High-Voltage Installation and Section 36 of the Canadian Electrical Code (CEC)

What is considered a High Voltage Installation

A high voltage installations is where equipment operates greater than 750V .

Key Hazards

• Inadvertent Contact: Awareness is vital because HV bus and lines are often uninsulated or lack sufficient insulation to prevent electrocution. Limits of approach must be strictly maintained; higher voltages require greater safety distances for workers and tools.

• Environmental Factors: In outdoor substations, snow accumulation under the bus can reduce the distance to overhead conductors, making safe summer routes impassable in winter.

• Equipment Similarity: Substations often feature repeating patterns (breakers, transformers, bus arrangements). Fatalities have occurred because workers mistakenly climbed energized equipment thinking it was the de-energized unit they were previously working on.

• Touch Potential: The potential difference between any point on the ground where a person stands and any point that can be touched simultaneously by either hand during a fault.

• Step Potential: The potential difference between any two points on the ground surface that can be touched simultaneously by a person's feet during a fault.

• Back Feed: Energizing a circuit from the opposite direction of normal flow (e.g., emergency generators or failure to isolate parallel feeds). Precautions include isolating all energy sources, potential transformers, and applying protective grounds.

• Mutual Induction: Generation of voltage in a conductor due to nearby changing magnetic fields. High values can build up in long, de-energized lines near energized lines. Precautions include applying grounds to dissipate energy.

• Capacitive Charge: Charge buildup in long lines, transformers, and motors. Even after removal from service, grounding must be applied to bleed the charge. Voltage can rise again after grounding removal due to dielectric absorption (polarization of the insulation).

• Arc Flash and Arc Blast: Similar to low-voltage environments but with higher energy levels due to proximity to the source. Mitigation requires Personal Protective Equipment (PPE) and hot line tools (hot sticks).

• High Voltage Transients: Occur during lightning storms or switching operations. Lightning can cause insulation breakdown; switching can raise system voltage well above the insulation rating.

Glove Classes

• Class 00: $0.5\,kV$

• Class 0: $1.0\,kV$

• Class 1: $7.5\,kV$

• Class 2: $17\,kV$

• Class 3: $26.5\,kV$

• Class 4:

Conductor material used in high voltage cable ?

• Typically copper (Cu) or aluminum (Al), usually stranded for flexibility.