Insulation Resistance (IR) Values March 23, 2012 85 Comments
Introduction: The measurement of insulation resistance is a common routine test performed on all types of electrical wires and cables. 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. The results obtained from IR Test are not intended to b e 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. Even when not required by the end customer, many wire and cable manufacturers use the insulation resistance test to track their insulation manufacturing processes, and spot developing problems before process variables drift outside of allowed limits. limits. Selection of IR Testers (Megger):
Insulation testers with test voltage of 500, 1000, 2500 and 5000 V are available. The recommended ratings of the insulation testers are given below:
Voltage Level 650V 1.1KV 3.3KV 66Kv and Above
IR Tester 500V DC 1KV DC 2.5KV DC 5KV DC
Test Voltage for Meggering:
When AC Voltage is used, The Rule of Thumb is Test Voltage (A.C) = (2X Name Plate Voltage) +1000. When DC Voltage is used (Most used in All Megger), Test Voltage (D.C) = (2X Name Plate Voltage).
Equipment / Cable Rating 24V To 50V 50V To 100V 100V To 240V 440V To 550V 2400V
DC Test Voltage 50V To 100V 100V To 250V 250V To 500V 500V To 1000V 1000V To 2500V
4100V
1000V To 5000V
Measurement Range of Megger: Test voltage
250V DC 500V DC 1KV DC 2.5KV DC 5KV DC
easurement ange
0MΩ to 250GΩ 0MΩ to 500GΩ 0MΩ to 1TΩ 0MΩ to 2.5TΩ 0MΩ to 5TΩ
Precaution while Meggering: Before Meggering:
Make sure that all connections in the test circuit are tight. 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.
During Meggering:
Make sure when testing for earth, that the far end of the conductor is not touching, otherwise the test will show faulty insulation when such is not actually the case. Make sure that the earth used when testing for earth and open circuits is a good g ood one otherwise the test will give wrong information Spare conductors should not be meggered when other working conductors of the same cable are connected to the respective circuits.
After completion of cable Meggering:
Ensure that all conductors have been reconnected properly. Test the functions of Points, Tracks & Signals connected throu gh the cable for their correct response. In case of signals, aspect should be verified personally. In case of points, verify positions at site. Check whether an y polarity of any feed taken through the cable has got earthed inadvertently.
Safety Requirements for Meggering:
All equipment under test MUST be disconnected and isolated. Equipment should be discharged (shunted or shorted out) for at least as long as the test voltage was applied in order to be absolutely safe for the person conducting the test. Never use Megger in an explosive atmosphere.
4100V
1000V To 5000V
Measurement Range of Megger: Test voltage
250V DC 500V DC 1KV DC 2.5KV DC 5KV DC
easurement ange
0MΩ to 250GΩ 0MΩ to 500GΩ 0MΩ to 1TΩ 0MΩ to 2.5TΩ 0MΩ to 5TΩ
Precaution while Meggering: Before Meggering:
Make sure that all connections in the test circuit are tight. 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.
During Meggering:
Make sure when testing for earth, that the far end of the conductor is not touching, otherwise the test will show faulty insulation when such is not actually the case. Make sure that the earth used when testing for earth and open circuits is a good g ood one otherwise the test will give wrong information Spare conductors should not be meggered when other working conductors of the same cable are connected to the respective circuits.
After completion of cable Meggering:
Ensure that all conductors have been reconnected properly. Test the functions of Points, Tracks & Signals connected throu gh the cable for their correct response. In case of signals, aspect should be verified personally. In case of points, verify positions at site. Check whether an y polarity of any feed taken through the cable has got earthed inadvertently.
Safety Requirements for Meggering:
All equipment under test MUST be disconnected and isolated. Equipment should be discharged (shunted or shorted out) for at least as long as the test voltage was applied in order to be absolutely safe for the person conducting the test. Never use Megger in an explosive atmosphere.
Make sure all switches are blocked out and cable ends marked properly for safety. Cable ends to be isolated shall be disconnected from the supply and protected from contact to supply, or ground, or accidental contact. Erection of safety barriers with warning signs, and an open commu nication channel between testing personnel. Do not megger when humidity is more than 70 %. Good Insulation: Megger reading increases first then remain constant. Bad Insulation: Megger reading increases first and then decreases. Expected IR value gets on Temp. 20 to 30 decree centigrade. If above temperature reduces by 10 degree centigrade, IR values will increased b y two times. If above temperature increased by 70 degree centigrade IR values decreases by 700 times.
How to use Megger:
Meggers is equipped with three connection Line Terminal (L), Earth Terminal (E) and Guard Terminal (G).
Resistance is measured between the Line and Earth terminals, where current will travel through coil 1. The “Guard” terminal is provided for special testing situations where one resistance must be isolated from another. Let’s us check one situation where the insulation resistance is to be tested in a two-wire cable. To measure insulation resistance from a conductor to the o utside of the cable, we need to connect the “Line” lead of the megger to one of the conductors and connect the “Earth” lead of the megger to a wire wrapped around the sheath of the cable.
