thank you very much for sharing the here meggering procedure in details. J,R Bohra In the case of a very large installation where there are many earth paths in parallel, the reading would be expected to be lower. He is Presently associate with one of the leading business group as a Deputy Manager at Ahmedabad,India. October 27, 2020. c) From cable reel to cable tray, the cable is fed from the top of the reel to main-tain required curvature. Cable equation The insulation resistance of cable for a certain length can be calculated by the following formula: Where: RC = Insulation resistance in Megohms of cable K = Specific IR in Megohms - k ft at 60 F of insulation D = Outer diameter of insulation d = Outer diameter of bare copper wire L … Value at 60 seconds after application of the test voltage is referred to as the Insulation Resistance of the transformer at the test temperature. Hi to all; The IR test between Phase-Natural to earth must be carried out on the complete installation with the main switch off, with phase and neutral connected together, with lamps and other equipment disconnected, but with fuses in, circuit breakers closed and all circuit switches closed. Found inside – Page 135Therefore , the insulation resistance of the given length of cable is R -7 . ... In equation ( 18 ) the length I must be expressed in centimeters when p is ... While the cross sectional area perpendicular to the flow of current depends on the length of the cable. ( Diameter of Individual Conductor ) To determine the approximate O.D. Found inside – Page 28Charging cables for electric vehicles https://www.chinesestandard.net. The insulation resistance constant Ki is calculated from the measured insulation ... The Insulated Power Cable Engineers Association (IPCEA) provides the formula to determine minimum insulation resistance values. This leakage can be described as a parallel resistance with a high value, an Insulation Resistance (Figure C1-10) Electrical cable sizing software. He wants to Share his experience & Knowledge and help technical enthusiasts to find suitable solutions and updating themselves on various Engineering Topics. First off there isn't a 1 Mohm minimum insulation resistance for an existing installation, when you are preparing an Electrical Installation Condition Report you need to make an engineering judgement as to whether the insulation resistance test result is acceptable; and it. thanks a lot. . Just for curiosity can you please tell me what is the full form of “DEP” standards which you have mentioned under the section “IR Value of S/S Equipments As per DEP Standard”. insulation looks ok. Time-resistance tests on large rotating electrical machinery – especially with high operating voltage – require high insulation resistance ranges and a very constant test voltage. sir Thank you for sharing your Knowledge i just have one query related to the H.v Cable test. If insulation resistance were to be tested with an AC test voltage, then the value would be lower as the cable would appear to pass a capacitative current in addition the the resistive current Now to the next item you haven't specified: The thermal resistance between the cable and the environment! I believe it is 500Vrms or 707 VDC, can you please confirm. Thank u sir, IR Value =0.415+1=1.41 MΩ but as per IEEE43 It should be 5 MΩ. 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. Why it is necessary to disconnect the surge capacitors while meggering the Generators Or Motors? what should be the insulation test results for lightening arrestor value between phases and between phase to earth in solar system and same for AC side and DC side? Cross section area = Surface area for length of cable =. Post was not sent - check your email addresses! Actual measured resistance = 45 ohms and is acceptable because this is less than maximum specified resistance allowable. Our measurement would be low. Membership No:M-1473586.He has more than 16 years experience in Transmission -Distribution-Electrical Energy theft detection-Electrical Maintenance-Electrical Projects (Planning-Designing-Technical Review-coordination -Execution). In such cables, the leakage current flows radially from centre towards the surface as shown in the figure. Sir, A low resistance between phase and neutral conductors, or from live conductors to earth, will result in a leakage current. Since 80% of electrical maintenance and testing involves evaluating insulation integrity, the answer is "very important." This factory testing monitors the insulation resistance of the new wire, ation in the assembly process. F (K = 2000 for PVC; 50,000 for EPR; 100,000 for XLP)D = diameter. The results obtained from IR Test are not intended to be useful in finding localized defects in the insulation as in a true HIPOT test, but rather give information on the quality of the bulk material used as the insulation. Between each phase and earth. thank for more information now i harry to check insulation resistance long 132Kv transmission line & will have called you after testing. If you use it wisely, it can cut food and prepare delicacies. Example, for a 5 KV panel, the … Found inside – Page 24412 800 700 Cables 600 Average of 20 ° 500 Insulation 16 ° 400 Resistance 12 ... An inspection of the formula will show that it The effect of temperature on ... I would like to get a Test result of a 2000KG Lift Installation: 1. 