To test the loop impedance our technician will use an earth loop impedence tester which is plugged into the power socket gpo to take a reading. Part of a series on electrical installation testing, other videos here. Earth electrode and looping, theory and applications. The earth loop impedance that has to be considered is that which comprises the impedance of the source, the line conductor up to the fault plus the protective conductor from the fault to. Earth electrode and earth loop impedance testing theory and applications. Loop testers are used to measure earth fault loop impedance and determine prospective fault currents. The most common form of testing for the earth fault loop impedance is using a earth fault loop impedance tester. Maximum earth fault loop impedance values for overcurrent protective devices in common use, for fault protection for fault protection, the limiting values of earth fault loop impedances, z s, are given in tables 41. Having a functional earth return circuit will allow the detection of circuit faults and facilitate a reaction from your mcb. Why is the test needed and which test method is it best to use. Of all the tests that contractors routinely perform on electrical installations, earth loop impedance testing creates the most confusion and uncertainty. The impedance of the earth fault current loop starting and ending at the point of earth fault. Basically, it is the measurement used to describe the restriction of current though the loop that would be caused by a fault.
The 1664 fc puts a lot of testing power in your hands to quickly and efficiently test to all local regulations, protect appliances, and share test results in real time over your smartphone. Earth electrode and earth loop impedance testing theory and. In a tt system where a connection to earth is not provided by the supply authority it is still necessary for an lv final circuit protective device to disconnect an earth fault within 0. Napits don holmes provides us with more essential technical information. Us7271577b2 testing loop impedance in an rccb electrical. Earth loop impedance test on 3 phase the earth images. Total impedance valueszs for the complete installation in ohms k. Course content earth fault loop impedance concepts. Another method is to measure the earth loop impedance with a loop test instrument that supplies a test current su. Neca technical have been receiving calls from members about readings obtained in relation to earth fault loop impedance from network operator inspectors. Earth fault loop impedance is the path followed by fault current when a low impedance fault occurs between the phase conductor and earth, i. Information about how the fault loop impedance is used by the elek cable pro software to calculate earth cable size.
In simple language, what is earth fault loop impedance. Earth loop impedance solutions electrical software. Cablecalc pro software is used to quickly and accurately calculate earth fault loop impedance and earth cable sizes in full compliance with the latest australian standards. Home bs7671 earth fault loop impedance earthing system electrical design iec standard what what is earth fault loop impedance. Calculation of earth fault loop impedance electrical.
I just need some clarification on the earth loop test thats required on a coc, where can i find the acceptable values for this test in the sans book. At safepower safety systems we use an earth loop impedence tester that will not trip out the circuits rcd that we are testing. Maximum impedance values ze and the actual impedance values in ohms j. And can this test be done with the standard loop tester if its over 100a at the main switch as i know we need to calculate for pscc if over 100a. Earth electrode and earth loop impedance testing theory and applications as two of the most common testing subjects debated amongst electricians as well as generating the highest percentage of calls to the megger technical support desk this series of presentations and supporting booklet hope to clarify some of the obstacles faced by an. Fault current is driven round the loop by the supply voltage. The voltage samples are subsequently transformed from time space to frequency space to allow the component. The earth loop impedance test measures the resistance of the path that a fault current would take between line and protective earth. Earth electrode and earth loop impedance testing theory and applications all too often time is lost on site because the principle of what the test is expected to prove is lost. How to determine earth fault loop impedance professional.
Less basically, as impedance is inversely proportional current you need to set a maximum. But sometimes, safety is taken for granted and attitudes only change when accidental shocks occur. A fault loop impedence test is done between the active conductor and the earth. Of all the tests that contractors routinely perform on electrical installations, earth loop impedance testing creates the most confusion and. When looking at making measurements of earth loop impedance, or prospective fault current pfc for that matter, it is always worth remembering. Measurement of fault loop impedance measurement of the fault loop impedance is carried out using the same frequency as the nominal frequency of the circuit 50 hz. Multifunction testers fluke 1664 fc installation tester. The loop impedance includes the resistance of phase and earth. An earth fault loop impedance test is the process of having your electrical installations and power points tested to avoid electric shock and injury. Relying more on technology, most australian lives have changed irreparably, mostly for the better. Participants will be able to demonstrate an understanding of the operation of loop impedance testers in accordance with asnzs standards and be able to carry out an earth fault loop impedance test of an installation. Earth system resistance test methods 8 earth loop testing 17 what is the loop and why do we test it.
