Low Tension Current Transformers, Precision Grade Current Transformers, Furnace Transformers, Core Balance CTs, Mumbai, India Low Tension Current Transformers, Precision Grade Current Transformers, Furnace Transformers, Core Balance CTs, Mumbai, India

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LOW TENSION CURRENT TRANSFORMERS

It is not possible to use line current directly for measurement and relaying purpose due to its high value and insulation problem. CURRENT TRANSFORMER which is widely known as 'CT' is a piece of electrical equipment which converts line current values which are suitable for the devices to which is connected e.g. measuring instruments, meters, protection relays.

BASIC FUNCTIONS OF CTs ARE :

  • To reduce line current to a value which is suitable for measuring
    instruments, relays etc.
  • To isolate the measuring instruments, meters, relays etc. from line
    voltage of an installation.
  • To protect measuring instruments against short circuit currents
  • To sense abnormalities in current and give current signals to protective
    relays to isolate the defective system.

CURRENT TRANSFORMERS ARE BROADLY CLASSIFIED AS :

  1. RING TYPE CTs : A CT which has an opening in the center to accommodate to primary conductor (busbar or cable) through it.
  2. BAR PRIMARY CTs :  A CT in which the primary winding consists of bar of suitable size and material forming an integral part of the CT.
  3. WOUND TYPE CTs : A CT having a primary winding of more than one full turn wound on the core.

FOLLOWING ARE FEW GENERAL TYPES OF CTs.

INTERPOSING CTs

1)INTERPOSING CTs : These CTs are used in conjunction with main CTs to alter the ratio of main CT or to provide isolation to meters or relays from main CTs secondary circuit. Primary current of these CTs are generally lower than 10 amp. Due to which they are always wound primary types.


SUMMATION CTs

2) SUMMATION CTs : When current flowing in more than one feeder is required to be metered, summation current transformer are used. These CTs are provided with more than one primary winding and one common secondary. The standard primary & secondary currents are 5 or 1 amp. Summation current transformers are generally manufacture confirming to ISS 6949.

3) BUSHING TYPE OR BUS DUCT CTs : These CTs are Ring type construction & can be mounted on Bus duct or Bushing turret of power transformer.

CORE BALANCE CTs










Core Balance Current Transformer

4) CORE BALANCE CTs : These are ring type CTs & suitable for the measurement of the sum of three phase currents in a 3 phase cable. Under normal operating conditions this sum is zero. In the event of an earth-fault the sum of the current. These CTs are generally used with English Electric make CTUM 15 static relay. It is necessary to specify leakage current to be detected along with minimum setting of the relay and size of cable at the time of ordering CT.                    

FURNACE TRANSFORMERS
Furnace Current Transformers

5) FURNACE TRANSFORMERS : These transformers are generally split core type which can be easily mounted on the bus of furnace transformer. Primary current of these transformers are of value 10,000 Amp & above. Special precaution is necessary to reduce the heat developed in the transformers due to eddy current during design and manufacture.

PRECISION GRADE CURRENT TRANSFORMERS

6) PRECISION GRADE CURRENT TRANSFORMERS :
These CTs are of accuracy of 0.1, 0.2 or 0.5 and used as a standard current transformers to check accuracies of other transformers. These current transformers are either wound primary or ring type manufactured in teakwood cases.

FOLLOWING ARE GUIDE LINE FOR ORDERING CTR.

  1. Primary current.
  2. Secondary current.
  3. VA Burden.
  4. Accuracy class.
  5. Instrument security factor.
  6. Accuracy limit factor.
  7. Environmental condition.
  8. Application.
  9. Fault current of the system.
  10. Voltage of the system.
  11. Any special features required.



| OIL IMMERSED INSTRUMENT TRANSFORMERS | | Resin Cast  Insulated INSTRUMENT Transformers |
| Current Transformers
| | Voltage Transformers | | HIGH VOLTAGE TESTERS |
| LOW TENSION CURRENT TRANSFORMERS
|

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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