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BS EN IEC 60255-181:2019

BS EN IEC 60255-181:2019

$215.11

Measuring relays and protection equipment – Functional requirements for frequency protection

Published By Publication Date Number of Pages
BSI 2019 96
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This part of IEC 60255 specifies the minimum requirements for functional and performance evaluation of frequency protection. This document also defines how to document and publish performance test results.

This document covers the functions based on frequency measurement or rate of change of frequency measurements. This document also covers frequency protection where additional blocking elements are used.

This document defines the influencing factors that affect the accuracy under steady state conditions and performance characteristics during dynamic conditions. The test methodologies for verifying performance characteristics and accuracy are also included in this document.

The frequency functions covered by this document are shown in Table 1:

PDF Catalog

PDF Pages PDF Title
2 undefined
6 Blank Page
7 English
CONTENTS
11 FOREWORD
13 1 Scope
Tables
Table 1 – Frequency protection designation
14 2 Normative references
3 Terms and definitions
16 Figures
Figure 1 – Operate time and operate time delay setting
18 4 Specification of the function
4.1 General
4.2 Input energizing quantities / energizing quantities
Figure 2 – Simplified protection function block diagram
19 4.3 Binary input signals
4.4 Functional logic
4.4.1 Operating characteristics
20 Figure 3 – Underfrequency independent time characteristic
21 Figure 4 – Overfrequency independent time characteristic
Figure 5 – ROCOF independent time characteristic (for negative or positive ROCOF)
22 4.4.2 Reset characteristics
23 4.5 Additional influencing functions/conditions
4.5.1 General
4.5.2 Specific characteristics for under/over frequency function
Figure 6 – Explanatory diagram for start, operate, disengage and reset
24 4.5.3 Specific characteristics for rate of change of frequency (ROCOF) function
4.6 Binary output signals
4.6.1 General
4.6.2 Start (pick-up) signal
4.6.3 Operate (trip) signal
4.6.4 Other binary output signals
25 5 Performance specification
5.1 General
5.2 Effective and operating ranges
Table 2 – Example of effective and operating ranges for over/under frequency protection
Table 3 – Example of effective and operating ranges for ROCOF protection
26 5.3 Accuracy related to the characteristic quantity
5.4 Start time for under/over frequency function
5.5 Start time for rate of change of frequency (ROCOF) function
27 5.6 Accuracy related to the operate time delay setting
5.7 Disengaging time
5.8 Reset hysteresis and reset ratio
28 5.9 Accuracy related to restraint/blocking elements
5.10 Performance with harmonics
5.11 Stability in case of sudden voltage change (phase shift and magnitude shift)
5.12 Voltage input requirements
29 6 Functional test methodology
6.1 General
31 6.2 Determination of steady state errors related to the characteristic quantity
6.2.1 Accuracy of the start value
Figure 7 – Example of test method for overfrequency
33 Table 4 – Test points for under/over frequency function
Table 5 – Reporting of the frequency accuracy
34 Figure 8 – Example of test method for positive ROCOF function
Table 6 – Reporting of the frequency accuracy (alternative solution)
36 Table 7 – Test points for ROCOF function
37 6.2.2 Reset hysteresis or reset ratio determination
Table 8 – Reporting of ROCOF accuracy
38 Figure 9 – Frequency ramps for assessing the reset hysteresisfor overfrequency functions
Figure 10 – Frequency ramps for assessing the reset hysteresisfor underfrequency functions
40 Table 9 – Test points of reset hysteresis for under/over frequency function
41 Table 10 – Reporting of the reset hysteresis for over/under frequency functions
42 Figure 11 – Test method for measurement of reset valuefor ROCOF functions: example for positive ROCOF function
45 Table 11 – Test points of reset value for ROCOF function
Table 12 – Reporting of the reset value for ROCOF function
46 6.3 Determination of the start time
6.3.1 General
6.3.2 Under/over frequency
47 Figure 12 – Start time measurement of overfrequency with sudden frequency change
48 Figure 13 – Start time measurement of overfrequency with constant slope frequency ramp
49 Table 13 – Test points of start time for overfrequency function
50 Table 14 – Test points of start time for underfrequency function