In this configuration the Megger should read the resistance between one conductor and the outside sheath. We want to measure Resistance between Conductor- 2To Sheaths but Actually Megger measure resistance in parallel with the series combination of conductor-to-conductor resistance (R c1-c2 c1-c2) and the first conductor to the sheath (R c1-s c1-s).
If we don’t care about this fact, we can proceed with the test as configured. If we desire
to measure only the only the resistance between the second conductor and the sheath (R c2-s c2-s), then
we need to use the megger’s “Guard” terminal.
Connecting the “Guard” terminal to the first conductor places the two conductors at almost equal potential . With little or no voltage between them, the insulation resistance is nearly infinite, and thus there will be no current between the between the two conductors. Consequently, the Megger’s resistance indication will be based exclusively on the current
through the second conductor’s insulation, through the cable sheath, and to the wire wrapped around, not the current leaking through the first conductor’s insulation.
The guard terminal (if fitted) acts as a shunt to re move the connected element from the measurement. In other words, it allows you to be selective in evaluating certain specific components in a large piece of electrical equipment. For example consider a two core cable with a sheath. As the diagram d iagram below shows there are three resistances to be considered.
If we measure between core B and sheath without a connection to the guard terminal some current will pass from B to A and from A to the sheath. Our measurement would be be low. By connecting the guard terminal to A the two cable cores will be at very nearly the same potential and thus the shunting effect is eliminated.
(1) IR Values For Electrical Apparatus & Systems: (PEARL Standard / NETA MTS-1997 Table 10.1) Max.Voltage Rating Of Equipment
250 Volts 600 Volts 5 KV 8 KV 15 KV 25 KV 35 KV 46 KV 69 KV
Megger Size
500 Volts 1,000 Volts 2,500 Volts 2,500 Volts 2,500 Volts 5,000 Volts 15,000 Volts 15,000 Volts 15,000 Volts
Min.IR Value
25 MΩ 100 MΩ 1,000 MΩ 2,000 MΩ 5,000 MΩ 20,000 MΩ 100,000 MΩ 100,000 MΩ 100,000 MΩ
One Meg ohm Rule for IR Value for Equipment:
Based upon equipment rating:
< 1K V = 1 MΩ minimum >1KV = 1 MΩ /1KV
As per IE Rules-1956:
At a pressure of 1000 V applied between each live conductor and earth for a period of one minute the insulation resistance of HV installations shall be at least 1 Mega ohm or as specified by the Bureau of Indian Standards. Medium and Low Voltage Installations- At a pressure of 500 V applied between each live conductor and earth for a period of one minute, the insulation resistance of medium and low voltage installations shall be at least 1 Mega ohm or as specified by the Bureau of Indian Standards] from time to time.
As per CBIP specifications the acceptable values are 2 Mega ohms per KV
(2) IR Value for Transformer:
Insulation resistance tests are made to determine insulation resistance from individual windings to ground or between individual windings. Insulation resistance tests are commonly measured directly in megohms or may be calculated from measurements of applied voltage and leakage current. The recommended practice in measuring insulation resistance is to alwa ys ground the tank (and the core). Short circuit each winding of the transformer at the bushing terminals.
Resistance measurements are then made between each winding and all other windings grounded.
Windings are never left floating for insulation resistance measurements. Solidly grounded winding must have the ground removed in order to measure the insulation resistance of the winding grounded. If the ground cannot be removed, as in the case of some windings with solidly grounded neutrals, the insulation resistance of the winding canno t be measured. Treat it as part of the grounded section of the circuit. We need to test winding to winding and winding to ground ( E ).For three phase transformers, We need to test winding ( L1,L2,L3 ) with substitute Earthing for Delta transformer or winding ( L1,L2,L3 ) with earthing ( E ) and neutral ( N ) for wye transformers. IR Value for Transformer
(Ref: A Guide to Transformer Maintenance by. JJ. Kelly. S.D Myer) Transformer Formula 1 Phase Transformer IR Value (MΩ) = C X E /
(√KVA) IR Value (MΩ) = C X E (P-n) / (√KVA) IR Value (MΩ) = C X E (P-P) / (√KVA)
3 Phase Transformer (Star) 3 Phase Transformer (Delta) Where C= 1.5 for Oil filled T/C with Oil Tank, 30 for Oil filled T/C without Oil Tank or Dry Type T/C.
