When done properly, this test will expose short circuit conditions or weak components that could compromise electrical safety and create a. When ac hipot tests are used for routine maintenance, the power transformer can be examined at rated voltage for 3 min instead of testing at 65% of factory test voltage. Ensure that all equipment to be tested is properly grounded and treat all highvoltage power equipment as energized until proven otherwise by using the proper lockouttagout procedures. Testing of power transformers seems like a similar experience. The procedure of the transformer ratio test is simple. Repeat the test for the other phases and the other secondary cores. This test allows the engineer and relay technicians to. Potential transformers secondaries can also be checked during this test. Pts potential transformers 5 potential transformers pts pts step down high voltages to the voltage needed by the meter usually. Section 7 of the ansineta standard for acceptance testing specifications for electrical power equipment and systems may be reproduced and used on a cut and paste basis for the particular type of equipment to be tested.
Iwanusiw, consultant eltel industries, bangalore, india. This transformer step down the voltage to a safe limit value which can be easily measured by the ordinary low voltage instrument like a voltmeter, wattmeter and watthour meters, etc. Potential transformers pts are necessary to a power system for metering and protective relaying to convert higher system voltages to lower control voltages that are more practical from an equipment, operation, and safety perspective. Poor grounding not only contributes to unnecessary downtime, but a lack of good grounding is also dangerous and increases the risk of equipment failure. All materials and relevant documentation to this testing works shall be checked by the responsible personnel prior to the commencement of testing activities. With a broad range of instrument transformer solutions and infield experience.
The following sections of the ansineta standard for acceptance testing specifications for. Testing power transformers highvoltage transformers are some of the most important and expensive pieces of. The ac hv test value should not surpass 75% of the factory test value. Potential transformer testing ptvt valence electrical training. In this book we have laid down important aspects on transformer. In this paper testing of distribution transformer is considered. So for ensuring proper performance of electrical power transformer, voltage and turn ratio test of transformer one of the important tests. The submittal shall be in each respective equipment manufacturers format and. Inspection and test procedures for instrument transformers. Hipot testing verifies the integrity of highvoltage ac primary wire insulation in an electrical system to ensure that it is safe to operate. Select the megger range corresponding to the ratings of the equipment under test.
Vector group test of power transformer electrical4u. Standard for acceptance testing specifications for. Operation, maintenance, and field test procedures for. A guide to transformer winding resistance measurements bruce hembroff, cet, manitoba hydro. Singlephase test procedures can be used to measure the ratio and.
This test also performed as a routine test of transformer. As test equipment becomes more sophisticated with better features and accuracy, we risk turning our. Some of the process failures that can be detected by a productionline hipot test include, for example, a transformer wound in such a. Power transformer testing procedures and schemes photo credit. As 12431982 voltage transformers for measurement and. Transformer testing has developed considerably over the past years. Home technical articles what is hipot testing dielectric strength test. Check nameplate ratings and hv, lv terminal markings. Testing power transformers high voltage transformers are some of the most important and expensive pieces of equipment required for operating a power system.
A potential transformer is a conventional transformer having primary and secondary windings. Voltage transformer testing swp page 1 of 19 standard work practice sp0508 ver 7 ergon energy corporation limited abn 50 087 646 062 1. Va rating certain standards require the use of a 500va hipot transformer energy and breakdown originally this was required to ensure hipot voltage output. Job safety analysis power transformer testing check this is the latest process zone version before use.
The vector group of transformer is an essential property for successful parallel operation of transformers. Such a failure could result from a new operator in the winding department the hipot test a versatile test. Connection on cpc100 will be same as the shown figure. Potential transformer testing ptvt valence electrical. Ansineta standard for acceptance testing specifications for electrical power equipment and systems, 2009. Use caution when conducting a ct ratio test and do not apply a voltage high enough that would cause the transformer to saturate.
The complete guide to electrical insulation testing. Hence every electrical power transformer must undergo through vector group test of transformer at factory site for ensuring the customer specified vector group of transformer. For good insulation, the resistance usually reads in the megohm range. The test procedure, however, does not require testing of the distribution transformer while operating at the test pul. Potential transformers pts or voltage transformers vts. Following is an approximate sequence for transformer testing. Threephase transformers may be checked with singlephase voltage. The megger insulation tester is a small, portable instrument that gives you a direct reading of insulation resistance in ohms or megohms. There are three basic styles used to transformer system voltages to control voltages. Neil dwyer, manager technical services ergon energy corporation limited abn 50 087 646 062 ergon energy queensland pty ltd abn 11 121 177 802 title. The megger insulation tester is essentially a highrange resistance meter ohmmeter with a builtin directcurrent generator.
