Auxiliary Contact in Relay or CBE 

Group Signalling Connection

by : Rifky Cahyadi

To understand Aux Group Signalling Principal, first we have to understand the single Aux Signalling

          

Fig 1 single signalling                        Fig 2. Group Signalling

Take a look at fig 1 above

 - N/O will close when main contact is close and will open when main contact is open

 - So when making group signalling, as figure 2 below, all the connection of the CBE on the N/O path should follow the rule, means all the path in the N/O need to be close when main contact is close and open when main contact is open

In this case we have to series the connection of the  C and N/O contacts of each breaker and name the signal as N/O in the group signalling. See example in figure 3a and 3b below

Figure 3. Group Signalling, example