Current transformers Sample Clauses
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Current transformers. Current transformers shall be single phase, secondary ratio transformers for outdoors assembly, in vertical position, with oil immersed or SF6 gas insulation and will be hermetically sealed. They shall be able to conduct the primary rated current for one minute, while the secondary circuit is open. The core shall be toroidal and made up of steel magnetic foils with very low specific losses, and the windings shall be made of insulated copper. In the case of the transformers that work in connection with the disconnectors, high frequency currents and voltages transferable to secondary and ground circuits shall be taken into consideration during the switching of adjacent live disconnectors. The manufacturer’s structural design shall be such that it prevents: g1) High current density in certain points of the equipment causing localized overheating. g2) Internal surges of very short duration causing dielectric breakdowns in liquid and solid insulators. Current transformers shall have the following additional characteristics: Current in continuous operation 500 - 1000 A (L.T) Coupling (*) Secondary current 1 A Short-circuit thermal intensity 40 kA Characteristics of measuring cores a) Precision class b) Power 0,2 % 15 VA (minimum) Characteristics of protection cores a) Precision class b) Power 5P20 15 VA (minimum)
Current transformers. C/Ts shall confirm to IS 2705 (part -I, II and III) in all respects. All C/Ts used for medium voltage application shall be rated for 1 kV. C/Ts shall have rated primary current, rated burden and class of accuracy as specified in schedule of quantities/drawings. Rated secondary current shall be 5A unless otherwise stated. Minimum acceptable class for measurement shall be class 0.5 to 1 and for protection class SP 10. C/Ts shall be capable of withstanding magnetic and thermal stresses due to short circuit faults of 31 MVA on medium voltage. Terminals of C/Ts shall be paired permanently for easy identification of poles. C/Ts shall be provided with earthing terminals for earthing chassis, frame work and fixed part of metal casing (if any). Each C/T shall be provided with rating plate indicating: CTs shall be mounded such that they are easily accessible for inspection, maintenance and replacement. Wiring for CT shall be with copper conductor PVC insulated wires with proper termination works and wiring shall be bunched with cable straps and fixed to the panel structure in a neat manner.
Current transformers. For current transformers, they shall have at least four secondary cores: • Three 5P20 protection cores. • One Class 0.2 core for measurement.
Current transformers. (A) All CTs for Type 1, 2 and 3 Meters must meet the following criteria: 1 IEC 6189-2 0.2s 2 1 set of CTs dedicated to the Main Meter only and 1 set supplying the Check Meters. Check Meter CTs can be used for other purposes provided that such Check Meter CTs comply with the accuracy requirements in paragraph 2.2 of these TSRs.
Current transformers. (A) All CTs for Type 1, 2 and 3 Meters must meet the following criteria: Type of Meter Relevant Standard Minimum Class Accuracy No. of sets Usage
1 IEC 6189-2 0.2s 2 1 set of CTs dedicated to the Main Meter only and 1 set supplying the Check Meters. Check Meter CTs can be used for other purposes provided that such Check Meter CTs comply with the accuracy requirements in paragraph 2.2 of these TSRs.
2 IEC 6189-2 0.2s 1 CTs must be dedicated to the CfD Settlement Activities, supplying both Main Meters and Check Meters. An additional set of CTs may be fitted for the Check Meter which may also be used for other purposes provided that Type of Meter Relevant Standard Minimum Class Accuracy No. of sets Usage such Check Meters comply with the accuracy requirements in paragraph 2.2 of these TSRs.
3 IEC 185 0.5 1 1 set of CTs for Main Meters and Check Meters’ CfD Settlement Activities purposes, but may also have other uses if the overall accuracy requirements in paragraph 2.2 of these TSRs are met.
Current transformers. Current Transformers shall comply with IEC 61869 in general. All ratios shall be obtained by secondary taps only. Generally, Current Transformers (CT) shall have five cores (four for protection and one for metering) whereas; CT in Tie bays shall have six cores (four for protections & two for metering) suitably distributed on both sides of CB (for 400kV and above voltage class). The burden and knee point voltage shall be in accordance with the requirements of the system including possible feeds for telemetry. Accuracy class for protection core shall be PX and for metering core it shall be 0.2S. The rated burden of cores shall be closer to the maximum burden requirement of metering & protection system for better sensitivity and accuracy.
Current transformers a. The insulation Silicon rubber or epoxy resin or equivalent material (Porcelain and oil type not accepted) and it must have environmental type test.
a. Current transformer shall be in accordance with IEC 61869-2 b. C.T’S ratio as in the Schedule (1) Outdoor pole mounted with creepage distance not less than 1188 mm.
Current transformers. The term "current transformer" used in section 5 does not preclude the use of other measuring techniques with a performance equal to that specified for such measurement transformers. For each circuit where a current transformer is used, it shall meet the requirements set out below. Where required, one set of current transformers to BS EN 60044-1:1999 with a minimum standard of accuracy to Class 0.5 shall be provided per circuit. Preferably the current transformers shall be dedicated for Allocation purposes, but the current transformers may be used for other purposes provided the overall accuracy requirements in section 5.2.4 are met. The total burden on each current transformer shall not exceed the rated burden of such current transformer.
Current transformers. All CTs for Type 1, 2 and 3 Meters must meet the following criteria: Type of Meter Relevant Standard Minimum Class Accuracy No. of sets Usage 1 IEC 60044-1 0.2s 2 1 set of CTs dedicated to the Main Meter only and 1 set supplying the Check Meters. Check Meter CTs can be used for other purposes providing the overall accuracy requirements in paragraph 2.2 of these TSRs are met 2 IEC 60044-1 0.2s 1 CTs must be dedicated to the CfD Settlement Activities, supplying both Main Meters and Check Meters. An Type of Meter Relevant Standard Minimum Class Accuracy No. of sets Usage additional set of CTs may be fitted for the Check Meter which may also be used for other purposes providing the overall accuracy requirements in paragraph 2.2 of these TSRs are met.
Current transformers. One set of current transformers in accordance with IEC Standard 185 and with a minimum standard of accuracy class 0.5S (irrespective of the secondary current rating of the current transformers) shall be provided. Preferably the current transformers shall be dedicated for Settlement purposes, but the CTs may be used for other purposes provided the overall accuracy requirements in clause 4.2.1 are met and evidence of the value of the additional burden is available for inspection by the SSA or its agent. The additional burden shall not be modified without prior notification to the SSA, and evidence of the value of the modified additional burden shall be available for inspection by the SSA or its Agent. CT test certificates showing errors at the overall working burden or at burdens which enable the working burden errors to be calculated shall be available for inspection by the SSA or its agent. The total burden on each current transformer shall not exceed the rated burden of such CT.