Systems & Electronics

IDB4N – Digital high impedance differential busbar protection

The protection relay IDB4N belongs to SIGMA-N digital protection line and it performs function as three poles high impedance differential busbar protection.



High impedance busbar differential



The IDB4N differential busbar protection is equipped with three measurement systems and it can be used to protect a busbar zone defined by up to 7 current transformer systems with equal characteristic.

The high impedance differential busbar detects phase-to-phase faults; it detects earth faults in electrical system with neutral solidly earthed or earthed through a resistance which value allow an earth fault current high enough if compared to the installed CT’s.

When an internal fault occurs, the protection system trip to open the circuit breakers which are on the boundaries of the protected zone (circuit breakers related to lines of generator systems).

The IDB4N busbar protection includes the following modules (installed in two 19″ racks):

  • IFX4N digital overcurrent relay
  • High impedance module (6U)

The IDB4N protection (IFX4N unit) manages overcurrent thresholds related to the three phase differential protection function and manages overcurrent thresholds (earth fault type or three phase differential) to identify the condition of defects of the CT’s or external circuits (open circuit or short circuit on cables).

All the protection functions are fully programmable by front panel keyboard or through a RS485 serial interface using a personal computer with set-up program.