Standard Current Transformers 

EPRO Gallspach GmbH’s Standard current transformers are used in the industry since decades. They are internationally well known for maximum reliability and accuracy. 
As the devices are purely inductive, properly handled, the lifetime is up to 30 years and more without any accuracy drift or any changes.


What is a standard current transformer?

A standard current transformer is a test device and is used for measurements on high current. The devices are used as measurement standards for measuring and/or for calibration of instrument transformers. The high accuracy of the standard CT plays a major role here.
The guaranteed range is, depending on customer's requirements up to 1-200% of rated current, this means in this range the accuracy of the device is guaranteed. The standard current transformers are designed in such a way that they are passive, i.e. they do not require an external supply.


Where standard current transformers are used?

International calibration and metrological institutes as PTB Germany, INMETRO Brazil, VMI Vietnam among many others are using these devices as national standard for accuracy measurement. In the private sector these devices are used in the labs of various manufacturers of instrument transformers and transformers and others for accuracy and power measurement.


In which execution are standard current transformers available?

The standard current transformers are available in dry-insulated and oil-insulated versions. The dry insulated standard CT´s have an insulation level of 1,1kV, while the oil-insulated types are available from 30kV to 200kV nominal voltage. The primary current rating varies between 1A and 50.000A, depending on the model. 

Are standard current transformers also available in mobile execution?

A big variety of the standard current transformers are also available in mobile execution for testing on site and transport in a truck. This mobile (outdoor) execution can be distinguished from the other devices by the light grey silicone rips on the outside.


How does an accuracy measurement work?

For the accuracy measurement on a test object (current as well as voltage), a control transformer, a test transformer, a standard current or voltage transformer and a measuring bridge are required.
By adjusting the control transformer upwards, the test transformer (current or voltage) generates a high voltage or a high current.
This current/voltage is measured by the standard voltage or current transformer and the test object and will be transmitted to the secondary side, i.e. converted to low voltage or low current.
The measuring bridge compares the ratio of the standard voltage or current transformer and the test object, in detail the values of errors in amplitude (%) and phase (minutes per angle).
The more accurate the standard voltage or current transformer is, the more accurate is the result of the measurement.
Please find at the bottom of this page the high accuracy of our devices for each type of standard transformer.

Where do i find more informations about standard current transformers?

Please see an overview of the available models here at the product data sheets. Please always consider that the mentioned datasheets are examples. Any customers request considering tappings on the primary side, different currents on the secondary, operation frequencies of 50 and 60 Hz and other wishes can be fulfilled.