Abstract
Industries can experience loss of productivity and equipment damage due to poor quality of power supply and unintended or unexpected service interruptions. Several factors such as unreliable power supply contribute to the poor service quality and revenue losses to the utilities. It is desirable that service interruptions are carefully recorded, from which the reliability indices are determined. These indices provide a good indication of the capacity of the utility in engaging and serving the customers. This chapter presents various reliability indices and explains their importance in engaging the customers through providing reliable power supply. A novel framework for reporting the reliability indices is suggested. Further, this chapter illustrates how this suggested framework can be applied to a typical energy supply industry (ESI) to improve overall revenues to the utilities and to provide high quality of power supply and service to the customers.
TopIntroduction
Stable, affordable and high-quality electrical power supply is essential in driving the economic growth and development in any country. The modern Energy Supply Industries (ESIs) are complex and rapidly expanding. Besides, careful planning and execution, significant capital and operational investments are required to service the energy industry. In any typical decentralized ESI, generation, transmission, and distribution are the major players and they generally exist in different geographical locations within the nation. Wu & Chang (2000) and Sekhar, et al. (2016), have reported that about half of the transmission system investments and losses, three quarters of power outages, and almost all non-delivered power problems as associated with unreliable and insufficiently operated power distribution networks. Both power utilities and customers experience loss of revenue due to supply interruption. Large industrial customers (mines, manufacturing plants, water utilities) and commercial customers (hospitals, banks, etc.) can experience loss of productivity, revenue, and/or human lives due to electricity supply interruptions. Billing processes and revenue collection mechanisms are equity based and thus higher energy tariffs are applied on industrial and commercial customers. Simultaneously, severe penalties can be applied on utility for poor supply quality and interruptions. Wu & Chang (2000) and Sastry (2007) have illustrated the impact of the frequency and duration of the interruptions on overall revenues and the related processes to determine the service interruption costs. Thus, reducing the service interruptions, enhancing the overall supply quality and gaining the customer confidence are some of the key goals to the power utilities. Reliability Indices as per the IEEE-1366 – 2012 standard provide an excellent means of measuring the quality of supply and quality of service (Sekhar, et al., 2016). Specifically, Distribution Companies (DisCos) need to incorporate reliability indices at various stages starting from design, operation and upgradation of the networks; mainly to curb losses associated with supply interruptions and poor quality of service. In order to achieve good level of service, DisCos need to acquire appropriate technologies for quick fault detection, faults isolation and service restoration (Sekhar, et al., 2016; Sastry, 2007). However, accurate data about the frequency and duration of the interruptions is required to make well-informed financial investments in the upkeep of the systems. A few reliability indices have been developed over the years to quantify service interruptions and poor supply quality. However, significance and end use of each of these indices vary widely; several key aspects about the system can be well-understood through proper interpretation. Some of the indices describe the frequency of supply interruptions, overall trend of incidents or system faults, and average supply restoration times etc. Data requirements and computational processes are different for these indices. On the other hand, it can be cumbersome and challenging to collect the data, as the process of determining these indices require data from different stakeholders such as consumers in the first place, power distribution system, billing division of the utility and even maintenance teams, etc. Modern ESIs are decentralized with different stakeholders controlling power networks in different geographical locations. Thus, it is a challenge to compile the data due to the size and complexities of contemporary ESIs.
Key Terms in this Chapter
Quality of Supply: The ability of a utility to produce and deliver power free from power quality problems. Compromised quality of supply in terms of cutting maintenance costs leads to lower reliability in a long run, which means lower quality of service for customers. This term can sometimes be used interchangeably with power quality. Quality of supply or levels of power problems are measured against the IEEE-519-1995 standards at different voltage levels in the power system.
Regulator: An organization or body responsible for setting rules and ensuring that the set rules are maintained across the stakeholders. In the ESI, a regulator sets the operating standard limits in accordance with the international standards and monitors the stakeholders to ensure they maintain the standard limits. A regulator also acts as the mediator between the service provider and the customer.
Electricity/Energy Supply Industry (ESI): An electricity or energy supply industry of a country. It gives an outline of key players in the energy sector and their roles, which range from regulator, trader, generator, transmitter and distributor.
Quality of Service: Is the ability to deliver high reliable service free from interruptions to customers. In terms of power supply this means delivering reliable power continually without power outages. This is measured using reliability indices.
Customer Engagement: Is typically a continuous process that is assisted by a digital platform to allow communication between the service provider and the service recipient (customer). The communication can be a complaint, an appraisal, or a notification.
Power Quality: It describes the fluctuations in voltage or current or frequency deviation from their ideal waveforms. The types of power quality problems are classified as transients, short duration variations (sags, swells and interruption), long duration variations (sustained interruptions, under voltages, over voltages), voltage imbalance, waveform distortion (dc offset, harmonics, inter harmonics, notching, and noise), voltage fluctuations and power frequency variations. Among them, three power quality problems identified to be of major concern to the customers are voltage sags, harmonics and transients.
Power Interruptions: A power outage or disruption in the supply of power because of an occurrence of a planned or an unplanned event. Planned events can be due to maintenance, upgrade, new connections while unplanned can be due to natural causes (wind, snow, lightning, heavy rain, etc.) or unnatural causes (faulty equipment, poor power quality, accidents, theft/vandalism, cyberattacks, etc.).
Continuity of Supply: Is the ability to supply electricity continuously without interruptions for as long as it is desired by the customer. Continuity indices at the point of connection (between transmission and distribution) can remedy the power interruptions and assure continuity of service for customers. Power interruptions can be planned or unplanned interruptions, however all should be minimised to ensure continuity of electricity supply, which leads to high quality of service delivery.
Reliability Indices: These are reliability metrics used to measure the reliability and quality of the service being provided. In the electricity sector, it measures how consistent can an electricity distributor provide good quality power with little to no interruption.