IEEE C57.12.90-2021

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IEEE Standard Test Code for Liquid-Immersed Distribution, Power, and Regulating Transformers

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IEEE	2021

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Description

Revision Standard – Active. Methods for performing tests specified in IEEE Std C57.12.00(TM) and other standards applicable to liquid-immersed distribution, power, and regulating transformers are described. Instrument transformers, step-voltage and induction voltage regulators, arc furnace transformers, rectifier transformers, specialty transformers, grounding transformers, and mine transformers are excluded. Resistance measurements, polarity and phase-relation tests, ratio tests, no-load loss and excitation current measurements, impedance and load loss measurements, dielectric tests, temperature tests, short-circuit tests, audible sound level measurements, and calculated data are covered in this standard.

PDF Catalog

PDF Pages	PDF Title
1	Front cover
2	Title page
4	Important Notices and Disclaimers Concerning IEEE Standards Documents
7	Participants
9	Introduction
10	Contents
12	1. Overview 1.1 Scope 1.2 Purpose 1.3 Word usage
13	2. Normative references
14	3. Definitions 4. General 4.1 Types of tests 4.2 Test requirements
15	4.3 Test sequence 4.4 Instrumentation 5. Resistance measurements 5.1 Determination of cold temperature 5.1.1 General 5.1.2 Transformer windings immersed in insulating liquid
16	5.1.3 Transformer windings out of insulating liquid 5.2 Conversion of resistance measurements 5.3 Resistance measurement methods 5.3.1 Voltmeter-ammeter method
18	5.3.2 Bridge method 5.4 Resistance measurement connections and reporting 5.4.1 Wye windings 5.4.2 Delta windings 5.4.3 Autotransformer windings 6. Polarity and phase-relation tests 6.1 Subtractive and additive polarity
19	6.2 Polarity tests: single-phase transformers 6.2.1 Polarity by ratio meter
20	6.2.2 Polarity by inductive kick 6.2.3 Polarity by alternating-voltage test
21	6.3 Polarity and phase-relation tests: polyphase transformers 6.3.1 Polarity of polyphase transformers 6.3.2 Phase-relation tests 6.3.2.1 Test of phase relation with ratio meter 6.3.2.2 Test for phasor diagram for transformers
23	6.3.2.3 Six-phase windings 6.3.2.4 Zigzag windings
24	7. Ratio tests 7.1 General 7.1.1 Taps 7.1.2 Voltage and frequency 7.1.3 Three-phase transformers 7.1.4 Three-phase transformers with inaccessible neutrals
25	7.2 Tolerances for ratio 7.3 Ratio test methods 7.3.1 Voltmeter method 7.3.2 Comparison method
26	7.3.3 Ratio meter
27	8. No-load losses and excitation current 8.1 General 8.2 No-load loss test
28	8.2.1 Connection diagrams
29	8.2.2 Voltmeter connections 8.2.3 Energized windings 8.2.4 Voltage and frequency
30	8.3 Waveform correction of no-load losses 8.4 Temperature correction of no-load losses
31	8.5 Determination of excitation (no-load) current 8.6 Frequency conversion of no-load losses and excitation current 9. Load losses and impedance voltage 9.1 General
32	9.2 Factors affecting the values of load losses and impedance voltage 9.2.1 Design 9.2.2 Process 9.2.3 Temperature 9.2.4 Measurements
33	9.3 Tests for measuring load losses and impedance voltage 9.3.1 Wattmeter-voltmeter-ammeter method
35	9.3.2 Impedance bridge methods
36	9.3.3 Transformer test procedures 9.3.3.1 Two-winding transformers and autotransformers
37	9.3.3.2 Three-winding transformer
38	9.3.3.3 Interlacing impedance voltage of a Scott-connected transformer 9.3.3.4 Test of three-phase transformer with single-phase voltage
40	9.4 Calculation of load losses and impedance voltage from test data 9.4.1 Correction of load loss measurement due to metering phase-angle errors
41	9.4.2 Temperature correction of load losses
42	9.4.3 Impedance voltage 9.4.4 Frequency conversion of load losses and impedance 9.5 Zero-phase-sequence impedance 9.5.1 Zero-phase-sequence impedance tests of three-phase transformers
44	9.5.2 Transformers with one neutral externally available, excluding transformers with interconnected windings 9.5.3 Transformers with two neutrals externally available, excluding transformers with interconnected windings
46	9.5.4 Autotransformers 9.5.5 General test method for zero-phase-sequence impedance measurement on transformers with interconnected windings (see Rosselli [B29])
