DESIGN ISSUES 7SS52 BB ISOLTATOR CONTACT

1.Bus voltage Fuse failure status should give to ABTS.

2.Any interlock should not block the protection trip.

3. SCADA A/R IN/OUT command common for set-1 & set -2 multiply the command with aux - relay in control panel and give command to Line panel protection through both set-1 & set-2 L/R switch. Command goes if both switch are in remote condition.

4.7SS52 Bus unit need fiber optic washer.

5. 7SS52 Bus unit need 1-0 or 0-1 isolator contact for bus image it should not be 1-1 & 0-0 status

Testing engineer command on this issue.

While checking Isolator image switching sequence in siemens busbar relay, found that

5.1. Selective Buszone blocking and error protection block is appearing for 5sec and disappearing at the time of close and open operation of disconnecctors in all feeders

5.2.This will make major disturbance in busbar protection and abnormal alarm in SOE,SCADA,Annunciation

5.3.While go through found that , at the time of sequence operation two inputs open and close existing in the relay this will lead non plausible of disconnectors case (1+1), it will lead to block the busbar until it persist

5.4. The actual contact given for disconnector image ( as per the approved drawing) to the relay in LCC panel is aoi,boi contacts (as per areva drawing ref) ie Early make and late break contacts, but actual to be given is ao,bo contacts (as per areva drawing ref) Early break, Early make contacts.