Critical components

In addition to our distribution stations, over the next 20 years (2012 to 2032), these critical components of our distribution system will meet or exceed their anticipated “end of life”:

Underground cables

  • Life expectancy: 30 to 70 years (depending on application and type).
  • Total quantity in system: 6,100 km.
  • Quantity projected to be in poor condition by 2032: 3,400 km*.
  • Incremental cost of replacement (over 20 years): $900 million.

Underground cables are insulated conductors (power lines) used to distribute electricity from source substations to distribution transformers.

Unlike overhead conductors, underground cables are typically insulated from the ground through a non-gaseous insulating medium (i.e.: plastic, rubber, paper, or oil) that can be installed directly in the ground.

The main advantage of using insulating material on underground cables is increased electric strength, allowing for the cables to be installed in proximity to one another. Numerous circuits can also be installed in small right-of-ways through the use of an underground duct line system.

  • Degradation: In the course of operation, cables are subjected to voltage stress, heat from loading and environmental elements. Underground cable aging is largely dependent on cable type and can be classified as either mechanical damage (caused by external factors) or operational stress.

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Manholes

  • Life expectancy: 80 years.
  • Total quantity in system: 2,400.
  • Quantity projected to be in poor condition by 2032: 350*.
  • Incremental cost of replacement (over 20 years): $30 million.

Manholes are concrete enclosures built in underground duct lines for installing and splicing underground cables. They provide a connection point in duct lines to facilitate underground cable splicing, facilitate the installation of new circuits in high density areas, and house the underground secondary network transformers in downtown Winnipeg.

  • Degradation: Manholes are subjected to environmental and vibrational stresses that may cause mechanical failures resulting in unplanned power outages. These factors include soil conditions, ground movement, mechanical vibration (traffic), and tree roots.

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Duct lines

  • Life expectancy: 100 years.
  • Total quantity in system: 265 km.
  • Quantity projected to be in poor condition by 2032: 25 km*.

Duct lines provide a path for multiple underground high and low voltage cables in a congested area. They are found throughout the province, but are most commonly used for major station feeder egresses and in congested locations such as downtown Winnipeg.

In locations with limited available space, these structures provide the ability to route many circuits along narrow corridors. Duct lines can be installed under roadways, sidewalks, or street boulevards, and are often installed during opportunities, such as major road or bridge repairs.

  • Degradation: Duct lines are subjected to environmental and vibrational stresses which may cause mechanical failures resulting in unplanned power outages. These factors include soil conditions, ground movement, mechanical vibration (traffic), and tree roots.

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Padmount transformers

  • Life expectancy: 50 years.
  • Total quantity in system: 17,000.
  • Quantity projected to be in poor condition by 2032: 170*.
  • Incremental cost of replacement (over 20 years): $3 million.

Transformers are an integral part of Manitoba Hydro’s electrical distribution system and are required to change utilization voltage levels. Padmount transformers transform voltage levels from medium voltage to low voltage.

  • Degradation: Transformers operate under many extreme conditions that affect their aging and impact their likelihood of failing in service. Over time, the insulation utilized in distribution transformers degrades and becomes increasingly prone to failure. The speed of the degradation varies and depends on a variety of factors; however, ambient temperature, wind, and loading history are the most important factors.

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Wood poles

  • Life expectancy: 75 years.
  • Total quantity in system: 1 million.
  • Quantity projected to be in poor condition by 2032: 117,000*
  • Incremental cost of replacement (over 20 years): $410 million.

Wood poles are an integral part of our overhead electrical distribution system and are used to provide adequate ground clearance and mechanical support of conductors and energized equipment installations. One-quarter (250,000) of our province’s wood poles were installed between 1945 and 1960.

Typical structures support one energized circuit; however it is common for multiple circuits to be installed on a common pole structure, particularly in urban environments.

  • Degradation: Poles are subjected to environmental stresses from climatic loads, decay, and mechanical damage, which may cause mechanical failures resulting in unplanned power outages.

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Overhead conductors

  • Life expectancy: 100 years.
  • Total quantity in system: 72,000 km.
  • Quantity projected to be in poor condition by 2032: 6,300*.
  • Incremental cost of replacement (over 20 years): $63 million.

Distribution conductors (power lines) deliver electrical energy from the distribution system to customers. The majority (94 per cent) of conductors used on the distribution system are overhead, with the remainder comprised of underground cable.

  • Degradation: Conductors have two primary modes of degradation: mechanical and electrical. The rate of each degradation mode depends on several factors, including the size and construction of the conductor, as well as environmental and operating conditions.
    • Mechanical degradation includes environmental stresses, such as icing and tree contact, which may result in failure and lengthy power outages.
    • Electrical degradation includes overloading due to general load growth and high fault levels, which may result in premature failure and power outages.

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Overhead transformers

  • Life expectancy: 75 years.
  • Total quantity in system: 142,000.
  • Quantity projected to be in poor condition by 2032: 4,800*.
  • Incremental cost of replacement (over 20 years): $15 million.

Transformers are an integral part of Manitoba Hydro’s electrical distribution system and are required to change utilization voltage levels.

Distribution class transformers are typically installed on distribution feeders and transform voltage levels from one medium voltage to another (interchange bank), or to low voltage (distribution transformer).

  • Degradation: Transformers operate under many extreme conditions that affect their aging potential for failure. Over time the transformers insulation degrades losing its dielectric strength. The speed of the degradation varies and depends on a variety of factors; however ambient temperature, wind, and loading history are the most important considerations. The majority of distribution transformer failures are triggered by an external event such as wildlife, tree contact, or lightning strike at the transformer resulting in internal and/or external damage to the unit.

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Street light standards

  • Life expectancy: 50 to 70 years.
  • Total quantity in system: 58,000.
  • Quantity projected to be in poor condition by 2032: 11,000*.
  • Incremental cost of replacement (over 20 years): $50 million.

Street light standards typically consist of tubular steel or aluminum that supports lights and are used to provide roadway lighting in urban and high traffic locations. The majority of Manitoba Hydro street lights are concentrated within the City of Winnipeg and, to a lesser extent, in other large urban centres in the province.

  • Degradation: Street lights are subjected to environmental conditions and mechanical damage. The nature and severity of the damage depends on the pole location and its environment. The main contributor to the structural breakdown of street light standards is corrosion, both above and below the soil surface. Corrosive environments are typically associated with the proximity of the street light to salt spray from vehicular traffic, but differences in soil chemistry also contribute to below grade corrosion.

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* Assets are continuously replaced as required. If replacement rates don’t increase, this is the number that will be in poor condition by 2032.