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PD IEC/TR 61869-100:2017 Instrument transformers - Guidance for application of current transformers in power system protection, 2017
- 30293146-VOR.pdf [Go to Page]
- CONTENTS
- FOREWORD
- INTRODUCTION
- 1 Scope
- 2 Normative references
- 3 Terms and definitions and abbreviations [Go to Page]
- 3.1 Terms and definitions
- 3.2 Index of abbreviations
- 4 Responsibilities in the current transformer design process [Go to Page]
- 4.1 History
- 4.2 Subdivision of the current transformer design process
- 5 Basic theoretical equations for transient designing [Go to Page]
- 5.1 Electrical circuit [Go to Page]
- 5.1.1 General
- 5.1.2 Current transformer
- 5.2 Transient behaviour [Go to Page]
- 5.2.1 General
- 5.2.2 Fault inception angle
- 5.2.3 Differential equation
- 6 Duty cycles [Go to Page]
- 6.1 Duty cycle C – O [Go to Page]
- 6.1.1 General
- 6.1.2 Fault inception angle
- 6.1.3 Transient factor Ktf and transient dimensioning factor Ktd
- 6.1.4 Reduction of asymmetry by definition of the minimum current inception angle
- 6.2 Duty cycle C – O – C – O [Go to Page]
- 6.2.1 General
- 6.2.2 Case A: No saturation occurs until t’
- 6.2.3 Case B: Saturation occurs between t’al and t’
- 6.3 Summary
- 7 Determination of the transient dimensioning factor Ktd by numerical calculation [Go to Page]
- 7.1 General
- 7.2 Basic circuit
- 7.3 Algorithm
- 7.4 Calculation method
- 7.5 Reference examples
- 8 Core saturation and remanence [Go to Page]
- 8.1 Saturation definition for common practice [Go to Page]
- 8.1.1 General
- 8.1.2 Definition of the saturation flux in the preceding standard IEC 60044-1
- 8.1.3 Definition of the saturation flux in IEC 61869-2
- 8.1.4 Approach “5 % – Factor 5”
- 8.2 Gapped cores versus non-gapped cores
- 8.3 Possible causes of remanence
- 9 Practical recommendations [Go to Page]
- 9.1 Accuracy hazard in case various PR class definitions for the same core
- 9.2 Limitation of the phase displacement ∆ϕ and of the secondary loop time constant Ts by the transient dimensioning factor Ktd for TPY cores
- 10 Relations between the various types of classes [Go to Page]
- 10.1 Overview
- 10.2 Calculation of e.m.f. at limiting conditions
- 10.3 Calculation of the exciting (or magnetizing) current at limiting conditions
- 10.4 Examples
- 10.5 Minimum requirements for class specification
- 10.6 Replacing a non-gapped core by a gapped core
- 11 Protection functions and correct CT specification [Go to Page]
- 11.1 General
- 11.2 General application recommendations [Go to Page]
- 11.2.1 Protection functions and appropriate classes
- 11.2.2 Correct CT designing in the past and today
- 11.3 Overcurrent protection: ANSI code: (50/51/50N/51N/67/67N); IEC symbol: I> [Go to Page]
- 11.3.1 Exposition
- 11.3.2 Recommendation
- 11.3.3 Example
- 11.4 Distance protection: ANSI codes: 21/21N, IEC code: Z< [Go to Page]
- 11.4.1 Exposition
- 11.4.2 Recommendations
- 11.4.3 Examples
- 11.5 Differential protection [Go to Page]
- 11.5.1 Exposition
- 11.5.2 General recommendations
- 11.5.3 Transformer differential protection (87T)
- 11.5.4 Busbar protection: Ansi codes (87B)
- 11.5.5 Line differential protection: ANSI codes (87L) (Low impedance)
- 11.5.6 High impedance differential protection
- Annex A (informative)Duty cycle C – O software code
- Annex B (informative)Software code for numerical calculation of Ktd
- Bibliography
- Figures [Go to Page]
- Figure 1 – Definition of the fault inception angle γ
- Figure 2 – Components of protection circuit
- Figure 3 – Entire electrical circuit
- Figure 4 – Primary short circuit current
- Figure 5 – Non-linear flux of Lct
- Figure 6 – Linearized magnetizing inductance of a current transformer
- Figure 7 – Simulated short circuit behaviour with non-linear model
- Figure 8 – Three-phase short circuit behaviour
- Figure 9 – Composition of flux
- Figure 10 – Short circuit current for two different fault inception angles
- Figure 11 – ψmax as the curve of the highest flux values
- Figure 12 – Primary current curves for the 4 cases for 50 Hz and ϕ = 70°
- Figure 13 – Four significant cases of short circuit currents with impact on magnetic saturation of current transformers
- Figure 14 – Relevant time ranges for calculation of transient factor
- Figure 15 – Occurrence of the first flux peak depending on Tp, at 50 Hz
- Figure 16 – Worst-case angle θtf,ψmax as function of Tp and t’al
- Figure 17 – Worst-case fault inception angle γtf,ψmax as function of Tp and t’al
- Figure 18 – Ktf,ψmax calculated with worst-case fault inception angle θψmax
- Figure 19 – Polar diagram with Ktf,ψmax and γtf,ψmax
- Figure 20 – Determination of Ktf in time range 1
- Figure 21 – Primary current curves for 50Hz, Tp = 1 ms, γψmax = 166° for t’al = 2 ms
- Figure 22 – worst-case fault inception angles for 50Hz, Tp = 50 ms and Ts = 61 ms
- Figure 23 – transient factor for different time ranges
- Figure 24 – Ktf in all time ranges for Ts = 61 ms at 50 Hz with t’al as parameter
- Figure 25 – Zoom of Figure 24
- Figure 26 – Primary current for a short primary time constant
- Figure 27 – Ktf values for a short primary time constant
- Figure 28 – Short circuit currents for various fault inception angles
- Figure 29 – Transient factors for various fault inception angles (example)
