Current transformer testing procedure pdf

The current transformer is solely assessed through its external behavior. In this book we have laid down important aspects on transformer testing in order to enhance the understanding of the testing procedures. If available, take down the ratings of the transformer. Inductive current and voltage transformers ct and vt and capacitive voltage.

Transformer testing has developed considerably over the past years. Procedure of polarity test of transformer connect the circuit as shown above with a voltmeter v a across primary winding and another voltmeter v b across the secondary winding. Efficient current transformer testing with omicron ct analyzer. Power transformer testing transformers may be tested using ac or dc voltage. Raise the conductor to the specified maximum test voltage and hold for 15 minutes. The equipment and test procedure developed at the bureau of standards for measuring the ratio and phase angle of current transformers up to currents of. The testing times have been greatly reduced using modern microprocessor based test. After the current transformers have been subjected to the dielectric type tests 3, 4 and 5 they shall be subjected to all the routine tests. Testing and protection of current transformer practical experiences. Measurement shall be carried out with direct current dc by the voltage drop method or the bridge method as specified in the manufacturer approved power transformer testing procedure. Current transformer white paper the basics of current transformers ratio the ct ratio is the ratio of primary current input to secondary current output at full load. Brooks testingpotentialtransformers 421 needstobemeasuredwithonlymoderateaccuracy.

Back to the basics current testing valence electrical. You can repeat the procedure above for each tap of a multi. It is typically used for test specimen that have small capacitance and as a result the power factor tan delta of the test circuit is. Testing potential transformers relay testing training. Following is an approximate sequence for transformer testing. Ac voltage is preferable to dc voltage for transformer testing because ac voltage simulates the internal stress that the transformers face during operating conditions. Our test systems provide highprecision, automatic testing and assessment of current transformers to iec 600441, iec 600446, iec 618692, ieee c57.

It evolved from the simple gonogo verdict into a sophisticated segment within transformer manufacturing. Testing and commissioning procedure for electrical installation 1. Abb field engineering services instrument transformer. D r a f t doble engineering company 85 walnut street watertown, massachusetts 024724037 usa pn 5000397 72a2244 rev. Ct analyzer current transformer testing, calibration and. On theother hand, when j is large, then theuse of a detector of highimpedance may shift theload from transformer of higher. The basics of current transformers nk technologies. Perform insulationresistance tests of the current transformer and.

Testing current transformers burden test only if we cannot get to the primary side of the ct we can check that the output is constant as burden changes. This test also performed as a routine test of transformer. So transformer ratio test is an essential type test of transformer. Traditional current transformer testing follows a blackbox approach. When the regulation began, the current was essentially constant in spite of the inductance of the windings and fluctuation of the battery voltage or lead resistance. Transformers are an electrical component that transmit electrical energy between at least two circuits. Testing swp sp0507 current transformer testing sp0508 voltage transformer testing p53 operate the network enterprise process as2374. The current transformer is solely assessed through its external behavior without considering what is happening. Magnetization and primary injection test of current. The following sections of the ansineta standard for acceptance testing specifications for. Procedure for current transformer factory and site.

The primary winding can consist merely of the primary current conductor passing once through an aperture in the current transformer. The need for a comprehensive current transformer testing regime is evident when the alternative is considered. Ct analyzer the number one in current transformer testing. A test set operator connects the leads, pushes the buttons, and records the. Primary interface connection from the transformer to the unit. Figure 5 shows the result of the curve fitting for core 1, considering the y axis to be the current. The instrument current transformers supply, and isolate, the secondary relays, meters and other instruments, providing the suitable and manageable secondary quantities which are proportional to those in the primary. Measure core insulation resistance at 500 volts dc if the core is insulated and if the core ground strap is removable. Equuipment for testing current transformers nvlpubsnistgov. 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. The first neta maintenance testing specifications for electrical power equipment and systems was published in 1975. Introduction the procedures stated in this document cover the activities in preliminary tests and inspections, functional performance tests. You can repeat the procedure above for each tap of a.

Standard for acceptance testing specifications for. Procedure for current transformer factory and site acceptance tests note. Optional measure the resistance of each winding at the designated tap position. The importance of current transformer tests is often underestimated. The complete guide to electrical insulation testing. Standard for testing specifications electrical power.

Knee point voltage and magnetization curve have to be tested by using current transformer test kit mct. Prior to testing, short the primary winding of the ct under test by connecting h1 and h2, then short the secondary winding of the ct under test by connecting x1 and x2x5. Electrical testing methods on instrument transformers. The voltage ratio shall be measured on each tapping and verified aginst manufacturer approved power transformer testing procedure. During normal operation, a current transformer ct transforms higher current into a more. Instruction manual for transformer ohmmeter dc winding. There are four typical types of current transformers. The following sections of the ansineta standard for acceptance testing. Testing and commissioning requirements for switchgear. This connection has all of the interfaces required to connect current and voltage inputs from a three phase transformer into the mto300 unit. A distinction has to be made between a metering class and a protection class current transformer. Transformers regulate the voltage in circuits, but in. A fault leading to an open secondary could cause the primary current.

Insulation tests on current transformers rated 600v or less are usually performed at vdc. Before proceding with transformer measurements the test engineer will become familiar with the safety rules of section 2. C electrical power from one voltage to another voltage keeping the frequency same by electromagnetic induction discover the worlds research 17. Thepoten tialcircuitofthewattmetermaynowbeusedasavoltmeterto.

Meggers range of current transformer test equipment allows you to construct an in depth test and maintenance programme to prevent problems before they occur. Excitation hysteresis curve corresponding to the internal magnetization processes of the magnetic core. Since 1989, revised editions of the maintenance testing specifications have been. This ms excel spreadsheet is actually detailed instruction for each procedure necessary for correct testing of power transformer. A routine series of diagnostics and testing for your current transformer should include ct saturation testing. If performed by means of direct voltage dc, reduce the test.