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By Charles Rhodes, P.Eng., Ph.D.

This web page addresses long term electricity and natural gas energy transmission planning and related safety issues. In the future natural gas pipes may be repurposed for hydrogen gas transmission / distribution.

A typical bulk electricity transmission corridor has a single row of galvanized steel lattice towers that are about 300 feet (100 m) high and that support two 500 kV RMS 3 phase delta AC circuits. Typically each phase conductor consists of four wires separated by spreaders to reduce the peak radial electric field at the wire surface. Each phase conductor typically has a maximum continuous current rating of 1500 amperes RMS. Thus each line of power pylons has a peak transmission capacity of:
2 X 3 phase circuits X 500 kV X (2 effective conductors / 3 phase circuit) X (1500 amps / effective conductor)
= 3,000,000 kVA
= 3,000 MVA
~ 3000 MW

In the year 2009 the average capital cost of building this 2 circuit 500 kVAC transmission through rural Ontario was about $4,000,000 / km.

Earthquakes, sabotage or ice storms can knock over a single line of tall power pylons. Hence from a public safety perspective for a single line of 500 kV electricity power pylons the energy transmission corridor width should be at least 200 m wide to allow for the power pylons falling in any direction.

Stopping CO2 induced climate change requires replacement of fossil fuels with electricity. In Ontario this replacement will more than triple the peak electricity demand. Thus instead of one row of 500 kV power pylons in an energy transmission corridor in the future three or four parallel lines of such pylons will be required separated by at least 100 m between adjacent lines. Thus the required transmission corridor width requirement will increase to become 400 m to 500 m.

1) It is difficult to obtain a transmission line corridor at any time and often it must follow a new highway corridor.
2) The transmission line corridor width should be sufficient for a single line of 500 kV pylons, even if that is not what is presently required. Otherwise there is no room for load growth (width = 600 feet ~ 200 m).
3) Where the corridor passes by an area which is zoned for future residential housing a few 500 kV towers should be installed, even if they are not currently needed. The issue is that absent those towers future residents will create political opposition that will overrule good engineering with respect to increasing the transmission capacity.
4) In Ontario new generation requires a permission to connect from the transmission line provider Hydro One. Permissions to Connect are issued on a first come first served basis, and have a limited time window for construction. This methodology prevents local over building of generation and prevents parties that lack sufficient capital from tying up available unused transmission. Capacity factor is also an issue in permission to connect.
5) Once one markets Interruptible Electricity transmission will be constantly used right up to the maximum generation plate rating.
6) The transmission must be over rated sufficiently to allow for two adjacent circuits to be out without affecting customers. Typically in Ontario each pylon carries two 500 kV 3 phase circuits, so a single pylon failure can take out two adjacent circuits.
7) The peak generation capacity is in large measure limited by available summer cooling. Summer cooling is limited by available large bodies of water or cooling towers. Selling cooling towers in urban areas is of difficulty at least comparable to selling transmission lines.
8) If you want to expropriate a transmission line corridor across private land and/or developed property you had better be prepared to pay the market value of that land and/or developed property. There is also the issue of the market value of adjacent properties.
9) If you want to build transmission economically you need to identify the required corridors a century ahead of time and get that property zoned for only transmission or agricultural use. If there is present non-compliant property use, 100 years in the future anyone presently affected will be dead. For reasons best appreciated by lawyers, estate litigation is a lot simpler.
10) There are a number of smart tricks for locating transmission such that its visual impact is minimal. They need to be used. An example of a well located transmission line is the one that runs east-west across Algonquin Park in Ontario. Someone used a lot of thought to follow the contours such that from ground or lake level the transmission is almost invisible unless one is almost directly underneath it. That type of route survey means that the surveyors must be prepared to get out in canoes, not sit in an office looking at Google overhead views.
11) Where a transmission line passes through a potentially dry forest, the cost of ongoing fire break maintenance is a serious consideration.
12) Where a transmission line is attached to a cliff there are serious issues related to access for maintenance.
13) In my view the biggest single problem with transmission line planning is getting politicians to recognize that today they need to make realistic plans for 100 years in the future.
14) There is a lot of merit in expropriation allowing occupancy until death. When I was a child the entire West Vancouver beach front was privately owned. It was expropriated in a manner that allowed the then owners to occupy the property until their death, but the property could not be transferred to another party. Over a period of about 60 years all the original owners died, so now the entire beach is in public hands. With sufficient forward planning this is the superior way to obtain transmission corridor right-of-way.
15) Acquisition of real estate for energy transmission corridors is one of the most challenging aspects of utility planning. Hence in defining future electricity transmission corridors planners should make these corridors at least twice as wide as present design rules suggest is necessary so that there is sufficient room to at least triple the present electricity transmission capacity for future displacement of fossil fuels.

