These tests are done mainly in a prototype unit not in all manufactured units in a lot. In addition some other tests are also carried out by the consumer at site before commissioning and also. The short circuit test is performed for determining the below mention parameter of the transformer. Unified method for teaching how to solve the equivalent circuit of. The common magnetic flux path is provided by an iron core. Ensure only trained persons shall operate the power tools. Measuring transformer ratio from one external terminal to another can reveal a great deal of information about the transformer.
Power transformer construction windings 750kva dry type transformer windings continued from tech. Thus, effective, regular maintenance and testing is even more essential to continued operation when. Pdf easy method for testing transformer differential relays. Losses of transformersthe transformers are made of 2 types of materials. Water and water saturated oil are both heavier than dry oil and sink to the bottom of any container. Some tests are done at manufacturer premises before delivering the transformer.
Transformer testing has developed considerably over the past years. Transformer pd and induced voltage withstand test system. Tm 5686 power transformer maintenance and acceptance. To prove that the transformer meets customers specifications and design expectations, the transformer has to go through different testing procedures in manufacturer premises. The core, which makes a path for the magnetic flux.
A transformer can be represented as shown in figure 1a. Each phase of a power transformer normally has a pair. Check the cable connections on the lv side and the markings. Where applicable capacitor dividers type check that all parts of the transformers are properly assembled.
For confirming the specifications and performances of an electrical power transformer it has to go through numbers of testing procedures. Maintenance and testing heat and contamination are the two greatest enemies to. Check nameplate ratings and hv, lv terminal markings. A single phase voltage transformer basically consists of two electrical coils of wire, one called the primary winding and another called the secondary winding. Mainly two types of transformer testing are done at manufacturer premisestype test of transformer and routine test of transformer. The transformer vector group is indicated on the name plate of transformer by the manufacturer.
Basics, maintenance, and diagnostics vii contents continued page 4. I am je of nagbhir sub station of 225 kv newly electrified section and testing started of current transformer when test ct ratio by injecting current in primary bushing of old ct which was 20 years old ct installed in circuit,after testing values not found according to ratio,100 amps inject and found in secondary terminal 3. The secondary coil, which receives energy from the primary winding and delivers it to the load. In order to correctly apply transformer differential protection the following compensations shall be provided. A neonsign transformer nst is a transformer made for the purpose of powering a neon sign. Some transformer tests are carried out for confirming the basic design expectation of that transformer. After, installation of power transformer, several precommissioning tests to be done before putting the transformer in service. Testing of power transformers seems like a similar experience. Testing transformer is very easy if you follow the procedure explained in this article. Oil samples should, therefore, be allowed to settle for 4 to 6 hours in case of small transformer or drums, and for 10 to 12 hours in case of large transformer. The tests this laboratory is able to carry out are the following.
The ac hv test value should not surpass 75% of the factory test value. Apply 3 phase supply voltage 415 v ac across the primary termination of the transformer. Transformers are subject to mechanical impact and vibration. A transformer is a specific form of a coupled circuit in which the coupling mechanism is the mutual inductances between two coils. Data about the transformer failure for the last 5 years was. This dissertation is a systematic study of artificial intelligence ai applications for the diagnosis of power transformer incipient fault. General inspection mechanical checks general visual inspection and compliance with the drawings and manuals. Power transformer construction core construction the windings consist of the currentcarrying conductors wound around the sections of the core, and these must be properly insulated, supported and cooled to withstand operational and. Transformer theory quiz questions electrician practice tests. References appendix a contains a list of references used. A variety of types of electrical transformer are made for different purposes. Testing power transformers highvoltage transformers are some of the most important and expensive pieces of equipment required for operating a power system. It is based on ampereturnbalance of all windings mounted on the same magnetic core lag. The preference is that all large power transformers 1 mva be tested with ttr test set.
The ai techniques include artificial neural networks ann, or briefly neural networks nn, expert systems, fuzzy systems and multivariate regression. Analysis of transformer failures imia 2003 5 overloading this category pertains to those cases where actual overloading could be established as the cause of the failure. Free online quiz test transformer theory and practice. The transformers that were studied were stepdown transformers 11kv220v used by wapda in distribution sectors. Check that all parts of the transformer are properly assembled and tight.
Ensure adequate lighting is provided in the working area at night time. The potential transformer is connected in parallel with the circuit. Factory tests are on transformer without load and without cables 3. A transformer is an electrical apparatus designed to convert alternating current from one voltage to another. Transforming transformers superconducting windings pdf. Cts for metering purposes must have a high degree of accuracy to ensure accurate billing while those used for protection must react quickly and correctly in the event of a fault.
Sep 26, 2017 for confirming the specifications and performances of an electrical power transformer it has to go through numbers of testing procedures. So for ensuring proper performance of electrical power transformer, voltage and turn ratio test of transformer one of the important tests. Hence, it is essential to inspect and calibrate those instrument transformers at regular intervals. The transformer the principle parts of a transformer and their functions are. Based on the windings connection, the vector group of the transformer is determined. The primary windings of the potential transformer are directly connected to the power circuit whose voltage is to be measured.
Figure 5 shows the result of the curve fitting for core 1, considering the y axis to be the current and x axis to be the voltage, the following expression give the standard. So transformer ratio test is an essential type test of transformer. Magnetization and primary injection test of current transformer for protective relaying jacob tsado 8 current transformers. The importance of current transformer tests is often underestimated. A transformer is a passive electrical device that transfers electrical energy from one electrical.