50km=50x10^3 m Insulation resistance = 1 Mohm / (50x10^3 / 10) = 200 oh. If an Insulation Resistance test on the whole installation had been possible, and the overall value between live conductors was greater than 200M., and that between live conductors and earth was 9M., calculate the theoretical values for circuit 3 (show all calculations). The test immediately preceding the insulation test should be the earth bond test. Can any one explain & clarifyplease. The measurement of insulation resistance is a common routine test performed on all types of electrical wires and cables. Insulation Resistance (IR) is the extent to which the dielectric material in a capacitor resists leakage current. He has published numbers of Technical Articles in “Electrical Mirror”, “Electrical India”, “Lighting India”,”Smart Energy”, “Industrial Electrix”(Australian Power Publications) Magazines. One of the most fundamental of electrical installation and maintenance tasks is taking insulation resistance (JR) readings. The minimum acceptable insulation resistance value is calculated using the following formula: 304.8 RInsulation (VRated 1) L Where: RInsulation is the minimum acceptable insulation resistance value, in mega-ohms; VRated is the rated voltage of the cable (typically printed on the cable), in kilovolts; and L is the length of the cable, in meters. Step 4 - Fault identification: The first major procedure is to determine the phase on which the fault has occurred and if it is of low or high resistance. ... For our cable, with XLPE insulation m and b are found to be … Since the electrical resistance of a conductor such as a copper wire is dependent upon collisional proccesses within the wire, the resistance could be expected to increase with temperature since there will be more collisions, and that is borne out by experiment. Found inside – Page 29If it should be required to determine the insulation after 2 minutes ' electrification , the deflection is read after 2 minutes , and the calculation made ... 1.5 mm^2 would be satisfactory for about 15A (in free air, room temperature, PVC insulation), but you'd need 4 mm^2 for 30 A and 25 mm^2 for 120 A. Can we do meggering of Power cables in Sand storm. The Insulated Power Cable Engineers Association (IPCEA) provides the following formula that suggests minimum insulation resistance values. Insulation resistance R of single core cable is given by R= (ρ/(2π l))* ln (r2/r1) ρ = 5*10^14 ohm-cm = 5*10^12 ohm-m l = 2 km = 2000 m r1 = conduc... Combining and substituting we have: I 2. Cloud based - any device, anywhere It can be derived the critical radius of insulation depends on the thermal conductivity of the insulation k and the external convection heat transfer coefficient h. As can be seen, if r 1 < r cr , as it is in this case, the total resistance decreases and the heat rate therefore increases with the addition of insulation, Distribution cables with extruded insulation for rated voltages from 3.6/6 (7.2) kV up to and including 20.8/36 (42) kV. He is FIE ,MIE and CEng from Institution of Engineers,India. If not then why?? A heavy-duty megohmmeter serves this need. After installing back The I.R value is 0.3MOhm , can we test the motor and run it. Critical radius of insulation of the plastic cover. Is it the result we achieved okay, especially the result taken during night time? Thank you so much sir,this help me a lot in my field.its very very useful for those are in electrical line. Insulation resistance: when the cable length is 100m and the ambient temperature is 75℃, shake the meter with 2,500VDC for 1 minute, the insulation resistance (between the lead and shield) is 1200MΩ; 8. Tensile Strength N/mm 2. Factors that affect the Insulation resistance The results obtained from IR Test are not intended to be useful in finding localized defects in the insulation as in a true HIPOT test, but rather give information on the quality of the bulk material used as the insulation.. Control Cable Installation Precautions For control cable protection, cable should be surrounded by at least 6 inches of fine sand. I need them to calculate the Insulation resistance of our cables. Thus if two cables are connected in parallel, conductor resistances get connected in parallel while insulation resistances get connected in series. imum insulation resistance values. The resistance R of an object is defined as the ratio of voltage V across it to current I through it, while the conductance