The Grid

The grid is unique and irreplaceable. 

It is a fundamental component of the “Legacy of the Industrial Age” infrastructure.  It will continue to be essential as it is reconfigured to accommodate modern, distributed and renewable power sources.

Overview

This module covers what “The Grid” is: how it works; how it is regulated, operated and protected; and how the grid of the future must function.

It covers the following topics:

·   A Power Failure example.

·   What is “The Grid”

·   The Biggest Machine on Earth

·   How the Grid is Regulated

·   The Transmission and Distribution Systems

·   How the Grid is Operated

·   Grid Design Challenges

·   The Future Grid

To understand the complexities of the grid, let’s first look at where a large part of the US grid failed, and why.

Introduction

On a hot afternoon in August of 2003, traffic lights and Broadway theaters went dark, air conditioners died, elevators and subway cars jerked to a halt, and emergency generators powered up across the nation’s largest city.

But no physical disaster had directly struck New York.

What had happened is that hundreds of miles away in Ohio, overloaded high-voltage power lines sagged onto tree branches. 

This insignificant event, compounded by operator errors and software failures, cascaded into a blackout that ran north to Ontario, Michigan and Massachusetts; south to Maryland; and east to Connecticut.

This incident illustrates that the grid covers large physical areas, has numerous interconnections and affects massive numbers of people; and is often called the largest machine on earth!

To get started, we first discuss the bulk power grid components and how the pieces fit together. 

What is the Grid?

The grid is a vital, complex collection of equipment, controls, processes, regulators and operators know — creating electricity on one end, and delivering it safely and in the proper strength and frequency to users on the other end. 

It starts with generating stations — centralized legacy assets that provide steady-state power, including nuclear, hydroelectric and fossil-fueled plants.

Intermittent and distributed renewable power sources are also now connected to the grid, such as wind turbines, and solar and battery farms.

Since generating plants do not have extremely high voltage, large transformers are used to step up, or increase, the generated voltage to kilovolts, or kvs, so that electricity can be efficiently moved long distances.

High-voltage transmission lines are the next step. They are mounted on the large towers seen in every landscape.

Transformers along the transmission system ensure that proper, stable levels of power are maintained.

Near major industrial customers, substations then step-down transmission voltage to lower voltages.

In your neighborhood, pole-mounted step-down transformers further reduce the voltage to match it to the appropriate national standards and end-user applications.

The Biggest Machine on Earth

In North America, the grid has over one trillion dollars in assets and 320,000 km of transmission lines, generates 950,000 MW of power with 3,500 utility organizations, serves 100 million industrial customers, and powers 300 million people.

Because of its size and population, North America actually has four discrete grids, called interconnections:

• The West
• Texas (called ERCOT)
• The East, and
• Quebec

Interconnections are electrically independent from each other, except for a few junctions that link them.

Each distinct interconnection has a different physical and regulatory operating model. 

For example, ERCOT was created by the Texas government to avoid federal regulations imposed when transporting power across state lines.

Each of the four interconnections is further separated into smaller state and local distribution regulatory entities, each with a specific geographical reach.

As you might guess, Europe has much more complex and extensive system. 

In Europe the grid must be interconnected across national borders, and powers more than 400 million users in 44 countries.  

The ambitious plan to extend and manage the European grid is discussed next, in the regulatory section of this module.

How the Power Grid is Regulated

Europe

In most advanced countries, essential public utilities like the bulk power system must operate within a regulatory construct.

This is often a web of national and regional entities.  Their goal is to ensure the safe and reliable operation of the system, as well as the ability to restore service quickly after an adverse event.

Energy networks within the European Union have historically been constructed and operated on a national basis by vertically integrated monopolies, usually in full or partial national ownership, with the country’s interest exercised either by central or regional governments.

The UK and France offer two examples:

The UK has government regulatory authorities similar to those in the US, but less complex. 

The UK National Grid operation is overseen by the “Office of Gas and Electricity Markets,” called OFGEM, which itself is governed by the Gas and Electricity Markets Authority. 

OFGEM is tasked “to protect the interests of existing and future consumers.”  The UK National Grid also includes sourcing and distribution of natural gas to users.

On the other hand, France’s grid regulator, the Energy Regulatory Commission is an independent public body regulating both electricity and gas markets.

 It also guarantees non-discriminatory access to the grid for all plants, generators and producers, as well as supervising new grid development according to EU policies.

The EU’s interest in enhancing cooperation and integration of EU country-wide energy networks has grown substantially since the 1980s.

