The goal is to determine if the insulation of a wire has been compromised. The following sections of the ansineta standard for acceptance testing specifications for. The megger technical library provides access to a range of additional content and resources such as technical guides, application notes and more. Megger is also called as a megaohmmeter and is a device used for the testing of insulation resistance of a cable. A megger insulation resistance tester is especially useful when you have carried out electrical work on your home and want to make sure you didnt damage insulation or make a wiring mistake. A catalogue, for quick reference, of the range of megger test instruments for the maintenance of electrical power systems. The instrument will continue to test, updating the display after each new test cycle, until the test button is pressed or the test procedure times out. The complete guide to electrical insulation testing. It is performed as a part of acceptance and maintenance test procedure to determine any problems due to poor design, assembly, handling, overloading, fault conditions or poor maintenance. Using ohms law vir, we can compute the value of the resistance. Com 99 washington street melrose, ma 02176 phone 7816651400 toll free 18005178431 visit us at. The procedure of insulation resistance test or megger test are given below.
It is recommended that the test voltage for polymerinsulated heating cables be 2500 vdc or vdc for mi cable. Loop test for continuity using a megger insulation tester. It is checked by touching the free ends of the leads together while the megger button is pressed on to check for zero. Structured cable certification tests 2 next, attenuation, and return loss are keys to ensuring that the cabling is capable of supporting highspeed applications. Troubleshooting with insulation resistance test instruments. The procedure of the insulation resistance test are given below first, disconnect all the line and neutral terminals of the transformer.
Newly laid cables may be tested to reveal any faults arising from transportation or installation. A guide to low resistance testing test equipment depot. Figure 3typical scale on the megger insulation tester. Megger offers a family of highquality insulation testers at voltages above 1 kv. Additional notes about using a megger insulation tester 33. A guide to diagnostic insulation testing above 1 kv 5 what causes insulation to degrade. This procedure is followed for all new products and covers areas in addition to those included in applicable standards. Some unknown facts was presented at the 2020 neta powertest conference in chicago, il.
This is certainly not a new test, and has been in use for a number of years. Only test a cable if the temperature of the conductor is above the dew point otherwise, moisture will form on. Megger working principle is to generate high voltage and measure resistance at high voltage. Reverse side of card at right is used to record the test data. High power test and diagnostics combination for medium voltage cables. Although all of its products are manufactured in the united states and england dallas, texas. The megger is the instrument uses for measuring the resistance of the insulation. These data may consist of system information, system test settings, information about the course of the cable test, the measured data test voltage, leakage current and the test result.
Diagnostic dc testing is probably the easiest and most convenient method of achieving. A guide to diagnostic insulation testing above 1 kv. The generator can be handcranked or lineoperated to develop a high dc voltage which causes a small current through and over surfaces of the insulation being tested fig. This is important, because the highvoltage current in threephase systems is far more lethal than a mere lowvoltage shock received in residential setting. A megohmmeter is used to measure the resistance of the crossedlink to an applied dc voltage. Insulation resistance testing is a nondestructive test procedure. Test the megger before use, whether it gives infinity value when not connected, and zero when the two terminals are connected together and the handle is rotated to do the test you ensure the cable is disconnected from any devices megger normally work on 500v, v testers for higher voltage testing. Insulation resistance test or megger test procedures with. A megger is an ohmmeter that measures resistance in the megohm scale. Weve assembled helpful technical guides on insulation testing from leading manufacturers in the field. A spot test should be performed at regular intervals every six months, for example to track the changes in insulation integrity.
Structured cable certification tests newark element14. Electrical stress insulation is designed for a particular application. Insulation resistance testing guide chauvin arnoux. It is commonly used in the industry for acceptance testing prior to energizing the cable and for maintenance testing programs. The leads used for connecting megger testing with the circuit should be fault free and the two connecting leads should have electrical continuity. Connection to cable under test connect the test lead to the cable under test. Megger insulation tester calibration procedure megger insulation tester is measuring resistance by generating a voltage. Wide range of megger technical guides, application notes, academic papers and product support material. Megger test sheath resistance test procedure for cables. The test measures the insulation resistance between the phases andor between phase and ground. Megger leads are connected to lv and hv bushing studs to measure insulation resistance ir value in between the lv and hv windings. Connection may be made to a live system with a voltage to earth ground less than 300v with an.
