Description
ABSTRACT
This work describes the low-voltage distribution network monitoring and control system developed for electricity distribution company which investigate low-voltage distribution network performances as well as to identify and study energy losses in low-voltage distribution networks. The main contribution of this work is represented by the real-life monitoring and control infrastructure implementation insights. Furthermore, the system we describe in this work became a part of company’s enterprise information system, thus becoming integrated with heterogeneous information sources. This integration generated additional values to the company since the collected measurements started to improve the quality of the decision-making system for everyday business processes.
TABLE OF CONTENTS
COVER PAGE
TITLE PAGE
APPROVAL PAGE
DEDICATION
ACKNOWLEDGEMENT
ABSTRACT
CHAPTER ONE
1.0 INTRODUCTION
- BACKGROUND OF THE PROJECT
- PROBLEM STATEMENT
- AIM AND OBJECTIVE OF THE PROJECT
- SIGNIFICANCE OF THE PROJECT
- SCOPE OF THE PROJECT
- BENEFIT OF MONITORING AND CONTROLLING AT THE LV NETWORK
CHAPTER TWO
LITERATURE REVIEW
- RELATED WORK
- ELECTRICITY NETWORK PROTECTIVE DEVICES
- ELECTRIC POWER TRANSMISSION
- DIFFERENTIAL RELAYS FOR PROTECTION
- DIFFERENTIAL PROTECTION SCHEMES
- CONVENTIONAL DISTRIBUTION NETWORK
CHAPTER THREE
METHODOLOGY
3.1 LOW VOLTAGE ELECTRICITY NETWORK MONITORING SYSTEM
3.2 SYSTEM CONTROL
CHAPTER FOUR
- RESULTS AND DISCUSSION
CHAPTER FIVE
- CONCLUSION
CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF THE STUDY
The Low Voltage (LV) network refers to the assets of distribution companies which carry power from distribution transformers to the electricity meters of industrial, commercial and residential customers.
In Nigeria LV networks are operated at 230 volts for single phase and 400 V for three phase at the frequency of 50 hertz. In rural areas LV networks tend to be mainly overhead, while LV networks in urban areas are more likely to be underground. Distribution transformers can be pole or ground-mounted. Pole-mounted transformers are generally smaller and supply fewer customers than ground-mounted transformers. Ground-mounted transformers are usually located in suburban areas and CBDs with underground LV networks, serving larger and more critical loads compared with pole-mounted transformers.
Electricity Distribution Businesses (EDBs) are responsible for maintaining and managing the LV networks to ensure supply is reliable, and voltage and frequency meet supply quality standards set out in the Electricity (Safety) Regulations 2010. LV networks have several attributes that make them worthy of special asset management attention:
- They transport electricity to almost all electricity customers.
- They consist of a significant portion of total network assets.
- Proximity to customers and general public makes management an important part of safety systems.
- LV networks are progressively needing to adapt to integrate a variety of high load consumer technologies, and host increased DER penetration, which can cause a variety of issues.
The efficient use of electric energy imposes the need for the introduction of efficient mechanisms for the optimal use of available electric energy. The electricity distribution system includes a complex power supply network in the form of an electrical grid which consists of a huge number of power lines and devices. Monitoring and management of such complex network represents a major challenge in the daily work of companies for electricity distribution and power supply. These companies have realized that information gathered from sensors and specialized measuring devices are gaining more and more importance in creating successful business plans. The efficient use of data provided from sensors and measuring devices can lead to reducing costs and delivering better services to the customers. If electricity distribution companies ensure that the data obtained from the sensors is exploited together with the data from other information systems, they will improve the quality of data and consequently the quality of decisions they make.
Smart grid, regarded as the next-generation power grid whose ultimate goal is to provide a self-healing network that has dynamic optimization techniques, uses real-time measurements to minimize network losses, maintain voltage levels, increase reliability, and improve asset management (Momoh, 2012). Smart grid initiatives within companies for electricity distribution and power supply are playing the key role in the process of monitoring energy losses and increasing energy efficiency. The issue of electrical energy losses is becoming more important every day, since companies will have to buy energy on the market at economic prices to make up for the losses. This means that any increase in losses that exceeds the predefined norms will directly reflect on the financial status of the company. These facts explain the interest in developing more efficient methods for detecting potential places with higher energy losses.
Up to now, the evolution of the distribution net- work toward the smart grid model has been essentially focused on two non-intersecting areas: high-voltage (mainly 110–35 kV and 110–10 kV electrical substations) and medium-voltage network automation and smart metering (Barbato et al, 2018). The former one is mainly focused on improving the quality of service, studying and deploying fault location, and isolation and service restoration systems, while the latter has been addressed to improve the customer relationship management, promote the customer awareness, and enable new smart home ser- vices. In most cases, the deep investigation of the low- voltage (LV) network has been left disregarded, even if it represents the asset bridging the high- and medium- voltage levels up to final customers.
The LV network segment is probably the most affected one by international regulatory changes that are promoting renewable energy sources, as a way to reduce greenhouse gas emissions, diversify the energy supply, diminish the dependence on imported fuels and, in general, allow the transition to more sustainable energy paradigms (Hayes et al, 2016). Thus, monitoring the real operating conditions of the LV networks in terms of power flows, phase unbalances, voltage levels, and other power quality indicators becomes essential to efficiently operate these kinds of networks. In terms of effectively managing the LV distribution network and the challenges presented by both electricity losses and renew- able technologies, electric distribution companies need access to accurate, timely data and actionable information.
