If the CT secondary open during load than the voltage across
the secondary reaches to a high value i.e some kilowatts and
the secondary current becomes zero hence reduced back emf.
The working flux increases and core gets saturated. The
secondary e.m.f increases due to increased flux
Due to the above reason the primary gets overheated and core
also gets heated and its dangerous for person working on
CT means current transformer which help us to measure the
large amount of current by step down the value of current
to low value. CT primary wdg handle the large amount of
current due to which large amount of heat is produce at
primary winding so we use insulating oil which help to
provide insulation as well as provide cooling. If we open
its secondary winding, the secondary current will reduce to
zero, which cause increase in voltage across its secondary
open terminal and that leads to increase in primary
current, with increase in primary current temperature of
oil in CT also increase and oil start burn which leads to
blast in CT
the secondary of CT open means, as the transformer
secondary will atempt to continue driving current across
the effectively infinite impedence.
this will produce a high voltage across open secondary
(range of several KV in some cases)which may cause arcing.
In normal power transformers primary current depnds upon
the secondary current ( load on secondary side, as load
increases its secondary current increases and also primary
current increases )
While in CT primary current is independent, if CT secondary
opens secondary current becomes zero while primary current
remains as it is. Both currents counter each other during
normal operation, and if secondary opens so secondary
current becomes zero and due to the primary current ( now
no counter effect present ) its core becomes saturated and
CT may blast.
keeping in view of parallel operation which of the 3 phase
transformer connection are possible?
a)delta-delta to delta-star b) delta-delta to star-delta c)
star-star to delta-delta d) delta-star to star-delta
If i have two 3000 kW motors and the whole facility requires
a 10 MVA transformer.
What would be better installing two 5 MVA transformers(one
for 1 motor ) or just a single 10 MVA transformer for both
Give reasons for your answer.