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Abstract

Current transformers or CTs take up a lot of space in HV cubicles. Through knowledge of how they work makes it possible to:

  • Reduce their dimensions and thus their cost,
  • Use standard CTs in a larger number of configurations.

The purpose of this study is to learn more about CT operation in association with protection relays and to lay down a few rules for sizing them properly. After a brief theoretical review of CT operation and current protection devices, the behaviour of the CTprotection relay combination is studied in two particularly important cases
in HV:

  • overcurrent relay supplied by a heavily saturated CT,
  • protection relay connected to two CTs in parallel in duplex cubicles.

This study is completed by experimental results.

Theoretical Review

Current transformers consist of a magnetic circuit in toroid form. The primary is made up of n1 turns or simply a single conductor crossing the toroid (n1 = 1). The secondary is wound in n2 regular turns around this toroid (see fig. 1 and 2).
Ampere’s theorem states that the sum of the ampere-turns is equal to the circulation of the magnetic field vector.

AUTHOR: Schneider Electric expert | Michel ORLHAC

Title:Current transformers for HV protection
Format:PDF
Size:0.3MB
Pages:20
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Current transformers for HV protection

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Page edited by E.C. (Google).

One Comment


  1. Mustafa assal
    Dec 19, 2011

    perfect

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