Current transformers play an important role in the monitoring and protection of electrical power systems. Generally there are two types of transformer in the market i. While operating principles of transformers remain the same, the challenges of. The potential transformer may be defined as an instrument transformer used for the transformation of voltage from a higher value to the lower value. Study of transformers, the faults that most commonly occur, the causes of these faults and their impact is conducted and discussed in this paper. A spark gap is a simple structure of two metal electrodes. Before commencement of any test make sure the surroundings near clear off from any. Connection on cpc100 will be same as the shown figure. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. This test also performed as a routine test of transformer.
Along with different precommissioning tests, different instruments associated to the transformer also to be checked. It evolved from the simple gonogo verdict into a sophisticated segment within transformer manufacturing. Steel itself is a conductor, and changing lines of magnetic flux also induce a voltage and current in this conductor. Transformer design to withstand switching must add strength 1. Series resonances are occurring between leakage reactance of transformer and capacitance to ground. In this book we have laid down important aspects on transformer.
Ensure all concerned personals shall use ppe and all other items as required. Cts are instrument transformers used for converting primary current into a reduced secondary current for use with meters, relays, control equipment and other instruments the importance of instrument transformer tests is often underestimated. Pdf overvoltages in power transformers caused by noload. Measure the voltage at the both primary and secondary termination at all the phases. Testing and commissioning instrument transformers free download as powerpoint presentation. 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. Ensure service areawork area openings are provided with barricade, tape, and safety nets. Overvoltages in power transformers caused by noload switching article pdf available in ieee transactions on power delivery 101. A transformer usually consists of two or more coupled windings on a magnetic iron core. Type test and routine test of transformer electrical mastar.
Less susceptibility to internal series resonances vancouver ieee transformers committee october 2427, 2016 12. When ac hipot tests are used for routine maintenance, the power transformer can be examined at. Open circuit and short circuit test on transformer. There are various test required on transformer to conform performance of transformer. Mar 31, 20 testing and commissioning instrumenttransformers free download as powerpoint presentation. Transformers have been used at powerplants since the inception of alternatingcurrent generation, a century ago. Scribd is the worlds largest social reading and publishing site. Transformer gassing oil quality and moisture content winding or core deformation a comparison of the sfra aigniture before and after movement or large fault conditions tap changer contact resistance powertech services also offers a fault testing service where a transformer faults during service. The equivalent resistance, impedance, and leakage reactance are known by the short circuit test. Transformers regulate the voltage in circuits, but in some cases these can go bad and cause a circuit to not.
Transformer winding resistance measurement shall be carried out at each tap. Separate source voltagewithstand test induced over voltage withstand test partial discharges measurements. Appendix d high voltage measurement and testing highvoltage measurement measurement difficulties are mainly due to the large physical structures which are necessary to control the electrical fields to prevent flashovers. Problems or faults occur due to poor design, assembly, handling, poor environments, overloading or. Transformers are an electrical component that transmit electrical energy between at least two circuits. The purchase, preparation, assembly, operation and maintenance of transformers represent a large expense to the power system. Testing transformer 3 easy methods to test transformers testing transformer is very easy if you follow the procedure explained in this article. 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. Nov 17, 2019 after, installation of power transformer, several precommissioning tests to be done before putting the transformer in service. The three phase transformer windings can be connected several ways. A guide to transformer ratio measurements abstract. 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.
Repeat the test for the other phases and the other secondary cores. A supply voltage vs is applied to the primary and the readings of the voltmeters v1, v2 and v3 are noted. The transformer is an electric electromagnetic induction machine whose function is to transfer electrical power between two different voltage systems at the same. In this article im only explain on how to test the linear transformer. Mainly two types of transformer are done by manufacturer before dispatching the transformer mainly 1 type test of transformer and 2 routine test. Magnetization and primary injection test of current. The performance of a transformer largely depends upon perfection of specific turns or voltage ratio of transformer. The transformer winding resistance is usually enough to limit the current flow from a 12 volt car battery, but adding series currentlimiting resistance a load box to the test circuit is advisable in any test circuit with an automotive battery.
The core of a transformer is made of iron whereas thewinding which is wrapped over the iron core is made up ofcopper. Voltage transformer testing swp page 3 of 19 standard work practice sp0508 ver 7 ergon energy corporation limited abn 50 087 646 062 if any risks cannot be managed or reduced to an acceptable level. It is a good idea to remove all as a safety precaution to prevent backfeeding dangerous voltages into the system during testing. Hipot test is typically used for acceptance testing or after transformer repair testing. Potential transformer testing ptvt valence electrical. Part winding resonance often results in internal winding voltages bil 5. Testing transformer3 easy methods to test transformers. Current transformers principle of operation of ct a current transformer is defined as as an instrument transformer in which the secondary current is substantially proportional to the primary current under normal conditions of operation and differs in phase from it by an angle which is approximately zero for an appropriate direction of the connections.
Common precommissioning tests of transformer insulation resistance values of various winding should be checked. Verify correct operation of transformer withdrawal mechanism and grounding operation. A presentation ontransformer testing using dpatt3bi 2. Artificial intelligence applications in the diagnosis of. The primary coil, which receives energy from the ac source. There are three basic styles used to transformer system voltages to control voltages. November 17, 2019 february 24, 2012 by electrical4u. It determines the copper loss occur on the full load. 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. This method statement will give a brief steps to be carried out for testing and pre commissioning of transformers. When the pt is withdrawn ensure that there is no longer any connection with the primary electrical system. Routine tests and type tests of transformers electrical4u. Instrument transformer basic technical information and.
Instrument transformers for metering purposes must have a high degree of accuracy up to class 0. The copper loss is used for finding the efficiency of the transformer. They convert line voltage from the 120347 v up to high voltages, in the range of 2 to 15 kv. Figure 5 shows the result of the curve fitting for core 1, considering the y axis to be the current and x axis to be the. Failed windings in the field may even still pass impulse test back at factory. Several energy efficiency programs now in place nema, doe, etc.