Temperature correction Factor (Base 20°C):
Temperature correction Factor Correction O O C F Factor 0 32 0.25 5 41 0.36
10 15 20 30 40 50
50 59 68 86 104 122
0.50 0.720 1.00 1.98 3.95 7.85
Example: For 1600KVA, 20KV/400V,Three Phase Transformer
IR Value at HV Side= (1.5 x 20000) / √ 1600 =16000 / 40 = 750 MΩ at 200C 0 IR Value at LV Side = (1.5 x 400 ) / √ 1600= 320 / 40 = 15 MΩ at 20 C 0 IR Value at 30 C =15X1.98= 29.7 MΩ
Insulation Resistance of Transformer Coil Transformer Megger Size Coil Voltage
0 – 600 V 600 V To 5KV 5KV To 15KV 15KV To 69KV
1KV 2.5KV 5KV 5KV
Min.IR Value Liquid Filled T/C
Min.IR Value Dry Type T/C
100 MΩ 1,000 MΩ 5,000 MΩ 10,000 MΩ
500 MΩ 5,000 MΩ 25,000 MΩ 50,000 MΩ
IR Value of Transformers: Voltage
Test Voltage (DC) LV side 415V 500V Up to 6.6KV 500V 6.6KV to 11KV 500V 11KV to 33KV 1000V 33KV to 66KV 1000V 66KV to 132KV 1000V 132KV to 1000V 220KV
Test Voltage Min IR (DC) HV Value side 100MΩ 2.5KV 200MΩ 2.5KV 400MΩ 2.5KV 500MΩ 5KV 600MΩ 5KV 600MΩ 5KV 650MΩ 5KV
Steps for measuring the IR of Transformer:
Shut down the transformer and disconnect the jumpers and lightning arrestors. Discharge the winding capacitance. Thoroughly clean all bushings Short circuit the windings.
Guard the terminals to eliminate surface leakage over terminal bushings. Record the temperature. Connect the test leads (avoid joints). Apply the test voltage and note the reading. The IR. Value at 60 seconds after application of the test voltage is referred to as the Insulation Resistance of the transformer at the test temperature. The transformer Neutral bushing is to be disconnected from earth during the test. All LV surge diverter earth connections are to be disconnected during the test. Due to the inductive characteristics of transformers, the insulation resistance reading shall not be taken until the test current stabilizes. Avoid meggering when the transformer is under vacuum.
Test Connections of Transformer for IR Test (Not Less than 200 MΩ):
Two winding transformer:
1. (HV + LV) – GND 2. HV – (LV + GND) 3. LV – (HV + GND)
Three winding transformer:
1. 2. 3. 4.
HV – (LV + TV + GND) LV – (HV + TV + GND) (HV + LV + TV) – GND TV – (HV + LV + GND)
Auto transformer (two winding):
1. (HV + LV) – GND
Auto Transformer (three winding):
1. (HV + LV) – (TV + GND) 2. (HV + LV + TV) – GND 3. TV – (HV + LV + GND) For any installation, the insulation resistance measured shall not be less than:
HV – Earth 200 M Ω LV – Earth 100 M Ω HV – LV 200 M Ω
Factors affecting on IR value of Transformer
The IR value of transformers are influenced b y
surface condition of the terminal bushing quality of oil quality of winding insulation temperature of oil duration of application and value of test voltage
(3) IR Value for Tap Changer:
IR between HV and LV as well as windings to earth. Minimum IR value for Tap changer is 1000 ohm per volt service voltage
(4) IR Value for Electric motor: For electric motor, we used a insulation tester to measure the resistance of motor winding with earthing ( E ).
For rated voltage below 1KV, measured with a 500VDC Megger. For rated voltage above 1KV, measured with a 1000VDC Megger. In accordance with IEEE 43, clause 9.3, the following formula should be applied. Min IR Value (For Rotating Machine) =(Rated voltage (v) /1000) + 1
As per IEEE 43 Standard 1974,2000
IR Value in MΩ IR (Min) = kV+1
For most windings made before about 1970, all field windings, and others not described below IR (Min) = 100 MΩ For most dc armature and ac windings built after about 1970 (form wound coils) IR (Min) = 5 MΩ For most machines with random wound stator coils and form-wound coils rated below 1kV
Example-1: For 11KV, Three Phase Motor.
IR Value =11+1=12 MΩ but as per IEEE43 It should be 100 MΩ
Example-2: For 415V,Three Phase Motor
IR Value =0.415+1=1.41 MΩ but as per IEEE43 It should be 5 MΩ.
As per IS 732 Min IR Value of Motor=(20XVoltage(p-p/(1000+2XKW))
IR Value of Motor as per NETA ATS 2007. Section 7.15.1 Motor Name Plate (V) 250V 600V 1000V 2500V 5000V 8000V 15000V 25000V 34500V
Test Voltage Min IR Value 25 MΩ 500V DC 1000V DC 100MΩ 1000V DC 100MΩ 1000V DC 500MΩ 2500V DC 1000MΩ 2500V DC 2000MΩ 2500V DC 5000MΩ 5000V DC 20000MΩ 15000V DC 100000MΩ
IR Value of Submersible Motor: IR Value of Submersible Motor Motor Out off Well (Without IR Value Cable) 20 MΩ New Motor 10 MΩ A used motor which can be reinstalled Motor Installed in Well (With Cable) 2 MΩ New Motor 0.5 MΩ A used motor which can be reinstalled
(5) IR Value for Electrical cable and wiring:
For insulation testing, we need to disconnect from panel or equipment and keep them isolated from power supply. The wiring and cables need to test for each other ( phase to phase ) with a ground ( E ) cable. The Insulated Power Cable Engineers Association (IPCEA) provides the formula to determine minimum insulation resistance values.
