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Insulation Resistance (IR) Values

MARCH 23, 2012 95 COMMENTS(HTTP://ELECTRICALNOTES.WORDPRESS.COM/2012/03/23/INSULATION-RESISTANCE-IR-VALUES/#COMMENTS)

Introduction:

The measurement of insulation resistance is a common routine test performed on all types ofelectrical wires and cables. As a production test, this test is often used as a customer acceptancetest, with minimum insulation resistance per unit length often specified by the customer. Theresults obtained from IR Test are not intended to be useful in finding localized defects in theinsulation as in a true HIPOT test, but rather give information on the quality of the bulkmaterial used as the insulation.

Even when not required by the end customer, many wire and cable manufacturers use theinsulation resistance test to track their insulation manufacturing processes, and spotdeveloping problems before process variables drift outside of allowed 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 IR Tester

650V 500V DC

1.1KV 1KV DC

3.3KV 2.5KV DC

66Kv and Above 5KV DC Test Voltage for Meggering:

When AC Voltage is used, The Rule of Thumb is Test Voltage (A.C) = (2X Name PlateVoltage) +1000.When DC Voltage is used (Most used in All Megger), Test Voltage (D.C) = (2X Name Plate

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Voltage).

Equipment / CableRating

DC TestVoltage

24V To 50V 50V To 100V

50V To 100V 100V To 250V

100V To 240V 250V To 500V

440V To 550V 500V To 1000V

2400V 1000V To 2500V

4100V 1000V To 5000V Measurement Range of Megger:

Test voltage MeasurementRange

250V DC 0MΩ to 250GΩ

500V DC 0MΩ to 500GΩ

1KV DC 0MΩ to 1TΩ

2.5KV DC 0MΩ to 2.5TΩ

5KV DC 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, andZERO 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 oneotherwise the test will give wrong informationSpare conductors should not be meggered when other working conductors of the samecable 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 through 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 any polarity of any feed takenthrough 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 testvoltage 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 contactto supply, or ground, or accidental contact.Erection of safety barriers with warning signs, and an open communication channelbetween 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 by twotimes.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) andGuard Terminal (G).

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Resistance is measured between the Line and Earth terminals, where current will travelthrough coil 1. The “Guard” terminal is provided for special testing situations where oneresistance must be isolated from another. Let’s us check one situation where the insulationresistance is to be tested in a two-wire cable.To measure insulation resistance from a conductor to the outside of the cable, we need toconnect the “Line” lead of the megger to one of the conductors and connect the “Earth”

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lead of the megger to a wire wrapped around the sheath of the cable.

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In this configuration the Megger should read the resistance between one conductor and theoutside sheath.We want to measure Resistance between Conductor- 2To Sheaths but Actually Meggermeasure resistance in parallel with the series combination of conductor-to-conductorresistance (Rc1-c2) and the first conductor to the sheath (Rc1-s).If we don’t care about this fact, we can proceed with the test as configured. If we desire tomeasure only the resistance between the second conductor and the sheath (Rc2-s), then weneed to use the megger’s “Guard” terminal.

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Connecting the “Guard” terminal to the first conductor places the two conductors atalmost equal potential. With little or no voltage between them, the insulation resistance isnearly infinite, and thus there will be no current between the two conductors. Consequently,the Megger’s resistance indication will be based exclusively on the current through thesecond 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 remove the connected element from themeasurement. In other words, it allows you to be selective in evaluating certain specificcomponents in a large piece of electrical equipment. For example consider a two core cablewith a sheath. As the diagram below shows there are three resistances to be considered.

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If we measure between core B and sheath without a connection to the guard terminal somecurrent will pass from B to A and from A to the sheath. Our measurement would be low. Byconnecting the guard terminal to A the two cable cores will be at very nearly the samepotential and thus the shunting effect is eliminated.

