The concepts of electrical environment zones and approach distances defined by the NF C18-510 standard are essential to any electrical authorization training. These are fundamental aspects to master in order to prevent all electrical risks.
When an operation must be carried out near live bare parts, the primary prevention measure is always to work de-energized after a lockout/tagout procedure. In many cases, it is not feasible to lock out or de-energize an installation or facility because operating conditions make de-energization dangerous or impossible. For example, if the electrical room of a supermarket needs to be repainted, it will generally not be possible to lock out the installation (cold chain interruption, public access, etc.).
In such cases, work must be carried out near live bare parts, which involves risks: compliance with approach distances and environment zones is paramount.
APPROACH DISTANCES
Safety distances are defined between an operator and an electrical installation or facility. These distances depend on the nominal voltage of a live bare part and on the type of installation or facility.
They are used to determine the various zones in the environment of open-air installations or facilities and indoor installations.
They also determine the safety distances to be observed for all visible or concealed electrical conduits in the environment.
Four types of distances are defined from a live bare part.
Investigation Limit Distance (DLI)
It is set at 50 meters from live bare parts. It also defines the outer boundary of the investigation zone.
⚡ It is from this DLI that the employer must carry out an electrical risk assessment.
Simple Vicinity Limit Distance (DLVS)
It defines the outer boundary of the simple vicinity zone:
⚡ It is from this DLVS that electrical authorization becomes mandatory. You must at minimum have completed H0B0 electrical authorization training or be accompanied by an authorized person.
Reinforced Vicinity Limit Distance (DLVR)
It differs depending on the voltage, as DLVR LV and DLVR HV:
- The DLVR LV is set at 30 cm from a live bare part in the Low Voltage domain. It is necessary to wear personal protective equipment (PPE) in this zone, at minimum insulating gloves and a face shield.
- The DLVR HV depends on the voltage of the live bare part in the High Voltage domain, as shown in the table below.
Minimum Approach Distance (DMA)
In Low Voltage, the DMA coincides with the DLVR.
⚡ In HV, the DMA is the absolute limit distance that must never be crossed: it protects against the risk of arc flash and varies according to voltage.
ELECTRICAL ENVIRONMENT ZONES
The safety distances presented above are used to define the electrical environment zones.
🔵 Zone 0:
Investigation zone (DLI) where non-authorized personnel can work without risk. The inner boundaries of the zone (DLVS) must be clearly marked. No electrical authorization is required in this zone.
🟢 Zone 1:
Simple vicinity zone (DLVS), access restricted to personnel authorized for the voltage domain of the zone or to personnel who have received safety instructions and are accompanied by an authorized person. You must at minimum hold a B0 authorization for Low Voltage and H0 for High Voltage.
🟡 Zone 2:
Reinforced vicinity zone (DLVR), access restricted to authorized personnel designated by the employer and permitted to work in the vicinity of live bare parts in High Voltage. You must hold H0V, H1V or H2V authorization.
đźź Zone 3:
High Voltage live work zone (DMA), accessible only to electricians trained and authorized for live work, where specific rules must be applied (concerns High Voltage only).
đź”´ Zone 4:
Low Voltage reinforced vicinity zone (DMA) where the rules for general LV interventions or LV live work apply, as well as other LV operations (switching, measurement, testing and verification). PPE (insulating gloves, face shield, etc.) must be worn when operating in this zone.
Analyzing the zones requires identifying the type of electrical environment. There are 3 types of electrical environments:
- Open-air zones
- Zones within rooms with restricted access for electricians
- Zones created by opening a switchboard, an electrical panel or the enclosure of electrical equipment
Open-air zones:
These are unobstructed spaces surrounding a live bare part. This type of environment mainly concerns overhead bare conductors under tension, in High Voltage or Low Voltage. In this environment, you have an investigation zone (Zone 0).
Rooms with restricted access for electricians:
These rooms are (normally) marked with an electrical hazard warning triangle because live bare parts may be present.
⚡ In these rooms, the investigation zone (Zone 0) does not exist. You immediately enter Zone 1 once you pass through the door: the inner face of the room or enclosure represents the boundary of Zone 1, regardless of the distance to the live bare part.
Here is an example of zone layout in a room with restricted access for electricians in Low Voltage:
Zones created by opening a switchboard, an electrical panel or the enclosure of electrical equipment
Whenever the enclosure of energized electrical equipment or the door of a switchboard or panel is opened, there is a risk of coming into contact with a live bare part: the requirements of the NF C18-510 standard must be applied. For example:
- Opening the door of an IP2X electrical panel located in a room
- Removing the casing of a computer tower that is energized
In such cases, the open-air zones and distances apply.
