conservation this thesis makes a significant contribution to the economy of the nation.