Medium-voltage instrument transformers
Low voltage current instrument transformers
CLT 20
The CLT 20 current instrument transformer are used for metering and protection purposes in LV indoor switching stations with the highest system voltage of 0.72 kV. Their rated secondary currents are 5A or 1A.
The ultimate operating current of the CLT 20 is 100 % IN, but if agreed with the manufacturer also other values may be delivered, such as 120 % IN. Active parts of the CLT 20 are placed in boxes made of high-quality plastic material. The insulation materials used meet the requirements on thermal insulation class E.
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Description
The CLT 20 current instrument transformer are used for metering and protection purposes in LV indoor switching stations with the highest system voltage of 0.72 kV. Their rated secondary currents are 5A or 1A.
The ultimate operating current of the CLT 20 is 100 % IN, but if agreed with the manufacturer also other values may be delivered, such as 120 % IN. Active parts of the CLT 20 are placed in boxes made of high-quality plastic material. The insulation materials used meet the requirements on thermal insulation class E.
Concerning their design the VLT 20 are wound transformers with primary terminals connected to the circuit using M10 screws.
The secondary terminals with contact screws are situated in the upper part of the transformer under a transparent cover which can be sealed. As regards the connection of secondary terminals we recommend using cable lugs of sizes corresponding to the cross-section of the connecting wire, or bare conductors of up to 2.5 mm diameter may also be used.
ATTENTION! DURING THE OPERATION OF CLT 20 IT IS NECESSARY TO PREVENT THAT THE OUTPUTS OF SECONDARY WINDING WILL BE COME DISCONNECTED.
If it can be foreseen that the transformer will no more be operated for an extended period of time, its secondary winding must be short-circuited.
As an additional service for the customer we may provide the transformers with official calibration certificate.
The transformer parameters may also be tailored to the specific requirements of the client, based on previous agreement with the manufacturer.
Parameters
- Highest voltage for equipment: 0.72 kV
- Power frequency test voltage: 3 kV
- Nominal primary current: 5 A or 1 A
- Nominal secondary current: 60 x In (max. 50 kA)
- Rated short-time thermal current, Ith: 2,5 x Ith
- Rated dynamic current, ldyn: 1,0 x In (1,2x In)
- Nominal frequency: 50 Hz (60 Hz)
- Thermal insulation class: E
- Operation conditions: corresponds to the -5/40 thermal class to ČSN EN 61869-1 standard; for mounting in indoor areas without water condensation
- Standard: ČSN EN 61869-1, ČSN EN 61869-2, IEC EN 61869-1, IEC EN 61869-2, GOST 15 150
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