LS 4


  • True RMS voltage (A and B side)
  • True RMS current (A side)
  • Synch-check functionality
  • Dead bus start functionality
  • Synchronous networks functionality
  • Remote control of frequency, voltage, and real power
  • Zero power transfer control (softload)
  • Configurable trip/control set points
  • Config. delays for each alarm
  • 7 configurable relay outputs
  • Two-line LC display
  • Synchronization over transformer possible


  • Overvoltage            (ANSI 59)
  • Undervoltage         (ANSI 27)
  • Overfrequency       (ANSI 81O)
  • Underfrequency     (ANSI 81U)
  • Phase/vector shift  (ANSI 78)
  • df/dt ROCOF           (81RL)


  • Calculation of setpoint values which are transmitted to the genset controls (e.g. GCP) for synchronization and load control
  • Circuit breaker close command issued when LS 4 is enabled and the two sources are synchronized.
  • Open command to the CB with a discrete input command or with the detection of one of the available protection functions.