Protection Engineering Basics and Schemes Protection Engineering | Page 46

In cascade we take multiple PT and combine those in
series and in a way in which we have multiple Primaries
on opposite of each PT, at the end of each PT there is
coupling winding which is connecting one PT with other
PT, at the final PT in cascade we have one secondary
winding, from which we take our secondary output.
Let suppose we have 500KV Line on which we need to
install our PT for protection and metering purpose, what
we do we take 4 PTs of 132KV , and connect their primary
in series and connect each PT via coupling winding with
each other in series , now what happened , in series all
primary voltages will be add up
132+132+132+132=528KV, we can reduce 528KV by using
Tap setting on PTs
Which, we now can use on 500KV line.
This arrangement we set up in one hollow cylinder, which
will be filled with insulated oil to maintain insulation in
between the PTs
pg. 46