(1) IR Values For Electrical Apparatus & Systems:

(PEARL Standard / NETA MTS-1997 Table 10.1)

Max.VoltageRating OfEquipment

Megger Size Min.IRValue

250 Volts 500 Volts 25 MΩ

600 Volts 1,000 Volts 100 MΩ

5 KV 2,500 Volts 1,000 MΩ

8 KV 2,500 Volts 2,000 MΩ

15 KV 2,500 Volts 5,000 MΩ

25 KV 5,000 Volts 20,000 MΩ

35 KV 15,000 Volts 100,000 MΩ

46 KV 15,000 Volts 100,000 MΩ

69 KV 15,000 Volts 100,000 MΩ

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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 oneminute the insulation resistance of HV installations shall be at least 1 Mega ohm or asspecified by the Bureau of Indian Standards.Medium and Low Voltage Installations- At a pressure of 500 V applied between each liveconductor and earth for a period of one minute, the insulation resistance of medium andlow voltage installations shall be at least 1 Mega ohm or as specified by the Bureau ofIndian 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 individualwindings to ground or between individual windings. Insulation resistance tests arecommonly measured directly in megohms or may be calculated from measurements ofapplied voltage and leakage current.The recommended practice in measuring insulation resistance is to always 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 windingsgrounded.

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Windings are never left floating for insulation resistance measurements. Solidly groundedwinding must have the ground removed in order to measure the insulation resistance of thewinding grounded. If the ground cannot be removed, as in the case of some windings withsolidly grounded neutrals, the insulation resistance of the winding cannot 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

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transformers, We need to test winding ( L1,L2,L3 ) with substitute Earthing for Deltatransformer or winding ( L1,L2,L3 ) with earthing ( E ) and neutral ( N ) for wyetransformers.

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)

3 Phase Transformer(Star)

IR Value (MΩ) = C X E (P-n) /(√KVA)

3 Phase Transformer(Delta)

IR Value (MΩ) = C X E (P-P) /(√KVA)

Where C= 1.5 for Oil filled T/C with Oil Tank, 30 for Oilfilled T/C without Oil Tank or Dry Type T/C.

Temperature correction Factor (Base 20°C):

Temperature correction Factor

OC OFCorrection

Factor

0 32 0.25

5 41 0.36

10 50 0.50

15 59 0.720

20 68 1.00

30 86 1.98

40 104 3.95

50 122 7.85

Example: For 1600KVA, 20KV/400V,Three Phase TransformerIR Value at HV Side= (1.5 x 20000) / √ 1600 =16000 / 40 = 750 MΩ at 200CIR Value at LV Side = (1.5 x 400 ) / √ 1600= 320 / 40 = 15 MΩ at 200C



IR Value at 300C =15X1.98= 29.7 MΩ

Insulation Resistance of Transformer Coil

Transformer

Coil Voltage

MeggerSize

Min.IR ValueLiquid Filled

T/C

Min.IRValue DryType T/C

0 – 600 V 1KV 100 MΩ 500 MΩ

600 V To 5KV 2.5KV 1,000 MΩ 5,000 MΩ

5KV To 15KV 5KV 5,000 MΩ 25,000 MΩ

15KV To 69KV 5KV 10,000 MΩ 50,000 MΩ

IR Value of Transformers:

Voltage TestVoltage(DC) LVside

Test Voltage(DC) HVside

Min IRValue

415V 500V 2.5KV 100MΩ

Up to 6.6KV 500V 2.5KV 200MΩ

6.6KV to 11KV 500V 2.5KV 400MΩ

11KV to 33KV 1000V 5KV 500MΩ

33KV to 66KV 1000V 5KV 600MΩ

66KV to 132KV 1000V 5KV 600MΩ

132KV to220KV

1000V 5KV 650MΩ

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 bushingsShort 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 ofthe test voltage is referred to as the Insulation Resistance of the transformer at the testtemperature.



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 shallnot 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) – GND2. HV – (LV + GND)3. LV – (HV + GND)

Three winding transformer:

1. HV – (LV + TV + GND)2. LV – (HV + TV + GND)3. (HV + LV + TV) – GND4. 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) – GND3. TV – (HV + LV + GND)

For any installation, the insulation resistance measured shall not be less than:

HV – Earth 200 M ΩLV – Earth 100 M ΩHV – LV 200 M Ω

Factors affecting on IR value of Transformer

The IR value of transformers are influenced by

surface condition of the terminal bushingquality of oilquality of winding insulationtemperature of oilduration 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 withearthing ( 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

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As per IEEE 43 Standard 1974,2000

