Browse FAQs

Which settings group is selected by a Sepam relay with Zone Selective Interlocking (ZSI)?

Published date: 14 December 2018

Which settings group is selected by a Sepam relay with Zone Selective Interlocking (ZSI) or logic discrimination?

Product Line
Sepam series 20
Sepam series 40
Sepam series 80


The ZSI Group and the Time-Based Discrimination Group are both available when Zone Selective Interlocking (ZSI) is used.
ZSI Group: Elements 1 and 2, as enabled

Time-Based Discrimination Group: Elements 2 and 3, as enabled

The following describes which group operates under different conditions when ZSI is used.
Condition 1: Sepam detects restraint signal
The ZSI delay count-down begins as soon as the restraint signal is detected. The ZSI Group cannot operate until this delay count-down ends and the restraint signal is no longer present. The Time-Based Discrimination Group can operate according to its regular defined behavior. For example, after the delay count-down ends:
  1. If the restraint signal is no longer present, the ZSI Group can operate.
  2. If the restraint signal is still present, the ZSI Group cannot operate until the restraint signal is no longer detected.
In the event that the ZSI Group does not operate before the Time-Based Discrimination Group is defined to react, the Time-Based Discrimination Group will operate first.

Condition 2: Sepam does not detect restraint signal
Either the enabled ZSI Group or the enabled Time-Based Discrimination Group can respond to the condition. The group which has the fastest defined behavior will operate first.

For more information on arc flash reduction with Sepam zone selective interlocking, please refer to FA241150

Was this helpful?

What can we do to improve the information ?

Can't find what you are looking for?

Reach out to our customer care team to receive information on technical support, assistance for complaints and more.