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Power quality

Learn more about the various factors that influence power quality, about power quality standards and about how power quality is assessed.

Our transmission system meets the quality and reliability standards of the Northeast Power Coordinating Council (NPCC), which regulates transmission providers in northeastern North America and has some of the most stringent criteria on the continent.

Our distribution system supplies power at voltages within the limits recommended in CSA Standard CAN3-C235-83 for low- and medium-voltage power systems.

If you find that your supply voltage is outside normal limits (for example, not between 110 V and 125 V for a 120-V supply), contact your commercial officer.

Standards and characteristics

In accordance with section 4.1 of the Conditions of Electricity Service [PDF], the voltage limits at the connection point correspond to ± 6% of rated voltage, as per standard CAN3-C235-83.

You’ll find more information about medium-voltage supply in Characteristics and Target Values of the Voltage Supplied by the Hydro-Québec Medium- and Low-Voltage Systems [PDF] (In French only).

In accordance with section 4.1 of the Conditions of Electricity Service [PDF], the voltage limits at the connection point correspond to ± 10% of rated voltage.

You’ll find more information about high-voltage supply in Characteristics of the Voltage Supplied by the Hydro-Québec Transmission System [PDF] (In French only).

Voltage disturbances

Power disturbances are waveform distortions. They can result from incidents on the medium- and high-voltage lines caused by contact with tree limbs, lightning or strong winds. They can hinder equipment operations, depending upon how sensitive the equipment is and the degree of waveform distortion.

However, it is possible to improve equipment compatibility with the supply voltage (commonly referred to as electromagnetic compatibility). Our technical services team is dedicated to assisting customers with all their needs by providing a full range of personalized services.

  • Consulting and expertise services: analysis and measurement of power system electrical phenomena as well as load behavior, explanation of standards, etc.
  • Signature service: expert analysis and diagnosis of power quality, which includes the installation of a measurement tool designed for real-time data capture. The results of the analysis of this data helps customers avoid recurring production losses.

Indoors

Outdoors

  • Escalators and passenger/freight elevators
  • Air conditioners
  • Fluorescent lights
  • Vending machines
  • Variable-frequency drive motors
  • Photocopiers
  • Welding machines
  • Telephone switching systems
  • Fans
  • Arc or induction furnaces
  • Accidents
  • Tree limbs in contact with lines
  • Lightning
  • Air pollution
  • Magnetic storms
  • Strong winds

Electromagnetic Compatibility

Electromagnetic compatibility is the ability of equipment to function satisfactorily in its electromagnetic environment without introducing intolerable disturbances to anything in that environment.

Under the Conditions of Electricity Service [PDF], your electrical installation must be designed, built, connected, protected, used and maintained in such a way that it does not cause disturbances on the power system. Disturbances can be caused by a number of phenomena: voltage and current fluctuations, flicker, harmonics, etc. In order to maintain power quality, Hydro-Québec must ensure that the various types of disturbances do not exceed the thresholds on its power system. If necessary, Hydro-Québec will ask you to conduct the appropriate studies. For example, standards C.22-03 [PDF] (in French only)  and C.25-01 [PDF] (in French only)  contain specific requirements regarding flicker and harmonics. It should also be noted that large, disturbance-causing equipment (welding machines, variable-frequency drives, power electronics, etc.) can be incompatible with sensitive equipment and can cause the allowable disturbance thresholds to be exceeded.

Hydro-Québec encourages you to look for equipment that meets the Canadian standards for immunity to disturbances . Equipment with electronic components is highly sensitive to power disturbances. Electromagnetic incompatibility between your equipment and the voltage delivered by Hydro-Québec can lead to damage or malfunction and can even shorten the service life of your equipment.

Questions about power quality?

Characteristics and Target Values of the Voltage Supplied by the Hydro-Québec Medium- and Low-Voltage Systems [PDF] (In French only).

This document describes the main characteristics of the voltage supplied by the Hydro-Québec distribution system. It lists the various phenomena that influence power quality and proposes measures for protecting your equipment and reducing the potential impacts of disturbances.



Characteristics and Target Values of the Voltage Supplied by the Hydro-Québec Transmission System [PDF].

The purpose of this document is to familiarize our customers with the different phenomena affecting voltage quality, to describe these phenomena and to encourage customers to use this information to adequately protect their equipment and minimize the possible impact of various disturbances.

Bulletins on power quality

To find all the PDF documents mentioned on this page, go to:

˲Technical documentation