Fault Analysis Of Load Behavior In 33Kv Transmission Network Using Symmetrical Component Techniques

1.0 INTRODUCTION
The Electric Power System is divided into many different sections. One of which is the transmission system, where power is transmitted from generating stations and substations via transmission lines into consumers. Both methods could encounter various types of malfunctions is usually referred to as a “Fault”.
Fault is simply defined as a number of undesirable but unavoidable incidents can temporarily disturb the stable condition of the power system that occurs when the insulation of the system fails at any point. Moreover, if a conducting object comes in contact with a bare power conductor, a short circuit, or fault, is said to have occurred. The causes of faults are many, they include lighting, wind damage, trees falling across transmission lines, vehicles or aircraft colliding with the transmission towers or poles, birds shorting lines or vandalism.
In this study, the causes and effects of faults in the overhead transmission lines were the focus of the research. Some of the many causes of faults, and some detection methods will be discussed in chapter two (2). Chapter three (3) will illustrate the mathematical model, and chapter four (4) will demonstrate the application of this model for some hypothetical situations.

1.1 BACKGROUND OF THE STUDY
One of the major problems industries in Nigeria face is to counter the sudden voltage fluctuations in the system which results in the deterioration of power quality and damages to equipment [1]. The consequences of power incidents show that industrial and digital firms are losing revenue per year due to power interruptions. The cost to replace equipment damaged because of voltage spikes is very high as these results to reduction in production. Electricity supply is also very important as it affects all sphere of life both social and economic development of any nation. Power supply to consumer must be reliable, adequate and of acceptable quality at a minimum cost, but this is not easily achievable as the reliability of supply and adequacy is being truncated by incessant faults along the line, which reduces the efficiency of the system.
The Manufacturers Association of Nigeria (MAN) and the National Association of Small Scale Industries (NASSI) estimated that their members spend an average of about N2billion (about $12 million) per week on self-power generation [2].
A series of power sector polls conducted by NOI Polls Ltd for the second quarter of 2013 revealed that about 130 million, representing 81 per cent, out of the 160 million Nigerians generated their own electricity through alternative sources to make up for irregular power supply. Study also showed a combined average of 69 percent or 110 million of Nigerians experienced greater spending on alternative electricity supply [3].
Nigeria’s electricity consumption on a per capita basis was among the lowest in the world when compared with the average per capita electricity usage in Libya which is 4,270KWH; India, 616KWH; China, 2,944KWH; South Africa, 4,803 KWH; Singapore, 8,307KWH; and the United States, 13,394KWH [1-3]. By Journal of Sustainable Development Studies, South Africa with a population of just 50 million, has an installed electricity generation capacity of over 52,000 MW [4].
The Electrical system is sub divided into generation, transmission and distribution sections. The subsystem that generates electrical energy is called generation subsystem or generating plants (stations). It
consists of generating units (consisting of turbine alternator Sets) including the necessary accessories. Speed governors for the prime Movers (turbines; exciters and voltage regulators for generators, and step-up transformers also form part of the generating plants. The subsystem that transmits the electrical energy over long distances (from generating Plants to main load centers) is called transmission subsystem. It consists of transmission Lines, regulating transformers and static/rotating VAR units (which are used to control Active/reactive powers)
The sub system that distributes energy from load centers to individual consumer points along with end energy converting devices such as motors, resistances etc is called Distribution Subsystems. It consists of feeders, step-down transformers, and individual Consumer connections along with the terminal energy converting electrical equipment Such as motors, resistors etc.
The electricity distribution network starts at the Injection substation, where power is delivered by overhead transmission lines and stepped down by Power transformer (15MVA) from 33KV to 11KV. But sadly, at each of these stages of power system, a vital obstacle called FAULTis encountered. A Fault in an electrical equipment is a defect in the electrical circuit due to which current is diverted from the intended path [5]. This fault is subdivided into Transient and permanent faults
Transient faults are faults, which do not damage the insulation permanently and allow the circuit to be safely re-energized after a short period, such as sudden loss of generation or an interconnecting line, or the sudden connection of additional load. The duration of the transient period is in the order of a second. System behavior in this interval is crucial in the design of power systems. Transient overvoltage occurring in our power system can cause operational breakdown and also cause failure in industrial and household equipment. These types of problems have been given serious consideration by engineers since most of the equipment that are used in the substation have a specific Basic Insulation Level (BIL) and if the overvoltage exceeds the safety or defined limit, insulation breaks down and failure of equipment occur. For that reason, several protective devices and schemes are applied to reduce the effect of transient overvoltage to control damage caused to the utility system and to avoid poor power quality.
Transient over voltages in power systems may be caused due to several reasons of which those occurring due to lightning strikes or switching operations of inductive or capacitive are the commonest [6].
Permanent faults result in permanent damage to the insulation. In this case, the equipment has to be repaired.

1.2 STATEMENT OF PROBLEM
Transmission power system is the subsystem that transmits the electrical energy over long distances (from generating Plants to main load centers). It consists of transmission Lines, regulating transformers and static/rotating VAR units (which are used to control Active/reactive powers). It was discovered that the major cause of power outage in the country is as a result of fault on the transmission subsystem. This fault starts from voltage fluctuation in the system which results in the deterioration of power quality and damages to equipment. This damage of equipment causes different sector of the country to lose revenue. Electricity supply is also very important as it affects all sphere of life both social and economic development of any nation. Because of the need to have a steady power supply in country lead to this study which focuses of the fault analysis of fault in a 33kv transmission network.

1.3 AIM OF THE STUDY
A fault in electrical equipment is a defect in the electrical circuit due to which current is diverted from the intended path [5]. This fault is subdivided into transient and permanent faults. The main aim of this work is to analyse fault of load behavior in 33kv transmission network using symmetrical component techniques.

1.4 OBJECTIVE OF THE STUDY
At the end of this study, student involved shall be able:
i. To study different types of fault,
ii. To study causes of fault in 33kv transmission network,
iii. To study some detection methods,
iv. To illustrate the mathematical model, and fault analysis using symmetrical components techniques.

1.5 SCOPE OF THE STUDY
From this study electrical fault were analyzed and from results obtained from Symmetrical method of fault analysis revealed that double Line to ground fault has the highest fault current and could cause adverse damages to equipments’ and as such must be avoided. The fault current calculated from Symmetrical component method of Fault analysis was validated.