ProductsIslanding Protection Device

Islanding Protection Device for a Distributed Generators by Interharmonics Injection Method
The interharmonics injection method, an proprietary method of Nissin Electric, offers superior reliability contributing to the spread of dispersed power system for various applications such as renewable energy. Since the first introduction of these devices in 2001, we have delivered over 200 units to approximately 100% of the prefectures in Japan.

When connecting renewable energy and other dispersed power sources to an existing power system, a method to detect island operation (the state of electricity being supplied from a dispersed power source in the event of an power outage) is required.
This device monitors system impedance by injecting minute interharmonics (non-integer multiple harmonics, such as 2.6 etc) into the system, and detects island operation by observing the changes in impedance after the transition to island operation.


  • Minimal effect on the system.
  • No interference among multiple dispersed power sources (including this product) which are set up on a single distribution line.
  • Detection is possible in only about 1 second.
  • Applicable to all types of dispersed power sources.
  • Only one Islanding Protection Device required for one power source facility regardless of the number of generators.


  • Rated input current:AC 5A
  • Rated input voltage:AC 110V
  • Rated control power source:DC 110V
  • Rated injection power source:AC 210V

Manufacturing Range

Grid connection protection relay factors

  • Island operation detection: Active/Passive
  • Overvoltage, Undervoltage
  • Short circuit direction
  • Frequency rise/drop
  • Ground Overvoltage

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