CTS Current Separating Transformers

CTS Current Separating Transformers

  • Typical accuracy ±0.01%
  • Broad range of primary and secondary currents
  • Safe operation with open secondary circuits
  • Signaling open current loop in the secondary circuits
  • Broad power output range
  • No screwing current
  • High allowable load impedance
  • Around a dozen family members

The CTS is a family of current separating transformer designed for galvanic separation of the measuring circuits. A built-in electronic compensation system simultaneously guarantees excellent parameters throughout the entire current range and a high output power.


Typical accuracy of ±0.01% makes the device an ideal solution for a wide range of applications. It is possible to use the transformer to test electricity meters with connected current and potential circuits (closed I-P links). A broad range of primary and secondary currents, a high output power, high allowable load impedance and enhanced accuracy enable the CTS to be integrated within a meter testing system. Once integrated, it can work both with directly connected and transformer connected meters, and both with closed and open I-P link meters, all with negligible influence on overall system accuracy.

The CTS can be controlled and supervised either remotely by the ASTeL meter test equipment, or locally by means of the START/STOP switch.


Bad contact or open circuit in the secondary circuit is indicated. Furthermore, in case of the open circuit the internal short is made in order to prevent operator injury and electric shock. Thus, working with open secondary circuits is possible and allowed.


CTS is available in a wide range of variants, with different output power and primary/secondary current ratio. Three and single phase versions are intended for testing regular meters while two phase versions are intended for testing single phase meters with neutral current measurement.



CTS modelCTS-120CTS-120-D2CTS-120-D1CTS-240CTS-200
Number of phases32133
Working current range of primary winding3 x 1mA … 120A (1)2 x 1mA … 120A (1)1 x 1mA … 120A (1)3 x 0.5mA … 120A (1)3 x 0.5mA … 100A (1)
Working current range of secondary winding3 x 1mA … 120A (1)2 x 1mA … 120A (1)1 x 1mA … 120A (1)3 x 1mA … 240A (1)3 x 1mA … 200A (1)
Ratio error≤ ±0.01% (2)
Angle error≤ ± 0.3’ (2)
Frequency range40 … 70Hz
Output powerver. 11.2V ∙ Isec (max 144VA @ 120A)0.6V ∙ Isec
(max 144VA @ 240A)
0.6V ∙ Isec
(max 120VA @ 200A)
ver. 20.8V ∙ Isec (max 96VA @ 120A)
ver. 30.5V ∙ Isec (max 60VA @ 120A)
Maximum load impedance in the range of 1 mA…5 Aver. 1240mΩ120mΩ
ver. 2160mΩ
ver. 3100mΩ
Maximum output voltagever. 11.2V0.6V
ver. 20.8V
ver. 30.5V
Maximum load impedance in the range of 5 A…120 Aver. 11.2V / Isec0.6V / Isec
ver. 20.8V / Isec
ver. 30.5V / Isec
Sensing the difference between the primary and secondary currentsYes,
signaled individually for each phase
Possibility of working with open secondary circuitsYes,
the smart disconnecting system make an internal short in case of the secondary circuit is open
ControlremoteOperation is controlled and supervised by a meter test equipment
localManual START/STOP switch

(1) Other values are available upon request.

(2) For the current range from 100mA to the maximum current.

Product card
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