Instrument Transformers, Current Transformer, Voltage Transformer, High Voltage Testing, Testing Laboratory, C.T's, V.T.'s, Mumbai, India Instrument Transformers, Current Transformer, Voltage Transformer, High Voltage Testing, Testing Laboratory, C.T's, V.T.'s, Mumbai, India
Instrument Transformers, Current Transformer, Voltage Transformer, High Voltage Testing, Testing Laboratory, C.T's, V.T.'s, Mumbai, India
 

 

 :::: CT PT Metering Set  :::

 

 CONSTRUCTION

 Oil Cooled , Out Door Type C.T.P.T. Metering Sets Are Made For Use On
 11 Kv To 33 Kv Systems & Are Suitable For Mounting On  Structures .


 BASICALLY A SET CONSISTS OF :
 
1. C.R.G.O. Cores
 2. H.V. & L.V. WDG.
 3. M.S. Tank with Secondary Terminal Box
 4. Bushing & Transformer Oil

 
SPECIAL FEATURES :
 
1) A Pressure Device Is Provided On The Top Cover Of The Tank Which Opreates In Case
    Of Abnormal Internal Pressure Development Due To Abnormal Operating Conditions.
 2) The Set Is Much More Compact Compared To C.T..P.T. Sets Of Other Makes .

         C.T. P.T. Metering Sets

 
Applications

 
The  C.T.- P.T. Metering  Sets  Of  This  Type  As  The  Name  Suggests  Are  Used  For  Measurement  Of  Power  On  High  Voltage  Side . The  C.T. – P.T.  Sets  Are  Installed  Before  The  Main  Transformer  &  The  Main  Line  Goes  Through  C.T. – P.T. Set.

              As  The  Accuracy  Of  The  C.T.- P.T. Set  Is  High  &  As  It  Is  Connected  Beforethe  Transformer , Measurement  Of  Power  Is  Much  More  Accurate  Compared  To  The  Metering  Done  On  L.T.  Side , The  Transformer  Losses  Are  Also  Included  In  The  Measurement .

CT. PT. Metering Set
Connection Diagram

Connections are done as per terminal markings on the connection diagram shown below

 


 

 Dimensions
 Overall maximum dimensions (approx.) of different C.T.- P.T sets are as below



 

 
* Note :
We also manufacture Resin, Cast, Indoor type
C.T.-P.T. metering sets upto 22kV
 

  Residual Voltage Transformer



 
 Residual Voltage Transformer
Residual Voltage Transformer Is Used To Detect Unbalanced Voltage In Three Phase System & To Supply Voltage To Directional Earth – Fault Relay.
 
For Directional Earth – Fault Relay , It Is Necessary That The Voltage Applied To The Voltage Coil Of The Relay Corresponds In Phase To That Of The Current In Current Coil  Such Voltage Will Be The Residual Voltage Of The System & Will Be The Phasor Sum Of The Three Line - To - Earth Voltages .
 
Residual Voltage Can Be Achived By Connecting Secondaries Of Three Single Phase V.Ts. Connected In Three Different Phases , In Open Delta Fashion . It Is , However , Economical To Use Three Phase V.Ts. Instead Of Three Nos. Single Phase R.V.Ts. Suitable Upto 33 Kv System Voltage
 


 

 
 In Normal Three Phase Three Limb V.T. When One Phase Experiences Earth Fault,
 The Resultant Flux Due To Two Healthy Lines Returns Through Transformer Limb Of
 Faulty Line, Including A Heavy Short Circuit Current In The Wdg. On The Limb . Also
 Voltage Induced In Secondary Open – Delta Wdg. Is Not True Residual Voltage . To
 Overcome This Difficulty Two Separate Limbs Are Provided In The Magnetic Circuit Of
 Three Phase Voltage Transformer To Form Five Limb Voltage Transformer As
 Shown In Fig. ( I ).
 

5 LIMB Construction Of Residual Voltage Transformer


 

The Use Of An Open – Delta Connected Wdg. To Give True Residual Voltage Is Demonstrated In Fig.( Ii ) With Three Cases :
 
A) Under Healthy Condition All Three Phases Will Be Balanced & Hencce Residual Voltage ‘ Vr ’ Will Be Zero.
 
B) In System With Unearthed Neutral, If There Is Earth Fault On One Line , Neutral Of V.T. Will Be Shifted, Such That Each Healthy Phase Wdg. Will Have Line – To – Line Voltage With 60 Phase Difference . The Resultant Open – Delta Voltage Shall Be Therefore , The Resultant Open – Delta Voltage Shall Be Therefore, Three Times Phase Voltage . ( Vr = 3 Vs )
 
C) In Solidely Earthed System , Neutral Of The V.T. Does Not Get Shifted Due To Earth – Fault On One Line. Therefore, The Resultant Open – Delta Residual Voltage Remains Phase Voltage Only. ( Vr = Vs )
 

 

 

 
 Primary Wdg. Of R.V.T. Is Connected In Star . The Secondary Wdg. Is Connected In
 Open – Delta. Some- Times Additional Secondary Wdg. Is Provided In R.V.T. For
 Measuring Purpose & Is Connected In Star . Ratio Of R.V.T. For Measuring Purpose
 Generally Specified
 
  As Line – To Line – Primary Voltage To Open – Delta Residual Voltage. IT , Therefore
  Becomes Necessary To Mention System Neutral Condition So As To Select
  Phase Voltage Of The Open – Delta Wdg. Correctly .
 
  When R.V.Ts. Are Used Along With Capaccitor Bank, Capaccitor Bank Gets
  Dischared Through Primary Wdg.
 









































































 

 

 





























 

 

 































 

  All Instrument Transformers are made to IS2705, BS3938, BS7626, IEC 60044-I, AS1675, ANSIC57.13, CAN3-C-13-M83, IEC 60044-2, IS 3156, AS AMMENDED

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