Safe switching and protection of high voltage electrical networks
A comparison of electromechanical, hybrid and fully electronic switching and protection solutions
There have been many developments in the battery technology. Energy density, charging times and costs have improved significantly. Battery packs and cell chemistries have been optimised for a wide range of applications. This also changes the priorities for switching and protection solutions. It is no longer just technical feasibility and price that count, but the total cost of ownership. High availability, easy integration, low power dissipation and safety in the event of a fault are becoming key criteria.
In the early days of high-voltage (HV) electrification, gas-filled HV contactors and HV fuses dominated.. Both technologies have proven their worth but also have their limitations depending on the application. Fuses can overheat and must be replaced after they have tripped. Pyrofuses ensure fast tripping but require expensive sensors and control systems. Conventional gas-filled contactors can quickly be overloaded by high short circuit currents. This is where semi-open and hybrid switchgear offer new approaches.
One example is the HVR10 from E-T-A. This hybrid high-voltage relay combines a mechanical contact system with arc-suppressing electronics. This protects the contacts, keeps the contact resistance low throughout the component’s service life and reliably switches high currents.
Two prototypes illustrate the range of solutions
E-T-A also develops platforms that help integrate switching and protecting more smoothly. The HVB10 high-voltage circuit breaker uses an electromechanical design. It switches the positive and negative battery terminals and acts as a contactor with built-in overcurrent and short circuit protection. This means there is no need for a separate fuse or pyrofuse. The protection system operates without electronic sensors, microcontrollers or software. The HVB10 functions as a passive safety component, like a high-voltage fuse. It also provides reliable physical isolation, regardless of the magnitude of the fault current. Depending on the type of fault, the device can be reset. Once the fault has been isolated, the unaffected loads can resume operation.
At the other end of the spectrum is the HV-SSR, a solid-state circuit breaker based on modern Junction Field Effect Transistor (JFET) technology. Its strength lies in its extremely short clearing time of less than ten microseconds between the short circuit event and the disconnection of the circuit. As a result, the short circuit current does not add up to critical levels. And the HV-SSR can be reset an almost unlimited number of times. An integrated pre-charging function replaces the pre-charge contactor and pre-charge resistor, which reduces the space required, the number of components and the overall complexity.
The HVB10, the hybrid HVR10 and the HV-SSR are examples of fundamentally different approaches, each with its own strengths and weaknesses. At the same time, they highlight the range of solutions that E-T-A offers in the field of high-voltage protection.
