Instrument Transformers Clause Samples
The Instrument Transformers clause defines the requirements and specifications for transformers used to measure electrical parameters such as current and voltage within a system. It typically outlines the types, ratings, accuracy classes, and installation standards for current and voltage transformers that are used in conjunction with metering, protection, and control equipment. By establishing clear criteria for these components, the clause ensures accurate measurement and reliable operation, thereby supporting system safety and compliance with regulatory standards.
Instrument Transformers. 1.6.1. Current transformer output shall remain within acceptable limits for all anticipated fault currents and for all anticipated burdens connected to the current transformer.
1.6.2. Current transformers shall be connected so that adjacent relay protection zones overlap.
1.6.3. Voltage transformers and potential devices shall have adequate volt-ampere capacity to supply the connected burden while maintaining their accuracy over the specified primary voltage range.
1.6.4. For each independent protection system, separate current and voltage transformer or potential device secondary windings shall be used, except on low-voltage devices.
1.6.5. Interconnected current transformer secondary wiring and voltage transformer secondaries shall each be grounded at only a single point.
Instrument Transformers. Current transformer output shall remain within acceptable limits for all anticipated fault currents and for all anticipated burdens connected to the current transformer.
Instrument Transformers. A. Current transformers can be primary wound or of toroidal type E with current ratios in accordance with those shown on the drawings and ESD. Secondary’s shall have a 5 amp rating. They shall be capable of continuously carrying 150 % of the rated current at 55° C ambient and will be of applicable ANSI relaying accuracy class as specified in the ESD. By itself the CT can be rated 600 volt class 10 kv BIL.
B. Voltage or Potential Transformers, if required, shall be single phase 19.95 kV-69.5V (Y-Yg connection). They shall be insulated for the line-line voltages of 12.47kV and 120v.They shall be of applicable ANSI relaying accuracy class and be provided with primary and secondary fusing. The accuracy class and burden of the PT shall be specified by the Engineering Contractor.
C. Instrument transformer secondary’s shall be provided with a safe means to isolate them from the relay inputs for relay testing and calibration.
Instrument Transformers. 6.6.1 Instrument transformers shall be completely encapsulated cast resin type, suitable for continuous operation at the ambient temperature prevailing inside the switchgear enclosure, when the switchgear is operating at its rated load and the outside ambient temperature is 50°C.
6.6.2 Polarity marks shall indelibly be marked on each instrument transformer and at the lead terminals at the associated terminal block. 50 MW (AC) Solar PV Power Plants at Tamil Nadu Tender No. SECI/C&P/TD/2020/TN/50 TS Page 31 of 123 Signature of Bidder
6.6.3 Voltage transformers shall be single phase units. Bus voltage transformers shall be housed in a separate panel on withdrawable truck.
6.6.4 HRC fuses of suitable rating shall be provided on primary side of voltage transformers. For secondary side, four pole Miniature Circuit Breakers (MCB) shall be provided with its supervision facility.
Instrument Transformers. 10.1 CTs and VTs shall conform to the requirement of IS:2705 and IS:3156 respectively. The ratings specified are indicative only and it shall be Vendor‟s responsibility to ensure that the ratings offered are adequate for the relays/meters provided considering lead resistance, etc.
10.2 CTs and VTs shall be of dry air insulated type.
10.3 Facility shall be provided in the terminal blocks for shorting and earthing the CTs.
10.4 VTs shall be provided with adequately rated primary and secondary fuses.