They interact with each other and cause a gradual spiral of decline in insulation quality. Length length is defined as the physical or sheath length of the cable. First we will disconnect all the line and neutral terminals of the transformer. Per ieee 4002001 dc should not be used as it can damage aged cable and will not detect most defects.
Insulation testing technical guides megger insulation. Standard for acceptance testing specifications for. In this video you will find out how to test 3phase induction motor. Remove the cable from service, disconnecting all other circuits or devices, as well as any cable accessories and protective end caps, and open the cable at both ends and ensure conductors are isolated from each other. If the resistance of the insulation is high, the pointer of the moving coil deflects towards the infinity, and if it is low, then the pointer indicates zero resistance. From power station to plug, megger test equipment helps you maintain the electrical network, monitor its condition and maintain supply to your customers. Like a visit to the doctors office, each test examines the test item in a different way.
The megger company registered the name megger in may 1903 and today offers a wide variety of ir testers. Megger cable test equipment provides access to all of the technology needed to make informed cable management decisions through the different stages of the cables life cycle. Dielectric testing may be destructive in the event of a fault, depending on the test levels and. Be sure to follow good safety measures to prevent electrical shock.
This test is often performed by applying an ac voltage but can also be done with a dc voltage. Readings should be within the specifications provided by the manufacturer. The test should also be performed after a motor is serviced. Figure 2 typical megger test instrument hookup to measure insulation resistance. Electrical test equipment application solutions from megger. In continuous mode the user connects the test leads and presses the test button, initiating the test procedure. Find here insulation testing and continuity, power protection, power transformer testing, power cable infrastructure, cable fault location, general electrical test. Megger testing procedures ieee electrical code issues. Vi repeat the procedure to test subsequent conductors with respect to conductors 2,3. A megohmmeter applies current for 1 minute through the cable before being measured and recorded. The result obtained is a voltage value usually expressed in kilovolts kv. To repeat a test, simply break contact with the potential probes and remake contact.
The test measurement data can be recorded on a test graph over time. Now resing process we first take resistance between. Megger employs some of the worlds greatest experts in cable test and diagnostics. At this time, the software can handle the measurement and test data of the following megger devices. This article takes an indepth look at the transformer turns ratio test, some of the challenges associated with interpreting test results, and.
Regardless of these efforts, it is not possible to. Megger group limited is a manufacturer of electric test equipment and measuring instruments for electrical power applications. Megger guide to electrical insulation testing pdf instrumart. Megger leads to be connected to lv and hv bushing studs to measure insulation resistance ir value in between the lv and hv windings. The megger test is a method of testing making use of an insulation. This document will focus only on the tests that are of importance for field installers which are described as installation and maintenance tests.
Test performed so performed to know the insulation resistance value is. I recommend at least a ac withstand or, better yet, a pd stress test. The following is a summary of insulation resistance ir testing commonly referred to as megger testing of low voltage cables rated less than 5 kv, recognized by nexans. O shortearth the cable conductors momentarily to discharge. This current usually at an applied voltage of 500 volts or more is measured by the ohmmeter, which has an indicating scale. To test a cable with a megger, you connect one probe to the outside of the cable and, with the power turned off, you touch the probe to the conducting wire at the point of connection. To perform an insulation spot test, apply the following procedure. That is, with the same test connections and with the same test voltage applied for the same length of time. Insulation resistance testing of low voltage cables in the. Application engineer imcorp power cable reliability consultants.
You do this by using a high voltage and looking for voltage leaking through the insulation. Transformer turns ratio ttr is one of the most common test used to assess the condition of the transformers windings and core. While cable import and storage are not limited, a maximum of 5 cables can be created using the cable editor of the report edition. After properly terminating the cable, connect the positive lead of the megger to the bus wires and the negative lead to the metallic braid as. Figure 4typical record of insulation resistance of a mill motor. A megger test or sheath resistance test is used to diagnose cable faults, either short circuit problem, water penetration, moisture or current leakage. It should correspond to the length derived from the length markings commonly found on the outside jacket of the. Push the test button of the megger to generate the voltage. T then use the range and vf keys to set the correct values. Using the megger to test a threephase motor is rather easy, though the safety hazards for this procedure are quite high. 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. There are five basic causes for insulation degradation. In addition to these uses of this test, the working principle, operation procedure, types, and applications have also been discussed.751 560 1492 725 1118 1586 260 1435 323 740 125 1032 1145 184 531 1630 1039 987 1132 649 996 446 571 1270 443 833 286 608 270 1277 1306 759 18 951 22 1377 1173 903