[ ] 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 : [ JESTY JOSE ] [ JOBIN ABRAHAM ] GUIDED BY : PROF. PARTH SHAH [ELECTRICAL DEPARTMENT] [ELECTRICAL DEPARTMENT] 1

 Outline  Current Transformer (CT) Current Transformer (CT)  CT Electrical Tests CT Electrical Tests  Potential Transformers (PT) Potential Transformers (PT)  PT Electrical Tests PT Electrical Tests  References References 2

 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. 3

 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 4

 Turns ratio tests5

 Exciting currents6

 Polarity test7

 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. 8

 PT Electrical Tests  Insulation Resistance test  Polarity test  Turn’s Ratio test 9

 Insulation Resistance test10

 Polarity test11

 Polarity test {cont.}12

 Turn’s Ratio test13

 References 1. S. RAO “TESTING, COMMISSIONING, OPERATION & MAINTENANCE OF ELECTRICAL EQUIPMENTS”, KHANNA PUBLISHERS, SIXTH EDITION Eighteenth Reprint 2014, ISBN : Paul Gill “ELECTRICAL POWER EQUIPMENT MAINTENANCE AND TESTING”, CRC Press, SECOND EDITION (USA) 2009, ISBN : Philip Kiameh “Electrical Equipment Handbook Troubleshooting and Maintenance”, McGraw-Hill, Inc., com-PTs-Back_to_the_Basics.pdf com-PTs-Back_to_the_Basics.pdf com-PTs-Back_to_the_Basics.pdf 5. rce=web&cd=20&ved=0ahUKEwjRyKjDlOXSAhXDMo8KHSy UBwYQFgh7MBM&url=http%3A%2F%2Ffiles.engineering.c om%2Fdownload.aspx%3Ffolder%3D5b c- 41d4-af4c-06845b308475%26file%3DNETA_ct- testing_Good.pdf&usg=AFQjCNFXzepNUMg1e- wYHi1usWEaUfkrjQ&sig2=vnOs0p3gS7kiNpi1iI3Jng&bvm= bv ,d.c2I rce=web&cd=20&ved=0ahUKEwjRyKjDlOXSAhXDMo8KHSy UBwYQFgh7MBM&url=http%3A%2F%2Ffiles.engineering.c om%2Fdownload.aspx%3Ffolder%3D5b c- 41d4-af4c-06845b308475%26file%3DNETA_ct- testing_Good.pdf&usg=AFQjCNFXzepNUMg1e- wYHi1usWEaUfkrjQ&sig2=vnOs0p3gS7kiNpi1iI3Jng&bvm= bv ,d.c2I14

ANY QUESTIONS? SUGGESTIONS ARE WELCOME! 15