• A-75, Sector 5, Noida - 201301 ( U.P. ) India

INDOTECH PROTECTION CURRENT TRANSFORMER

 Indotech Protection Current Transformer(CT) – The protection current transformer is used to reduce the currents in power systems, producing proportional currents in the unit’s secondary windings that remain isolated from the main circuit. The replica current is then used as an input to a protective relay, which can then automatically isolate part of the power circuit should it experience a fault. In doing so, the protection current transformer allows the unaffected areas of the circuit to continue in operation. These transformers form part of  Indotech comprehensive product offering, which includes Indoor and outdoor current and voltage transformers, along with bushing and combination model types.

TYPE OF TRANSFORMERS : PROTECTION

When the ratio is low it becomes difficult to obtain good results with the single primary turn. For that purpose wound primary CT’s are used where both primary and secondary turns are wound on the torroidal core. The ranges available are from 5/5A to 100/5A. Also Secondary 1A can be provided. Optional mounting arrangements are provided as the CT is mounted between two bakelite plates and brass terminals are provided for connections of primary & secondary.

PRINCIPAL OF OPERATION

The standards define a voltage transformer as one in which “the secondary voltage is substantially proportional to the primary voltage and differs in phase from it by an angle which is approximately zero for an appropriate direction of the connections.”

This, in essence, means that the voltage transformer has to be as close as possible to the “ideal” transformer. In an “ideal” transformer, the secondary voltage vector is exactly opposite and equal to the primary voltage vector, when multiplied by the turns ratio

Limits of Errors & Phase Displacement As per ISS 2704/81
Class Percentage Current Error at Percentage of Rated Current Phase Displacement in Minutes at Percent of Rated Current
 

0.1

0.2

0.5

1.0

5%

0.4

0.75

1.5

3.0

20%

0.2

0.35

0.75

1.5

100%

0.1

0.2

0.5

1.0

120%

0.1

0.2

0.2

1.0

5%

15

30

90

180

20%

8

15

45

90

100%

5

10

30

60

120%

5

10

30

60