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ANSI/ EEE Std 421 B-1979 (Reaffirmed 1984)
IEEE Standard for High-Potential-Test Requirements for Excitation Systems for Synchronous Machines
Published by The Institute of Electrical and Electronics Engineers, Inc .June 1, 1979
345 East 47th Street, New York, NY 10017, USA SH07344
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ANSI/IEEE Std 421B-1979 (Reaffirmed 1984)
An American National Standard
IEEE Standard for High-Potential-TestRequirements for Excitation Systems for Synchronous Machines
Sponsor
Power Generation Committee of the IEEE Power Engineering Society
Approved December 15,1977 Reaffirmed June 14,1984
IEEE Standards Board
Approved July 21, 1981
American National Standards Institute
@
Copyright 1979 by
The Institute of Electrical and Electronics Engineers, Inc 345 East 47th Street, New York, NY 10017, USA No part of this publication may be reproduced in anyform, in an electronic retrieval system or otherwise, without prior written permission of the publisher.
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Approved December 15,1977
IEEE Standards Board Irvin N. Howell, Jr, Vice Chairman
William R. Kruesi, Chairman
Ivan G. Easton, Secretary William E. Andrus Jean Jacques Archambault Mark Barber Edward J. Cohen Warren H. Cook Louis Costrell R. L. Curtis David B. Dobson
R. 0. Duncan Charles W. Flint Jay Forster Ralph I. Hauser Joseph L. Koepfinger Irving Kolodny Benjamin J. Leon Thomas J. Martin
Donald T. Michael Voss A. Moore William S. Morgan William J. Neiswender Ralph M. Showers Robert A. Soderman Leonard W.Thomas, Sr B. W. Whittington
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Foreword (This Foreword is not a part of IEEE Std 421B-1979, IEEE Standard High-Potential-Test Requirements for Excitation Systems for Synchronous Machines.)
The IEEE Working Group on High-Potential Testing of the Excitation Systems Subcommittee of the Power Generation Committee was activated in February 1969. The subcommittee recognized the need for a standard because of obsolete conflicting standards and changes in excitation-system equipment. Excitation systems no longer consist only of a rotating machine and a simple voltage regulator, but have developed into various types of systems with many regulating loops. The application of semiconductors and other new components in modem excitation systems of increased size and complexity required new guides for high-potential testing. A new standard would ensure more consistent testing of equipment. Members of the IEEE Working Group of the Excitation Systems Subcommittee of the Power Generation Committee which prepared this standard are: D. H. Miller, Chairman A. A. Berthe G. M. Cotzas T. L. Dillman T. K. Essandoh
D. I. Gorden P. R. H. Landrieu J. R. Mather J. R. Michalec
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Contents SECTION
PAGE
1. Scope ......................................................................
7
2. Standards References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7
3. High-Potential Tests ........................................................... 3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 TypeofTests ............................................................
8 8 8
4 . Frequency and Waveshape of Test Voltage..........................................
8
5. Duration and Application of Test Voltage 6.
7. 8.
9.
.......................................... 8 Measurement of Test Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Temperature a t which Tests Shall be Made .......................................... 8 Standard Test Voltages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 8.1 Exciter Output Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 8.2 Allothercircuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Revision of American National Standards Referred to in This Document . . . . . . . . . . . . . . . . . .9
APPENDIX
Appendix A Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Appendix B Technical Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11 11
APPENDIX FIGURE
Fig B1 High-Potential Test Voltages (Comparison of Various Standards)
. . . . . . . . . . . . . . . . . .12
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IEEE Standard for High-Potential-TestRequirementsfor Excitation Systems for Synchronous Machines
1. Scope
ANSI C19.3-1973, Industrial Control Apparatus - General
This standard applies to high-potential testing of complete excitation systems and their components for synchronous machines. The components of the excitation system are described in IEEE Std 421-1972, Criteria and Definitions for Excitation Systems for Synchronous Machines. Also included are auxiliary devices that are exposed to excitation system stresses. Examples of such auxiliary devices are temperature indicators, transducers, meters, etc. This standard does not cover the synchronous-machine field winding or field circuit breaker and discharge resistor. This standard supplements existing standards for components used on excitation systems: ANSI C19.3-1973, Industrial Control Apparatus - General; ANSI C19.4-1973, Industrial Control Apparatus Enclosures; ANSI C19.5-1973, Industrial Control Apparatus - Switching or Controlling Devices; ANSI C19.6-1973, Industrial Control Apparatus - Control-Circuit Devices and Assemblies; ANSI C19.7-1973, Industrial Control Apparatus - Controllers and Controller Assemblies; ANSI C34.2-1968 (R1973), Practices and Requirements for Semiconductor Power Rectifiers; ANSI C37.18-1968 (R1975), Requirements for Field Discharge Circuit Breakers for Rotating Electric Machinery; ANSI/IEEE C57.12.00-197 3, General Requirements for Distribution, Power, and Regulating Transformers; ANSI/IEEE C57.12.90-1973, Test Code for Distribution, Power, and Regulating Transformers; and NEMA I C s 1 9 7 0 (R1975), Industrial Controls and Systems.