The European Network of Transmission System Operators for Electricity was established in 2009 to pursue further liberalization of the gas and electric markets.

The organization currently represents 42 transmission system members from 35 countries across Europe.  

A recent 10-year plan outlined a significant number of grid infrastructure projects to improve reliability and resilience of the European grid, especially considering the rapid implementation of distributed wind, solar and battery renewables.

US Regulatory Bodies

As in a European country, each US state has its own utility commission, usually referenced by their acronym, such as PUCO for the Public Utilities Commission of Ohio.

They have legal authority to:

• Expand the bulk power system within that state,
• Approve electric rates,  and
• Mange the cost of maintaining or expanding the power system.

National US regulation of the bulk power system that crosses state boundaries is the province of the Federal Energy Regulatory Commission, or FERC.  

It has responsibility to ensure that the grid is operated according to specific standards, and that electric rates are “fair and equitable.” 

The third major organization regulating the US grid is actually a non-profit corporation, the North American Electric Reliability Corporation, called NERC.

NERC develops and enforces reliability and security standards, annually assesses seasonal and long‐term reliability, monitors the bulk power system, and provides education, training, and certification for industry personnel.

The Transmission and Distribution Systems

The grid exists because electricity obviously cannot be provided simply by using an extension cord stretching from a power plant to each user.

The grid is critical because:

• The users are often far from where the power is generated, especially with renewables; and
• The necessity of achieving both reliability and redundancy requires several alternative paths from the generator to the consumer. 

We’ll talk more about reliability and redundancy later, but first let’s learn about the two important pathways for power transmission.

To transfer power from the legacy generators, the backbone of the grid is the national transmission and distribution system in Europe, or the interstate system in the US. 

To finally get the power to consumers and end users, the grid is connected to a local distribution network, or utility.  

Delivery of power to users’ starts with a Transmission System: a series of towers, carrying high-voltage lines, called conductors, to move electricity over great distances.

They are seen everywhere, and on a closer look you’ll notice towers of different shapes and heights, with differing numbers of conductors and supporting arms. 

These different designs accommodate different voltages — from a massive 765 kilovolts down in iterations to 69,000 kvs.

Higher-voltage systems supply major metropolitan areas, while lower-voltage systems supply less-populated areas.

This transmission line backbone is referred to as the “overhead” because it’s almost entirely above ground. In rare instances it’s placed underground, at about ten times the cost.

Transmission towers require specific clearances on either side, typically known as Rights of Way, to keep trees, buildings and other obstructions far from the very high-voltage conductors.

Along the route – from the generating stations to the power transmission system to end users – is a series of substations, with two main functions.

As we saw earlier, some are used to step-up, or increase, the voltage fed into the transmission system so that larger amounts of electricity can efficiently be moved long distances.

Substations must also step-down, or reduce the line voltage to a more usable rating to match end-user requirements. 

That’s the job of what is now called the Distribution System, the other half of the power delivery system.

Finally, once the power gets closer to a residential user, it needs to be stepped-down one more time.  This is typically done by pole-mounted or pad-mounted transformers, visible in your neighborhood.

This is why the entire package is often referred to as the T&D, or Transmission and Distribution system. 

As you will now see, grid operators routinely pursue three major objectives:

How the Power Grid is Operated

• Reliability – Keeping the grid power levels constant and without any noticeable interruptions,
• Resilience – Quickly restoring the loss of power anywhere on the system, and
• Dispatching – Matching the lowest-cost generation option to the grid’s varying load requirements and minimizing congestion on the transmission system.

The term for the consumer need for electricity is called the load.

 Load changes continuously, but generally follows annual patterns;

• more demand in summer and winter, and
• lower demand in what are called the “shoulder” months of spring and fall.

During an average day, electricity consumption also follows what is commonly called the “duck curve”:

• Decreasing after midnight,
• Climbing again around 7:00 am as people get up and go to work,
• Dipping around noon, and
• Climbing to a peak around 8:00 pm.

 Though this is a California example, Europe has as distinct usage patterns which vary slightly from country to country.

Today, a major impact on the duck curve occurs when countries utilize large-scale solar power. 

This impact is most intense at midday, just when demand is at its lowest point, but maximum solar energy is available.

This supply-demand mismatch is just one example of what is called congestion on the grid; and unless there is storage available, the solar power is wasted.

Managing congestion has become one of the major challenges in operating the grid.

It will continue it will require continued investment in R&D especially in data management and information technology.

Local Grid Management

To make all this work below the national level, numerous and specialized organization types are involved with managing the transportation and distribution segments of the grid system.

