Voltage Collapse In A Fragile Grid: The Nigeria Experience

ABSTRACT

A modern electric power system network (PSN) is typically a large and complex engineering system whose healthy existence is crucial to industrial and socio-economic development of Nations. Voltage collapse contributes to large extent to system blackouts and it is one of the major concerns for today’s electric power system operations. The Nigerian National grid (NNG) experiences on an average of thirty-five (35) system collapse every year over the past ten (10) years. This paper presents an overview of system collapse on the Nigerian National Grid.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

INTRODUCTION

• BACKGROUND OF THE STUDY
• PROBLEM STATEMENT
• AIM AND OBJECTIVES OF THE STUDY

1.4    SCOPE OF THE STUDY

1.5    SIGNIFICANCE OF THE STUDY

1.6      PROJECT JUSTIFICATION

CHAPTER TWO

LITERATURE REVIEW

• REVIEW OF THE STUDY
• REVIEW OF RELATED STUDIES
• ANALYSIS AND METHODS FOR VOLTAGE STABILITY
• CAUSES OF VOLTAGE COLLAPSE
• CLASSIFICATION OF SYSTEM COLLAPSE ON THE NIGERIA NATIONAL GRID

CHAPTER THREE

• THE NIGERIA NATIONAL GRID
• CAUSES OF VOLTAGE COLLAPSE IN NIGERIAN POWER SYSTEM
• PROBLEMS OF THE NIGERIAN POWER SECTOR
• VOLTAGE COLLAPSE ANALYSIS METHOD

CHAPTER FOUR

• PRESENTATION AND ANALYSIS OF RESULTS

CHAPTER FIVE

• CONCLUSION AND RECOMMENDATION

REFERENCES

CHAPTER ONE

1.0                                                        INTRODUCTION

1.1                                           BACKGROUND OF THE STUDY

The main function of a power system network is to generate and transmit power to load centres at specified voltage and frequency levels  and  statutory  limits  exist  for the variation about base levels. The generator in the system generates either 11kV or 16kV (Almeida et al., 2010). These voltages are stepped up to either 330kV or 132kV for the purpose of transmission. The high voltages levels are then stepped down to supply high load centers. The 330kV is then stepped down to 132Kv and this is further stepped down to 33kV which is the primary distribution voltage (NERC, 2007). The nominal voltage level is further stepped down to 11kV. As the system load changes, the resulting changes in real and reactive power demand cause variations in the network voltage and frequency levels. As the system load changes, the resulting change in real and reactive power demands causes variation in the system voltage and frequency levels. The power system is equipped with controllers that reduce these variations to acceptable levels well within the statutory limits. In the operation and control of a power system network (PSN), voltage stability is a major concern to the power system engineer as the power system network nowadays operates very close to its stability limits (Almeida et al., 2010). This is due to increasing load demand, industrialization, environmental and economic factor which hampers the construction of new transmission lines and generating stations. This has caused most PSNs to be weak, heavily loaded and prone to voltage instability (Arya et al., 2006).

Voltage Stability is a serious concern of today power system for its secure and reliable operation. Power system stability is dependent mainly on the degree of maintaining the synchronism of the whole system. Voltage stability can be defined as the ability of a power system to maintain steady and  acceptable voltage at all buses in the system at normal operating conditions, after being subjected to a disturbance (Taylor et al., 2014). It is desired that the power system remains in the equilibrium state under normal conditions, and reacts to restore the status of the system to acceptable conditions after a disturbance, i.e. the voltage after a disturbance is restored to a value close to the pre-disturbance situation.

Out of the all blackouts round the globe the primary reasons for the blackouts are observed to be voltage collapse.

Voltage collapse can therefore be defined as instability of a heavily loaded PSN that leads to declining voltage and eventually blackout. This has severe consequence on the system security and negates the essential service of delivering uninterrupted reliable power to the customers. In a progress of a voltage collapse phenomenon. The system voltage decreases slowly as the demand increases until a critical point is reached. At this point, any slight increase in demand will give rise to a large decrease in voltage, until the demand could no longer be satisfied which eventually leads to voltage collapse. This work studies voltage collapse in a fragile system network according to Nigerian experience.

1.2      PROBLEM STATEMENT

Voltage collapse is the major reason for all blackout around the globe. Voltage Collapse is instability of a heavily loaded electric power system, which leads to declining voltages and blackout, and it is typically associated with reactive power limitations of the power system. There is a need to perform studies to ensure that the reliability of the power system is maintained at all system condition and its different operating horizons. This paper analyzes the voltage stability of a system by finding a continuum power flow solutions with base load and obtaining steady state voltage stability limit the critical point. The in-between result of the process is used to determine voltage stability index and further to identify portion of the system prone to such voltage collapse.

1.3      AIM AND OBJECTIVES OF THE STUDY

The main aim of this work is to carry out a study on voltage collapse in a fragile system network with respect to Nigerian experience. The study seeks to achieve the following objectives:

1. To determine the causes of voltage collapse in Nigeria power network
2. To review the past voltage collapse experience in Nigeria power network

• To study the impact of voltage collapse in Nigeria power network.

1.4      SCOPE OF THE STUDY

Voltage stability is a major concern in power system networks as the power system nowadays operates very close to its stability limit (Arya et al., 2006). This is due to increasing load demand, industrialization, environmental and economic factor which affects the generating stations. This have affected some power system networks that are heavily loaded, weak and prone to voltage instability (Arya et al., 2006). A power system is said to be in a state of instability when a disturbance causes a gradual and uncontrollable decline in voltage. Voltage instability is caused as a result of fault in the system (contingencies), lightning, imbalance between supply and demand side and faults from control devices (NERC, 2007). Inability of power system network to meet the reactive power requirement leads to voltage collapse and eventually blackout. The scope of this study covers the study of voltage collapse with the case study of Nigeria experience. There are other factors that can cause blackout but this study is limited to voltage collapse.

1.5                                            SIGNIFICANCE OF THE STUDY

This research work will serve as a means of studying the causes and impact of voltage collapse.

This research sought to teach the reader on how to come up with a new way of voltage stability improvement thereby solving the challenge of voltage collapse.

1.6                                                 PROJECT JUSTIFICATION

Power systems are increasingly becoming more overloaded and constantly being operated close to their voltage stability limits. Voltage stability is the ability of a power system to maintain acceptable voltage levels under normal operating conditions and after being subjected to disturbances such as a sudden increase in load or loss of a major generation plant. Major national power outages have been documented in the recent past in countries in Africa such as in Nigeria.

The use of right methods for voltage stability improvement has been a growing trend due to the huge capital outlay required to construct new transmission and distribution lines, pressure on land as well as environmental concerns worldwide.

There is need to study about voltage collapse and their causes which will lead to making recommendation on how to improve system reliability in Nigeria grid network.