HV winding is always placed on the LV winding in a CT for several reasons: 1) It reduces the amount of insulation required between the HV winding and the core. 2) It reduces leakage fluxes and core loss. 3) It reduces the risk of voltage shock if insulation breaks down. This placement is done primarily to reduce manufacturing costs by minimizing insulation needs.

1. Why always HV winding is placed on LV winding in CT
CapacitiveInsulators
SaturationPoint & Operating Point
Urooj Abid (syedauroojabid@gmail.com)
NED University Of Engineering & Technology
K-Electric Internship

2. Instrumentation Transformer & Types Of
Instrumentation Transformer

3. Instrumentation Transformer
Instrument transformers are high accuracy classelectricaldevicesused to isolate or
transform voltage or current levels.Instrument Transformers are used in AC system for
measurement of electrical quantitiesi.e. voltage,current, power, energy, power factor,
frequency. Instrument transformersare also used with protectiverelays for protectionof
power system.Basic function of Instrument transformersis to step down the AC System
voltage and current. The voltage and current level of power system is very high. It is
very difficultand costly to design the measuring instrumentsfor measurementof such
high level voltage and current. Generally measuring instrumentsare designed for 5 A
and 110V. The measurement of such very large electricalquantities,can be made
possibleby using the Instrument transformerswith these small rating measuring
instruments. Therefore these instrument transformersare very popular in modern power
system.

4. Instrumentation Transformer
Types Of Instrumentation Transformer
Current Transformer Potential Transformer
Currenttransformersare mainly use to measure the
huge alternativecurrent in electricalequipments.In
Some high voltage lineswhere measuring
equipments are difficultto connect, these type of
current transformersare use with other ammetersto
measure the current under alternativecurrent
circuits.To measure the current of high voltage line
thiscurrent transformerstep down the current level
in to known ratio.Normallythe current transformer
is connected to the line withseries connection. In
current transformerthe number of turns of coils in
secondary is greater primary.When the primaryto
secondary current ration of current transformeris
200: 10 then itssteps up the voltage 20 times.Clip
on type current transformersare the most use current
transformersin electricalindustry.
Potential transformersare extremelyaccurate and
normally the type of these potentialtransformersis
falls under step down transformercategory. All
potentialtransformersare generally fallsunder the
shell-typetransformerand it’s not much different
from the ordinary two windingtransformerswhich
discussed. Secondary of potentialtransformersare
normally completelyinsteadto protect against the
high voltage. Potential transformeris connect to line
on parallel way. High voltage primaryof potential
transformeralso should be grounded for additional
protection for the operator of the potential
transformer.

5. Instrumentation Transformer
Types Of Instrumentation Transformer
Current Transformer Potential Transformer

6. Types Of Current Transformer

7. Types Of Current Transformer
Metering Class Current Transformer Protection Class Current Transformer
Metering Current Transformers (CTs) are used with the
measuring instruments,such as ammeters, voltmeters,
kilowatt-hour meters, etc to: Isolatethe instruments from
the power circuits,Standardize the instruments,usually at
5 amps or 1 amp. The scale of the instrument(according to
the CT ratio), then becomes the only non-standard feature
of the instrument.
ProtectiveCurrent Transformers are designed to measure
the actualcurrents in power systems and to produce
proportional currents in their secondary windings which are
isolatedfrom the main power circuit.These replica currents
are used as inputs to protectiverelays which will
automaticallyisolatepart of a power circuitIn the event of
an abnormal or fault conditiontherein, yet permit other
parts of the plant to continue in operation.

8. Relays

9. RelaysA relay is an electrically operated switch. It consists of a set of input terminals for a single or multiple
control signals, and a set of operating contact terminals. The switch may have any number of contacts in
multiple contact forms, such as make contacts, break contacts, or combinations thereof. Relays control
one electrical circuit by opening and closing contacts in another circuit. As relay diagrams show, when a
relay contact is normally open (NO), there is an open contact when the relay is not energized. When a
relay contact is Normally Closed (NC), there is a closed contact when the relay is not energized. In either
case, applying electrical current to the contacts will change their state. Relays are generally used to
switch smaller currents in a control circuit and do not usually control power consuming devices except
for small motors and Solenoids that draw low amps. Nonetheless, relays can "control" larger voltages
and amperes by having an amplifying effect because a small voltage applied to a relays coil can result in
a large voltage being switched by the contacts. Protective relays can prevent equipment damage by
detecting electrical abnormalities, including over current, undercurrent, overloads and reverse currents.
In addition, relays are also widely used to switch starting coils, heating elements, pilot lights and audible
alarms. In order to know how relay work you can check out the link:
https://www.explainthatstuff.com/howrelayswork.html

10. Why always HV winding is placed on LV
winding in CT

11. LV windingis placed nearer to core as the amount of insulationrequired to isolate LV from core is less as compared when
you place HV nearer to core.
So overall cost of insulation& hence transformermanufacturingcost reduces.
It also reduces the leakage fluxes.
It also reduces the core loss .
It reduces the voltage shock if the breakdown of the insulation takes place.
So basicallyit’s all about economics!

12. Capacitive insulators

13. Capacitive Insulators
Capacitiveinsulators are used as high voltage side capacity for voltage detecting
systemsbetween the medium voltage section and the interface.

14. Saturation Point & Operating Point

15. Saturation Point & Operating Point
Saturationpoint is the point near to the
constantpoint value near which the
value of replica 0r response is nearly
unchanged even when we increase the
amount of current to a real large value
Operating point is value at which the
equipment is working or can say it is the
set point value of an equipment.
Operating point can be consider
anywhere in the graph according to the
requirement.

16. Thank You