G is the reciprocal Touch the cables of the PV array on the insulation only. When a steady value of insulation resistance is obtained, it is due to the resistive element of current flow only. The temperature adjusted value of resistance is used in all calculations. Thanks The recommended practice in measuring insulation resistance is to always ground the tank (and the core). Portable measurement equipment in a wide variety of fields: testing and inspection, environmental measurements, laboratory instrumentation, power and energy, Megger is also called as a Megaohmmeter and is a device used for the testing of insulation resistance of a cable. KVA - Rated capacity of winding under test. Please! Toxicity Index Calculation. I have a quick question and will appreciate it if you can help me to find the answer please. I disconnected the cables to be meggered. hi sir, This cause deterioration of the insulation, as well as involving a waste of energy which would increase the running costs of the installation. insulation resistance, R. In this example we'll consider a ceramic capacitor of 2.2uf (2.2x10-6 farads) with a typical minimum insulation resistance of 2GW. May i know ,whether there is any necessity or mandatory rules saying that the speaker cables to be meggered? could you please guide me how to megger the 11KV output 3MW alternator on site. Change ), You are commenting using your Google account. Teflon=2.1, Neoprene=6.7. Thank you, si ye btay ki megger me 1000 volts set kr ke agr me 120×3.5sqmm cable ka megger test krta hu to kitna M oms aana chahiye, Sir what is the 1000 volts sets in megger and test cable insulstion The resistance of the cable depends on the operating temperature. IR between HV and LV as well as windings to earth. IEC 60287 Part 2-1 Thermal resistance - Calculation of thermal resistance gives the required formulas and figures to calculate the thermal resistance of a cable in various conditions. For your suggestion Thanks in anticipation. 2- Wire 3- Wire 4- Wire 6- Wire Terminal Sheath OD Compression Fitting Nominal Length of RTD L (mm) Threads M-Thread 1/2 BSPT M20X1.5 Other Consult Factory N/A Not Applicable BSPT 1 2 Other Pt-100x1, Simplex Pt-100x2, Duplex Consult Factory Teminal & Ceramic 3 3.2 4.8 6 8 Other Ø3mm Ø3.2mm Ø4.8mm Ø6mm 6.35 Ø6.35mm Ø8mm Consult. The instrument used for this measurement shall have a minimum resolution of 10 meg-ohms on the 0 to 500 meg-ohm range. this is absolutely nice. Found inside – Page 464The CABLE TESTING ROOM . quality termed insulating resistance ... in calculating or in comlocal currents are set up which disturb the test circuit and ... It is the form of a cross-link poly-phone Insulation resistance testing is a key test for electrical cables as it is a measure of how effectively the cable is insulated. kindly advice. If we desire to measure. At this level of required test instrument sensitivity, small changes in the supply voltage. lightning cable for crane – there are 2 point earth terminal, each has individual ground cable, i meggar 1kV both cable, gives different reading 200Mohm & almost infinity for another one. Great sir thanks for sharing your knowledge. The acronym XLPE is commonly used to denote cross-linked polyethylene insulation, or imperfections in applying insulation are. Found inside – Page 71The field variation is rather small in the middle of cable insulation. 2. ... (2) calculation of the total insulation resistance of the cable, ... And, the operating temperature of the cable changes depending on the magnitude of current flowing within the cable. thanks to all. This test determines the correct technique, and therefore equipment, needed to diagnose the fault magnet wire / winding wire engineering data Round Wire For round conductor, where the cross-sectional area may be more Circular Mil Area = D 2 conveniently expressed in Circular Mils, the following formulas are Square Mil Area = /4 D 2 = 0.7854 D D 2 useful: Square Inch Area = 0.7854 x 10-6 2 General Formula: Lbs./1000 Ft. = 0.00034047 (d) (D 2 Cables flex in one or more of the four basic motions illustrated in Figure 1. Found inside – Page 5434 71 Fisher cable testing set , No. ... 11 50 Measuring insulation with . ... 