Hi Team,

Can you please advise me what the potential issue we can face if two M.E.N links are connected together indirectly. In below case both systems are overall at same potianl as this isnatlltio is a train station and they create thwower own traction earth zone.

what is your opinion abou this and what potentila issue we forsee, I know we do have parallel path here, and there can be cirucalting currents espeically if both netraul have potential difference.

System Overview:

We have two incoming supplies:

1. Utility Supply:
   • Comes through an isolation transformer （Delta primary / Wye secondary）.
   • Feeds into DB1, which contains the only MEN link in the system.
   • MSB1 then feeds into DB2 through a 4-pole ATS （Automatic Transfer Switch） with overlapping neutral.
   • DB2 does not have a MEN link.
2. Essential Supply Transformer （EST）:
   • Fed from the OLE （25kV） traction supply and stepped down to 240V single-phase.
   • The secondary side （Active + Neutral only） goes into a Power Conditioner, which converts it to 3-phase.
   • That 3-phase output is then connected to the ATS input at DB2.

Earthing Arrangement:

• MSB1’s MEN link connects to:
  • Local earth electrodes.
  • An ECC （Earth Collector Cabinet）, which is the main earth hub at the station (common earthing point for traction, DBs, etc.), which goes to teh trail as traction bonds.
• EST’s LV earth bar:
  • Has a neutral-to-earth bond, effectively acting like another MEN point.
  • Also have a a traction bond from LV/HV earth bar to the rail.
  • Also connects to the earth collector cabinet, linking it indirectly to MSB1's MEN.
• There is no dedicated protective earth conductor running from the EST to DB2 (only A+N to the Power Conditioner, and 3-phase from there to the ATS).

 

Hi Team,

Can you please advise me what the potential issue we can face if two M.E.N links are connected together indirectly. In below case both systems are overall at same potianl as this isnatlltio is a train station and they create thwower own traction earth zone.

what is your opinion abou this and what potentila issue we forsee, I know we do have parallel path here, and there can be cirucalting currents espeically if both netraul have potential difference.

System Overview:

We have two incoming supplies:

1. Utility Supply:
   • Comes through an isolation transformer （Delta primary / Wye secondary）.
   • Feeds into DB1, which contains the only MEN link in the system.
   • MSB1 then feeds into DB2 through a 4-pole ATS （Automatic Transfer Switch） with overlapping neutral.
   • DB2 does not have a MEN link.
2. Essential Supply Transformer （EST）:
   • Fed from the OLE （25kV） traction supply and stepped down to 240V single-phase.
   • The secondary side （Active + Neutral only） goes into a Power Conditioner, which converts it to 3-phase.
   • That 3-phase output is then connected to the ATS input at DB2.

Earthing Arrangement:

• MSB1’s MEN linkconnects to:
  • Local earth electrodes.
  • An ECC （Earth Collector Cabinet）, which is the main earth hub at the station (common earthing point for traction, DBs, etc.), which goes to teh trail as traction bonds.
• EST’s LV earth bar:
  • Has a neutral-to-earth bond, effectively acting like another MEN point.
  • Also have a a traction bond from LV/HV earth bar to the rail.
  • Also connects to the earth collector cabinet, linking it indirectly to MSB1's MEN.
• There is no dedicated protective earth conductor running from the EST to DB2 (only A+N to the Power Conditioner, and 3-phase from there to the ATS).

How do you switch between the two supplies?