IEEE C57.13.5:2019 pdf free download – IEEE Standard for Performance andTest Requirements for InstrumentTransformers of a Nominal SystemVoltage of 115 kV and Above
class ll instrument transformer: An instrument transformer rated l1l5 kV and above,with capacitiveinsulation, and which is constructed and tested in accordance with IEEE Std C57.13.5 supplemented withrequirements ofIEEE Std C57.13-2016.
design pressure (of a pressurized gas enclosure): Pressure used to determine the thickness of an enclosure.lt is, at least, the upper limit of the gas pressure reached within the enclosure when the instrument transformeris subjected to the maximum ambient air temperature increased by the gas temperature rise due to the flow ofrated current and the losses caused by the rated voltage.
internal arc protection class I: A special transformer design with a feature that, during an internal line-to-ground arc test with the arc taking place at a location, which is technically the most probablc, the debris of thctransformer will be confined to a circle, centered at the transformer. The diameter of this circle is equal to thesum of twice the height of the transformer and the diameter of the transformer.
internal arc protection class lII: A special transformer design with a feature that, during an internal line-to-ground arc test with the arc taking place at a location, which is technically the most probable, will not fracturethe insulator or housing of the transformer.
NOTE—The above definitions regarding the classification of intermal arc protection apply only to the test conditionsspecified in this standard.The instrument transformers may have different performance during an in-service internal arcfault. Refer to Annex Gfor more information regarding the interpretation of internal are protection.The performance doesnot apply to any internal pressure relief device (e.g.,rupture disc and protective cover, if applicable) provided with thetransformer.”‘
minimum functional pressure (or density) for gas-filled instrument transformers: Pressure(Pa),referredto the standard atmospheric air conditions of +20 °C and 101.3 kPa(or density), which may be expressed inrelative or absolute terms, at which and above which rated characteristics of the instrument transformer aremaintained.
prescribed extinction voltage:The lowest line-1o-ground voltage required for the transformer at which thepartial discharge is determined to exist if the reference level is met when the voltage applied to the transformeris gradually decreased without interruption from the power frequency withstand voltage or pre-stress voltagevalue during the partial discharge test. The reference partial discharge level for the transformers covered inthis standard is 10 pc.
rated arc proof current: Maximum current for which the internal arc classification applies.
rated filling pressure (or density) for gas-illed instrument transformers: Pressure(in Pa), referred to thestandard atmospheric air conditions of +20 °C and 101.3 kPa (or density), which may be expressed in relativeor absolute terims, to which the instrument transformer is filled before being put into service.
rated voltage factor: A multiplier applied to the rated (primary) voltage to derive the maximum voltage atwhich a transformer must comply with the relevant thermal requirements for a specified time and with therelevant accuracy requirements.
NOTE—Refer to Annex H for additional information.
terminals: Conductive element belonging to the instrument transformer provided for connecting thatinstrument transformer to one or more external conductors. Terminals are normally connected to one ormore conductors by means of connectors, which are generally not considered to be part of the instrumenttransformer itself.