In our existing system we have open delta connected Busbar PT which gives sensing to MK VIe for busbar voltage inputs.

Now we are planning to replace open delta type PT (which has grounded reference secondary) with star type PT. So we need to install a new 1:1 interposing PT to get ground reference for voltage input to MK Vie sychronization ckt.

The secondary phase to phase voltage for both type of PTs is 120Volts.

The Synch resistors are rated at 500 Ohms (Wattage is 225W as per BH data sheet)

What should be the burden of this interposing PT ? and what is requirement of this synch resistor

Attached : existing synch ckt drawing

 

Now we are planning to replace open delta type PT (which has grounded reference secondary) with star type PT

First question that comin is why you want/need to do such modification?

 

Now we are planning to replace open delta type PT (which has grounded reference secondary) with star type PT

First question that comin is why you want/need to do such modification?

Actually we have bought new Medium Voltage Busbar, the busbar manufacturer offers only star connected PT. This is the primary reason that we have planned to replaced open delta type bus PT with star connected one

 

120 volts on 500 ohm resistor will draw 28.8 watts (120^2/500). The aux PT will also have the burden of the sync lamp, sync-scope, and whatever the MarkVIe draw would be. We had a similiar set up. As I recall, our AUX PTs were 150 VA. I dont have access to the info any more but sounds reasonable. Hope this helps.