Section 8 in Rajasthan Electricity Regulatory Commission (Metering) Regulations 2007
8. Instrument Transformers.
(1)The current transformers and voltage transformers (including CT-PT set) shall meet the relevant Indian Standard (IS) requirements and the accuracy class shall not be inferior to that of the meter instrument vide Annexure-1 & Annexure-2.(2)The total burden connected to each Instrument transformer shall not exceed its rated burden. The rated burden and connected burden of the Instrument transformer may normally be such that actual burden remains between 25% to "100% of the rated burden.(3)Dedicated Instrument Transformers or its dedicated core shall be provided for metering.(4)The errors of the instrument transformers shall be checked in the laboratory or at site. If such facilities are not available, test certificates issued by the supplier or by the accredited test laboratory shall be referred to.(5)11kV/33kV CT-PT sets may preferably be of dry type, if available. EHV grade oil shall be used in oil filled CT-PT sets. Inhibitors like DBC Powder may be added to the oil.(6)Current Transformers:(i)"Interface meters" and "Energy accounting and audit meters" shall have three single phase current transformers. The secondary current rating of the CTs shall normally be 5.0 Amp or 1 Amp except for 400kV and 220kV sub-stations where it shall be 1 Amp.(ii)Consumer meter.External current transformers, where required to be provided, on consumer meters shall generally have 5 Amps secondary current rating. The licensee shall prepare norms for selection of the CT ratio for consumer connections.(7)Voltage transformers.(i)The secondary voltage shall be 110/√3 volts per phase.(ii)No fuse whether on HT or LT side of the VT/CVT shall be provided in consumer meters. In case of existing installations also, the PT fuses shall be dispensed with