51 Table 15 – Reporting of start time for under/over frequency functions
52 6.3.3 Rate of change of frequency
Figure 14 – Example of start time reporting for under/over frequency protection function
53 Figure 15 – Start time measurement of positive ROCOF function
54 Table 16 – Test points of start time for ROCOF function
55 6.4 Determination of the accuracy of the operate time delay
6.4.1 General
6.4.2 Description of test method
Figure 16 – Histogram for the start time test results for ROCOF
Table 17 – Reporting of typical start time for ROCOF function
56 Figure 17 – Operate time delay measurement of overfrequency and positive ROCOF
57 6.4.3 Reporting of the operate time delay accuracy
Table 18 – Test points to measure operate time delay
Table 19 – Test points for accuracy of the operate time delay
58 6.5 Determination of disengaging time
6.5.1 General
6.5.2 Under/over frequency
Table 20 – Reporting of operate time delay accuracy for under/over frequency functions
59 Figure 18 – Disengaging time measurement of overfrequencywith sudden frequency change
Figure 19 – Disengaging time measurement of overfrequency with constant slope frequency ramp
60 Table 21 – Test points of disengaging time for overfrequency function
Table 22 – Test points of disengaging time for underfrequency function
61 6.5.3 Rate of change of frequency
Figure 20 – Disengaging time measurement of ROCOF
Table 23 – Reporting of disengaging time for over/under frequency functions
62 Table 24 – Test points of disengaging time for ROCOF function
63 6.6 Performance with harmonics
6.6.1 General
6.6.2 Accuracy of the under/over frequency start value in the presence of harmonics
Figure 21 – Histogram for the disengaging time test results for ROCOF
Table 25 – Typical disengaging time for ROCOF protection
64 Figure 22 – Example of an increasing pseudo-continuous ramp for overfrequency functions
65 Table 26 – Superimposed harmonics
66 Figure 23 – Voltage signal with superimposed harmonics
68 6.6.3 Accuracy of the ROCOF start value in the presence of harmonics
Table 27 – Test points for under/over frequency function in the presence of harmonics
69 Table 28 – Test points for ROCOF function in the presence of harmonics
70 6.7 Stability in the case of sudden voltage change (phase shift and magnitude change)
6.7.1 General
6.7.2 Performance in case of voltage phase shift and magnitude change
72 Figure 24 – Representation of the input energizing quantity (voltage, RMS) injection sequence
73 6.7.3 Performance in case of voltage magnitude drop and restoration
74 Figure 25 – Representation of the input energizing quantity (voltage, RMS) injection sequence with the power system frequency values
75 7 Documentation requirements
7.1 Type test report
Table 29 – Under/over frequency settings for stability testswith voltage drop/restoration
76 7.2 Other user documentation
77 Annex A (normative)Test signal equation with constant frequency variation (df/dt)
78 Annex B (normative)Calculation of mean, median and mode
B.1 Mean
B.2 Median
B.3 Mode
B.4 Example
79 Annex C (informative)Example of frequency measurement and calculation
C.1 Definitions
C.2 Signal observation model
81 C.3 General requirements on frequency measurement
C.3.1 General requirements on frequency measurement
C.3.2 Periodic algorithm
82 Figure C.1 – Zero-crossing algorithm
Figure C.2 – Level-crossing algorithm
83 C.3.3 Analysis algorithm
84 C.3.4 Error minimization algorithm
87 C.3.5 Discrete Fourier transformation (DFT)
89 Annex D (informative)Performance with inter-harmonics
D.1 General
D.2 Proposed test: accuracy of the under/over frequency start value
D.2.1 Description of the generated frequency ramp
Figure D.1 – Example of an increasing pseudo-continuous rampfor overfrequency function
90 D.2.2 Protection function settings
Table D.1 – Superimposed inter-harmonics
91 D.2.3 Test points and calculation of frequency accuracy in the presence of inter�harmonics
D.2.4 Reporting of frequency accuracy in the presence of inter-harmonics
Table D.2 – Test points for under/overfrequency functionin the presence of inter-harmonics
92 Annex E (informative)Management of sudden frequency change without discontinuity in voltage waveform
93 Figure E.1 – Example of voltage waveform without discontinuity at to = 0,02 s
94 Figure E.2 – Example of voltage waveform with discontinuity at to = 0,02 s
95 Bibliography

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BS EN IEC 60255-181:2019
$215.11