R = K x Log 10 (D/d)
R =IR Value in MΩs per 1000 feet (305 meters) of cable. K =Insulation material constant.( Varnished Cambric=2460, Thermoplastic Polyethlene=50000,Composite Polyethylene=30000) D =Outside diameter of conductor insulation for single conductor wire and cable
( D = d + 2c + 2b diameter of single conductor cable ) d – Diameter of conductor c – Thickness of conductor insulation b – Thickness of jacket insulation
HV test on new XLPE cable (As per ETSA Standard) Application
Test Voltage Min IR Value 100 MΩ New cables – Sheath 1KV DC 1000 MΩ New cables – Insulation 10KV DC 10 MΩ After repairs – Sheath 1KV DC 1000MΩ After repairs – 5KV DC Insulation 11kV and 33kV Cables between Cores and Earth (As per ETSA Standard) Application
Test Voltage Min IR Value 1000 MΩ 11KV New cables – Sheath 5KV DC 100 MΩ 11KV After repairs – Sheath 5KV DC 33KV no TF’s connected 1000 MΩ 5KV DC 33KV with TF’s connected. 5KV DC 15MΩ
IR Value Measurement (Conductors to conductor (Cross Insulation))
The first conductor for which cross insulation is being measured shall be connected to Line terminal of the megger. The remaining cond uctors looped together (with the help of crocodile clips) i. e. Conductor 2 and onwards, are connected to Earth terminal of megger. Conductors at the other end are left free. Now rotate the handle of megger or press push button of megger. The reading of meter will show the cross Insulation between conductor 1 and rest of the conductors. Insulation reading shall be recorded. Now connect next conductor to Line terminal of the megger & connect the remaining conductors to earth terminal of the megger and take measurements.
IR Value Measurement (Conductor to Earth Insulation)
Connect conductor under test to the Line terminal of the megger. Connect earth terminal of the megger to the earth. Rotate the handle of megger or press push button of megger. The reading of meter will show the insulation resistance of the conductors. Insulation reading shall b e recorded after applying the test voltage for about a minute till a steady reading is obtained.
IR Value Measurements:
If during periodical testing, insulation resistance of cable is found between 5 and 1 MΩ /km at buried temperature, the subject cable should be programmed for replacement. If insulation resistance of the cable is found between 1000 and 100 KΩ /km, at buried temperature, the subject cable should be replaced urgently within a year. If the insulation resistance of the cable is found less than 100 kilo ohm/km., the subject cable must be replaced immediately on emergency basis.
(6) IR Value for Transmission / Distribution Line: Equipment. S/S .Equipments EHVLines. H.T. Lines. LT / Service Lines.
Megger Size Min IR Value 5000MΩ 5 KV 10MΩ 5 KV 5MΩ 1 KV 5MΩ 0.5 KV
(7) IR Value for Panel Bus:
IR Value for Panel = 2 x KV rating of the panel.
Example, for a 5 KV panel, the minimum insulation is 2 x 5 = 10 MΩ.
(8) IR Value for Substation Equipment: Generally meggering Values of Substation Equipments are. .Typical IR Value of S/S Equipments Equipment Megger Size IR Value(Min) 1000 MΩ (Phase-Earth) 5KV,10 KV 1000 MΩ Circuit Breaker (Phase-Phase) 5KV,10 KV 50 MΩ Control Circuit 0.5KV 1000 MΩ (Pri-Earth) 5KV,10 KV 50 MΩ CT/PT (Sec-Phase) 5KV,10 KV 50 MΩ Control Circuit 0.5KV 1000 MΩ (Phase-Earth) 5KV,10 KV Isolator 1000 MΩ (Phase-Phase) 5KV,10 KV
Control Circuit 0.5KV L.A (Phase-Earth) 5KV,10 KV Electrical Motor (Phase-Earth) 0.5KV LT Switchgear (Phase-Earth) 0.5KV LT Transformer (Phase-Earth) 0.5KV
50 MΩ 1000 MΩ 50 MΩ 100 MΩ 100 MΩ
IR Value of S/S Equipments As per DEP Standard IR Value at IR Value at Equipment Meggering Commissioning Maintenance
Switchgear Cable(min 100 Meter) Motor & Generator Transformer Oil immersed Transformer Dry Type Fixed Equipments/Tools Movable Equipments Distribution Equipments Circuit Breaker
Relay
HV Bus LV Bus LV wiring HV & LV
Time (MΩ) 200 MΩ 20 MΩ 5 MΩ
Time(MΩ) 100 MΩ 10 MΩ 0.5 MΩ
(10XKV) / KM (KV) / KM
Phase-Earth HV & LV
10(KV+1)
2(KV+1)
75 MΩ
30 MΩ
HV LV Phase-Earth
100 MΩ 10 MΩ 5KΩ / Volt
25 MΩ 2 MΩ 1KΩ / Volt
Phase-Earth Phase-Earth
5 MΩ 5 MΩ
1MΩ 1MΩ
Main Circuit Control Circuit D.C CircuitEarth LT CircuitEarth LT-D.C Circuit LT-LT
2 MΩ / KV 5MΩ 40MΩ 50MΩ 40MΩ 70MΩ
(9) IR Value for Domestic /Industrial Wiring:
A low resistance between phase and neutral conductors, or from live conductors to earth, will result in a leakage current. This cause d eterioration of the insulation, as well as involving a waste of energy which would increase the running costs of the installation. The resistance between Phase-Phase-Neutral-Earth must never be less than 0.5 M Ohms for the usual supply voltages. In addition to the leakage current due to insulation resistance, there is a further current leakage in the reactance of the insulation, because it acts as the dielectric of a capacitor. This current dissipates no energy and is not harmful, but we wish to measure the
resistance of the insulation, so DC Voltage is used to prevent reactance from being included in the measurement . 1 Phase Wiring:
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 con nected together, with lamps and other equipment disconnected, but with fuses in, circuit breakers closed and all circuit switches closed. Where two-way switching is wired, only one of the two stripper wires will be tested. To test the other, both two-way switches should be o perated and the system retested. If desired, the installation can be tested as a who le, when a value of at least 0.5 M Ohms should be achieved.
