This foreword is not a part of ieee std 1181978, standard test code for resistance measurement. Standard for acceptance testing specifications for electrical. You will also need a thermometer or similar temperature measurement device. Similar procedure with use of an ammeter is described. Insulation resistance measurement methods springerlink. To the test object, a direct current dc is applied, which is much lower than the breakdown voltage. Pdf measurement of winding resistance and insulation. This measurement important to determine the winding condition for electric motor,electric cables,electrical installation,transformer,circuit breaker,heater and electrical equipment. A guide to diagnostic insulation testing above 1 kv. Secondly measure insulation resistance between low voltage windings and high voltage windings. Insulation resistance of rotating machinery onboard isolated 500v power supply to measure the insulation. The minimum value for insulation resistance is a relative factor, however, most of hv synchronous machine users have adapted themselves for ieee std. As mentioned before polarization index is defined normally as the division of insulation resistance in 10 to 1 min. K0019e02 september 2015 construction power, energy, environment service, maintenance insulation resistance measurement of solar panels insulation tester ir4053.
Cable insulation resistance measurements made during. Resistance measurements are then made between each winding and all other windings grounded. A common rule of thumb is insulation resistance changes by a factor of two for each 10 degrc change. This instrument adopts the dc voltage convertor of low. Figure 2typical megger test instrument hookup to measure insulation resistance. How to calculate minimum insulation resistance of motors. An insulation resistance diagnostic system was recently developed and exercised during a series of cable fire tests sponsored by the commercial u.
This insulation resistance measurement system was able to identify and quantify the changes in insulation resistance occurring between the separate conductors and the conductors. Understanding insulation resistance testing pdf 0712. Understanding insulation resistance testing pdf 0712 technical assistance 800 34391. The test method is determined by the type of equipment being tested and the reason for testing.
According to one aspect, a battery insulation resistance measurement method includes determining a voltage of a battery, determining a voltage of a first terminal of the battery with respect to a ground. Insulation measurement glossary, performance, measuring method. Pf pdf insulation resistance measurement methods a traditional method of periodical measurement of insulation resistance in live dc networks is a so called three voltmeters method. Measuring insulation resistance for threephase motor while.
An insulation resistance test is a method by which the security and proper functionality checks of electrical equipment and appliances is examined. Measurement variations of insulation resistancepolarization. Cable insulation resistance measurements made during cable. Pdf a new method for insulation resistance measurement at low. The insulation resistance testing also can avoid serious damage,fire or. The guard terminal is useful when measuring very high resistance values. The test measures the insulation resistance between the phases andor between phase and ground. If a capacitor is tested at 200v and measures a dielectric leakage current of 10na the insulation resistance must be 20gw. Specifications are subject to change and revision without notice. Standard test methods for dc resistance or conductance of. The test method is determined by the type of equipment being tested. Insulation resistance measurement has been recommended and used for over 50years to evaluate the condition of electrical insulation. As it ages, its insulating performance deteriorates. Insulation resistance testing is performed when troubleshooting electric motors and related equipment.
The measurement of insulation resistance is a common routine test performed on all types of electrical wires and cables. The measurement of insulation resistance is carried out by means of a mega ohmmeter a high resistance range ohmmeter. The megger insulation tester is a small, portable instrument that gives you a direct reading of insulation resistance in ohms or megohms. Battery insulation resistance measurement methods, insulation resistance measurement methods, insulation resistance determination apparatuses, and articles of manufacture are described. Quality is crafted into every major megger insulation. Ideal for electricity board and industrial companies for predictive and. The standard duration of voltage application are 1 minute or 10 minutes. Insulation resistance riso of nongalvanically isolated pv. Johnson, then chairman of the power system instrumentation and measurements committee.
Direct readings are available from digital meters and on some testers like the megger mto series, two measurement channels are available allowing two resistance measurements at the same time. Insulation resistance test and oil test of distribution transformer. Jan 31, 2019 resistance is one of the most basic elements encountered in electrical and electronics engineering. The temperature causes the insulation resistance value to. The value of resistance in engineering varies from very small value like, resistance of a transformer winding, to very high values like, insulation resistance of that same transformer winding. After a benchmark is established, periodic measurements should be taken and recorded along with notation of temperature, humidity and duration of the megger test. Insulation resistance of rotating machinery onboard isolated 500v power supply to measure the insulation resistance. The most important reason for testing insulation is to insure public and personal safety. A traditional method of insulation resistance measurement in live dc networks is a so called three voltmeters method. Second, the range of a megohmmeter is in megohms, as its name implies, instead of ohms as in a multimeter. Jul 25, 2018 the standard duration of voltage application are 1 minute or 10 minutes. Insulation resistance of new transformer should be greater than 1 giga ohm and old transformer should greater than 300 mega ohm.
Measurement of insulation resistance ir part 2 fluke insulation resistance tester up to 10kv allows testing of high voltage systems such as control gears, engines, generators and cables. Pdf insulation resistance measurement 3 magnetic current. See the site fixed equipment for measurement and testing of electrical networks, energy management and optimization systems. Insulation resistance testing guide chauvin arnoux. Megger mit1020 10kv insulation resistance testers are all. Technical challenges in the measurement of insulation. The voltage, we apply for measurement of insulation resistance, is direct voltage.
