Direct measurement of current in high voltage system is not possible because of insulation problem of measuring instruments. It is also not possible to use current flowing through the system directly, for protection purpose due to its high value & high insulation problem. In such conditions Current Transformers are used.
Basic Functionalities of Current Transformer are :
- To reduce the line current to a value which is suitable for standard Measuring Instruments, Relays etc.
- To isolate the Measuring Instruments, Meters, Relays etc. from high voltage side of an installation.
- To protect Measuring Instruments against short circuit currents.
- To sense abnormalities in current & give current signals to protective relays to isolate the defective system.
The transformers are oil filled, assembled in M.S.Tanks & Chambers together with suitable Porcelain Bushing. High quality C.R.G.O. Silicon Steel is used in the transformer. High quality crepe insulating paper is used to build up main insulation. Semiconducting shield is used to give linear distribution of Electric stress along the length of the bushing. Filtered & de-aerated EHV grade oil is filled in CTs while CT is under vaccum. To seal it, the space left for expansion on the top is filled with dry & pure Nitrogen through non returnable valve at pre-determined pressure.
Electrical Specifications :
- TYPE : Live or Dead Tank
- OPERATING VOLTAGE :11kV, 22kV, 33kV, 66kV, 110kV, 132 kV, 220kV, 400 kV.
- PRIMARY CURRENT :Upto 2500 Amps.
- SECONDARY CURRENT :5A & 1A (Others on request).
- SHORT TIME THERMAL CURRENT & ITS DURATION :Upto 40kA for 1 second (Others on request).
- RATED BURDEN :5,10,15,20, 30VA (Others on request)
- FREQUENCY :50Hz.
- OPERATING TEMP. : -10°C to 40°C
- CONFORMS TO : IEC -185 / IEC – 44 -1 / IS – 2705.ive relays to isolate the defective system.
Mechanical Construction :
132kV Dead Tank CT
66kV Live Tank CT
Ordering Information :
While ordering mention all the Electrical Specification required.