In order to understand how substations can impact the environment and what ENMAX Power does to reduce that impact, it is important to have a basic understanding of the purpose of a substation and the land, equipment and buildings that make up a substation.

Insulating Oil
Transformers and certain types of breakers contain mineral oil, which is essential for both insulation and cooling. This oil is relatively inert, indeed quite similar in many ways to clear motor oil. However, the quantity of oil at a substation is very large -– a single transformer with its associated equipment can contain up to 40,000 litres of oil. A major oil release would be a significant environmental incident, so ENMAX Power takes prudent steps to avoid such releases.

To manage this environmental risk, ENMAX Power uses a comprehensive leak detection and management program. A thorough check for leaks is an integral part of the monthly substation inspection routine. All leaks, no matter how small, are monitored on a regular basis.  When a small leak is found it is marked on the inspection form and the information is entered into a computer database. In this way, the leak can be continually monitored by field crews and can be repaired if it gets worse. If a more serious leak is found, it is promptly repaired.

Polychlorinated Biphenyl’s (PCBs)
PCBs, originally used as chemical stabilizers in electrical equipment insulating oils, were common in equipment manufactured until the late 1970’s. Eventually, scientific knowledge advanced to the point where it was determined that PCBs take a very long time to break down chemically into harmless substances after they have entered the environment. Therefore, federal regulations have prohibited PCB use in all new equipment and have strictly controlled the use and transportation of PCBs found in older equipment.

At ENMAX Power, we have a PCB management plan in place to actively eliminate PCBs from our entire electric transmission and distribution system. All of our substation transformers and bulk oil breakers now contain either no PCBs at all, or PCB concentrations well below the current mandated limit. Very small quantities of PCBs in higher concentrations still remain in some sealed equipment (e.g. bushings, capacitors in some older protective relays and liquid filled cables).

The small amount of PCB-containing equipment remaining represents a very low risk of harm to the environment or to human health. Moreover, all such equipment is being systematically taken out of service and replaced with non-PCB equipment as it reaches the end of its life-cycle.

Sulfur Hexafluoride (SF6)
SF6 is an extremely effective electrical insulation gas used in a variety of high voltage equipment. That makes it very desirable for safeguarding reliability of operations. Unfortunately SF6 is also a powerful greenhouse gas, having nearly 24,000 times the global warming potential of carbon dioxide. We currently use this very effective product, and are very diligent in ensuring that as little as possible of our SF6 inventory escapes to the atmosphere.

We at ENMAX Power are very proud of our highly successful SF6 management practices that keep SF6 losses to the atmosphere at a minimal level. For example, in 2003 our operations resulted in only 36 kilograms of SF6 losses, compared to our total SF6 inventory of 5,300 kg. This represents a release rate of only 0.7% of inventory, which is significantly better than the performance of the Canadian electric industry as a whole. Much of our success in this area is due to the diligent efforts of a group of highly dedicated ENMAX employees who have pioneered new and more effective ways of managing SF6 to reduce its environmental impact.

Herbicides and Pesticides
Buried beneath the gravel in a substation yard is a grid of wires that functions as the grounding for the high voltage equipment. It is important to prevent this ground grid from being compromised by vegetation growth, in order to ensure safety for our employees and the public. For this reason substation yards are regularly maintained by using a variety of herbicides, the majority of which are based on a chemical known as glyphosate.

These herbicides are neither flammable nor explosive and have no material impact on underground works or ground water. We ensure that extra precautions are taken when applying herbicides close to water bodies. We do not use any chemical pesticides to control animal populations in or near our substations.