1.2 PROBLEM STATEMENT
The efficient use of electric energy imposes the need for the introduction of efficient mechanisms for the optimal use of available electric energy. The electricity distribution system includes a complex power supply network in the form of an electrical grid which consists of a huge number of power lines and devices. It has been discovered that the major causes of distribution network failure is low system monitoring. Monitoring and control of such complex network represents a major challenge in the daily work of companies for electricity distribution and power supply. These companies have realized that information gathered from sensors and specialized measuring devices are gaining more and more importance in creating successful business plans. The efficient use of data provided from sensors and measuring devices can lead to reducing costs and delivering better services to the customers. If electricity distribution companies ensure that the data obtained from the sensors is exploited together with the data from other information systems, they will improve the quality of data and consequently the quality of decisions they make.
1.3 AIM AND OBJECTIVES OF THE STUDY
The purpose of these systems is to monitor different LV distribution network segments. The objectives of the study are:
- To increase the rate of power supply
- To reduce transformer failure rate
- To use sensors to collect data of distribution centre
1.4 SCOPE OF THE STUDY
This work describes the LV monitoring system developed for Electric Power Industry to monitor electricity distribution. The developed system measures, communicates and stores real-time data, and translates it into actionable information needed by power distribution companies to meet described challenges regarding LV distribution networks. Different sensors have been used to collect near real-time data (among which are current, voltage, power, and energy values) about low-voltage (LV) electrical substations in a distribution network. The data collected by this system is transmitted to its data center, where it is analyzed and presented as situational analysis of the LV distribution network conditions.
1.5 SIGNIFICANCE O F THE STUDY
This study will serve a tools for providing daily load profiles and voltage level data to help a company create plans for ‘‘stress points,’’ energy losses in the network and maintain statutory voltage levels.
1.6 BENEFIT OF MONITORING AND CONTROLLING AT THE LV NETWORK
Monitoring at the low-voltage (LV) level provides Electricity Distribution Businesses with data that can identify issues and assist with planning, design and control of LV networks. The efficient use of monitoring data can reduce costs, optimize investment, and improve customer service and safety.
- Monitoring provides visibility so electricity distribution companies can determine if the networks are performing within capability and are able to operate within regulatory limits. Monitoring data can inform actions that optimize network utilization and reduce line losses.
- Measuring power quality in LV networks makes it possible to address issues as they are identified. Improved power quality reduces losses and thereby enhances the effective capacity in the networks so capital expense of additional network capacity can be avoided.
- Monitoring will provide data that could identify unknown issues and support new approaches to network and asset management.
CHAPTER FIVE
CONCLUSION
This work describes the LV distribution network monitoring and control system developed for electricity distribution company. The system has been successfully designed, implemented, and validated by successful deployment in the production environment. Based on two successful production deployments, we may conclude that the pro- posed concepts of active LV distribution network monitoring, system architecture, and functionalities work as expected.
The system concepts and solutions extend the monitoring and control of the electricity distribution grid to LV level and enhance the reliability of power supply. The developed LV distribution network monitoring system collects various near real-time sensor data from measurement devices deployed in medium-level to low- level electrical substations. Collected data are stored in a data center and used for real-time monitoring of the LV network distribution. Different tools are used to analyze collected data and to find efficient mechanisms for the optimal use of available energy and improve the systems for managing and monitoring power networks. Since the power grid is a very complex system, the solution that provides these mechanisms has to be very sophisticated and customized.
The importance of the deployed system started to grow significantly when collected measurements data from the LV distribution network became available throughout the company. The collected measurements started to improve the quality of the decision- making system for everyday business processes. By including LV distribution network monitoring data, the distribution company is provided with data that can be used for monitoring real-time energy consumption, but what is more important, to provide the base for calculating electricity losses in the grid and to provide information that will help end customers to save energy and control their spending. The authors of this article were interested in the possibility to monitor the efficiency of the deployed system by monitoring the level of energy losses and electricity theft.
At the moment, the measurement devices are installed only in LV electrical substations. In the near future, these or some other measurement devices can be installed not only within electrical substations but also for specific segments of the LV network grid, individual customers or groups of customers. This way, the system will provide more precise info about the state of a LV distribution network grid.
Potential problems have been highlighted with existing distribution network protection schemes when generation is connected. Phase and earth fault currents may vary over a wide range making protection scheme design difficult. Back up protection relays may suffer from under reach resulting in mal-operation. With the use of auto-reclose schemes out of phase reclosing of the generator may occur. In addition maintaining generator synchronism with the network supply is difficult for symmetrical faults close to the generator.
Investigation is under way into a distance / directional scheme which gives adequate performance without the requirement for a wound voltage transformer and network communications. This minimizes scheme costs by utilizing existing network equipment and reducing the present number of customer outages.
The use of distance protection allows the problems with relay grading to be reduced. Co-ordination is simplified with upstream protection which is likely to be differential or distance protection. Distance relays give local back up protection. This avoids the requirement for remote back up protection which causes wider scale supply interruptions. Fault clearance times are minimized which improves generator transient stability.
