The overview of distribution system Essay

CHAPTER1

OVERVIEW OF DISTRIBUTION SYSTEM

1.1 Introduction

A typical power flow involves generation, transmission and distribution. Atmost interest lies in the supply of electrical power to the consumers which is known as distribution. The system which distributes electric power for local consumer utilization is known as distribution system. A distribution system's network carries electrical energy from the transmission system and delivers it to the consumers. The primary purpose of an electricity distribution system is to meet the customers demands for energy after receiving the bulk electrical energy from transmission or subtransmission substation.

In general, the distribution system is the electrical system between the substations fed by the transmission system to the consumers meters. The modern distribution system begins as the primary circuit leaves the substation and ends as the secondary service enters the customer's meter socket by way of a service drop. Distribution circuits serve many customers or end users. The voltage used in distribution system for the short and long distances vary from 2300V to about 33000V depending on utility standard practice, distance, and capacity of load to be served. Distribution circuits are fed from a distribution transformer located in an electrical substation, where the voltage is stepped down from the high values used for power transmission.

1.2 Distributed generators in distribution system

In modern power distribution systems, integrating small nonconventional generation sources has become attractive. These technologies have less environmental impact, easy siting, high efficiency, enhanced system reliability and security, improved power quality, lower operating costs due to peak shaving, and relieved transmission and distribution congestion [1]. The distributed generator (DG) units used are highly modular in structure as well as helpful in providing continuous power supply to the consumers.

However, depending on the rating and location of DG units, there is also a possibility for voltage swell and an increase in losses. In this scenario, to exploit the complete potential of distributed generation, proper siting and sizing of DGs become important.

Therefore, an attempt to develop a sizing algorithm that transforms an existing distribution network to a sustainable autonomous system is made. In such an operation, the generation and corresponding loads of the distribution network can separate from the feeder network and form a microgrid without affecting the transmission grids integrity.
Most of the current microgrid implementations combine loads with sources placed at favorable sites that allow intentional islanding and try to use utmost the available energy [2]. In such an operation, stable generation and voltage profile are necessary to independently supply power to customers [3]. Hence obtaining the number of locations (sites) at which the DG is placed becomes significant.

In order to obtain DGs maximum potential benefits, proper location and optimal penetration level need to be calculated. The main purpose is to optimize location and sizing of DG on distributed systems for solving the problem of line loss reduction. The optimal calculation realizes the highest voltage eligible ratio and minimum power loss by adjusting the reactive output of DG in precondition of system security.