3 Phase Wiring:
In the case of a very large installation where there are many earth paths in parallel, the reading would be expected to be lower. If this happens, the installation should be subdivided and retested, when each part must meet the minimum requirement.
The IR tests must be carried out between Phase-Phase-Neutral-Earth with a minimum acceptable value for each test of 0.5 M Ohms.
IR Testing for Low voltage circuit voltage Test voltage IR Value(Min) 0.25MΩ Extra Low Voltage 250V DC 0.5MΩ Up to 500 V except for 500 V DC above 500 V To 1KV 1000 V DC 1.0MΩ
Min IR Value = 50 & Plugs).
MΩ / No of Electrical outlet. (All Electrical Points with fitting
Min IR Value = 100 fitting & Plugs).
MΩ / No of Electrical outlet. (All Electrical Points without
Required Precautions:
Electronic equipment like electronic fluorescent starter switches, touch switches, dimmer switches, power controllers, delay timers could be damaged b y the application of the high test voltage should be disconnected. Capacitors and indicator or pilot lamps must be d isconnected or an inaccurate test reading will result. Where any equipment is disconnected for testing purposes, it must be subjected to its own insulation test, using a voltage which is not likel y to result in damage. The result must conform with that specified in the British Standard concerned, or be at least 0.5 M Ohms if there is no Standard. About these ads
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About Jignesh.Parmar Jignesh Parmar has completed his B.E(Electrical) from Gujarat University. He has more than 1 1 years experience in Power Transmission-Power Distribution-Electrical energy theft detectionElectrical Maintenance-Electrical Projects(Planning-Designing-coordination-Execution). He is Presently associate with one of the leading business group as a Assistant Manager at Ahmedabad,India. He is Freelancer Programmer of Advance Excel and design useful Excel Sheets of Electrical Engineering as per IS,NEC,IEC,IEEE codes. He is technical Author for "Electrical Mirror" and "Electrical India" Magazines. He is Technical Blogger and Familiar with English, Hindi, Gujarati, French languages. He wants to Share his experience & knowledge and help technical enthusiasts to find suitable solutions and updating themselves on various Engineering Topics.
85 Responses to I nsulati on Resistance (I R) Valu es
1.
modupalli says: March 23, 2012 at 10:16 pm
Outstanding Stuff…. Thanks For Sharing.. Reply
o
Deja jacob says:
March 25, 2014 at 1:01 am WHAT ARE THE GOOD RESISTANCE VALUE? Reply
Jignesh.Parmar says:
March 25, 2014 at 4:10 pm
GOOD means…. ALL suspected value according to equipments are already given…
2.
vilas K. says: April 11, 2012 at 8:30 am Dear Sir Hats Off !! & many thanx for your invaluable contribution in enriching the experience of Elect. Engineers & making them available the fabulous data at a glance.. Pl keep posted. If U can throw some light on selection of MCB/MCCB & contactors in relation to their diff characteristics. Reply
o
Jignesh.Parmar says: April 11, 2012 at 2:19 pm You can find Type of MCB/MCCB and Char of All type of Contactor from ELECTRICAL NOTES page of this Blog Reply
3.
varghese says: April 15, 2012 at 12:25 pm
dear sir… is a great work…. thanks could u pls explain the effects of rise in temperature on insulation resistance of transformer.
Reply
4.
Barun Majumder says: May 7, 2012 at 10:48 am Dear sir many many thanks for sharing valuable article of electrical engineering . I want to know more about electrical design (Distribution, industrial & commercial ) and protection system from your end point to point . If you have any book/site for those design please let me know the name. I am working as a design engineer but i am not enough confident about my design and protection system. i want your valuable assistance in this field . Thanking you Yours faithfully Barun Majumder Kolkata Reply
5.
kumereshan P S says: May 13, 2012 at 4:17 am Sir, great work,i want to know the IS standards for IR value of Sub station equipment With regards Kumereshan Reply
anand says:
o
October 5, 2012 at 8:19 am thank for good infrm abot elecyrhghc Reply
6.
