June 7, 2021
By William (Bill) Burr
Section 36 – High Voltage Installations applies to installations operating above 750 volts, which require special rules and conditions because high voltage arcs can travel through free air and along the surface of some materials. In addition, non-current-carrying metal parts can carry dangerous voltages along their surfaces in a ground-fault situation without effective bonding to ground.
Rule 36-000 Scope — this is a supplementary or amendatory section of the code and applies to all electrical installations operating above 750 volts. Note that the rules of the code for installations operating at 750 volts or less also apply. The Scope also mandates that the supply authority and the inspection department be consulted before commencing any installation covered by this section. Also noted is that the rules of this section do not affect factory assembled equipment approved under the Canadian Electrical Code, Part II standards. Refer to Appendix B and the CEC Handbook for additional information.
Rule 36-002 denotes some special terminology that applies to this section — Boundary fence, Ground grid conductor, Maximum ground fault current, Potential rise of ground grid, Station, Step voltage, and Touch voltage. The CEC Handbook contains an explanation of touch and step voltages with good diagrams. In addition, see Table 52.
Rule 36-004 Guarding — requires that the live parts of high-voltage electrical equipment shall only be accessible to authorized persons.
Rule 36-006 Warning Notices — specifies the required wording, specifications and various locations where warning notices and signs are required.
Rule 36-100 Conductors — stipulates that bare or insulated conductors not enclosed in grounded metal must be used only
• in electric equipment vaults in accordance with Rules 26- 350 to 26-356
• in cable trays in accordance with Rule 12- 2202, or
• in service rooms accessible only to authorized persons
That insulated conductors or cables used indoors or attached to buildings outdoors shall be
• installed in metal conduit
• installed in electrical metallic tubing
• installed as metal-enclosed busways
• cables with a continuous metal sheath, steel wire armour, or of the interlocking armour type, or
• Type TC tray cable installed in cable tray in accordance with Rule 12- 2202
High-voltage TC cables installed in the same tray with low-voltage conductors must have
• a metal barrier not less than 1.34 mm thick separating them
• permanent marking of the location of conductors imbedded in concrete or masonry
• conductive coverings stripped back from terminals to prevent current leakage
• a minimum mechanical strength of #6 AWG for service conductors
Rule 36-102 Radii of Bends — notes that the minimum bending radii for cables must conform to Table 15.
Rule 36-104 Shielding of Thermoset Insulated Conductors — high-voltage cables with thermoset insulation operating at more than 2000 volts must have a metallic shield layer over the insulation, bonded to ground in accordance with Rule 10-304 to equalize the dielectric stress on the insulation layer, except where the conductors meet the conditions outlined in sub rules (2), (3), and (4). Appendix B provides additional information.
Rule 36-106 Supporting of Exposed Conductors — conductors not enclosed in grounded metal must be sufficiently insulated from their supports to withstand any stresses imposed by a possible short circuit in the supply system.
Rule 36-108 Spacing of Exposed Conductors — conductors and other bare live parts must conform to the spacing outlined in Tables 30 and 31. Where the conductors are connected to terminals with less spacing, they are required to meet the required spacing at the first support point.
Rule 36-110 Guarding of Live Parts and Exposed Conductors — conductors not in contact with grounded metal and bare live parts must be accessible only to authorized persons, and isolated by elevation or barriers in accordance with Tables 32, 33, and 34. For voltages more than these tables and for conductors crossing highways, railways and communication lines, use the requirements in CAN/CSA-C22.3 No.1. Where a span following Table 34 exceeds 50 meters, increase the clearance by 1% of the excess.
Rule 36-112 Terminating Facilities — where cables are terminated they must be protected from moisture or mechanical damage.
Rule 36-114 Joints in Sheathed Cables — where sheathed cables are spliced or tapped, the covering insulation and shielding must be electrically and mechanically equivalent to that on the conductors or cables. In addition, the continuity of any bonded metal or conducting sheath must be maintained or the joint must be made in a suitable splicing box that maintains the bonding path continuity.
