IEEE C57.138-1998 pdf download IEEE Recommended Practice for Routine Impulse Test for Distribution Transformers
1.1 Scope
This recommended practice covers routine impulse tests performed on distribution transformers, as requiredin IEEE Std C57.12.00-1993, and described in subclause 10.4 of IEEE Std C57,12.90-1993.
Distribution transformers covered by this recommended practice are liquid-immersed, single- and threephase overhead-type up to 500 kVA; single-phase pad-mounted compartmenta-type and underground-typeup to 167 kVA; three-phase pad-mounted compartmental-type and underground-type up to 2500 kVA. Thesetransformers are covered by EEE Std C57.12.20-1988 through lEEE Std C57.12.26-1992.
This recommended practice covers only those aspects of impulse testing that are specific to routine testing ofdistribution transformers. For more thorough coverage of impulse testing of transformers in general, theIEEE Guide for Transformer Impulse Tests, IEEE Std C57.98-1993, should be consulted.
1.2 Purpose
This recommended practice is to assist manufacturers of distribution transformers in the setup and operationof a routine impulse test, and to assist distribution transformer users and purchasers in understanding theroutine impulse test and how it differs from design tests.
2.References
When the following ANSI/1EEE standards and guides referred to in this recommended practice are superseded by a general revision approved by the American National Standards Institute, the latest revision shallapply.
This recommended practice shall be used in conjunction with the following publications:
IEEE Std 4-1995.EEE Standard Techniques for High-Voltage Testing.
3. General test procedures
For information on the correct test sequence when impulse voltage tests are to be performed, refer to IEEEStd C57.12.90-1993.
The routine impulse test normally consists of one reduced and one full-wave impulse, or two full-waveimpulses. The ful-wave impulses are at a crest voltage equal to the rated BlL of the terminal being tested.Chopped wave tests are not included in the routine test. Each line terminal of a winding rated above 600 ythat is brought out through a suitable bushing is to be tested. For transformers that have two or more wind-ings rated above 600 V, all line terminals of each such winding are to be tested. Neutral terminals, and termi-nals of windings rated 600 V and below, are not to be tested in the routine impulse test.
4. Fault detection methods
Routine impulse testing of distribution transformers as specified in IEEE Std C57.12.90-1993. subclause10.4 requires that the test equipment demonstrate the ability to detect a single-turn fault. A typical fault canbe simulated by placing a shorted turn of wire around the core leg and over the coil of a core and coil assembly. Methods of providing such detection sensitivity are discussed in the sections that follow and in theAnnex that accompanies this document.
IEEE C57.138-1998 pdf download
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