Choose your region and language



Spark prevention unit (SPU)

Reducing wildfire hazards which may be caused by thermally overloaded surge arresters

Spark Prevention Unit (SPU) is designed for surge arresters that are installed in wildfire risk areas. It monitors the current and the thermal load of the surge arrester. In case of a thermal overload, it interrupts the current flow and disconnects the surge arrester thus preventing any arcing, sparking or ejection of hot particles that may have the potential to start a wildfire.

When operated, SPU gives an indication that is easily visible from the ground level, so that the arrester can be replaced upon visual indication. However, such an operation means the protective function of surge arrester cannot be performed and thus the line equipment are exposed to the risk unless the arrester and SPU are identified and replaced. To make this process of monitoring easier, SPU can also be equipped with a wireless monitoring device.

Medium-voltage surge arresters equipped with SPU from Hitachi Energy are approved for vegetation clearance exemption according to CalFire (California Regulation). They are also considered spark-free according to class A of Australian Standard AS 1307.2.

Wireless SPU indicator

The Wireless SPU indicator can be assembled around the SPU, and can transmit the information about the the status of the SPU (operational or tripped), its geographical location, the time of the tripping event as well as the status of its batteries to customer over long-range wireless communication network, to facilitate better planning of maintenance and replacement of devices.


  • For use with Hitachi Energy surge arresters in medium-voltage distribution networks
  • Especially made for areas with risk of wildfires
  • For remote areas which are difficult to access for line inspection or are irregularly inspected

Why Hitachi Energy?

  • Over 100 years of experience in overvoltage protection
  • Unique and patented design
  • Inhouse production of metal-oxide (MO) resistors
  • Approved for vegetation clearance exemption according to CalFire regulation
  • Easy to install
  • Local and global Hitachi Energy application support

Brief performance data

Nominal Discharge Current In 10 KApeak
High Current Impulse Ihc (4 / 10 μs) 100 kApeak
Service conditions:  
Ambient air temperature Tamb −40 to +55 °C
Altitude up to 1800 m (for higher altitudes contact Hitachi Energy)
Frequency of system voltage 40 to 62 Hz
Wireless indicator details  
Communication LoRaWAN
Communication range

Up to 5 km in urban areas

Up to 15 km in rural areas

Know more

Part of categoryPress Release
Digital technology to prevent environmental fires
30-11-2022 | 2 min read

Hitachi Energy launches digital wildfire prevention technology for a resilient grid

BBC Humanising Energy: Fighting wildfires with innovation in Australia

power plant engineer for substation

Contact us

Submit your enquiry and we will contact you