Rule 36-116 Elevator Shafts — high-voltage insulated conductors or cables are not permitted in elevator shafts unless installed in conduit imbedded in and surrounded by not less than 50mm of masonry or concrete.
Rule 36-118 Conductors over Buildings — states that high voltage conductors shall not be installed over buildings.
Control and protective equipment
Rule 36-200 Service Equipment Location — as per Rule 6-206, service equipment must comply with the location requirements of the supply authority and be at the service entrance point either inside the building or in an outdoor fenced switch yard.
Rule 36-202 Rating and Capacity — it is important that the type and ratings of circuit breakers, fuses and switches are sufficient to provide protection and current-limiting from the high levels of energy during a short circuit. Compliance with Rule 14-012, the requirements of the supply authority, and the rules for other electrical equipment is required.
Rule 36-204 Overcurrent Protection — all ungrounded conductors must have overcurrent protection by a circuit breaker or fuse having adequate rating and interrupting capacity. Fuses must be accessible to authorized persons only and be preceded by a group-operated visible break load-interrupting device or visible break air-break device that may be closed, with safety to the operator, with a fault on the system.
Rule 36-206 Indoor installation of Circuit Breakers, Switches, and Fuses — these must be totally enclosed or installed in an area with non-combustible construction, and for dielectric liquid-filled equipment must conform to Rule 26-012.
Rule 36-208 Interlocking of Fuse Compartments — to prevent access to energized fuses, the cover or door of the fuse compartment must be interlocked with the isolating means so that there is
• no access to the fuses unless the isolating or disconnecting means immediately ahead of the fuses is in the de-energized position
• no access to the fuses where the fuses may be energized from either side, unless the isolating or disconnecting means on both sides of the fuses are in the de-energized position
• no possibility to place the switch into the closed position until the fuse compartment has been closed and the interlock re-engaged
Rule 36-210 Protection and Control of Instrument Transformers — in addition to complying with Rule 26-262, instrument voltage transformers must have a disconnecting means on the supply side of the fuses.
Rule 36-212 Outdoor Installations — field assembled high-voltage switches and fuses must conform to the spacing outlined in Table 35. Horn-gap switches must be mounted horizontally and be capable of being locked in the open position.
Rule 36-214 Disconnecting Means — a load breaking device is required wherever high-voltage insulated conductors or cables fed from a station enter a building.
• It must be located either
– at the entry of the insulated conductors or cable into the building, or
– at the supply station, and
– be capable of being operated from within the building.
• Except where the load breaking device is the draw-out type, the contacts must be visible for inspection in the open position.
• It must also be provided with a group-operating isolating switch on the supply side that provides
– visible inspection of the contacts in the open and closed position
– interlocking to prevent operation under load
– positive indicators of position
• Where there is more than one source of voltage or possibility of feedback in a station, the visibility of contacts, as above, must be provided in all circuits where a feedback could occur. The Appendix B note provides a further explanation in understanding this concept.
Grounding and bonding
Rule 36-300 Material and Minimum Size of Grounding Conductors and Ground Grid Conductors and Connections – conductors ideally should be copper and sized per Rules 36-302 to 36-310 and Table 51. Materials other than copper can be used if
• the current carrying capacity is equal or greater than that specified for copper conductors
• consideration is given to galvanic action when buried in ground or in contact with dissimilar metals
• methods of connecting maintains the required current-carrying capacity of the connection for the life of the electrode design
Reference should also be made to IEEE 80, IEEE 837 and CSA C22.2 No. 41 for additional information.
Rule 36-302 Station Ground Electrode — provides the specifications for constructing a station ground electrode either outdoors or indoors to meet the requirements of Rule 36-304.
Rule 36-304 Station Ground Resistance — outlines the specifications necessary to provide the maximum permissible resistance of the station ground electrode, to limit the potential rise of all parts of the station ground grid to 5000 volts and to the tolerable step and touch voltages specified in Table 52. In special circumstances, in accordance with Rule 2-030, higher voltage rise may be permitted up to the insulation level of communication equipment.
