TESTING AND COMMISSIONING OF ELECTRICAL EQUIPMENTS. TESTING OF CURRENT TRANSFORMER AND VOLTAGE TRANSFORMER. PREPARED BY: JOBIN ABRAHAM.

1. [2180901] TESTING AND
COMMISSIONING OF
ELECTRICAL EQUIPMENTS
TITLE : TESTING OF CURRENT TRANSFORMER AND
VOLTAGE TRANSFORMER
UNIVERSITY : GUJARAT TECHNOLOGICAL UNIVERSITY
COLLEGE : VADODARA INSTITUTE OF ENGINEERING
DEPARTMENT : ELECTRICAL ENGINEERING [E.E.– I]
SEMESTER : VIII
COMPILED BY :
130800109027 [ JESTY JOSE ]
130800109028 [ JOBIN ABRAHAM ]
GUIDED BY : PROF. PARTH SHAH
[ELECTRICAL DEPARTMENT] 1

2.  Outline
 Current Transformer (CT)
 CT Electrical Tests
 Potential Transformers (PT)
 PT Electrical Tests
 References
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3.  Current Transformer (CT)
 A current transformer (CT) is a type of transformer that
is used to measure AC Current. It produce an alternating
current (AC) in its secondary which is proportional to the
AC current in its primary. Current transformers, together
with voltage transformers (VTs) or potential transformers
(PTs), which are designed for measurement, are known as
an Instrument transformer.
 The main tasks of instrument transformers are:
 To transform currents or voltages from a usually high
value to a value easy to handle for relays and
instruments.
 To insulate the metering circuit from the primary high
voltage system.
 To provide possibilities of standardizing the
instruments and relays to a few rated currents and
voltages.
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4.  CT Electrical Tests
 Error measurement tests
 Turns ratio tests
 Exciting currents
 Current transformer for balanced differential protective
schemes
 Polarity test
 Insulation tests
 Overvoltage Interturn Test
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5.  Turns ratio tests
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6.  Exciting currents
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7.  Polarity test
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8.  Potential Transformers (PTs)
or Voltage Transformers (VTs)
 PTs or VTs are the most common device used. These
devices use standard transformer theory with 2-3 windings
(one primary with one or two secondary windings) with a
magnetic connection via an iron core. The high side
winding is constructed with more copper turns than the
secondary(ies) and any voltage impressed on the primary
winding is reflected on the secondary windings in direct
proportion to the turns ratio or PT ratio. The secondary
windings often have 2 taps with a nominal voltage of
115/67V, 120/69V, or 120/208V. This style of PT is the
most accurate style in use. A typical PT is shown in Figure
1.
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9.  PT Electrical Tests
 Insulation Resistance test
 Polarity test
 Turn’s Ratio test
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10.  Insulation Resistance test
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11.  Polarity test
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12.  Polarity test {cont.}
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13.  Turn’s Ratio test
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14.  References
1. S. RAO “TESTING, COMMISSIONING, OPERATION &
MAINTENANCE OF ELECTRICAL EQUIPMENTS”, KHANNA
PUBLISHERS, SIXTH EDITION Eighteenth Reprint 2014,
ISBN : 81-7409-185-8.
2. Paul Gill “ELECTRICAL POWER EQUIPMENT MAINTENANCE
AND TESTING”, CRC Press, SECOND EDITION (USA) 2009,
ISBN : 9781574446562.
3. Philip Kiameh “Electrical Equipment Handbook
Troubleshooting and Maintenance”, McGraw-Hill, Inc.,
2003.
4. https://relaytraining.com/files/papers/relaytraining.com.
com-PTs-Back_to_the_Basics.pdf
5. https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&sou
rce=web&cd=20&ved=0ahUKEwjRyKjDlOXSAhXDMo8KHSy
UBwYQFgh7MBM&url=http%3A%2F%2Ffiles.engineering.c
om%2Fdownload.aspx%3Ffolder%3D5b022082-151c-
41d4-af4c-06845b308475%26file%3DNETA_ct-
testing_Good.pdf&usg=AFQjCNFXzepNUMg1e-
wYHi1usWEaUfkrjQ&sig2=vnOs0p3gS7kiNpi1iI3Jng&bvm=
bv.149760088,d.c2I
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15. ANY QUESTIONS?
SUGGESTIONS ARE WELCOME!
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