In the US, they consist of Regional Transmission Operators, abbreviated as RTOs, and Independent System Operators, or ISOs.

These are complex organizations with high-security control centers that oversee specific geographic areas of the grid’s transmission system.

Local Distribution Utilities, called LDUs, can access the transmission system to connect power to their industrial and residential customers.

LDUs are responsible to physically maintain both the transmission and distribution systems in their service territories, and make up approximately 40% of the US transmission system.

In regions where no RTO or ISO exists, the LDU is responsible to operate both the transmission and distribution systems.   

In the United Kingdom there are analogous organizations named the Distribution Network Operators, or DNOs, and Transmission Network Operators, TNOs.

For the rest of Europe, the grid transmission system operators are now part of the European Network of Transmission System Operators for Electricity, discussed earlier in the regulatory section of this module.

Around the world, “The Grid” is facing numerous physical and operational challenges, which we will now discuss.

Grid Challenges

With increased demands for power as more countries expand electricity usage, the grid is now tasked with moving ever-larger flows of electricity, especially in less-developed countries.

As we have learned, renewable generation can often be long distances from the markets and end users.

The primary challenge to expanding, upgrading and modernizing the grid in developed countries is public opposition.

A number of concerns have been expressed by environmental organizations:

• Safety of the high transmission lines – they seem to have caused fires in many locations
• Rights-of-way destroying the countryside and even new residential locations, and
• Personal hygiene deterioration if there is close access to high-voltage lines

Environmental organizations have had success in opposing increases in transmission assets — even from renewable sources.

The second challenge is the need to accommodate and integrate large-scale renewable generation sources, especially utility-scale onshore and offshore wind power – one of the fastest-growing renewable forms.

Finally, other scattered, small-scale sources also need to be efficiently connected to the grid, – such as residential and industrial solar and energy storage units.

The opportunity for reverse, or bidirectional, flow of power carries numerous engineering challenges, now being addressed in many applications. 

Reverse flow is often complicated by stringent tariff rates.  You can learn more about this challenge in our module on Energy Storage Management.

To contribute to the grid’s resilience, all new generation sources must be “dispatchable,” meaning they can be called up quickly by the transmission system operator.

We’ll certainly have some form of the legacy grid with us for years to come, with engineering and regulatory adjustments to accommodate and manage the exciting modern renewable sources. 

Future Grid Innovations

In August of 2020 a heat wave slammed California. The California ISO struggled to increase electricity supply, because:

•            A gas-fueled 500 MW peaking power plant had shut down,

•            Demand for air-conditioning surged,

•            Wind power suddenly backed off, and

•            Solar generation dropped naturally when the sun set

 This simultaneous supply dip-demand spike led to rolling blackouts across the state for the first time in 20 years.

California has thousands of large-scale battery storage units installed at utilities, businesses and even homes. Since they were all connected to the grid for charging, many were now called on to provide storage-to-grid to cover the lost power.

This is the first time that reverse-grid activity of this scale was undertaken.  It was successful, and ultimately supplied more than 300 MW to the grid – enough to replace most of the lost generation.

It became clear that for reliability and resiliency, the future grid needs fully dispatchable generation units to be always online, like the gas-fueled plant in California. 

Looking far ahead… we could have power systems nothing like what we have today, focused on creating electricity locally, and with little or no carbon emissions.

This could include tens of thousands of mini-grids and micro-grids – small self-contained “islands” with their own sources of energy – such as natural gas turbines, solar panel farms, and even small modular nuclear reactors.

They may not be connected to the bulk power grid at all. 

Summary

From our discussion of the bulk power grid, you should now understand that:

Grid failures are rare; but when they do occur there are enormous economic, safety, and lifestyle consequences.

The purpose of the grid is to produce and provide electricity as reliably, safely, efficiently, and inexpensively as possible to all users.

Although there are technical, operational, and regulatory differences, grids in all advanced nations are basically configured the same way: generation, transmission, distribution, and power demand fulfillment.

The Bulk Electric Power System, also known as “The Grid,” makes up what can be considered “the biggest machine on earth.”

In North America, there are four discrete grid interconnections. Europe has what amounts to a single, synchronized grid that crosses the borders of almost all EU countries.

The backbone of the grid is the high-voltage transmission system, connected to the distribution system, which provides the “final mile” connection to individual businesses, facilities, and homes.

The grid as it is currently configured will not disappear anytime soon.  However, the march of carbon-free technologies, including renewables, will demand the creation of a very different grid structure in the very near future.