47	10. Dielectric tests 10.1 General 10.1.1 Factory dielectric tests 10.1.2 Test requirements 10.1.3 Measurement of test voltages
48	10.1.4 Type of power transformer 10.1.5 Factory dielectric tests and conditions 10.1.5.1 Test sequence 10.1.5.2 Temperature 10.1.5.3 Assembly 10.1.5.4 Transformers for connection to gas-insulated equipment 10.1.6 Tests on bushings
49	10.1.7 Dielectric tests in the field 10.2 Switching impulse test procedures 10.2.1 Number of tests 10.2.2 Switching impulse waves 10.2.2.1 Polarity
50	10.2.2.2 Waveshape 10.2.2.3 Time to crest 10.2.2.4 Time to first voltage zero 10.2.2.5 Ninety-percent time 10.2.3 Failure detection 10.2.4 Tap connections
51	10.2.5 Connection of neutral terminal(s) during switching impulse tests 10.3 Lightning impulse test procedures 10.3.1 General
52	10.3.1.1 Full-wave test
53	10.3.1.2 Reduced full-wave test 10.3.1.3 Chopped-wave test
54	10.3.1.4 Front-of-wave test 10.3.1.5 Wave polarity 10.3.1.6 Impulse oscillograms
55	10.3.2 Connections for impulse tests of line terminals 10.3.2.1 Terminals not being tested
56	10.3.2.2 Windings for series or multiple connections 10.3.2.3 Windings for delta or wye connections 10.3.2.4 Tap connections
57	10.3.2.5 Protective devices that are an integral part of the transformer
58	10.3.3 Impulse tests on transformer neutrals 10.3.4 Detection of failure during impulse test 10.3.4.1 Ground current oscillograms 10.3.4.2 Other methods of failure detection
59	10.4 Routine impulse test for distribution transformers 10.4.1 Terminals to be tested 10.4.2 Procedure 10.4.2.1 Method 1
60	10.4.2.2 Method 2 10.4.2.3 Failure detection 10.4.3 Terminals not being tested
61	10.4.4 Windings for series or multiple connections 10.4.5 Windings for delta or wye connections 10.4.6 Tap connections 10.5 Low-frequency tests
62	10.5.1 Induced-voltage test for transformers with series or multiple connections 10.6 Applied-voltage tests 10.6.1 Duration, frequency, and connections 10.6.2 Relief gap 10.6.3 Application of test voltage 10.6.4 Failure detection 10.7 Induced-voltage tests for distribution and Class I power transformers 10.7.1 Test duration
63	10.7.2 Test frequency 10.7.3 Application of voltage 10.7.4 Grounding of windings 10.7.5 Need for additional induced tests 10.7.6 Failure detection 10.7.7 Special induced voltage test for distribution and Class I power transformers with a wound core
64	10.7.7.1 Minimum test duration and application of voltage 10.7.7.2 Test frequency 10.7.7.3 Grounding of windings 10.7.7.4 Failure detection 10.8 Induced-voltage test for Class II power transformers 10.8.1 General
65	10.8.2 Test procedure
66	10.8.3 Connections 10.8.4 Frequency 10.8.5 Failure detection 10.9 Partial discharge measurement 10.9.1 Internal partial discharges
67	10.9.2 Instrumentation 10.9.3 Calibration 10.10 Insulation power-factor tests 10.10.1 Preparation for tests 10.10.2 Instrumentation 10.10.3 Voltage to be applied
68	10.10.4 Procedure 10.11 Insulation resistance tests
69	10.11.1 Preparation for tests 10.11.2 Instrumentation 10.11.3 Voltage to be applied 10.11.4 Procedure
70	11. Temperature-rise tests 11.1 Test methods 11.1.1 Actual loading 11.1.2 Simulated loading 11.1.2.1 Loading back method
72	11.1.2.2 Short-circuit method
73	11.2 Resistance measurements 11.2.1 Cold-resistance measurements 11.2.2 Hot-resistance measurements
74	11.3 Temperature measurements 11.3.1 Ambient temperature measurements 11.3.1.1 Air-cooled transformers
75	11.3.1.2 Water-cooled transformers 11.3.2 Liquid temperature rise determination
76	11.3.3 Average winding temperature-rise determination
77	11.3.4 Other temperature measurements 11.4 Correction of temperature-rise test results 11.4.1 Correction for differences between winding rated current and test current 11.4.2 Correction of liquid temperature rise for differences in required total loss and actual loss
78	11.4.3 Correction of liquid temperature rises for differences in altitude 11.4.4 Frequency conversion of temperature-rise test results
79	12. Short-circuit tests 12.1 General 12.2 Test connections 12.2.1 Two-winding transformers and autotransformers without tertiary windings 12.2.1.1 Fault location
80	12.2.1.2 Fault type
81	12.2.1.3 Tap connection for test 12.2.2 Multiwinding transformers, including autotransformers 12.2.2.1 Fault location and type