It evolved from the simple gonogo verdict into a sophisticated segment within transformer manufacturing. Manufacturers test thousands of distribution transformers at worldwide locations each week. The working procedure on how transformers work types. Transformer testing type tests and routine tests of.
Purpose and scope the purpose of this standard work practice swp is to provide guidelines for testing methods for capacitive and inductive voltage transformers. Transformers regulate the voltage in circuits, but in some cases these can go bad and cause a circuit to not. So transformer ratio test is an essential type test of transformer. When the guard potential is at or near ground potential, then it is referred.
Applying a saturation voltage will result in readings that wont be accurate. It is not a complete stepbystep procedure for performing tests and. The phase sequence or the order in which the phases reach their. There are various test required on transformer to conform performance of transformer. The testing times have been greatly reduced using modern microprocessor based test equipment. Testing procedures for hv voltage transformers electrical. Inspect transformer and parts for shipping damage and moisture. The testing organization shall be an independent, third party entity which shall. Check that all parts of the transformer are properly assembled and tight. An electrical test procedure for determination of copper. Operation, maintenance, and field test procedures for protective relays and associated circuits iii acronyms and abbreviations a ampere ac alternating current amp ampere ansi american national standards institute bes bulk electric system carma capital asset and resource management application ccvt coupling capacitor voltage transformers co. The commercial importance of such transformers has stimulated the development of accurate methods in recent. Potential test, is designed to stress the insulation of your.
Potential transformer testing ptvt i cowrote an article for the neta world magazine in 20042005 that covers several different manual techniques for potential transformer testing that explains several lowtech solutions for potential transformer testing. The primary incentive is to make sure the transformers meet manufacturing. Back to the basics potential transformer testing ptvt. P otential transformers pts are necessary to a power system for metering and protective relaying to convert higher system volt ages to lower control voltages that are practical from an equipment, operation, and safety perspective. Ratio tests are performed by applying a suitable voltage below saturation to the secondary of the ct under test while the primary side voltage is measured to calculate the turns ratio from the expression above. Mainly two types of transformer are done by manufacturer before dispatching the transformer mainly 1 type test of transformer and 2 routine test. Without an effective grounding system, we could be exposed to the risk of electric. Hipot test is a contraction for high potential hv testing. The purchase, preparation, assembly, operation and maintenance of transformers represent a large expense to the power system. Neta test forms tests performed by testing organization. In addition some other tests are also carried out by the consumer at site before commissioning and also periodically. The goal of partial discharge measurement is to certify that no harmful partial discharge sources exist.
Potential transformer pt definition the potential transformer may be defined as an instrument transformer used for the transformation of voltage from a higher value to the lower value. Section 7 inspection and test procedures section 8 system function test. During construction, and before, startup, new electrical systems and components must meet application specifications, manufactures tolerances, installation and construction codes and standards, and system design specifications. Instrument transformer can subdivided into two types. Some of the process failures that can be detected by a productionline hipot test include, a transformer wound in such a way that creepage and clearance have been reduced. Highvoltage transformers are some of the most important and expensive pieces of. This guide provides a general overview of the regulatory framework and approval process and explores the specific manufacturing responsibilities and test procedures associated with electrical safety testing. Cold guard or hot guard connections refer to the potential of the guard terminal or connection.
Power transformer testing procedures and schemes eep. Many of the details of a complete and effective testing procedure can be obtained from this source. Oil immersed natural cooled with forced oil circulation. Before conducting a transformer winding resistance test, it is important to observe all safety warnings and take proper precautions. Create pdf from any technical article and save it on your disc. General inspection mechanical checks general visual inspection and compliance with the drawings and manuals. For primary side, apply voltage depending on rating of voltage rating of vt. Instrument transformer theory and testing steve hudson, pe. Page 1 of 8 reference sp0504r01 ver 1 reference owner. Transformers are an electrical component that transmit electrical energy between at least two circuits. To test the insulation integrity you will need a megohmmeter or highpotential test set rated to produce the specified maximum test voltage. An electrical test procedure for determination of copper sulfide contamination in transformer windings. Insulation power factor testing of power transformers oleh w.
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