IEEE C57.13.5-2009 pdf download IEEE Standard for Performance and Test Requirements for Instrument Transformers of a Nominal System Voltage of 115 kV and Above
3.Definitions
For the purposes of this document, the following terms and definitions apply. The Atherifafive IEEE StandardsDictionary: Glossary ofTerms & Definitions should be referenced for terms not defined in this clause.
capacitive insulation system: An arrangcment of internal insulation and clctrodes to distribute both thcalternating and impulse voltages along the bushing of the instrument transformer with capacitive dielectriclayers andor electrode(s) to achieve an improved co-ordination between the internal and external insulation forthe purpose ofincreasing the over-voltage withstand capability.
Internal arc protection class I: A special transformer design with a feature that, during an internal line–t0-ground arc test with the arc taking place at a location, which is technically the most probable, the debris of thetransformer 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 ll: 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.
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NOTE-The above definitions regarding the classification- Internal arc protection class [ and Intenal arc protectiorClass ll regarding the classification of internal arc prolection apply only to the test conditions specified in this standardThe instrument transformers may have different performance during an in-service internal arc fault. Refer to Anncx D formore information regarding the interpretation of internal arc protection. The performance does not apply to any internalpressure relief device (e.g.. rupture disc) provided with the transformers.
prescribed extinction voltage: The lowest line-to-ground voltage required for the transformer at which thepartial discharge is determined to exist if the reference intensity is met when the voltage applied to thetransformer is gradually decreased without interruption from the power frequency withstand voltage or pre-stress voltage value during the partial discharge test, The reference partial discharge intensity for thetransformers covered in this standard is 10 pC.
rated voltage factor: A multiplier applied to the rated (primary) voltage to derive the maximum voltage atwhich a transformer must comply with the relevant therma-requirements for a specified time and with therelevant accuracy requirements.
NOTE-Refer to Annex F for additional information.