Table of Contents

1 Overview
  1.1 Scope
  1.2 Purpose
2 Normative references
3 Definitions
4 Current transformer characteristics and classification
  4.1 Current transformer equivalent circuit and phasor diagrams
  4.2 Current transformer secondary excitation characteristics
  4.3 Knee-point voltage
  4.4 Current transformer accuracy
  4.5 Dynamic characteristics
  4.6 The effects of remanence
  4.7 Fundamental transformer equation
5 General application of current transformers
  5.1 Current transformer burdens
  5.2 Ratio selection
  5.3 Long-term and short-term thermal ratings
  5.4 Current transformer secondary output accuracy class voltage
  5.5 Connecting current transformers in series
  5.6 Three-phase connections
  5.7 Auxiliary current transformers
  5.8 Bus configuration
  5.9 Current transformer location
  5.10 Minimizing the effects of current transformer saturation
  5.11 Determining current transformer steady-state performance
       using secondary excitation curves
6 Effects of current transformer saturation on relays
  6.1 Saturation effects on electromechanical relays
  6.2 Saturation effects on static relays
  6.3 Saturation effects on differential relays
  6.4 Unbalanced current measurement
  6.5 Current transformer performance under geomagnetic-induced
       current conditions
7 Specific applications of current transformers
  7.1 Overcurrent relays
  7.2 Differential protection
  7.3 Distance protection
  7.4 Other types of high-speed protection
Annex A (informative) IEC standards on current transformers
Annex B (informative) List of ANSI C accuracy class values
        and burdens
Annex C (informative) Remanent flux in current transformers
Annex D (informative) Optical current sensor systems
Annex E (informative) Bibliography

Abstract

Specifies the characteristics and classification of current transformers (CTs) used for protective relaying. It also describes the conditions that cause the CT output to be distorted and the effects on relaying systems of this distortion. The selection and application of CTs for the more common protection schemes are also addressed.

General Product Information

Published
Document Type	Standard
Status	Current
Publisher	Institute of Electrical & Electronics Engineers
Pages
ISBN
Supersedes	IEEE DRAFT C37.110 : D21 OCT 94