Us20110115490a1 battery insulation resistance measurement. Insulation measurement glossary, performance, measuring. 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. Insulation resistance testing test equipment depot. By injecting a known dc voltage lower than the voltage for dielectric testing and then measuring. Ieee standard 432000, recommended practice for testing insulation resistance of rotating machines, recommends the insulation test voltage to apply, based on winding rating, and minimum acceptable values for electric motor windings.
Instead, we installed a known resistance r0 as shown in fig. How is ir testing done, in view of the fact that at least 80% of electrical maintenance and testing involves evaluating insulation integrity. And if the equipment temperature is below the dew point, a humidity measuring. The motor used at that time is in a sound condition, and the insulation resistance reading through the measurement with an insulationresistance meter was 100 m. Insulation resistance testing is a nondestructive test procedure. Tester, with excellent test voltage regulation, direct measurement readout and an external guard. Insulation resistance measurement 3 magnetic current test winding resistance meter i i i i i1 p1 p2 i2. This can lead to the inverter not connecting to the grid due to the insulation resistance of the entire pv plant being too low, even though all components work without problems. The working group to revise ieee std 118, standard test code for resistance measurement, was organized by william j.
Insulation resistance measurement is based on ohms. Timeresistance testing method this method is fairly independent of temperature and often. Before examining the various measurement methods in detail, it would be useful to look again at the factors that influence the insulation resistance measurement. As a production test, this test is often used as a customer acceptance test, with minimum insulation resistance per unit length often specified by the customer. Oct 22, 2016 if the insulation resistance of a new, cleaned or repaired motor that has been stored for some time is less then 10 mohm, the reason might be that the windings are humid and need to be dried. Recommended test voltages for routine maintenance insulation resistance tests of equipment rated to 4,160v and above. For commercial installations regular insulation measurement is required. From the data of insulation resistance,we can make a perfect and clear decision either the electrical equipment in good condition or not. Measuring insulation resistance for threephase motor. Type of insulation period of exploatation, year 05 515 1530 density of the current mam. The complete guide to electrical insulation testing. Insulation resistance testing introduction insulation resistance testers can be used to determine the integrity of windings or cables in motors, transformers, switchgear, and electrical installations.
This procedure must be continued for subsequent tests to accurately determine if the rate of insulation breakdown is occurring at an abnormal rate. It is recommended totrack periodic measurements, accumulated over months and years of service or in connection with servicing and overhaul of rotating machines. Standard for acceptance testing specifications for. Ieee std 432000 recommends a procedure for measuring insulation resistance of armature and field windings in rotating machines rated 1. Measurement variations of insulation resistancepolarization index during utilizing time in hv electrical machines a survey article pdf available january 2015. If the insulation resistance of a new, cleaned or repaired motor that has been stored for some time is less then 10 mohm, the reason might be that the windings are humid and need to be dried. In this example well consider a ceramic capacitor of 2. Major megger insulation resistance testers coleparmer. Leakage current measurement reference design for determining. Understanding the value of electrical testing for power. Tida00440 leakage current measurement reference design.
The reference design uses an onboard isolated 500v dc power supply and isolated signal conditioning circuit to measure the leakage current for determining the insulation resistance. Because of that, insulation resistance can also be referred as 1 minute insulation resistance or 10 minute insulation resistance depending upon the duration of the test. Pdf measurement variations of insulation resistance. Measurement of winding resistance and insulation resistance of 3 phase 11 kv 433 v, 16kva oil cooled type transformer. Technical challenges in the measurement of insulation resistance. To measure insulation resistance, a dc voltage of 500v or v is applied between the windings and the ground of the motor as shown below. An introduction to insulation resistance testing aemc instruments. Portable measurement equipment in a wide variety of fields. Insulation resistance riso of nongalvanically isolated.
Understanding insulation resistance testing aemc instruments. It can be adjusted to all testing voltages that are specified in ieee 432000. Us20214788a1 battery insulation resistance measurement. So, to compare new readings with previous ones, youll have to correct your readings to some base temperature. Megger guide to electrical insulation testing pdf instrumart. How to measure electric motor insulation resistance.
Pdf test of insulation resistance is prerequisite for leakage effect evaluation in many electrical measurements. Understanding insulation resistance testing pdf 0206 rev. The testing times have been greatly reduced using modern microprocessor based test equipment. Measurement of insulation resistance of dc shunt motor. It is commonly used in the industry for acceptance testing prior to energizing the cable and for maintenance testing programs. With a little recordkeeping and common sense, however, you can get a good picture of the insulation condition from values that are only relative.
The temperature causes the insulation resistance value to vary quasiexponentially. Troubleshooting with insulation resistance test instruments. Insulation resistance meter p n photovoltaic array e products used information valid as of september 2015. Thus it can be determined in advance, when the insulation deteriorates and becomes a danger. When temperature increases, insulation resistance decreases, and vice versa. Formulas for insulation equivalent resistance calculation are derived with help of thevenins theorem.