IR Value in MΩ

IR (Min) = kV+1 For most windings made beforeabout 1970, all field windings, andothers not described below

IR (Min) = 100 MΩ For most dc armature and acwindings 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 MΩExample-2: For 415V,Three Phase MotorIR 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

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Motor Name Plate(V)

TestVoltage

Min IRValue

250V 500V DC 25 MΩ

600V 1000V DC 100MΩ

1000V 1000V DC 100MΩ

2500V 1000V DC 500MΩ

5000V 2500V DC 1000MΩ

8000V 2500V DC 2000MΩ

15000V 2500V DC 5000MΩ

25000V 5000V DC 20000MΩ

34500V 15000V DC 100000MΩIR Value of Submersible Motor:

IR Value of Submersible Motor

Motor Out off Well (WithoutCable)

IR Value

New Motor 20 MΩ

A used motor which can bereinstalled

10 MΩ

Motor Installed in Well (WithCable)

New Motor 2 MΩ

A used motor which can bereinstalled

0.5 MΩ

(5) IR Value for Electrical cable and wiring:

For insulation testing, we need to disconnect from panel or equipment and keep themisolated from power supply. The wiring and cables need to test for each other ( phase tophase ) 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, ThermoplasticPolyethlene=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 conductorc – Thickness of conductor insulationb – Thickness of jacket insulation

HV test on new XLPE cable (As per ETSA Standard)

Application Test Voltage Min IRValue

New cables – Sheath 1KV DC 100 MΩ

New cables –Insulation

10KV DC 1000 MΩ

After repairs – Sheath 1KV DC 10 MΩ

After repairs –Insulation

5KV DC 1000MΩ

11kV and 33kV Cables between Cores and Earth (As per ETSA Standard)

Application Test Voltage Min IRValue

11KV New cables – Sheath 5KV DC 1000 MΩ

11KV After repairs –Sheath

5KV DC 100 MΩ

33KV no TF’s connected 5KV DC 1000 MΩ

33KV with TF’s connected. 5KV DC 15MΩ

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IR Value Measurement (Conductors to conductor (Cross Insulation))

The first conductor for which cross insulation is being measured shall be connected to Lineterminal of the megger. The remaining conductors looped together (with the help ofcrocodile 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 willshow the cross Insulation between conductor 1 and rest of the conductors. Insulationreading shall be recorded.

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Now connect next conductor to Line terminal of the megger & connect the remainingconductors 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 willshow the insulation resistance of the conductors. Insulation reading shall be recorded afterapplying 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 /kmat 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 buriedtemperature, 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 cablemust be replaced immediately on emergency basis.

(6) IR Value for Transmission / Distribution Line:

Equipment. Megger Size Min IR Value

S/S .Equipments 5 KV 5000MΩ

EHVLines. 5 KV 10MΩ

H.T. Lines. 1 KV 5MΩ

LT / Service Lines. 0.5 KV 5MΩ

(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 MeggerSize

IRValue(Min)

Circuit Breaker

(Phase-Earth) 5KV,10 KV 1000 MΩ

(Phase-Phase) 5KV,10 KV 1000 MΩ

Control Circuit 0.5KV 50 MΩ

CT/PT

(Pri-Earth) 5KV,10 KV 1000 MΩ

(Sec-Phase) 5KV,10 KV 50 MΩ


Isolator

(Phase-Earth) 5KV,10 KV 1000 MΩ

(Phase-Phase) 5KV,10 KV 1000 MΩ


L.A (Phase-Earth) 5KV,10 KV 1000 MΩ

ElectricalMotor

(Phase-Earth) 0.5KV 50 MΩ

LT Switchgear (Phase-Earth) 0.5KV 100 MΩ

LTTransformer

(Phase-Earth) 0.5KV 100 MΩ

IR Value of S/S Equipments As per DEP Standard

Equipment MeggeringIR Value at

CommissioningTime (MΩ)

IR Value atMaintenance

Time(MΩ)

Switchgear

HV Bus 200 MΩ 100 MΩ

LV Bus 20 MΩ 10 MΩ

LV wiring 5 MΩ 0.5 MΩ



Cable(min 100Meter)