The issues related to electricity transmission lines and forest fire control have been well known for at least 60 years.
1) Build transmission towers large enough that wind cannot cause either phase to phase or phase to ground shorts.
2) Build a service access road alongside the transmission which enables foresters to easily cut and remove vegetation. That road should also serve as a temporary fire break. Such roads often need fences and cattle gates.
3) Pay foresters to biannually cut back vegetation and remove the debris. In suitable conditions trees can grow a lot in two years and can overwhelm a power transmission line in four years.
4) Maintain a forest fire protection service with watch towers that have line of sight view of the entire transmission right-of-way.
5) Maintain a fleet of large water bombers that can be dispatched at literally 5 minutes notice. If a fire is not suppressed during the first hour it can soon become unmanageably large.
6) Maintain a force of smoke jumpers or helicopter borne fire fighters to completely extinguish small fires. Again that force must be ready to go 24/7.
7) Maintain a force of daytime fire fighters fully equipped to back up the smoke jumpers.
All of these measures cost serious money. At various times different parties have tried to cut corners on these costs, always with long term devastating results. The bottom line is that these measures must be adequately funded which means that power transmission and forest fire suppression are not free, despite claims to the contrary by various parties.

The whole concept of politicians being elected or CEOs being chosen to cut these costs is fundamentally wrong. All that happens is that during the next severe fire season the costs are shifted onto someone else.

A major problem with the present Ontario Long Term Energy Plan is lack of long term perspective, particularly with respect to acquisition of urban electricity transmission corridors.

If Ontario is to reduce CO2 emissions from fossil fuels the law of conservation of energy demands the following:
1. The ability to bring large amounts of additional non-fossil electricity into urban areas from elsewhere in Ontario.
2. The ability to efficiently store surplus energy during times and seasons of energy surplus and to efficiently recover and use that energy during times and seasons of energy deficiency.
3. Meeting point #1 will require at least two additional north-south 500 kV dual circuit transmission lines into the Greater Toronto Area each of which must pass either west or east of Lake Simcoe.
4. For reliability the north-south energy transmission corridors will need to be connected together, probably via an east-west energy transmission corridor routed through the north edge of East Gwillimbury and on west past Bradford. This east-west corridor will also have to accommodate a new highway #412 interconnecting Hwy 400 and Hwy 404.
5. In the long term meeting point #2 will likely require two new 500 kV dual circuit transmission lines between the GTA and Niagara Falls to access the hydraulic energy storage capacity between Lake Erie and Lake Ontario and new 500 kV interties to Quebec.
6. In the long term displacing fossil fuels in the transportation and heating sectors will require additional high voltage transmission between the perimeter of Toronto and the core of Toronto.
7. The acquisition of these electricity transmission corridors will be one of the major challenges facing the Independent Electricity System Operator (IESO) in the years to come. The more there is political procrastination about this issue the more difficult it will become due to on-going property development along the required energy transmission corridors and on neighboring lands.
8. A high priority for the IESO is to identify the required energy transmission corridors and reactor sites and to get Ontario legislation passed that:
a) Prevents any further new development along these corridors and at these reactor sites;
b) Provides a long term mechanism for Hydro One Networks Inc. (HONI) and electricity distributors to purchase property along these corridors at fair market value as these properties come on the market.
9. By exercising this purchase mechanism, over a period of about 40 years most of the properties in the path of the contemplated new energy transmission corridors and at the required reactor sites could be acquired at fair market price without dispute or political conflict.
10. The IESO should also consider use of the same corridors for future roadway, hydrogen gas and commuter rail services. A major issue with commuter rail services is the requirement for large parking areas adjacent to each rail station. For example, it would likely be prudent for the provincial government to purchase the Buttonville Airport as a future commuter rail station. In the interim this property could continue to be used as an airport. Similar areas of land should be purchased near Aurora, Newmarket, Sharon, Queensville and Keswick to allow for a 500 kV power line and a commuter rail line parallel to Hwy 404.
11. Hydro One should also purchase an east-west 500 kV energy transmission corridor through the north edge of East Gwillimbury and on west through Bradford while this land is still available at a reasonable price. In the future this corridor will be essential to provide east-west energy transmission redundancy and an east-west highway connection north of the GTA.
12. In summary, lack of long term planning, particularly with respect to acquisition of energy transmission corridors and reactor sites in and around the GTA is one of the most glaring deficiencies of the present Ontario Long Term Energy Plan.