Tuulia Paloranta says: May 29, 2012 at 5:49 am Honestly i am not quite good on electric thing and this one is very good for me to study so well and learn a lot many thanks for this article. Reply
7.
keyur says: June 8, 2012 at 2:53 pm Thanks for sharing your valuable exp. and it is very helpful for me because I am diploma holder and I am working in gulf country as electrical supervisor so it is useful for me and Thanks keyur Reply
8.
MANOHAR says: June 14, 2012 at 5:20 am Dear sir I need calculation formula of IR Values of an elect drives Reply
9.
Madanmohan says: June 16, 2012 at 5:50 am Wonderful explanation. Really very much useful document. Thnak you very much Reply
10.
sathesh says:
July 9, 2012 at 5:59 pm Very nice sir.. Thanku.. Reply
11.
rehan says: July 13, 2012 at 9:58 pm good information, thanks for your time. Reply
12.
custom milagros says: July 15, 2012 at 4:20 pm 2 thumbs up. Reply
13.
Gurmeet Singh says: July 20, 2012 at 4:49 am Very -2 Thanks sir Reply
14.
preeti says: July 25, 2012 at 11:52 am thanks, very good information Reply
15.
osarenkhoe nosa glory says:
August 11, 2012 at 9:15 am this is absolutely nice. a well written document. thanks. Reply
16.
Naveen says: August 12, 2012 at 6:23 am Thank you Sir, much appreciated Reply
17.
A. Hasasn says: August 12, 2012 at 2:15 pm Dear Sir; Really your this article is very very important for electrical related people.Your this contribution is excellant. A lot of thanks sir. Kind Regardrs Reply
18.
K.M.Pandey says: August 18, 2012 at 5:04 am Respected Sir. This article very important and useful for all those person who a re related with Electrical field. Thanks a lot for sharing your knowledge with all people. Really you are nice and gentleman. With regards, K.M.Pandey, Reply
o
subodh kumar pandey says:
August 26, 2012 at 1:20 pm very very important for electrical engineers. lot of thanks Reply
19.
ahmed nawaz says: September 21, 2012 at 3:40 pm Ch.Ahmed Nawaz thanks sir for giving very usefull information. Reply
20.
radhakishan pawar says: September 30, 2012 at 6:28 am thanks sir i have no word to explain how much it is useful to student.
thanks again…… Reply
21.
THAKOR SANJAY says: October 5, 2012 at 1:17 pm
I AM A TESTING ENGINEER…….THIS I NFO. IS VERY USEFUL FOR ME VERY VERY THANKS FOR THIS … Reply
22.
Vilas G. says: October 11, 2012 at 11:01 am Thanks . valuable note for electrical engineers.
Reply
23.
Steve Arreola says: October 23, 2012 at 8:44 pm Thank you much for taking the time to share this information Reply
24.
Mr. Judy Diano says: October 31, 2012 at 11:45 am Thank you so much,for sharing Sir, I learned a lot of your link GOD BLESS Reply
25.
arshad says: November 30, 2012 at 6:23 pm thanks for beautiful notes Reply
26.
Jet Paliangayan says: December 3, 2012 at 12:11 pm how to do IR test for single core pvc/xlpe/pvc cables Reply
27.
jamestryre says: December 12, 2012 at 2:49 am great info, thx
Reply
28.
Thiyaga says: December 19, 2012 at 10:41 am Incredible work. Hats off for your awesome articles. pl keep posting more and more Reply
29.
sambasivarao chagantipati says: December 25, 2012 at 7:46 pm Very useful information Reply
30.
rohtash verma( Himachal pradesh) says: December 29, 2012 at 2:02 am Thanks parmar ji very use full information regarding IR value of electric motors Reply
31.
M.Zaman says: January 8, 2013 at 10:56 am thanks for valuable information. Reply
32.
FELIX Jr. says: January 10, 2013 at 7:44 am
Please, you must also include here the Polarization Index (PI) as well for it’s significance and explain why it is required with respect to the IR test being done on the electrical equipment and the electrical cables and installations, as an additional information for the new commissioning engineers and enthusiasts. Supressing other comments are not at all interesting and helpfull. Reply
Jignesh.Parmar says:
o
January 10, 2013 at 2:38 pm Yes You are right PI value is as important as IR Value specially HV Equipments. Here I gave only Overview of IR Testing and it’s value. To rise comment is totally depend upon the reader. In near future I will definitely cover the Topic o f PI. Reply
deepak parmar says:
June 6, 2013 at 12:18 pm I want to know the acceptable leakage current values in the HV testing as per IEC standards. And thanks for the info provided above
33.
sateesh says: January 21, 2013 at 11:18 am excellent explanation about IR test thanks a lot. Reply
34.
vincent says: February 4, 2013 at 7:23 pm
Good knowledge.thank you. Reply
35.