Methods of testing external loop impedance and prospective fault current. Minimum trip current needed to comply with earth loop impedance test h. Iee regulations require earthfault loop impedance measurements in electrical installations. Loop testing could be described as a dark art it is the most difficult measurement taken by the electrical contractor on his day to day business. For your own safety and to get the maximum benefit from your. Earth electrode and earth loop impedance testing theory. Some impedance test meters include a 2 wire non tripping loop test. To test the loop impedance, simply plug a earlth loop impedance tester into a gpo and take a reading. Fluke 1664 fc multifunction installation tester helps expedite installations. When measuring low zs values does your meter lie my ht instruments zg47 3 phase power yzer with earth ground testing prospective fault cur how to determine values cmc 356 universal relay test set and missioning tool uni t earth resistance digital rcd multifunction loop impedance tester ut595 earth loop impedance testing demystified meggerlearn how. Locking test button 3 wire no trip loop test 2 wire high loop test phasephase loop test pfc display introduction general description 4 thank you for purchasing the megger earth loop impedance tester.
An alternating test current is applied across the phase earth connections of a supply and a plurality of voltage samples are then taken across the connections. Earth loop impedance, rcd, and insulation test best. Trade skills 4u tutor andy summers talks you through earth fault loop impedance and prospective fault current testing. Simon wood of megger answers these and other frequently asked questions. In response to queries we have developed an earth fault loop impedance calculator which may assist in scenarios faced. Best known as loop testing, it addresses the rapidly expanding development and deployment of increasingly sophisticated electronic equipment, which places greater demands on instrumentation and testing capabilities. Lutron1 this app note explains lutrons recommendations when performing earth loop impedance, residual current device rcd, and insulation tests. Earth fault loop impedance test megger the earth images. In order to achieve this, suitable maximum earth fault loop impedance must be provided, as noted in. Loop testing could be described as a dark art it is the most difficult measurement taken by.
A method and apparatus for testing the loop impedance in residual current circuit breaker rccb protected circuits is provided. What you can learn from loop impedance testing on a branch. I have recently been doing factory coc and most if not all the main dbs and sub dbs main swiches. Which maximum earth fault loop impedance values should you. The maximum earth fault loop impedance values zs in bs 7671 or the equivalent tables in the iet onsiteguide osg and iet guidance note 3 inspection and testing gn 3. Asnzs 3000 wiring rules applies throughout australia and new zealand and is references in whole or. In order to achieve this, suitable maximum earth fault loop impedance must be provided, as noted in regulation 411. The test measures the earth resistance and also detects the voltage between the auxiliary electrodes, and if this exceeds 10 v, the test is inhibited. A loop test may stop or even be prevented from starting if there is a connection problem with the test leads or instrument fuse, an earth problem on the circuit being tested, or a. Lutron1 this app note explains lutrons recommendations when performing earthloop impedance, residual current device rcd. The higher the impedance, the lower the fault current will be and the longer it will take for the circuit protection. To test the loop impedance a technician will use an earth loop impedence tester which is plugged into the power socket gpo to take a reading. However, with testing existing live circuits, you must either have a unique earth loop impediance tester which will not trip out the particular circuits rcd or you must confirm that all appliances on that particular circuit which you are.
As there is a neutral connection on this type of supply, either a 2 or a 3 wire test would be suitable for testing the earth loop impedance, however, the 3 wire test would not be suitable for. Earth fault loop impedance zs is the impedance in ohms of the circuit path formed during a fault between earthed metal work and live parts. Determining earth fault loop impedance voltimum uk. In an electrical system, a ground loop or earth loop occurs when two points of a circuit which are intended to have the same ground reference potential but instead these two points have a different potential between them. What is earth fault loop impedance quality electrics is. A common complaint about earth loop impedance testing is that if several tests are carried out on the same circuit, it often happens that each test gives a different result. What you can learn from loop impedance testing on a. Mft1700 multifunction testers loop testing megger lt300 loop impedance tester electrical verification requirements megger mft1741 multifunction tester earth electrode and loop impedance testingmade 2 measure varying earth loop impedance test resultswhy do non trip electrical loop testers provide differing resultslearn how earth fault loop impedence testing done. It is important because efl impedance affects the time for a protective. Loop impedance testers and loop testers from megger, kewtech, martindale and metrel. Another method is to measure the earth loop impedance with a loop test instrument that supplies a test current sufficiently low not to trip the rcd, such as 15 ma.
Designed to comply with an ip54 rating, the 4118a is comprised of a custom microprocessor to achieve high accuracy and reliability. This can be caused, for example, in a signal circuit referenced to ground, if enough current is flowing in the ground to cause two points to be at different potentials. Kyoritsu 4118a digital loop impedance tester with psc. Earth fault loop impedance is the path followed by fault current when a low impedance fault. Cable pro software for calculating fault loop impedance and earth cable size. Alternating current ac loop impedance testing, a testing procedure longestablished in europe, is only recently beginning to find its way into u. Loop testers earth loop testing and earth loop impedance. All prescribed electrical work is required to be tested whether its. Our highlytrained staff are fully mobile and offer earth loop impedance test services across the nation. You can also determine the earth fault loop impedance by calculation the earth fault loop test makes sure that the protective devices operate within the required time. A loop impedance test is a process of having the electrical earth of all your electrical installations and power points tested to discover any faults within your electric circuit.