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CTB 25 Current instrument transformers CTB 25 are designed for measurement and protection of high voltage distributing equipment for indoor design for the highest voltage...
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Current instrument transformers CTB 25 are designed for measurement and protection of high voltage distributing equipment for indoor design for the highest voltage of system of 25 kV.
The value of secondary current is 5 A or 1 A with the possibility of combination. The accuracy classes for the circuits of measurement are 0.2, 0.5, 1, 3, for the circuits of protection are 5P, 10P. The transformers fulfill the required accuracyclass at intervals from 25 % to 100 % of rated load.
The terminal working current is 120 % IN, in case of the agreement of the producer and the customer it is possible to deliver also the other values, for example 200% IN.
Transformers CTB 25 are designed as passaging, where the primary conductor is made by two and more windings, according to the required parameters. The primary terminals of transformers are provided with the screws M12x35mm. The special parts with the holes of diameter of 14 mm, eventually pin with epoxy adapter (see dimensional sketch),can be supplied for the connection of lead- -in passes along the horizontal axis of the instrument.
The secondary winding is wound on the magnetic core made of directed plates, eventually made of the alloy of nickel,iron and copper “permalloy”. The maximum number of cores can be from 1 to 3 according to the request of customer. The construction of transformers allows the switching of ranges of the primary current on the secondary side.
All active parts of transformer are compound-insulated with epoxy-mixture. This material performs both the electrical insulating and the mechanical functions.
The mounting position of transformers is arbitrary. Transformers are fixed by the means of four screws M12 in theholes in the basic plate. We recommend use terminal ends corresponding to the used cross-section of the conductor for attaching to the secondary outlets.
The secondary terminal plate is provided with cover with sealing screw. Inside, there is the set with jumpers and small screws for the possibility of earth connection and short circuiting of the wiring. (See “The Instructions for the mounting and operation”).
Transformers CTB 25 fulfilled all the tests according to the ČSN EN 60044-1.
