IEC TR 61912-2 : 1.0

LOW-VOLTAGE SWITCHGEAR AND CONTROLGEAR - OVER-CURRENT PROTECTIVE DEVICES - PART 2: SELECTIVITY UNDER OVER-CURRENT CONDITIONS

International Electrotechnical Committee

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FOREWORD
INTRODUCTION
1 Scope
2 Normative references
3 Terms, definitions and abbreviated terms
  3.1 Alphabetical index of terms
  3.2 Terms and definitions
  3.3 Abbreviated terms
4 Scope of selectivity requirements
  4.1 General
  4.2 Motor protection circuit-breaker/Manual motor starter
5 Selectivity determination
  5.1 Circuit-breaker as UD
      5.1.1 Selectivity between circuit-breakers
      5.1.2 Selectivity between a circuit-breaker (UD) and
            a fuse to IEC 60269-1 (DD)
      5.1.3 CB/CPS - Selectivity between a circuit-breaker
            to IEC 60947-2 (UD) and a CPS to IEC 60947-6-2
            (DD)
      5.1.4 Circuit-breaker/MOR - Selectivity between a
            circuit-breaker (UD) and a motor protection
            overload relay to IEC 60947-4-1 or
            IEC 60947-4-2 (DD)
  5.2 Fuse(s) to IEC 60269-1 as UD
      5.2.1 Fuse/circuit-breaker - Selectivity between a fuse
            to IEC 60269-1 (UD) and a circuit-breaker (DD)
      5.2.2 FU/FU - Selectivity between fuses to IEC 60269-1
            (UD and DD)
      5.2.3 FU/CPS - Selectivity between fuse(s) to IEC 60269-1
            (UD) and a CPS to IEC 60947-6-2 (DD)
      5.2.4 FU/MOR - Selectivity between fuse(s) to IEC 60269-1
            (UD) and a motor overload protection relay to
            IEC 60947-4-1 or IEC 60947-4-2 (DD)
6 Residual current devices (RCDs)
  6.1 General
  6.2 Selectivity - RCD/RCD
      6.2.1 Selectivity between RCDs in the case of
            earth-leakage current
      6.2.2 Selectivity between RCDs in the case of
            earth-fault (ground-fault) current
7 Zone Selective Interlocking (ZSI)
  7.1 General
  7.2 Operating principle
  7.3 Example
8 Over-current protection relay (OCR) - Single input energizing
  quantity measuring relays with dependent or independent time
Annex A (informative) - Examples of selectivity between
        over-current protection devices Examples of the grades
        of selectivity applicable to circuit-breakers
Annex B (informative) - Standing loads - Effect of standing
        loads on selectivity in the overload zone
Bibliography

Abstract

Provides an application guide for the determination of selectivity between over-current protective devices of low-voltage switchgear and controlgear, summarises the definitions of the terminology and provides examples of application.