- Figure 30 – Worst-case fault inception angles for each time step (example for 50 Hz)
- Figure 31 – Primary current for two different fault inception angles(example for 16,67 Hz)
- Figure 32 – Transient factors for various fault inception angles(example for 16,67 Hz)
- Figure 33 – Worst-case fault inception angles for every time step(example for 16,67 Hz)
- Figure 34 – Fault occurrence according to Warrington
- Figure 35 – estimated distribution of faults over several years
- Figure 36 – Transient factor Ktf calculated with various fault inception angles γ
- Figure 37 – Flux course in a C-O-C-O cycle of a non-gapped core
- Figure 38 – Typical flux curve in a C-O-C-O cycle of a gapped core,with higher flux in the second energization
- Figure 39 – Flux curve in a C-O-C-O cycle of a gapped core, with higher flux in the first energization
- Figure 40 – Flux curve in a C-O-C-O cycle with saturation allowed
- Figure 41 – Core saturation used to reduce the peak flux value
- Figure 42 – Curves overview for transient designing
- Figure 43 – Basic circuit diagram for numerical calculation of Ktd
- Figure 44 – Ktd calculation for C-O cycle
- Figure 45 – Ktd calculation for C-O-C-O cyclewithout core saturation in the first cycle
- Figure 46 – Ktd calculation for C-O-C-O cycleconsidering core saturation in the first cycle
- Figure 47 – Ktd calculation for C-O-C-O cycle with reduced asymmetry
- Figure 48 – Ktd calculation for C-O-C-O cycle with short t’al and t’’al
- Figure 49 – Ktd calculation for C-O-C-O cycle for a non-gapped core
- Figure 50 – Comparison of the saturation definitionsaccording to IEC 60044-1 and according to IEC 61869-2
- Figure 51 – Remanence factor Kr according to the previous definition IEC 60044-1
- Figure 52 – Determination of saturation and remanenceflux using the DC method for a gapped core
- Figure 53 – Determination of saturation and remanence flux using DC method for a non-gapped core
- Figure 54 – CT secondary currents as fault records of arc furnace transformer
- Figure 55 – 4-wire connection
- Figure 56 – CT secondary currents as fault records in the second fault of auto reclosure
- Figure 57 – Application of instantaneous/time-delay overcurrent relay (ANSI codes 50/51) with definite time characteristic
- Figure 58 – Time-delay overcurrent relay, time characteristics
- Figure 59 – CT specification example, time overcurrent
- Figure 60 – Distance protection, principle (time distance diagram)
- Figure 61 – Distance protection, principle (R/X diagram)
- Figure 62 – CT Designing example, distance protection
- Figure 63 – Primary current with C-O-C-O duty cycle
- Figure 64 – Transient factor Ktf with its envelope curve Ktfp
- Figure 65 – Transient factor Ktf for CT class TPY with saturation in the first fault
- Figure 66 – Transient factor Ktf for CT class TPZ with saturation in the first fault
- Figure 67 – Transient factor Ktf for CT class TPX
- Figure 68 – Differential protection, principle
- Figure 69 – Transformer differential protection, faults
- Figure 70 – Transformer differential protection
- Figure 71 – Busbar protection, external fault
- Figure 72 – Simulated currents of a current transformerfor bus bar differential protection
- Figure 73 – CT designing for a simple line with two ends
- Figure 74 – Differential protection realized with a simple electromechanical relay
- Figure 75 – High impedance protection principle
- Figure 76 – Phasor diagram for external faults
- Figure 77 – Phasor diagram for internal faults
- Figure 78 – Magnetizing curve of CT
- Figure 79 – Single-line diagram of busbar and high impedance differential protection
- Figure 80 – Currents at the fault location (primary values)
- Figure 81 – Primary currents through CTs, scaled to CT secondary side
- Figure 82 – CT secondary currents
- Figure 83 – Differential voltage
- Figure 84 – Differential current and r.m.s. filter signal
- Figure 85 – Currents at the fault location (primary values)
- Figure 86 – Primary currents through CTs, scaled to CT secondary side
- Figure 87 – CT secondary currents
- Figure 88 – Differential voltage
- Figure 89 – Differential current and r.m.s. filtered signal
- Figure 90 – Currents at the fault location (primary values)
- Figure 91 – Primary currents through CTs, scaled to CT secondary side
- Figure 92 – CT secondary currents
- Figure 93 – Differential voltage
- Figure 94 – Differential current and r.m.s. filtered signal
- Figure 95 – Differential voltage without varistor limitation
- Tables [Go to Page]
- Table 1 – Four significant cases of short circuit current inception angles
- Table 2 – Equation overview for transient designing
- Table 3 – Comparison of saturation point definitions
- Table 4 – Measured remanence factors
- Table 5 – Various PR class definitions for the same core
- Table 6 – e.m.f. definitions
- Table 7 – Conversion of e.m.f. values
- Table 8 – Conversion of dimensioning factors
- Table 9 – Definitions of limiting current
- Table 10 – Minimum requirements for class specification
- Table 11 – Effect of gapped and non-gapped cores
- Table 12 – Application recommendations
- Table 13 – Calculation results of the overdimensioning of a TPY core
- Table 14 – Calculation results of overdimensioning as PX core
- Table 15 – Calculation scheme for line differential protection
- Table 16 – Busbar protection scheme with two incoming feeders [Go to Page]