Lockout / tagout (LOTO) is a safety procedure used to ensure electrical or mechanical equipment is fully isolated from hazardous energy and cannot be accidentally re-energized during servicing or maintenance. In EV charging infrastructure, lockout/tagout is critical when working on chargers, switchboards, feeders, or associated equipment, helping protect technicians from electric shock, arc flash, unexpected startup, and stored energy hazards.
What Is Lockout / Tagout?
LOTO is a controlled isolation process that prevents the release of hazardous energy by:
– Lockout: physically locking an isolation device (breaker, disconnect switch) in the OFF position
– Tagout: attaching a warning tag stating who locked it out, why, and when
The objective is to ensure only authorized personnel can restore power after work is completed and the area is safe.
Why Lockout / Tagout Matters in EV Charging
EV charging systems involve high currents, multiple circuits, and sometimes high-voltage DC equipment. LOTO reduces risks such as:
– Accidental energization of a charger while someone is working inside
– Exposure to energized conductors in distribution boards and cable terminations
– Arc flash incidents during maintenance or troubleshooting
– Unexpected activation of contactors or relays due to remote commands
Because many chargers are connected to a backend (CPMS) and can receive remote control signals, LOTO ensures maintenance work remains safe regardless of software commands.
Where LOTO Is Applied in EV Charging Installations
Common locations and scenarios include:
– Main breaker or feeder isolator supplying a charger or charger group
– Local disconnect switch near the charger (if installed)
– Switchboards and distribution panels during installation, inspection, or repairs
– DC power cabinets and dispensers (where applicable)
– Metering equipment and control panels connected to live circuits
LOTO is used during commissioning, corrective maintenance, upgrades, and component replacement.
Typical Lockout / Tagout Steps
A standard LOTO process typically follows these steps:
– Identify all energy sources (AC supply, control power, auxiliary circuits, stored energy)
– Notify affected users and shut down equipment following procedure
– Isolate energy using the correct disconnect or breaker
– Apply lock(s) and tag(s) to the isolation point
– Release or secure stored energy (capacitors, mechanical movement, spring energy)
– Verify isolation using appropriate test instruments (prove–test–prove)
– Perform work only after zero-energy state is confirmed
– Remove tools, restore guards, and re-energize only by authorized personnel
Verification is essential—never assume a circuit is dead based only on a breaker position.
Key Considerations and Best Practices
In EV charging environments, LOTO programs should account for:
– Multiple feeds (AC power + auxiliary power + communication cabinets)
– Remote start/stop signals from a backend or building automation system
– Clear labeling of breakers, feeders, and charger IDs
– Group lockout procedures for multi-person work
– Documentation and training for authorized personnel
LOTO is typically part of broader electrical safety requirements alongside PPE, risk assessments, and arc flash procedures.
Limitations and What LOTO Does Not Replace
LOTO does not replace proper electrical competence or safe working practices:
– It does not eliminate the need for correct PPE and insulated tools
– It does not guarantee safety if the wrong isolation point is locked
– It does not address unsafe wiring design or inadequate protection devices
Effective LOTO requires accurate site documentation and disciplined execution.
Related Glossary Terms
Commissioning documentation
Electrical isolation
Arc flash
Electrical safety
Main breaker
Disconnect switch
Risk assessment
Preventive maintenance
Uptime
Service procedures