Rule 36-306 Station Exemption — provides exemption from conducting soil resistivity, analysis of touch and step voltages or measurement of resistance of the station ground electrode or touch voltage near the ground electrode where the phase-to-phase voltage is less than 7500 volts, the ground surface covering meets Rule 36-304(5), and the ground potential rise (GPR) will not exceed touch and step voltages in Table 52.
Rule 36- 308 Connections to the Station Ground Electrode — requires that all non-current carrying metal equipment and structures forming part of the station must be grounded to the station ground electrode, and provides the sizes of grounding conductor and methods of connection of various items.
36-310 Gang-operated Switch Handle Grounds — provides methods for grounding of switches to the ground electrode and requirements for a metallic gradient control mat to maintain the touch voltage to Table 52 tolerances.
36-312 Grounding of Metallic Fence Enclosures of outdoor stations — specifies the location of the fence and the various points and methods of connection of parts of it to the station ground electrode, and requires that:
• touch voltages within 1 meter of a boundary fence, located close to the station fence, must not exceed the tolerable values of Table 52 (the CEC Handbook provides several good diagrams showing effective connections to the station ground electrode)
• the station ground electrode must be connected to the fence by a tap conductor at
– each end post
– corner post
– gate post
– at intermediate posts at intervals not exceeding 12 m
by a conductor of not less than No. 2/0 AWG copper
• the tap conductor at each hinge gate post must be clamped or bonded to the gate frame by a copper braid or a flexible copper conductor of at least No. 2/0 AWG
• the tap conductor must be connected to
– the fence post
– the bottom tension wire
– the fence fabric (where the conductor may be woven in at least two places)
– the top rail
– each strand of barbed wire
with the connection to the bottom tension wire, the fence fabric, and barbed wire strands made with bolted or equivalent connectors, and with the top rail connections bonded at every joint by a jumper equivalent to No. 2/0 AWG copper. When there is a metal boundary fence in proximity to the station fence, the touch voltages within 1 m of all parts of the boundary fence shall not exceed the tolerable values specified in Table 52.
In the next installment, we will be discussing Section 38 – Elevators, Dumbwaiters, Material Lifts, Escalators, Moving walks, Lifts for Persons with Physical Disabilities, and Similar Equipment.
William (Bill) Burr is the former Chair of the Canadian Advisory Council on Electrical Safety (CACES), former Director of Electrical and Elevator Safety for the Province of BC, and former Director of Electrical and Gas Standards Development and former Director of Conformity Assessment at CSA Group. Bill can be reached at Burr and Associates Consulting firstname.lastname@example.org.
* Source: CSA C22.1:21, Canadian Electrical Code, Part 1 – Safety Standard for Electrical Installations. © 2021 Canadian Standards Association. Please visit store.csagroup.org. With the permission of CSA Group, material is reproduced from CSA Group standard CSA C22.1:21, Canadian Electrical Code, Part 1 – Safety Standard for Electrical Installations. This material is not the complete and official position of CSA Group on the referenced subject, which is represented solely by the Standard in its entirety. While use of the material has been authorized, CSA Group is not responsible for the manner in which the data are presented, nor for any representations and interpretations. No further reproduction is permitted. For more information or to purchase standard(s) from CSA Group, please visit store.csagroup.org or call 1-800-463-6727.
It should be noted that the CEC Technical Committee has recently discussed and imminently approved an amendment to the definition of voltage in line with the IEC:
• for ac circuits, any voltage not exceeding 30 V ac
• for dc circuits, any voltage not exceeding 60 V dc
• for ac circuits, any voltage exceeding 30 V but not exceeding 1000 V ac,
• for dc circuits, any voltage exceeding 60 V dc but not exceeding 1500 V dc.
• for ac circuits, any voltage exceeding 1000 V ac,
• for dc circuits, any voltage exceeding 1500 V dc.
This amendment will not be published until the 26th edition of the Code in 2024, hence one should confirm with the local Authority Having Jurisdiction whether these increased voltage levels should be observed in the meantime.