HV & LV (10XKV) / KM (KV) / KM

Motor & Generator Phase-Earth 10(KV+1) 2(KV+1)

Transformer Oilimmersed

HV & LV 75 MΩ 30 MΩ

Transformer DryType

HV 100 MΩ 25 MΩ

LV 10 MΩ 2 MΩ

FixedEquipments/Tools

Phase-Earth 5KΩ / Volt 1KΩ / Volt

MovableEquipments

Phase-Earth 5 MΩ 1MΩ

DistributionEquipments

Phase-Earth 5 MΩ 1MΩ

Circuit BreakerMain Circuit 2 MΩ / KV

Control Circuit 5MΩ

Relay

D.C Circuit-Earth

40MΩ

LT Circuit-Earth

50MΩ

LT-D.C Circuit 40MΩ

LT-LT 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 deterioration of the insulation, as well asinvolving 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 currentleakage in the reactance of the insulation, because it acts as the dielectric of a capacitor. Thiscurrent dissipates no energy and is not harmful, but we wish to measure the resistance ofthe insulation, so DC Voltage is used to prevent reactance from being included in themeasurement.

1 Phase Wiring:

The IR test between Phase-Natural to earth must be carried out on the complete installationwith the main switch off, with phase and neutral connected together, with lamps and otherequipment disconnected, but with fuses in, circuit breakers closed and all circuit switchesclosed.Where two-way switching is wired, only one of the two stripper wires will be tested. To testthe other, both two-way switches should be operated and the system retested. If desired,the installation can be tested as a whole, when a value of at least 0.5 M Ohms should beachieved.

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3 Phase Wiring:

In the case of a very large installation where there are many earth paths in parallel, thereading would be expected to be lower. If this happens, the installation should besubdivided and retested, when each part must meet the minimum requirement.

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The IR tests must be carried out between Phase-Phase-Neutral-Earth with a minimum

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acceptable value for each test of 0.5 M Ohms.

IR Testing for Low voltage

circuit voltage Test voltage IRValue(Min)

Extra Low Voltage 250V DC 0.25MΩ

Up to 500 V except forabove

500 V DC 0.5MΩ

500 V To 1KV 1000 V DC 1.0MΩ Min IR Value = 50 MΩ / No of Electrical outlet. (All Electrical Points with fitting &Plugs).

Min IR Value = 100 MΩ / No of Electrical outlet. (All Electrical Points without fitting &Plugs).

Required Precautions:

Electronic equipment like electronic fluorescent starter switches, touch switches, dimmerswitches, power controllers, delay timers could be damaged by the application of the hightest voltage should be disconnected.Capacitors and indicator or pilot lamps must be disconnected or an inaccurate test readingwill result.Where any equipment is disconnected for testing purposes, it must be subjected to its owninsulation test, using a voltage which is not likely to result in damage. The result mustconform with that specified in the British Standard concerned, or be at least 0.5 M Ohms ifthere is no Standard.

FILED UNDER UNCATEGORIZED

About Jignesh.ParmarJignesh Parmar has completed his B.E(Electrical) from Gujarat University. He has more than 11years experience in Power Transmission-Power Distribution-Electrical energy theft detection-Electrical Maintenance-Electrical Projects(Planning-Designing-coordination-Execution). He isPresently associate with one of the leading business group as a Assistant Manager atAhmedabad,India. He is Freelancer Programmer of Advance Excel and design useful ExcelSheets 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 withEnglish, Hindi, Gujarati, French languages. He wants to Share his experience & knowledge andhelp technical enthusiasts to find suitable solutions and updating themselves on variousEngineering Topics.

95 Responses to Insulation Resistance (IR) Values

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modupalli says:March 23, 2012 at 10:16 pmOutstanding Stuff…. Thanks For Sharing..

ReplyDeja jacob says:March 25, 2014 at 1:01 amWHAT ARE THE GOOD RESISTANCE VALUE?

ReplyJignesh.Parmar says:March 25, 2014 at 4:10 pmGOOD means…. ALL suspected value according to equipments are already given…

vilas K. says:April 11, 2012 at 8:30 amDear Sir Hats Off !! & many thanx for your invaluable contribution in enriching theexperience of Elect. Engineers & making them available the fabulous data at a glance.. Plkeep posted. If U can throw some light on selection of MCB/MCCB & contactors in relationto their diff characteristics.

