Infrastructure refers to the equipment required to generate and deliver electricity to consumers. There is a continuous life-cycle management process for equipment which is required to accommodate the evolution of network architecture, power capacity, operations, safety and reliability.
Infrastructure illustration
For the last 100 years the architecture of the electrical grid in Ontario has been built around the concept of high output generators strategically located around the province with a high voltage transmission network to supply local distribution companies and their customers.
It is no longer the status quo.
Transmission
There are over 30,000 circuit km of transmission lines in service in Ontario. They operate at voltages of 115kV, 230kV and 500kV. The high voltages enable transmission of large amounts of energy over vast distances while minimizing losses.
Ontario operates the second largest transmission system in Canada with over 30,000 km of lines
The transmission system has extremely high reliability due to rigorous engineering, construction maintenance and operational standards. It has built-in redundancy through a ‘grid’ architecture with sophisticated protection and control.
To avoid the technical details you can imagine that a ‘grid architecture’ consists of multiple elements interconnected with common points somewhat like a tennis net. A grid provides high reliability as you can break a single element and rely on the other segments to provide connectivity.
A high performance telecommunication system is in place to meet the operational requirements of the transmission system. The operational requirements of a grid are highly complex due to the large number of connection points for generation and distribution load. Powerful computers are required to manage the operation of the transmission system.
Over the last two decades Ontario has lost several major transmission connected generators due to the retirement of coal-fired facilities. The change impacts the system’s ability to support the required voltage levels and forced the installation of transmitter-owned static VAR compensation facilities. These facilities add cost and complexity to the transmission system.
Distribution
Distribution in Ontario is generally considered to be supplied by lines of 44kV or less. According to the 2017 Yearbook of Electricity Distributors published by the OEB, Ontario has 225,091 km of distribution lines. That’s enough to go around the circumference earth almost six times.
Ontario has 225,091 km of distribution lines
The distribution system is also highly reliable however it does not have the same transmission-level architecture or requirements. Traditionally the distribution system consists of a radially fed network feeding load customers.
I can leverage an analogy to describe the distribution network. A radially fed network is like a tree that draws nutrients from the ground and delivers them through a large trunk, to smaller branches and ultimately to the last twig and leaf. If a branch breaks on a tree, you lose everything on that branch, however the tree remains intact along with the remaining foliage.
With the radially fed and primarily load-based architecture, engineering and operations are straightforward and have been in place for decades. Reliability for customers at the ends of the distribution system will be less than those closer to the source of supply.
High density urban distribution will have a variation of the radial architecture to permit alternative sources to feed load customers or improve reliability. Other architectures may include parallel, ring and meshed.
Due the simplicity of the legacy distribution system, technological innovation has been slow to make inroads. The concept of Smart Grid represented a serious culture shock for many utilities that lacked the foresight and workforce capability to embrace it.
Distributed Generation
The proliferation of small-scale energy sources embedded within the distribution system represents a significant architectural change to the legacy radial load-only implementation. I will refer to the new architecture as ‘distributed generation’. Distributed generation has cost, power quality, operational, safety and reliability implications which impact customers.
Traditional protection and control schemes are no longer adequate for maintaining safety, reliability and quality of power. In some cases the distribution system may not have the necessary capacity as the mix of load and generation changes. In most cases the distribution system requires upgrading to accommodate new sources of ‘embedded’ generation.
The distribution system with embedded generation will require additional operational oversight due to the increasingly complex infrastructure. Regulatory processes must also keep pace with the changing landscape to ensure customers’ service levels are maintained.
Ontario has seen over 27,400 generators connected to the distribution system since 2010
Since 2010 there have been more than 1,400 embedded generators larger than 10kW installed on the distribution system. There have been over 26,000 generators 10kW or smaller installed.
Generation
The era of large concentrated generating facilities on the scale of our existing nuclear plants has come to a close. The last major public power project was the Darlington nuclear facility which was brought on-line in stages beginning in 1990. It has a combined output capacity of over 3,500 MW with all units available. New generation is being added on a much smaller scale to replace existing end-of-life facilities and to meet forecasted demand. Renewable generation is forming part of the mix, however due to the intermittent nature of renewable energy it must be supported by other forms of power such as natural gas.
According to the OEB in 2015 we had 323 transmission connected generators
Migration from large concentrated generation to widely distributed smaller output sources has triggered changes to how the system is designed, constructed, operated and maintained.
Design and construction of the electrical system must accommodate vastly different power flows and configuration contingencies than in the past. Suffice to say that managing safety, power quality, stability and capacity is substantially more complex than ever before.
Operations and maintenance
Grid operations involves a greater number of players, some of whom have goals that conflict with the principles of system security and reliability. The majority of generation capacity in Ontario is investor owned and has the primary objective of generating a profit. Operations must manage generator outages and grid configurations to maintain system stability and security for a variety of failure contingencies.
Operating and maintenance procedures must consider a new set of economic variables as generator constraints can have significant contractual costs.
It’s a brave new world….
Derek
Next Article… Technological Innovation