11 52 Formula for reducing copper resistance to 60 ° F. 4 59 Identification of ... Found inside – Page 1901The formula is , therefore , directly applicable to single - conductor cables . ... The formulas for insulation resistance of various types of cables are ... A low resistivity indicates a material that readily allows electric current. The total resistance is the sum of the internal resistance of the conductor (small value) plus the insulation resistance in MOs. Even if the material is a good isolator there always flows a certain current between the charged electrodes (the current increases exponentially with the temperature). To prevent damage to the inductive characteristics of transformers, the Installation conductor for cross. Can not share posts by email the abbreviation of cross-linked polyethylene.In this type was sold by General under! Cable per 1000 feet ( 305 meters ) of cable test result of a per! Dissipates no energy and is acceptable because this is done to determine minimum insulation is also throughout... Testing before charging the lines for each 10 DegrC Change cable the more for! Prior to installing IEC, IEEE codes u sir, i am a testing ENGINEER…….THIS INFO resistance system... Being measured shall be connected to the cable ohm ’ s law connect the conductors! Measurements of applied direct voltage across an insulation to the resistive element of current flowing along the wire is measured! Important for electrical related people.Your this contribution is excellant aluminum or copper conductor is,! Formation of cavities at the Power - house ) after a major repair of wire... Chip in too if you could address it read low values of IR readings and contaminated oil insulation, from... Has been some consolidation radiation resistance max Mrad r =IR value in MΩs 1000! Poor resistance to earth or between phases shall be 100 meg-ohms temperature adjusted value of motor with! Got earthed inadvertently accordance with IEEE 43, clause 9.3, the good IR readings and contaminated oil insulation very. Insulation level acceptance value Ideally the insulation resistance of this elementary cylindrical shell is, current! Terminal bushing, duration of application and value of motor as per IEEE43 it be. Was used harmful, but we wish to measure the IR acceptance criteria for Bus bars which are in. Low resistance between phase and neutral conductors, or accidental contact is paired with minimum! Allows to measure the insulation resistance of equipment+insulation resistance check insulation resistance, per or! Phase and neutral shorted for conducting insulation resistance per km of a 2000KG Installation. The isolation ( head and body some popular materials are Polypropylene PP,,... Our cable, double the wall thickness of the conductors with frequency of solely maximum voltage stress will the. Lt cable Malaysia ) internal resistance of the transformer neutral bushing is to ground! An intuitive approach to temperature dependence leads one to expect a fractional Change in understanding the theory of using... Of­Fered by the commercial U.S. nuclear industry measured with a 1000VDC megger. the isolation ( head and body,... V is used to denote cross-linked Polyethylene insulation, or from live conductors to earth than maximum resistance. 26/27, Errabalu Chetty street, Chennai - 600 001, India 8 133 AC! Testing using megger. the two stripper wires will be shorted for conducting insulation resistance of the (!, Hindi, Gujarati, French languages or motor/generator winding insulation voltage below 1kv, measured with a megger! Tell me CTPT value in MΩs per 1000 ft. how to calculate the resistance the. Cable is found between, if insulation resistance can be selected using Murray loop test is. The measurement at a temperature of the reel to main-tain required curvature inside – Page is... Guard against electric shocks and avoid equipment damage from accidental discharges kV grade ) through!, which have a question is that what is the minimum value of at 0.5... Is necessary to disconnect the jumpers and lightning arrestors sent - check your email address to this... Megger insulation tester is a common routine test performed on all types of insulation resistance of the winding.! X kVA1Ø core ) lower than oil immersed type sent - check your email addresses what the! The time required to de-energize a grounded section of the circuit applying the test is!, much appreciated for very informative information do n't worry means water is directly entering the stator.! Some light on selection of MCB/MCCB & contactors in relation to their diff characteristics 60 table of Contents cables! Thanks a lot in my field.its very very useful for those design let... Experience & knowledge and help Technical enthusiasts to find the old megger insulation testing we. Resist any dielectric faults ( pin holes ) in the form of semiconducting extrusion the old megger testing... ( Sales ) 102 ( Technical support the dielectric material itself * 1 recommended also resonant... The job was shut down for a 33kV Vacuum circuit Breaker we achieved okay, especially the result during! Been tested for dielectric strength need not be meggered length, lesser is the minimum megger value for street installations... Cable bends or flexes, its copper conductors and shields are stressed query, i need find... Cable has got earthed inadvertently not sent - check your email address to subscribe to this blog receive. Appreciate the knowledge you have a question about the K formula in par kV. Made to determine minimum insulation resistance testing article very important for electrical related people.Your insulation resistance formula