Electric vehicle (EV) charging is changing the way electrical systems handle loads, and this change involves more than just installing more circuit breakers.
EV chargers act as dedicated loads in residential, commercial, and public charging facilities. The charging process often lasts for extended periods, and the charging equipment contains power electronics that affect the protection requirements of the electrical circuit.
However, EV charging has not changed the basic principles of circuit breaker selection. Rated current, conductor protection, short-circuit protection, and installation conditions remain the core elements of circuit breaker selection. What has changed are the load characteristics and the protection requirements that designers need to focus on.
1. EV Charging Adds Specific Electrical Circuits
EV chargers require a suitable supply circuit. This circuit needs to meet the electrical requirements of both the charging equipment and the installation system.
This provides two benefits:
- Safety and load considerations: EV charging is a typical continuous high-power load. A dedicated circuit ensures that all the capacity of that circuit is used for charging, preventing overloads caused by other appliances sharing the circuit and reducing fire risk.
- Ease of protection and control: A dedicated circuit allows for more precise configuration and installation of required protection devices, such as specific types of residual current devices. It also facilitates independent energy metering and smart management.
IEC 60364-7-722:2018 specifies requirements for low-voltage electrical installations that supply power to electric vehicles. This standard covers circuits that supply power to EVs, as well as circuits where power flows back from the vehicle to the system.
Disjuntores still need to be matched to the circuits they protect. Designers need to consider the charger’s rated current, circuit voltage, conductor ampacity, and the required short-circuit protection.
These selection principles are not new requirements introduced by EV supply equipment. EV power supply simply creates a new application scenario where these principles need to be applied to a specific charging load.
2. Charging Keeps Circuits Energized for Extended Periods
Depending on the charging equipment and operating mode, EV charging circuits remain energized for extended periods.
This operating condition makes the thermal performance of circuit breakers a factor to consider. Current flowing through a circuit breaker generates heat. The ambient temperature around the breaker, the mounting method, the enclosure, and adjacent equipment also affect its operating temperature.
Designers need to evaluate the circuit breaker’s performance under actual installation conditions.
Extended energization also exists in other types of electrical loads. EV charging is not the only application with this condition. The operating characteristics of the charging process make thermal conditions an important consideration in circuit design.
3. Residual Current Protection Requires Attention
EV charging equipment has specific requirements for electric shock protection and residual current protection.
IEC 61851 specifies electrical safety and protection requirements for conductive EV charging systems, including protection against electric shock and residual current protective devices.
RCDs are used primarily for residual current protection. RCBOs combine residual current protection with overcurrent protection in a single device.
Different charging systems may have different protection requirements. Purchasers need to review the technical documentation of the charging equipment and determine the protection configuration based on the applicable electrical codes.
4. Multiple Chargers May Increase Load Requirements on the Distribution System
One EV charger corresponds to one electrical load. When multiple chargers operate simultaneously, the entire distribution system needs to handle a larger combined load.
When a system includes multiple charging points, designers need to evaluate the combined electrical demand when multiple charging devices operate at the same time. This evaluation may affect the selection of upstream circuits, distribution equipment, and protection devices.
Upstream circuit breakers need to match the circuits supplying the charging equipment. Designers also need to consider the coordination between branch circuit protection and upstream protection.
For systems with multiple charging points, circuit breaker selection needs to be evaluated in the context of the entire distribution structure, not by considering each charger individually.
5. Charging Systems Still Require Circuit Protection
EV charging equipment has built-in protection features, but these are limited to the internal protection of the equipment. The overall charging system and associated circuits still rely on disjuntores ou fusíveis for protection.
The scope of protection provided by a circuit breaker depends on its location and design within the distribution system. Branch circuit breakers protect the corresponding charging circuits. Upstream breakers provide protection for a broader section of the system. Protection devices at different levels also need to be coordinated according to the system design.
When multiple EV charging circuits connect to the same distribution system, designers also need to consider the relationship between branch protection devices and upstream protection devices.
Conclusão
EV charging changes the way circuit breakers are applied, not the fundamental rules of circuit breaker selection.
Designers still need to match circuit breakers to circuits, conductors, voltage, current, and fault conditions. EV charging adds specific considerations related to charging duration, residual current protection, and distribution for multiple charging points.
For purchasers, looking only at the charger’s rated current is not sufficient. The circuit breaker needs to be evaluated in the context of the entire charging circuit and the distribution system.
A sound protection solution for EV charging needs to start from the actual circuit design, the requirements of the charging equipment, and the electrical standards applicable to that installation.