ReplyJignesh.Parmar says:April 11, 2012 at 2:19 pmYou can find Type of MCB/MCCB and Char of All type of Contactor from ELECTRICALNOTES page of this Blog

Replyvarghese says:April 15, 2012 at 12:25 pmdear sir… is a great work…. thanks

could u pls explain the effects of rise in temperature on insulation resistance of transformer.

ReplyBarun Majumder says:May 7, 2012 at 10:48 amDear sir many many thanks for sharing valuable article of electrical engineering . I want toknow more about electrical design (Distribution, industrial & commercial ) and protectionsystem from your end point to point . If you have any book/site for those design please letme know the name.I am working as a design engineer but i am not enough confident about my design andprotection system. i want your valuable assistance in this field .

Thanking youYours faithfullyBarun Majumder

Kolkata

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Replykumereshan P S says:May 13, 2012 at 4:17 amSir,great work,i want to know the IS standards for IR value of Sub station equipment

With regards

Kumereshan

Replyanand says:October 5, 2012 at 8:19 amthank for good infrm abot elecyrhghc

ReplyTuulia Paloranta says:May 29, 2012 at 5:49 amHonestly i am not quite good on electric thing and this one is very good for me to study sowell and learn a lot many thanks for this article.

Replykeyur says:June 8, 2012 at 2:53 pmThanks for sharing your valuable exp. and it is very helpful for me because I am diplomaholder and I am working in gulf country as electrical supervisor so it is useful for me andThankskeyur

ReplyMANOHAR says:June 14, 2012 at 5:20 amDear sir

I need calculation formula of IR Values of an elect drives

ReplyMadanmohan says:June 16, 2012 at 5:50 amWonderful explanation. Really very much useful document. Thnak you very much

Replysathesh says:July 9, 2012 at 5:59 pmVery nice sir.. Thanku..

Replyrehan says:July 13, 2012 at 9:58 pmgood information, thanks for your time.




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Replycustom milagros says:July 15, 2012 at 4:20 pm2 thumbs up.

ReplyGurmeet Singh says:July 20, 2012 at 4:49 amVery -2 Thanks sir

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Replyosarenkhoe nosa glory says:August 11, 2012 at 9:15 amthis is absolutely nice. a well written document. thanks.

ReplyNaveen says:August 12, 2012 at 6:23 amThank you Sir, much appreciated

ReplyA. Hasasn says:August 12, 2012 at 2:15 pmDear Sir;Really your this article is very very important for electrical related people.Your thiscontribution is excellant. A lot of thanks sir.Kind Regardrs

ReplyK.M.Pandey says:August 18, 2012 at 5:04 amRespected Sir.

This article very important and useful for all those person who are related with Electricalfield. Thanks a lot for sharing your knowledge with all people. Really you are nice andgentleman.With regards,K.M.Pandey,

Replysubodh kumar pandey says:August 26, 2012 at 1:20 pmvery very important for electrical engineers.lot of thanks








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Replyahmed nawaz says:September 21, 2012 at 3:40 pmCh.Ahmed Nawaz

thanks sir for giving very usefull information.

Replyradhakishan pawar says:September 30, 2012 at 6:28 amthanks sir i have no word to explain how much it is useful to student.thanks again……

ReplyTHAKOR SANJAY says:October 5, 2012 at 1:17 pmI AM A TESTING ENGINEER…….THIS INFO. IS VERY USEFUL FOR MEVERY VERY THANKS FOR THIS …

ReplyVilas G. says:October 11, 2012 at 11:01 amThanks . valuable note for electrical engineers.

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ReplyMr. Judy Diano says:October 31, 2012 at 11:45 amThank you so much,for sharing Sir, I learned a lot of your link GOD BLESS

Replyarshad says:November 30, 2012 at 6:23 pmthanks for beautiful notes

ReplyJet Paliangayan says:December 3, 2012 at 12:11 pmhow to do IR test for single core pvc/xlpe/pvc cables

Replyjamestryre says:December 12, 2012 at 2:49 amgreat info, thx

Reply













Thiyaga says:December 19, 2012 at 10:41 amIncredible work. Hats off for your awesome articles. pl keep posting more and more

Replysambasivarao chagantipati says:December 25, 2012 at 7:46 pmVery useful information

Replyrohtash verma( Himachal pradesh) says:December 29, 2012 at 2:02 amThanks parmar ji very use full information regarding IR value of electric motors

ReplyM.Zaman says:January 8, 2013 at 10:56 amthanks for valuable information.

