The application of voltage to an items of equipment from the system. This specification covers the design, manufacture, assembly, testing at the. Brooks testingpotentialtransformers 421 needstobemeasuredwithonlymoderateaccuracy. These devices use standard transformer theory with 23 windings one primary with one or two secondary windings with a magnetic connection via an iron core. Direct measurement of high voltages is possible up to about 200 kv, and several forms of voltmeters have been devised which can be connected directly across the test. Electrical safety testing reference guide iso 9001 certified. Standardhigh voltage transformer svthvt mobile ct test. If the input power does not climb to the expected value, then the problem lies not with the transformer. Potential transformers pts are necessary to a power system for metering and protective relaying to convert. A capacitance potential device is a voltagetransforming equipment.
Hipot test is suggested for all voltages, particularly those above 34. There are three basic styles used to transformer system voltages. Up to 33kv, these are of electromagnetic type single and three phase voltage transformers. By means of cascading, the size of the transformer. Electrical tests on power transformers, current transformers, voltage transformers, rotating machines, grounding systems, lines and cables, and circuit breakers can be performed with the. Temperature rise test of transformer is included in type test of transformer. The potential transformer is mainly classified into two types, i. The purpose of this article is to help a test set operator understand the tests they perform, and hopefully add or reenforce a test technique to the test technician s repertoire. High voltage winding to low voltage winding and ground b. Stationary and mobile transformer transformer testing. Instrument transformer theory and testing steve hudson, pe. In most cases, transformers are designed as liquid filled particularly as oil immersed type. Purpose and scope of the study the office of energy policy and systems analysis epsa, in consultation with the.
Capacitor potential transformer is a combination of capacitor potential divider and a magnetic potential transformer. The complete guide to electrical insulation testing. Basic offline pd test equipment transformer to energize test object to rated voltage or higher sensor is normally a high voltage capacitor blocks high voltage 5060 hz while a short. To ensure that the product is fit for its intended use standards iec standards iec 60076 part 1 part 14 specification for transformers. 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. Potential transformers pts or voltage transformers vts pts or vts are the most common device used. Threephase transformers may be checked with singlephase voltage. The emergency rating of potential transformers is defined at one minute of operation, thus enough time for protective equipment to operate.
Th e test shall start with a voltage lower than the full test voltage, and it shall be quickly increased up to the desired value. The accuracy and reliability of the test data is directly. Voltage transformer testing competency assessment sp0508c06. C electrical power from one voltage to another voltage keeping the frequency same by. The capacitor voltage transformer cvt uses a capacitance potential divider and is used at higher voltages due to a lower cost than an electromagnetic pt. Allow at least 1 minute for each test or until the reading stabilizes. Transformer testing serves for the accuracy test including polarity check and demagnetisation for current and voltage transformers in low voltage, middle voltage and high voltage grids according to iec standard 600441, 600442, 600447, 600448 and 6185092 or ansi ieee c57. They provide low voltage by transforming the network medium voltage. Testing potential transformers relay testing training.
Series resonances are occurring between leakage reactance of transformer. A transformer winding that is carrying dc current will generate a large voltage across the winding when disconnected. Testing of power transformers 9 a 6 appendix 92 a 6. Testing of current transformers, voltage transformers or auxiliary transformers internal to the power transformer are not included in this swp. There are three basic styles used to transformer system voltages to control voltages. Transformer testing 35 electrical component testing 36 examples of high performance testers 37 sentry series testers 37. Distribution transformers are the end equipment before electricity reaches the consumer. A potential transformer is a conventional transformer having primary and secondary windings. The electromagnetic potential transformer is a wirewound transformer. The test is successful if no breakdown occurs at full test voltage during the test. It can be designed to step up or step down voltages and works on the magnetic induction principle.
High voltage testing 149 the high voltage is applied across the device under test by means of a transformer. If the input power climbs to the expected value, the primary of the transformer is bad. Transformer protection application guide this guide focuses primarily on application of protective relays for the protection of power transformers, with an emphasis on the most prevalent protection schemes and transformers. 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. A few disadvantages to designing a system with low voltage distribution transformers. Voltage transformer testing swp page 2 of 19 standard work practice sp0508 ver 7 ergon energy corporation limited abn 50 087 646 062 sp0508r01. Linetoneutral ln voltage is system voltage divided by 1. Testing potential transformers valence electrical training services. Understanding insulation resistance testing pdf 0712. The result obtained is a voltage value usually expressed in kilovolts kv.
If a very high voltage is required, the transformer is usually build up in stages by cascading. Potential transformer testing ptvt valence electrical. These can be single or three phase voltage transformers available for different range of operating voltages that are used for outdoor relaying and metering applications. Measurement of high voltage university of moratuwa.
An ac voltage exceeding volts measured between the phase conductors. Transformer testing transformers are tested at or above the rated voltage to be certain there are no excessive leakage paths to ground or between windings. Icf assessment of large power transformer risk mitigation strategies 4 1. Pdf the application of voltage transformer simulator in electrical. Basics, maintenance, and diagnostics xi contents continued page 9. Standard voltage transformer svt the mobile instrument transformer test system consists of serveral. Strategy and other partial discharge documents or consult. Assessment of large power transformer risk mitigation. Dielectric testing may be destructive in the event of a fault, depending on the test. A record of the relative humidity near the equipment at the time of the test. Factory tests are on transformer without load and without cables 3.
The objective of testing is to ensure quality to ensure that the products manufactured have met the requirements of customer specificationstandard to prevent accidents which may occur if a failed product is put into service. Conventional wound type transformer is very expensive because of the requirement of the insulations. Also you should make tests at about the same temperature, or correct them to the same temperature. This test is often performed by applying an ac voltage but can also be done with a dc voltage.
Instrument transformer basic technical information and. Factory tests not achieving as much winding stress as field conditions 2. The standard voltage transformer svt is suitable to test the voltage transformer of single and double pole transformers. Pdf the voltage transformer test is an important means to monitor its operating state. Understanding insulation resistance testing aemc instruments. The primary winding is connected directly to the power circuit either between two phases or between one phase and ground, depending on the rating of the transformer and on the requirements of the application.
Induced potential test frequency response analyzer dissolved gas analysis tests dc winding resistance transformer core ground test polarization recovery voltage test ac hipot test the ac hipot test is used to assess transformer windings condition. Pdf transformer is a static device which transforms a. Voltage transformer testing job safety analysis sp0508c03. A transformer is an electrical apparatus designed to convert alternating current from one voltage to another. A potential transformer must be capable of operating at 110% above rating voltage continuously provided the secondary burden in volt amperes at this voltage does not exceed the thermal rating. These are conducted with the transformer completely disconnected from the line and load.
Basics of high voltage test techniques abstract high voltage hv testing utilizes the phenomena in electrical insulations under the in. Standardhigh voltage transformer svthvt mobile ct test system. Reduces overall efficiency of the system due to internal losses within the transformer added heat to. Medium voltage transformer testing 7200db1001 data bulletin 112010 electrical equipment should be installed, operated, serviced, and maintained only by qualified personnel.
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