standard current transformers
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.
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 1-120 % 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.
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.
The standard current transformers are available in dry-insulated and oil-insulated versions. The dry insulated standard CT´s have an insulation level of 1,1 kV, while the oil-insulated types are available from 30 kV to 200 kV nominal voltage. The primary current rating varies between 1 A and 50.000 A, depending on the model.
Dry insulated standard current transformers mostly are used in the field of instrument transformer testing as here the user has to measure very high currents at a low voltage level. Oil insulated standard current transformers are used mostly in transformer test labs as in this application the user has to measure high currents under high voltage level.
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.
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.
Please find more informations in the datasheets in Downloads. 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.