ReplyFELIX Jr. says:January 10, 2013 at 7:44 amPlease, you must also include here the Polarization Index (PI) as well for it’s significanceand explain why it is required with respect to the IR test being done on the electricalequipment and the electrical cables and installations, as an additional information for thenew commissioning engineers and enthusiasts. Supressing other comments are not at allinteresting and helpfull.

ReplyJignesh.Parmar says:January 10, 2013 at 2:38 pmYes 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 of PI.

Replydeepak parmar says:June 6, 2013 at 12:18 pmI want to know the acceptable leakage current values in the HV testing as per IECstandards.

And thanks for the info provided above

sateesh says:January 21, 2013 at 11:18 amexcellent explanation about IR testthanks a lot.

Reply




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vincent says:February 4, 2013 at 7:23 pmGood knowledge.thank you.

ReplyAnderson says:February 6, 2013 at 5:41 pmExcelente trabajo, quiero saber cuales son las normas que rigen estas pruebas y si existealguna estandarización de resultados. Gracias

ReplyDebra Scriver says:February 11, 2013 at 10:53 pmThanks for such a great article. Very interesting and informative. Thanks Buddy

ReplyDiganta ku. Ray says:February 23, 2013 at 3:12 pmThank you so much sir,this help me a lot in my field.its very very useful for those are inelectrical line.

ReplyJAYESH PATEL says:February 28, 2013 at 4:57 amhow many Insulation Resistance of the Whole Installation permissible ?how many Insulation Resistance Between Conductors ?how many Insulation Resistance Between Each Conductor & Earth ?

Replyhonest forex signals says:March 4, 2013 at 5:26 amHello very nice blog!! Man .. Excellent .. Amazing .. I will bookmark your web site and takethe feeds additionally?

I am glad to find numerous helpful info here in the put up, we want work out morestrategies on this regard, thank you for sharing.

. . . . .

Replyfayyaz says:March 10, 2013 at 10:12 pmthks good information can you mail me how to check insulation of dc 24 volt system.also i want to know how insulation monitor works.

Replykhan wasim says:March 11, 2013 at 5:01 pmThanks a lot



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Replysonu kumar says:March 14, 2013 at 2:40 pmthanks for this valueable data.

ReplyAshok O Kale Kale says:March 21, 2013 at 12:05 pmThanx .

ReplyDEBASHISH BHATTACHARYA says:April 2, 2013 at 5:10 pmExcellent 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 usedfor 11 KV , 22 KV , 33 KV and 66 KV.

RegardsDebashish Bhattacharya

ReplyGerald says:April 3, 2013 at 10:50 amThanks for sharing…

ReplyCPR vittal says:May 1, 2013 at 12:46 pmexcellent article.the formula for insulation resistance of a cable per 1000 ft.how to calculate it per meter or per feet.pl explain

Replyjigyesh sharma says:May 8, 2013 at 1:49 amwhat precautions i should take when CT is connected in HT board and i have do megger.?

Replyibnu says:May 11, 2013 at 2:53 amlightning cable for crane – there are 2 point earth terminal, each has individual groundcable, i meggar 1kV both cable, gives different reading 200Mohm & almost infinity foranother one. why? can accept the value?

Replyibnu says:May 11, 2013 at 2:57 amcan 11kv cable, meggar at 1kv only, during before & after hipot test? (hipot at 30.5kv)



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Replyparveen kumar says:May 11, 2013 at 2:33 pmdear sir i want to know why used in transformer secondary side very thin wire

ReplyFELIX Jr. says:May 12, 2013 at 4:57 amYes, you can use 1kV DC- MEGGER TESTER prior to HIPOT Testing if your electrical cableis rated 11kV and HIGHER and if it has 130 % rated insulation. After HIPOT test, ifsuccessful, you can megger it again with 1kV only at no more than 1 minute just to makesure no damage has occurred during and after HIPOT TEST.

