Influencing factors of power quality

Voltage limits at the connection point of delivery as specified in CAN3-C235-83

Normal operating conditions

	Minimum (volts)	Maximum (volts)
Single-phase 120/240 V	112/194	125/216
3-phase quadruplex 120/208 V (Y)	112/194	125/216
3-phase quadruplex 347/600 V (Y)	318/550	360/625
3-phase triplex 600 V	550	625

Extreme operating conditions

	Minimum (volts)	Maximum (volts)
Single-phase 120/240 V	106/212	127/254
3-phase quadruplex 120/208 V (Y)	110/190	127/220
3-phase quadruplex 347/600 V (Y)	306/530	367/635
3-phase triplex 600 V	530	635

Note: If the voltage remains within the limits for normal operating conditions, no improvements or corrective action are necessary. If it falls into the range for extreme operating conditions, improvements or corrective action should be planned according to a definite schedule though not necessarily on an emergency basis. If the voltage surpasses these limits, Hydro‑Québec must take urgent action to remedy the situation.

You’ll find more information about low voltage in Characteristics and Target Values of the Voltage Supplied by the Hydro‑Québec Medium- and Low-Voltage Systems [PDF 894 Kb - in French only].

According to standard CAN3-C235-83, the voltage limits at the connection point correspond to ±6% of rated voltage (usually 25 kV, that is, 14.4/24.94 kV, 3-phase wye, grounded neutral). 

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 894 Kb - in French only].

Indoors

• Escalators and passenger/freight elevators
• Air conditioners
• Fluorescent lights
• Vending machines
• Variable-frequency drive motors
• Photocopiers
• Welding machines
• Telephone switching systems
• Fans

Outdoors

• Accidents
• Tree limbs in contact with lines
• Lightning
• Air pollution
• Magnetic storms

Under the Conditions of Electricity Service [PDF 4.69 MB], your electrical installation must be designed, built, connected, protected, used and maintained in such a way that it does not cause disturbances in 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 of its power system. If necessary, Hydro‑Québec will ask you to conduct the appropriate studies. For example, standards C.22-03 [PDF 1 MB – in French only] and C.25-01 [PDF 1 MB – 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 power disturbances (the CAN/CSA-CEI/IEC 61000-4-X series). 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.

Low-voltage electrical service

To find out more about the requirements for low-voltage connections, see Hydro‑Québec standards E.21‑10 (Blue Book) [PDF 7.66 MB – in French only] and E.21-11 (Green Book) [PDF 2,6 MB – in French only]. Hydro‑Québec reserves the right to require that you conduct an electromagnetic compatibility assessment in accordance with C.22-03 [PDF 1 MB – in French only] and C.25-01 [PDF 252 Kb - in French only].

Medium-voltage electrical services

To find out more about the requirements for medium-voltage connections, see Hydro‑Québec standard E.21-12 (Red Book) [PDF 6.5 MB – in French only]. Hydro‑Québec reserves the right to require that you conduct an electromagnetic compatibility assessment in accordance with C.22-03 [PDF 1 Mo - in French only] and C.25-01 [PDF 252 Kb - in French only].

Filters placed in series at the entrance to a variable-frequency drive can improve immunity against transient surges on the power grid.

It is your responsibility to guard against the consequences of a power loss, particularly on just one phase, whether or not your equipment is protected by fuses.