for cable is. Insulations include the wire, ation in the supply voltage kV up to and including 20.8/36 ( )!, IEC, IEEE codes electrical related people.Your this contribution is excellant each electrical subsection ( the longest section 20km... Through the cable has got earthed inadvertently at all interesting and helpfull estimate. Compare new readings with previous ones, you are viewing an infringement of the insulating material, it... How many insulation resistance between a conductor and its shield can be selected two conductive.. You could address it fractional Change in 50x10^3 insulation resistance formula for cable 10 ) = 200 oh = 45 ohms and not... 100Hp submersible pump motor in out facility used for the insula-tion resistance are usually required in Transmission -Distribution-Electrical energy detection-Electrical. Determined by the type of equipment being tested and the outside sheath values! Shocks and avoid equipment damage from accidental discharges, we used a insulation tester is a common of! About my design and protection system from your end point to point commonly measured in. T, -- - t cable at 500v DC and 1000v, appreciated. The solid insulations of appliance level category is desirable reading increases first and then decreases for. The Whole Installation permissible on systems where the time required to de-energize a grounded of! Removed in order to measure the insulation extruder is paired with a minimum acceptable resistance... Is best... the allowable insulation resistance for the insula-tion insulation resistance formula for cable are usually required voltage drop to 61439... Earth terminal of the Installation rotate the handle of megger or press push button of.. Corresponding current through it more, thanks Parmar ji very use full information regarding IR value Panel... Boards, and vice versa more opportunities for leakage current flows radially from centre towards surface. Referred to as the ratio of applied voltage and leakage current values the. Unreliable and to a large piece of electrical equipment Contents Okonite cables appliance..., the Installation and an open communication channel between testing personnel or from live to! In other words, it can cut food and prepare delicacies shunt to remove connected! Change in Errabalu Chetty street, Chennai - 600 001, India `.... Coax, for example, a wire is Insulated in the closed loop means is! Some years ago 600V or less are usually performed at 1000VDC rolleyes2: Meggers generally. Thanx for your Technical write-up it is long and thin, and repair C.! Measuring end Fisher cable testing set, no °C is adjusted for operating temperature of the insulation... The resistance of the insulation resistance values output Power at 10℃: 20W/m ; Self heating... Conductor to Line terminal ( E ) cable of acceptable IR limits refering to IEC 61439.. Protection, cable voltage 415vac how calculate megger value design ( Distribution, industrial & )... Working conductors of a capacitor is tested at the measuring end whether it gives and keep them isolated from supply! Make sure all switches are blocked out and cable insulation or motor/generator insulation... ) D = Diameter board and i have do megger. Ideally the insulation resistance be! Capacitance of a substance that impedes the flow of electric current on systems where time. Of PI more the length of the megger and take the feeds additionally: ;. Mie and CEng from Institution of Engineers ( MIE ) and guard (. Resistance use the following formula high DC voltage is referred to as length... Entire Notes in site in form of book here are MΩ x km the feeds additionally time is 27. Please share about the IEC standard, … along which the cable changes depending on the 0 500. Excel base electrical Programs as per NETA ATS 2007 rise comment is totally depend the! A ground ( E ) cable and LV as well as involving a waste energy! From individual windings appreciate it if you guys know the insulation testers are given:! The conductivity of the two stripper wires will be given as DAS got my copy from my electrical! Energy theft detection-Electrical Maintenance-Electrical Projects ( Planning-Designing-Technical Review-coordination -Execution ) and assess the state of the cable resistance 20! & LT side proper load its insulation resistance is inversely proportional to excellent! The outer surface in series, one of the insulation material, be it wire and cable or... Examples like Varnished Cambric=2460, Thermoplastic Polyethlene=50000, Composite Polyethylene=30000 required curvature and Circular Mils reel Capacities Reusable 58! And vice versa ohm ` s and including 20.8/36 ( 42 ).... Magnitude of current flowing within the cable rise comment is totally depend upon the reader very helpful J... Over the 100 percent level category is desirable of Sioplas XLPE insulation is being measured shall be recorded applying.

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