By FMSJr. / Abu Dhabi, UAE

ReplyNasurudheen Kamal Basha says:May 13, 2013 at 9:22 amUseful stuff.. Thanks for sharing!!

ReplyMOHAMMAD says:June 17, 2013 at 11:02 amTHANKS ALOT VERY GREATFUL INFO

ReplyPushkar Singh says:June 23, 2013 at 11:12 amThanks for sharing excellent information.Pushkar Singh ONGC

ReplyA V N Phanindra says:July 4, 2013 at 7:01 amthank u so much sir its very brief and simple to understand clearly.

ReplyASMA says:July 20, 2013 at 10:16 amWHAT WOULD BE THE MEGGAR REULT OF A GOOD CONDITION 25 KVATRANSFORMER?I WILL BE OBLIGED..KINDLY HELP ME.

ReplyFELIX Jr. says:July 21, 2013 at 5:29 amGOOD DAY ! Your posted question about the MEGGER result for a good condition for25kVA Transformer is very general as you did not specify the input and output voltagesof this electrical equipment and if it is oil immersed or dry type. At anyrate, assumingit’s oil filled step-up transformer, outdoor pole mounted, for a good IR result for



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primary winding, normally it should not be less than 500Megaohm and the secondarywinding’s IR reading should be not less than 300Megaohm with respect to earth andhigher between windings. Again, these are assumptions only and the higher the voltagerating of the transformer the higher IR reading should result. Defective insulations willread low values of IR readings and contaminated oil insulation, for oil immersed typetransformers. For dry type Transfomers, the good IR readings of the windings are alsoin that vicinity but lower than oil immersed type.

ReplyJ.R Bohra says:July 20, 2013 at 11:48 pmvery very helpfulThanksJ,R BohraUnique Engineer Noida

ReplyDiptiranjan Nayak says:July 23, 2013 at 5:10 amThank u sir,I am clear about IR value.

Replyraghav says:July 26, 2013 at 4:37 amdear sir,i need more information about how to calculate ir values and what principle it requires tocalculate ir values?

ReplyMusa says:August 22, 2013 at 3:25 amAnybody can answer my query?

We have 25kV AC system for Overhead Line Equipment (OHE). This system is installed forElectrified Train system (Railway project).

We have conduct IR testing before charging the lines for each electrical subsection (thelongest section about 20km). The result we achieved 0.5MOhm – 5MOhm (taken duringnight time) and 200MOhm – 700MOhm (taken during night time). The temperature duringnight time is around 27 – 28 degree Celsius (in Malaysia).

We injecting megger size 5kV and result achieved as above. As mentioned in the article (ithink it is similar to our system – IR value for transmission/ distribution line) which isstated Min. IR values shall be 10MOhm.

Is it the result we achieved okay, especially the result taken during night time?

Replysampath says:


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September 3, 2013 at 6:28 amthank for more information now i harry to check insulation resistance long 132Kvtransmission line & will have called you after testing

ReplySYAM says:September 4, 2013 at 9:00 amDear Jignesh,

Just for curiosity can you please tell me what is the full form of “DEP” standards which youhave mentioned under the section “IR Value of S/S Equipments As per DEP Standard”.

Hope you will reply

Regards

SYAM

ReplySekar Ram says:September 12, 2013 at 12:58 pmMr JigneshThis is one of the greatest selfless efforts I have seen. This is pure social service. Hats off!!

ReplyStephen says:September 13, 2013 at 1:46 pmHello. Question, if we have 5 conductors per phase on a lugs and we want to megger thegroups, ie: phase to phase and phase to ground and the readings are above 1 M ohm, is thatOK? We had previously meggered all the cabels individually prior to installing. The jobwas shut down for a while, and this is for a precaution, prior to re-energizing.

Replyvijay says:September 25, 2013 at 11:39 amdear jignesh sir,

Can i have the entire notes in site in form of book? How much does it cost?

Replyvijayendrarao kv says:November 2, 2013 at 10:48 amvery very useful and very thanks for made me doubt clear..