The past political difficulties related to acquiring corridors for 500 kV power lines has led to development of combined energy transmission and surface transportation corridors. Such corridors, such as Hwy 407, are typically 500 m wide with a large diameter high pressure natural gas transmission pipeline running down the center of the corridor. The 300 m corridor width on one side of the natural gas transmission pipeline is sufficient to accommodate two rows of 500 kV dual circuit transmission towers and a railway. These electricity transmission towers can collectively move about 6000 MW of electricity. The 200 m corridor width on the other side of the natural gas pipeline is sufficient to accommodate a large divided highway.

From a land use planning and zoning perspective it is a good idea to zone the energy transmission corridor 800 m wide and restrict the land use within 400 m of the large diameter high pressure gas pipeline axis to agricultural uses. This planning concept accomplishes the dual objective of increasing the safety setback from the large diameter high pressure gas pipeline and reducing the impacts of highway noise, railway noise and electricity transmission line proximity on nearby populations.

One of the major challenges in Canada is the low load factor of natural gas pipelines. For multiple practical reasons, including low marginal cost, gas is the heating fuel of choice. However, in much of Canada there are a few winter days during which the space heating load is 3X most other winter days. The summer heating load is typically less than (1 / 3) of the average winter heating load. In many high rise residential buildings the average heating load in August is in the range of (1 / 10) to (1 / 20) of the peak winter heating load. Hence the gas pipe line:
load factor = (averge load) / (peak load)
is less than 20%. For much of every year the gas pipeline delivery capacity is severely under utilized but for a few days per year the pipeline delivery capacity is stretched to its limit.

The gas distribution companies presently have to recover their pipeline financing and maintenance costs out of gas sales to consumers. Hence gas supply contracts are often structured as take-or-pay arrangements to ensure that the gas customer pays for his/her share of the pipeline financing and maintenance costs irrespective of the amount of gas he/she actually consumes.

An inherent problem with take-or-pay gas contracts is that they provide little or no financial incentive for gas conservation as required for minimizing CO2 emissions. At this time there is no simple solution to this problem. Replacing gas heating capacity with sufficient electricity capacity to meet the peak winter thermal load is extremely expensive. The issue of how to finance the gas piping network by some means other than gas take-or-pay contracts has yet to be seriously faced. One alternative is to use reject heat from electricity generation together with terminal heat pumps for winter heating and to supplement that heat on cold days with a synthetic liquid fuel produced during low load seasons.

A major problem with routing large diameter high pressure gas pipelines through urban areas is that these pipelines are subject to occasional spontaneous rupture failure. Each such rupture failure causes an initial combustion free rupture explosion, a huge roaring noise, a deafening delayed ignition explosion and a tremendous ongoing fire. The explosions and fire usually destroy nearby electricity and water services. In practice the fire can only be extinguished by valving off the pipeline both upstream and downstream from the rupture. The radiant energy from the gas fire at the rupture can cause spontaneous ignition of buildings up to 250 m from the pipe rupture location. The initial rupture explosion throws rocks, pipe sections and other debris high into the air. This falling debris and burning embers can cause lethal damage hundreds of metres away. The pressure pulse from the delayed ignition explosion can blow out windows as far as 1.6 km from the rupture location.

With respect to the radiant thermal energy released by the flame from a ruptured large diameter high pressure natural gas pipeline, it is possible to calculate a safety setback distance Rs that is a function of the natural gas pipeline's diameter and operating pressure. This calculation is contained on an adjacent web page titled NATURAL GAS PIPELINE SAFETY SETBACK.

R = radial distance from a natural gas pipeline rupture

Rs = radius from pipe rupture at which the infra red radiation intensity is equal to the solar irradiance (the solar intensity in space incident on the Earth). At R = Rs the infrared radiation causes negligible property or skin damage.

(Rs / 2) = radius from pipe rupture at whch the infrared radiation intensity is 4 X the solar irradiance. Generally:
R = (Rs/ 2)
is the closest that a municipal fire fighter can approach a burning natural gas flame.

(Rs / 4) = radius from pipe rupture at which the infrared radiation intensity is 16 X the solar irradiance. Generally for:
R < (Rs / 4)
wood and similar materials rapidly spontaneously ignite. Generally for:
R < (Rs / 4)
there is total destruction regardless of the fire fighting measures that are employed.