ANSI C19.5-1973, Industrial Control Apparatus - Switching or Controlling Devices ANSI C19.6-1973, Industrial Control Apparatus - Control-Circuit Devices and Assemblies ANSI C19.7-1973, Industrial Control Apparatus - Controllers and Controller Assemblies ANSI C34.2-1968 (R1973), Practices and Requirements for Semiconductor Power Rectifiers ANSI C37.18-1968 (R1975), Requirements for Field Discharge Circuit Breakers for Rotating Electric Machinery ANSI C50.10-1977, General Requirements for Synchronous Machines ANSI/IEEE C57.12.00-197 3, General Requirements for Distribution, Power, and Regulating Transformers ANSI/IEEE C57.12.90-1973, Test Code for Distribution, Power, and Regulating Transformers IEEE Std 4-1978, Standard Techniques for High-Voltage Testing IEEE Std 95-1977, Recommended Practices for Insulation Testing of Large AC Rotating Machinery with High Direct Voltage IEEE Std 421-1972, Criteria and Definitions for Excitation Systems for Synchronous Machines
2. Standards References The following standards publications referenced in this standard.
ANSI C19.4-1973, Industrial Control Apparatus - Enclosures
are
NEMA I C s 1 9 7 0 (R1975), Industrial Controls and Systems
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IEEE Std 421B-1979
IEEE STANDARD FOR HIGH-POTENTIAL-TEST REQUIREMENTS
3. High-Potential Tests
5. Duration and Application of Test Voltage
3.1 General. High-potential tests, as used herein, are those tests required to establish the adequacy of the various insulations of the excitation-system components to withstand the voltage stresses imposed during normal or transient conditions. Transient conditions include faults, asynchronous operation, or other unusual operation. It is the responsibility of the manufacturer to design and test for the worst case stress.
The test voltage shall be applied continuously for a period of 60 s. The test voltage shall be successively applied t o each electric circuit with all other electric circuits and metal parts grounded. [See ANSI C19.3-1973 through ANSI C19.7-1973 and NEMA ICS-1970 (R1975), Industrial Controls and Systems.] Interconnected polyphase windings may be considered as one circuit.
3.2 Type of Tests. High-potential tests fall under two categories: acceptance and service tests. 3.2.1 Acceptance. Acceptance tests at standard test voltage shall be made on all circuits after final assembly at the factory. Rotating equipment shall be tested after all functional testing is complete. Controls and other equipment shall be tested before functional testing. Acceptance tests made in the field during installation shall be conducted at 75 percent of the standard test voltage. 3.2.2 Service. Service tests can be made at any time after installation to verify the integrity of insulation. The voltage applied during service tests shall not exceed 65 percent of the standard test voltage.
6. Measurement of Test Voltage The test voltage shall be measured by avoltmeter. The voltmeter shall derive its voltage directly from the test voltage, through a voltage divider, through an auxiliary ratio transformer, or by means of a voltmeter coil placed in the testing transformer. The voltmeter shall indicate the rms voltage or, if direct voltage is used, the voltmeter shall indicate the peak voltage [See ANSI C19.3-1973 through ANSI C19.7-1973, IEEE Std 4-1978, and NEMA ICS1970 (R1975).]
7.Temperature at which
NOTE: Users are cautioned to follow the manufacturers’ recommendations for protecting semiconductor components when performing high-potential tests.
Tests Shall be Made High-potential tests shall be conducted at ambient temperature [(See ANSI C19.3-1973 through ANSI C19.7-1973 and NEMA ICS1970 (R1975).]
4. Frequency and Waveshape of Test Voltage
8. Standard Test Voltages The frequency of the test voltage shall be 25 t o 60 Hz, and the shape of the wave shall be a sine wave with a deviation factor not greater than 10 percent with the equipment under test connected t o the test apparatus. As an alternate to the preceding, direct voltage (dc) may be used, in which case the peak test voltage shall be 1.7 times the rms value of the corresponding alternating voltage. [See IEEE Std 41978, Standard Techniques for High-Voltage Testing, and IEEE Std 95-1977, Recommended Practices for Insulation Testing of Large AC Rotating Machinery with High Direct Voltage.]