82	12.3 Test requirements 12.3.1 Symmetrical current requirement, two-winding transformers 12.3.2 Symmetrical current requirement, multiwinding transformers, and autotransformers 12.3.3 Asymmetrical current requirement
83	12.3.4 Number of tests 12.3.5 Duration of tests 12.4 Test procedure 12.4.1 Fault application 12.4.2 Calibration tests 12.4.3 Terminal voltage limits 12.4.4 Temperature limits
84	12.4.5 Current measurements 12.4.6 Tolerances on required current 12.4.7 Frequency conversion of short-circuit test 12.5 Proof of satisfactory performance
85	12.5.1 Visual inspection 12.5.2 Dielectric tests 12.5.3 Waveshape of terminal voltage and current 12.5.4 Leakage impedance
86	12.5.5 Dissolved gas analysis (DGA) 12.5.6 Excitation current 12.5.7 Other diagnostic measurements 13. Audible sound emissions 13.1 General 13.1.1 Introduction
87	13.1.2 Applicability 13.2 Instrumentation 13.2.1 Sound level meter 13.2.2 One-third octave filter
88	13.2.3 Narrowband filter 13.2.4 Wind screen 13.2.5 Calibration 13.3 Test conditions 13.3.1 Test environment 13.3.2 Transformer location 13.3.3 Determination of total sound level of a transformer 13.3.3.1 No-load audible sound level
89	13.3.3.2 Load audible sound level
90	13.3.4 Frequency conversion of measured audible sound levels 13.4 Microphone positions 13.4.1 Reference sound-producing surface
91	13.4.2 Safety considerations 13.4.3 First measurement position 13.4.4 Number of microphone locations 13.4.5 Height of microphone locations 13.5 Sound pressure level measurements 13.5.1 A-weighted sound pressure level measurements
92	13.5.2 One-third octave sound pressure level measurements 13.5.3 Narrowband sound pressure level measurements 13.5.4 C-weighted sound pressure level measurements 13.5.5 Sound pressure level measurements using the sound-pressure method 13.5.5.1 Measuring ambient sound pressure level 13.5.5.2 Correction for ambient sound
93	13.5.5.3 Wall sound reflection correction K
94	13.5.5.4 Near-field correction
95	13.5.6 Sound pressure level measurements using the sound-intensity method 13.5.6.1 Environmental correction
96	13.6 Determination of audible sound level of a transformer 13.6.1 Average sound pressure level (LP) 13.6.2 Determination of total sound pressure level of a transformer 13.6.2.1 Addition of no-load and load audible sound levels 13.6.2.2 Determination of total sound pressure level of a transformer at different loading conditions
98	13.6.3 Sound power level calculation (Lw) 13.7 Presentation of results
100	14. Calculated data 14.1 Reference temperature
101	14.2 Losses and excitation current 14.2.1 Determination of no-load losses and excitation current 14.2.2 Load losses 14.2.3 Total losses 14.3 Efficiency 14.4 Voltage regulation of a constant-voltage transformer 14.4.1 General 14.4.2 Reference temperature 14.4.3 Load loss watts and impedance volts
102	14.4.4 Voltage regulation computation, two-winding transformers 14.4.4.1 Exact formula for the calculation of regulation 14.4.4.2 General expression for calculation of transformer regulation
103	14.4.4.3 Three-phase to two-phase transformers
104	Annex A (informative) Partial discharge measurement using radio-influence voltage instrumentation and its failure detection A.1 Partial discharge measurement A.1.1 Internal partial discharges A.1.2 Instrumentation A.1.3 Calibration
105	A.2 Failure detection
106	Annex B (normative) 50/60 Hz frequency conversion of measured performance parameters B.1 No-load loss and excitation current
107	B.2 Load loss
108	B.3 Temperature-rise test
109	B.4 Short-circuit test
110	B.5 Audible sound B.5.1 A-weighted sound level conversion of no-load noise B.5.1.1 50/60 Hz conversion of ONAN (core) sound level B.5.1.2 50/60 Hz conversion of ONAF sound level B.5.1.2.1 Conversion from 50-Hz tested sound levels to corresponding 60-Hz levels
111	B.5.1.2.2 Conversion from 60-Hz tested sound levels to the corresponding 50-Hz levels B.5.1.2.3 Numerical example B.5.1.3 Load sound level conversion B.5.2 Frequency spectrum conversion
112	Annex C (informative) Connections diagrams for short-circuit testing
115	Annex D (informative) Tap position during induced test on Class II power transformers D.1 General
116	D.2 Background information
117	Annex E (informative) Bibliography
119	Back cover