Medium Voltage Current Transformers
Fibre & Fibre Glass Products designs and manufactures Current and Potential Transformers in its unit in Vadodara. Fibre & Fibre has facility of in-house fabrication, Painting and Testing.
FIBRE AND FIBRE GLASS PRODUCTS, DESIGNS THE TRANSFORMERS AS PER CUSTOMER REQUIREMENTS
Application :
Role of current transformers in electrical systems is of prime importance as they are the means of stepping down current to measurable values. Secondary current is of proportionately lower value to the primary current. Current Transformers can thus be used with ammeters for the measurement of current and with relays for protection of electrical instruments.
Basic Feature :
- To reduce primary voltage to a measurable value
- To protect electrical systems with the help of relays
- To reduce risk to humans by isolating measuring side from high current/voltage side.
Design Criterion
As per customer specification, Current Transformer is manufactured in Live-Tank or Dead- Tank design. In Live –Tank design the secondary winding is insulated with multiple layers of high quality pre-dried insulating paper. The complete job lies in upper tank that is on system voltage. Whereas in Dead-Tank design the primary is insulated with multiple layers of high quality pre-dried insulating paper. In this case complete job lies in dead tank that is on earth potential.
Semi conducting paper is used to make a capacitor layers to control discharge. The CT is designed to meet specified thermal and dynamic short circuit currents.
The secondary winding consists of core made from CRGO (Cold Rolled Grain Oriented). Super enameled copper wire is uniformly wound on core with the help of toroid winding machines.
The transformer is dried and filled with filtered transformer oil under Vacuum. A tan-delta value of 0.005 or less can be achieved. The transformer can be removed from the Vacuum Impregnation Plant after achieving the required value for tan-delta.
To hermetically seal the transformer from the outside, Nitrogen gas is filled above the oil. The metal parts can be painted or galvanized as per customer requirement/specification. All fasteners used are Hot-dip galvanized. Stainless steel fasteners can be used on request.
| ELECTRICAL CHARACTERISTICS OF CURRENT TRANSFORMERS (CONFIRMING TO IS : 2705 & IEC : 60044-1) |
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| TYPE: OUTDOOR, AIRCOOLED | ||
| Nominal System Voltage ( kV) | 11 | 33 |
| Highest System Voltage(kV) | 12 | 36 |
| Power Frequency withstand voltage 1 Min(kV) | 28 | 70 |
| Impulse withstand voltage(Kvp) | 75 | 170 |
| Rated Burden | 2.5 VA TO 30 VA | |
| Rated Frequency(Hz) | 50Hz | 50Hz |
| Creepage Distance Phase to Earth (m.m.) | 300 | 900 |
| Rated Primary Current (Amp.) | 5 Amp. To 2000 Amp. | |
| Rated Continuous Thermal Current (Amp.)(Max) |
125% of rated primary current | |
| Rated Secondary Current (Amp.) | 1 Amp. To 5 Amp. ( or as per customer requirement) |
|
| Rated Short Time Thermal Current | 3KA to 40KA for one / three second. |
|
| Rated Dynamic Current (KA-Peak) | 2.5 times of short time current | |
| Accuracy Class (IS/IEC Standard) | 0.2s (Min.) for Metering & 5P, 10P & PS for Protection |
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| Rated Instrument Security Factor | 5 | |
| Rated Accuracy Limit Factor | 10, 20, 30 | |