Anderson says: February 6, 2013 at 5:41 pm Excelente trabajo, quiero saber cuales son las norma s que rigen estas pruebas y si existe alguna estandarización de resultados. Gracias Reply
36.
Debra Scriver says: February 11, 2013 at 10:53 pm Thanks for such a great article. Very interesting an d informative. Thanks Buddy Reply
37.
Diganta ku. Ray says: February 23, 2013 at 3:12 pm Thank you so much sir,this help me a lot in my field.its very very useful for those are in electrical line. Reply
38.
JAYESH PATEL says: February 28, 2013 at 4:57 am how many Insulation Resistance of the Whole Installation permissible ? how many Insulation Resistance Between Conductors ? how many Insulation Resistance Between Each Conductor & Earth ? Reply
39.
honest forex signals says: March 4, 2013 at 5:26 am Hello very nice blog!! Man .. Excellent .. Amazing .. I will bookmark your web site and take the feeds additionally? I am glad to find numerous helpful info here in the put up, we want work out more strategies on this regard, thank you for sharing. ..... Reply
40.
fayyaz says: March 10, 2013 at 10:12 pm thks good information can you mail me how to check insulation of dc 24 volt system. also i want to know how insulation monitor works. Reply
41.
khan wasim says: March 11, 2013 at 5:01 pm Thanks a lot Reply
42.
sonu kumar says: March 14, 2013 at 2:40 pm thanks for this valueable data. Reply
43.
Ashok O Kale Kale says: March 21, 2013 at 12:05 pm Thanx . Reply
44.
DEBASHISH BHATTACHARYA says: April 2, 2013 at 5:10 pm Excellent information. Really appreciate the knowledge you have shared with readers. Sir can you pls tell me what should be minimum value of IR for PVC make busboot used for 11 KV , 22 KV , 33 KV and 66 KV. Regards Debashish Bhattacharya Reply
45.
Gerald says: April 3, 2013 at 10:50 am
Thanks for sharing… Reply
46.
CPR vittal says: May 1, 2013 at 12:46 pm excellent article. the formula for insulation resistance of a cable per 1000 ft. how to calculate it per meter or per feet. pl explain Reply
47.
jigyesh sharma says: May 8, 2013 at 1:49 am what precautions i should take when CT is connected in HT board and i have do megger.? Reply
48.
ibnu says: May 11, 2013 at 2:53 am 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. why? can accept the value? Reply
49.
ibnu says: May 11, 2013 at 2:57 am can 11kv cable, meggar at 1kv only, during before & after hipot test? (hipot at 30.5kv) Reply
50.
parveen kumar says: May 11, 2013 at 2:33 pm dear sir i want to know why used in transformer secondary side very thin wire Reply
51.
FELIX Jr. says: May 12, 2013 at 4:57 am
Yes, you can use 1kV DC- MEGGER TESTER prior to HIPOT Testing if your electrical cable is rated 11kV and HIGHER and if it has 130 % rated insulation. After HIPOT test, if successful, you can megger it again with 1kV only at no more than 1 minute just to make sure no damage has occurred during and after HIPOT TEST. By FMSJr. / Abu Dhabi, UAE Reply
52.
Nasurudheen Kamal Basha says: May 13, 2013 at 9:22 am Useful stuff.. Thanks for sharing!! Reply
53.
MOHAMMAD says: June 17, 2013 at 11:02 am THANKS ALOT VERY GREATFUL INFO Reply
54.
Pushkar Singh says: June 23, 2013 at 11:12 am Thanks for sharing excellent information. Pushkar Singh ONGC Reply
55.
A V N Phanindra says: July 4, 2013 at 7:01 am thank u so much sir its very brief and simple to understand clearly. Reply
56.
ASMA says: July 20, 2013 at 10:16 am WHAT WOULD BE THE MEGGAR REULT OF A GOOD COND ITION 25 KVA TRANSFORMER? I WILL BE OBLIGED..KINDLY HELP ME. Reply
FELIX Jr. says:
o
July 21, 2013 at 5:29 am GOOD DAY ! Your posted question about the MEGGER result for a good condition for 25kVA Transformer is very general as you did not specify the input and output voltages of this electrical equipment an d if it is oil immersed or dry type. At anyrate, assuming it’s oil filled step-up transformer, outdoor pole mounted, for a good IR result for primary winding, normall y it should not be less
than 500Megaohm and the secondary winding’s IR reading should be not less
than 300Megaohm with respect to earth and higher between windings. Again, these are assumptions only and the higher the voltage rating of the transformer the higher IR reading should result. Defective insulations will read low values of IR readings and contaminated oil insulation, for oil immersed type transformers. For dry type Transfomers, the good IR readings of the windings are also in that vicinity but lower than oil immersed type. Reply
57.
J.R Bohra says: July 20, 2013 at 11:48 pm very very helpful Thanks J,R Bohra Unique Engineer Noida Reply
58.