ReplyMichel says:November 29, 2013 at 10:49 amthanks Bro that is too goooooooooooooood for us

ReplyESAKKIPANDI says:






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December 5, 2013 at 5:16 amthe explanation is excellent

Replyrahul jangme says:January 5, 2014 at 2:41 pmthank you sir

Replyali says:January 12, 2014 at 1:18 pmthank you so much Dr

ReplyDoma Hudu says:February 8, 2014 at 2:26 pmthank sir. I need a copy via my e-mail. please am wait for your response Sir.

ReplySrinivasan says:February 12, 2014 at 3:40 amThank you sir. Useful detail information.

Replyaby says:February 20, 2014 at 10:17 amSir,appreciate your ideas and procedures.May i know ,whether there is any necessity or mandatory rules saying that the speakercables to be meggered?if yes,then what should be the applied voltage?

Replyroop says:February 23, 2014 at 6:17 amdear mr Parmar first of all thanks for sharing the information

Replyroop says:February 23, 2014 at 6:22 amwe are building a 9 km road tunnel, we usually facing problem with ht cable, whenever it isdamaged it took 3 to4 hour for jointing, lot of production loss please advise any alternatemeans of transmission of ht cable or any ht joint available around the world to do thejointing quickly.

ReplyFelix Jr San Buenaventura says:March 26, 2014 at 4:44 am

THESE ARE GOOD INFORMATION AND REFERENCE FOR ALL ELECTRICAL











THESE ARE GOOD INFORMATION AND REFERENCE FOR ALL ELECTRICALENGINEERS AND COMMISSIONING ENGINEERS BE IT IN DESIGN ENGINEERINGOR IN COMMISSIONING WORKS OF PROJECTS RELATED TO ELECTRICAL POWERGENERATION, TRANSMISSION AND IN DISTRIBUTION SYSTEMS THE WORLDOVER. TIKE !, SALAMAT PO !, GRACIAS !, QZI QZI !, TERIMA KASIH !

ReplySB says:March 27, 2014 at 7:26 amThank you ever so much! For sharing such good info, extremely relevant.

Replyrd says:June 14, 2014 at 8:28 amWhat is the minimum acceptable insulation resistance for 1.8 kv DC cables? temperature isaround 50 deg C. My understanding is that IR decreases when there is increase intemperature. So how do i calculate Insulation resistance considering the temperature?

Replyjake says:July 30, 2014 at 6:29 amwhat can we expect for transformer being energize not meeting the minimum standard forinsulation resistance?the future effect of it?

Replygolfziimo says:August 4, 2014 at 12:38 pmthank you for good information

ReplyAen Bali says:August 14, 2014 at 6:36 amPlz tell me CTPT value in HT & LT side proper load

50 Hp

Replyreshi says:August 28, 2014 at 12:50 pmDear sir ,we have hayward tyler 480V, 60HZ , 100HP submersible pump motor in out facility usedfor boiler water circulation. The demin water is used for the stator cooling in the closed loopmeans water is directly entering the stator winding.

The motor was send to workshop for mechanical repair. After installing back The I.R valueis 0.3MOhm , can we test the motor and run it.

For your suggestion Thanks in anticipation.

Replypraneeth says:







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September 4, 2014 at 3:34 pmthank U for the post,very helpfulvery few people share their knowledge.hats off.

ReplyAbdul Hameed says:September 18, 2014 at 6:36 amgood information. appreciate it very much. thanks to all

Replynacykoe says:September 25, 2014 at 11:17 amIR instrument from IEC or IEEE standard?

ReplyJagadish says:October 1, 2014 at 3:31 amWhat should be the minimum value of Insulation resistance for Low Voltage Switchgearpanels?

ReplyV V G says:October 12, 2014 at 6:01 amDear SirIn our one of the applications we need to check the High Voltage test in our product,(Automotive part).where customer is asking ask to check the HV test with 1.5KV

As per customer demand,now we need to make a HV instrument to detect the currentleakage when applyinh High volt(1.5KV) between two terminals.(open circuit)Customer requirement is that when the distance between the terminals if it is less than1.2mm our instrument must detect it.Now we are facing the problem as how to derive the resistance between two terminals(inair) when we applying high volt.Kindly help us

RegardsVVG

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