8.1 Exciter Output Circuit. For exciters rated 350 V dc or less, the ac rms test voltage shall be 1 0 times the rated output voltage of the exciter, but with a minimum of 1500 V. For exciters rated more than 350 V dc, the ac rms test voltage shall be 2800 V plus two times the rated output voltage of the exciter. The exciter output circuit includes armature windings of rotating machines, commutators, brushes, rectifier circuits, transformer windings, and all components not isolated from the exciter output. 8
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FOR EXCITATION SYSTEMS FOR SYNCHRONOUS MACHINES
IEEE
Std 421B-1979
8.2.1 For circuits rated above 60 V or above 60 VA, the ac rms test voltage shall be 1000 V plus twice the rated voltage. 8.2.2 Circuits rated at 60 V or less and 60 VA or less need not be given a high-potential test.
The synchronous-machine field winding is not included as it is covered by ANSI C50.101977, General Requirements for Synchronous Machines. Field discharge circuit breakers and discharge circuits shall be tested as required by ANSI C37.18-1968 (R1975), Requirements for Field Discharge Circuit Breakers for Rotating Electric Machinery. The exciter rated output voltage (for determination of the test voltage) shall not be less than the voltage required at the associated generator field terminals when the generator is operated at rated kilovolt-amperes, rated power factor, and rated voltage with the generator field winding at normal operating temperature.
9. Revision of American National Standards Referred t o in This Document When the American National Standards referred to in this document are superseded by a revision approved by the American National Standards Institute, the revision shall apply.
8.2 All Other Circuits (electrically isolated from the exciter output circuit)
9
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Appendixes (These Appendixes are not a part of IEEE Std 421B-1979, IEEE Standard for High-Potential-Test Requirements for Excitation Systems for Synchronous Machines.)
Appendix A Background
however, in 1969 it was somewhat outdated. NEMA ICS-1970 (R1975) is very similar to ANSI C19.1-1959. There were other standards on transformers, field circuit breakers, and similar components, but nothing to apply t o modem circuits using semiconductor signal and power components. More instrumentation and protection was being connected t o the synchronous-machine field circuit. This indicated a need for special components that were built and tested to withstand the voltage and power levels involved. The considerations were both reliability and safety .
For many years the only existing standard concerning excitation-system high-potential testing was ANSI C50.5-1955, Rotating Exciters for Synchronous Machines (withdrawn). This applied t o dc commutator-type exciters which were disappearing from new application. Other standards used as guides for highpotential testing were ANSI C50.10-1977, which covered the high-potential-test requirements of the synchronous-machine field winding, but never completely agreed with ANSI C50.5-1955. ANSI C19.1-1959, Industrial Control Apparatus (withdrawn), could have been used t o cover an excitation control;
Appendix B Technical Considerations
The standard test voltages are listed by circuits because high-potential testing applies voltage stress from circuit t o circuit, or from circuit t o ground, and is a test of the integrity of insulation - where little current flows unless there is a test failure. High-potential testing is an overvoltage test. Other dielectric tests may include insulation resistance, power factor, etc. The standard test voltage levels are based on what is considered good design practice for this type of equipment. For the exciter output circuit the worst case stress is usually due to the induced voltage from the synchronous-machine field winding caused by asynchronous operation. It is the responsibility of the manufacturer to design and verify that the equipment will withstand the voltage
levels that result for the worst case condition. Where generator field circuit breakers and discharge circuits are used for rapid deexcitation, they are not t o be considered part of the exciter output circuit. Field circuit breakers and discharge circuits should be high-potential tested per ANSI C37.18-1968 (R1975), which specifies the same test voltage as ANSI C50.101977 for the main field winding. Thus if a generator field circuit breaker is used, the input side of the circuit breaker will be tested per this standard, while the output side of the circuit breaker will be tested per ANSI C37.181968 (R1975). The standard was written to agree with existing standards as much as possible. The test voltage for the exciter output circuit was chosen as
11
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IEEE Std 421B-1979
7000
5000
8
a
2000
a +
v,
1000 0
0
IO0
200
300
400
500
600
700 800
900 1000
EXCITER RATED OUTPUT DIRECT VOLTAGE
Fig B1 High-Potential Test Voltages (Comparison of Various Standards) stresses and, therefore, should be subjected t o a more strenuous high-potential test. All other circuits, rated at 60 V or less and 60 VA or less (low-voltage and low-power circuits), are exempt from high-potential testing because voltage stresses and transients that may occur during testing can damage semiconductors, integrated circuits, and similar components. At the low operating voltage level of these signal circuits, testing of the insulation is not critical.
an extension of ANSI C50.5-1955, but is less than the test voltage required by the synchronous-machine field winding per ANSI C50.10-1977 (see Fig Bl). The reasoning for choosing a test voltage lower than ANSI C50.10-1977 (for rated voltages above 350 V dc) is that experience indicates that higher test voltages are not necessary and would impose an unnecessary cost penalty on users. In addition, synchronous-machine field windings are subjected t o higher mechanical and thermal
12
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