Diptiranjan Nayak says:
July 23, 2013 at 5:10 am Thank u sir, I am clear about IR value. Reply
59.
raghav says: July 26, 2013 at 4:37 am dear sir, i need more information about how to calculate ir values and what principle it requires to calculate ir values? Reply
60.
Musa says: August 22, 2013 at 3:25 am Anybody can answer my query? We have 25kV AC system for Overhead Line Equipment (OHE). This system is installed for Electrified Train system (Railway project). We have conduct IR testing before charging the lines for each electrical subsection (the longest section about 20km). The result we achieved 0.5MOhm – 5MOhm (taken during night time) and 200MOhm – 700MOhm (taken during night time). The temperature during night time is around 27 – 28 degree Celsius (in Malaysia). We injecting megger size 5kV and result achieved as above. As mentioned in the article (i think it is similar to our system – IR value for transmission/ distribution line) which is stated Min. IR values shall be 10MOhm. Is it the result we achieved okay, especially the result taken during night time? Reply
61.
sampath says: September 3, 2013 at 6:28 am
thank for more information now i harry to check insulation resistance long 132Kv transmission line & will have called you after testing Reply
62.
SYAM says: September 4, 2013 at 9:00 am Dear Jignesh,
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”. Hope you will reply Regards SYAM Reply
63.
Sekar Ram says: September 12, 2013 at 12:58 pm Mr Jignesh This is one of the greatest selfless efforts I have seen. This is pure social service. Hats off!! Reply
64.
Stephen says: September 13, 2013 at 1:46 pm Hello. Question, if we have 5 conductors per phase on a lugs and we want to megger the groups, ie: phase to phase and phase to ground and the readings are above 1 M ohm, is that OK? We had previously meggered all the cabels individually prior to installing. The job was shut down for a while, and this is for a precaution, prior to re-energizing.
Reply
65.
vijay says: September 25, 2013 at 11:39 am dear jignesh sir, Can i have the entire notes in site in form of book? How much does it cost? Reply
66.
vijayendrarao kv says: November 2, 2013 at 10:48 am very very useful and very thanks for made me doubt clear.. Reply
67.
Michel says: November 29, 2013 at 10:49 am thanks Bro that is too goooooooooooooood for us Reply
68.
ESAKKIPANDI says: December 5, 2013 at 5:16 am the explanation is excellent Reply
69.
rahul jangme says: January 5, 2014 at 2:41 pm
thank you sir Reply
70.
ali says: January 12, 2014 at 1:18 pm thank you so much Dr Reply
71.
Doma Hudu says: February 8, 2014 at 2:26 pm thank sir. I need a copy via my e-mail. please am wait for your response Sir. Reply
72.
Srinivasan says: February 12, 2014 at 3:40 am Thank you sir. Useful detail information. Reply
73.
aby says: February 20, 2014 at 10:17 am Sir, appreciate your ideas and procedures. May i know ,whether there is an y necessity or mandatory rules saying that the speaker cables to be meggered? if yes,then what should be the applied voltage? Reply
74.
roop says: February 23, 2014 at 6:17 am dear mr Parmar first of all thanks for sharing the information Reply
75.
roop says: February 23, 2014 at 6:22 am we are building a 9 km road tunnel, we usually facing problem with ht cable, whenever it is damaged it took 3 to4 hour for jointing, lot of production loss please advise an y alternate means of transmission of ht cable or any ht joint available around the world to do the jointing quickly. Reply
76.
Felix Jr San Buenaventura says: March 26, 2014 at 4:44 am THESE ARE GOOD INFORMATION AND REFERENCE FOR ALL E LECTRICAL ENGINEERS AND COMMISSIONING ENGINEERS BE IT IN DESIGN ENGINEERING OR IN COMMISSIONING WORKS OF PROJECTS RELATED TO ELECTRICAL POWER GENERATION, TRANSMISSION AND IN DISTRIBUTION SYSTEMS THE WORLD OVER. TIKE !, SALAMAT PO !, GRACIAS !, QZI QZI !, TERIMA KASIH ! Reply
77.
SB says: March 27, 2014 at 7:26 am Thank you ever so much! For sharing such good info, extremely relevant. Reply
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About Jignesh Parmar:
Jignesh Parmar has completed his B.E(Electrical) from Gujarat University. He is member of Institution of Engineers (MIE),India. Membership No:M-1473586.He has more than 12 years experience in Transmission -Distribution-Electrical Energy theft d etection-Electrical Maintenance-Electrical Projects (Planning-Designing-Technical Review-coordination Execution). He is Presently associate with one of the leading business group as a Assistant Manager at Ahmedabad,India. He has published numbers of Technical Articles in "Electrical Mirror", "Electrical India", "Lighting India", "Industrial Electrix"(Australian Power Publications) Magazines. He is Freelancer Programmer of Advance Excel and design useful Excel base Electrical Programs as per IS, NEC, IEC,IEEE codes. He is Tech nical Blogger and Familiar with English, Hindi, Gujarati, French languages. He wants to Share his experience & Knowledge and help technical enthusiasts to find suitable solutions and updating themselves on various Engineering Topics. Follow Blog via Email
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