Home Energy Nuclear Fusion Electricity Climate Change Lighting Control Contacts Links



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

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

A typical bulk electricity transmission line consists of 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. Each phase conductor typically has a maximum rated current capacity of 1500 amperes RMS. Thus this transmission system has a total rated capacity of: 2 circuits X 500 kV X 2 effective conductors per circuit X 1500 amps / effective conductor
= 3,000,000 kVA
~ 3000 MW

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

Stopping CO2 induced climate change requires replacement of fossil fuels with electricity. In Ontario this replacement will approximately triple the peak electricity demand. Thus instead of one row of 500 kV transmission towers in an energy transmission corridor in the future three parallel rows of such towers will be required separated by 100 m between adjacent rows. Thus the minimum total corridor width requirement will become 400 m.

Assembly of real estate for energy transmission corridors is one of the most challenging aspects of utility operation. Hence in defining future electricity transmission corridors planners should make these corridors twice as wide as present design rules suggest so that there is sufficient room to triple the present electricity transmission capacity in the future for displacement of fossil fuels.

A major problem with the present Ontario Energy Plan is lack of long term perspective, particularly with respect to acquisition of 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 the Greater Toronto Area (GTA) 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 new north-south 500 kV dual circuit transmission lines 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 past Bradford. This east-west energy transmission corridor will likely also have to accommodate a new highway 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 to get Ontario legislation passed that:
a) Prevents any new development along these corridors;
b) Provides a long term mechanism for Hydro One Networks Inc. (HONI) to purchase property along these corridors at fair market price 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 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, natural gas and commuter rail services. The main issue with commuter rail services is the requirement for large parking areas adjacent to each rail station. For example, it might 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 through Bradford while this land is still readily available. In the future this corridor will be essential to provide east-west energy transmission 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 in and around the GTA is one of the most glaring deficiencies of the present Ontario 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 400 m wide with a large diameter high pressure natural gas transmission pipeline running down the center of the corridor. The 200 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 in the radius range 200 m to 400 m from 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 natural gas pipeline and reducing the impacts of highway noise, railway noise and electricity transmission line proximity on nearby populations.

A major problem with routing large diameter high pressure natural gas pipelines through urban areas is that these pipelines are subject to occasional long term 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 natural gas fire can only be extinguished by valving off the pipeline both upstream and downstream from the rupture. The radiant energy from the natural gas fire 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 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 natural gas 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 a power line right-of-way can occupy one or two PIR widths.

In the province of Ontario the TSSA 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 recommendations. However, failure to adopt TSSA recommendations could potentially lead to litigation against a municipality for negligence, so most Ontario municipalities adhere to TSSA recommendations as standard practice.

Both the Province of Ontario and local municipalites have failed to make adequate planning provision for energy 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 cost of this urban natural gas generation fiasco to Ontario electricity ratepayers is 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 use and new development of real estate along the identified future electricity transmission corridors. The electricity transmission corridor real estate assembly 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 some 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 at the end of the five year lease terms.

This web page last updated December 6, 2015.

Home Energy Nuclear Fusion Electricity Climate Change Lighting Control Contacts Links