(Rs / 4) < R < (Rs / 2) = region of secondary ignition. Combustion in this region is primarily triggered by burning embers originating from combustion in the region:
R < (Rs / 4).
Property damage in the region:
(Rs / 4) < R < (Rs / 2)
occurs because municipal fire fighters are not equipped to work in zones of high infrared radiation intensity. Damage in this zone can be reduced by use of water bombers if they are immediately available.

In an area of uniform property development, absent the immediate availability of water bombers, the dollar value of the fire damage in the region:
(Rs / 4) < R < (Rs / 2)
will likely be 75% of the total fire damage.

In recognition of the danger to the public of large diameter high pressure natural gas pipelines the Ontario Technical Standards and Safety Authority (TSSA) has defined a distance which it terms the Potential Impact Radius (PIR). For practical natural gas pipelines:
(1 PIR) ~ (Rs / 4)

The TSSA now recommends a minimum setback of (1 PIR) implying a safety corridor width of (2 PIR). This choice by TSSA is a balance between public safety and cost of real estate acquisition. This choice by TSSA in combination with a usual municipal fire fighting capability reduces the fire damage resulting from a natural gas pipeline rupture by about a factor of three as compared to no setback, without transferring an undue real estate purchase cost burden on to the pipeline owner and hence the utility ratepayer.

A second advantage of this TSSA recommendation is that it is sufficient to allow most adults who are independently mobile to escape with their lives. People who are not independently mobile such as small children or infirm persons should never be in the region:
R < (2 PIR)
and to avoid them being reliant on rapid response by municipal fire fighters, should not live within the region:
R < (4 PIR).

Ideally the minimum setback should be:
(Rs / 2) ~ (2 PIR)
and the minimum safety corridor width should be:
Rs ~ (4 PIR).
However, legally defining safety corridors in that manner doubles the real estate acquisiton cost burden that must ultimately be borne by the utility rate payer.

A compromise is to force the pipeline company to acquire a dedicated corridor (2 PIR) wide and through zoning to prevent property development in strips (1 PIR) wide on each side of the dedicated pipeline corridor. Thus a total safety corridor (4 PIR) wide can be realized. In some circumstances a roadway and/or an electricity transmission right-of-way can occupy one or two PIR widths.

In the province of Ontario the TSSA (Technical Standards and Safety Authority) only makes safety setback recommendations with respect to natural gas pipelines. It is up to each municipal government to adopt bylaws that give legal force to the TSSA guidelines. However, failure to adopt TSSA guidelines could potentially lead to litigation against a municipality for negligence, so most Ontario municipalities adhere to TSSA guidelines as standard practice.

Both the Province of Ontario and local municipalites have failed to make adequate planning provisions for future electricity transmission corridors. Until provincial and municipal politicians address this problem this issue will constrain the potential electricity system development. The Ontario Power Authority (OPA) foolishly attempted to resolve urban transmission bottlenecks by use of natural gas fired generation located in urban areas. However, use of this generation is contrary to necessary CO2 emission reductions and needs dedicated large diameter high pressure natural gas pipeline transmission corridors through urban areas for supplying natural gas to the generators. Local populations, acting reasonably, rejected the concepts of locating natural gas fired generation in dense urban areas and running large diameter high pressure natural gas pipelines within road allowances. The immediate cost of this urban natural gas generation fiasco to Ontario electricity ratepayers was over one billion dollars.

The appropriate course of action is for the IESO to face the electricity transmission corridor planning issue head on and to identify future electricity transmission corridors through urban areas with at least a fifty year time horizon. These electricity transmission corridors will be required to allow for future population density growth and to allow electricity to displace fossil fuels in the heating and transportation sectors.

Proper long term grid planning requires restricting land use and new real estate development within and adjacent to the identified future electricity transmission corridors. The electricity transmission corridor real estate acquisition process takes decades. Successive Ontario and municipal governments have repeatedly procrastinated about facing this issue. The electricity transmission corridor planning issue needs to be removed from the hands of elected politicians, whose time horizon is typically only two years, not fifty years. No matter how well electricity transmission corridors are planned, there will always be NIMBY opposition that affects short term political decisions. To minimize this opposition property along identified future electricty transmission corridors should be purchased by Hydro One at fair market value as the property becomes available. Hydro One could then lease the property to others in five year increments with the specific lease provision that Hyro One has no obligation to renew such leases.

This web page last updated March 19, 2022.

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