Well a PT uses windings to drop voltage step down transformer high voltage to lower voltage just a transformer only !!! next CVT uses two capacitors in series to drop voltage or split ac like a filter circuit its a tuned 60 cycle resonant cap & coil circuit on primary side . and like a voltage divider circuit but uses capacitors . combined for protection relaying work fault trip zone portection function circuit its also for phase shift ,there really a coupling capacitor voltage splitter circuit centered tap to a reactor coil on primary side input of trans CCVT which is dropped to around 6kv pri input , the center tap of these series caps feed coil and coil feeds trans pri one cap is connected to ground one cap gos to hv line. But multi caps are used in series for the incoming hv line 165kv transmission line , not just two caps by example to make it simple and theres a iron choke coil called a reactor coil it cancels out the caps at 60 cycles for phase shift on output from primary to secondary of CVT transformer theres also a supression circuit on CVT secondary side thats what electricians call it but its just a old snubber circuit for discharge of a potential high voltage spike or back feed kick protection when a major fault occurs on hv transmision line voltage drops off sharply. But the whole circuit works in a delay of false tripping by capacitance stored energy in the caps to hold voltage on primary this controls the tripping time in seconds before a trip of deff relay coils circuits on secondary side which is 115 volts to supply differ relay coils as stated and to control all this with total CVT package circuit and must be included in explaining the difference of both PT and CVT . if you need a full detailed run down how it works just ask? best to ya
Last edited by nick; 10-29-2008 at 05:33 AM.
Reason: but its all done today with a microcontrol , its not easy to explain on a post