Insulation Tester 1 CI 02 I2

Ca l i b r a t i on Pr oc e dur e

I nst r ument Wr i t t enBy

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I NSULATI ON TESTER

:EbyJoy QA/QC QC Engi neer

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Chec kedBy :Mi yadHydr os e Techni calSupervi sor

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Appr ov edBy :I z z uddi nTMohamme mmed T e c hni c alDi r e c t o r

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1.

No:CI /01/I 2 Re v i s i o n: 3 Di st r i but edt o:TD, LM, M, MR Al luser s.Or i gi nal:QAFi l e I ssuedDat e: 11/12/2014 Effect i vef r om : 15/12/2014

Purpose

Inorder to provide the written calibration procedure procedure for insulation testers. Insulation testers are used to verify that electrical installations are safe, to test windings on motors and to test insulation resistance resistance on various appliances. It is essential that the tester provides the correct correct test voltage as the voltage may inuence the measurement measurement results. 2.

Scope

The calibration reuireme reuirements nts speci!ed in this this document apply to all portable didital insulation testers. Insulation Test "oltage, Insulation Test #esistance, Insulation Test current current would come under the scope of calibration in i n an inulation tester. tester. $ncertainty budgeting of insulation tester calibration will be e%plained in this procedure. &.

'ocation

The calibration will be carried carried out in the 'ab or customer customer premises premises depending depending on the customer reuirement. (or better accuracy, lab calibration is preferred. ).

*nvironmental *nvironmental conditions to be maintained

Temperatur Temperature+ e+ 22-  2 /umidity+ 0#/  1#/ 0.

3aster *uipment $sed

0.1Transmille &24 *lectrical Test -alibrator5for Insulation #esistance "oltage, I. #esistance, I. current.6 0.2I*T labs 7ecade #esistance bo% for continuity resistance measurement measurement or any calibrated resistance standard. 0.&Standard 3ultimeter 0.)3ultiproduct calibrator which can source voltage 5if the insulation tester has a voltage measurement funtion6 0.08uard (unction chec9er for chec9ing the 8uard terminal functioning. :. -alibration -apability :.1Insulation #esistance; 19< to 1 8< 5$pto 0 " insulation tester can be veri!ed, if using the adpator6 :.2Insulation "olatge; 0", 1", 20", 0", 1", 20", 0" Page 1 of 13



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:EbyJoy QA/QC Engi neer


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Appr ov edBy :I z z uddi nTMohammed T e c hni c alDi r e c t o r

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No:CI /01/I 2 Re v i s i o n: 3 Di st r i but edt o:TD, LM, MR Al luser s.Or i gi nal:QAFi l e I ssuedDat e: 11/12/2014 Effect i vef r om : 15/12/2014

:.&Insulation -urrent;.0m4 and 1 m4 :.)-ontinuity #esistance =. #eference international standards>guidelines>3anuals =.18uidance on the calibration of Insulation Testers, T8;2;1, South 4frican 4ccreditation body =.2Transmille &2 *lectrical Test calibrator manual. ?. -alibration Procedure ?.1Precautions before and during calibration a. Set the function switch to the appropriate position before measuring. b. @arm;up time for the reference instrument is & minutes and for the $$T, refer the operation manual of the instrument. -alibration can only carried out after the warm;up time. c. 7o not try to calibrate the insulation resistance if it is damamged or if metal parts are e%posed. 4lso chec9 the meter for crac9s or missing plastic. d. *nsure that the test leads are placed and !rmly connected in the proper input terminals. -onnect the common test lead before the live test lead and remove the live test lead before the common test lead. e. *%amine the test leads for damaged insulation or e%posed metal. -hec9 test lead continuity. #eplace damaged leads. f. *nsure that the insulation tester is switched oA when opening the battery compartment. g. 4lways remove the test leads before replacing the battery in the tester. h. The instrument must not be low battery while carrying out the calibration. i. #emove the teast leads and the range selector switch to the B(( position after use. ?.2 Insulation #esistance 3easurement a. 4 resistor of 9nown value and voltage coeCcient should be connected to the insulation tester for calibration5#efer fgure 16. -onnect the insulation tester5unit under test6 to the Dlac9 E #ed )mm terminals of Transmille &245which acts as the standard resistor6. b. Set insulation voltage range on the tester. -alibrate the instrument on at least two points along the scale of each range. c. *nter the reuired resistance from 19F to 1,3F on the 9eyboard followed by G*nterH in transmille &2 to set the output. 4n alternative way to Page 2 of 13



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Di st r i but edt o:TD, LM, MR Al luser s.Or i gi nal:QAFi l e I ssuedDat e: 11/12/2014 Effect i vef r om : 15/12/2014

select the reuired resistance is to use the digital -ontrol to increment > decrement the digit indicated by the cursor. The 'eft and #ight arrow 9eys allow the selected digit to be changed. d. 3easure the insulation #esistance set by Transmille &2 by pressing the test button in the insulation tester for 1 minute at the selected voltage range. 4t the end of the 1 min record the resistance indicated by the unit under test. #epeat the measurement for 0 times at each point. e. -are should be ta9en not to e%ceed the voltage and current limits mar9ed on the speci!cation of the calibrator when applying voltage from the insulation tester. @hile applying voltages above 09", an voltage adaptor needs to be used along with the electrical test calibrator inorder to test insulation tester above 19" voltage capacity.

Figure 1

?.&Insulation "oltage 3easurement (Figure 2);3ethod 1 Page 3 of 13



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a. The output voltage is measured on each range to ensure that the tester delivers at least the minimum speci!ed voltage. b. This measurement should be conducted at the load recommended by the manufacturer, normal case we ta9e the load as 18<. The output voltage measured as well as the value of the load shall be stated on the calibration certi!cate. c. The voltage applied by the insulation tester can be measured by Transmille &2 *lectrical Test calibrator. d. To measure the insulation voltage, -onnect the insulation tester to the )mm soc9ets at the top of the calibrator using the set of silicon test leads, or the leads supplied with the instrument. e. (rom the Insulation #esistance menu displayed on the &24, select the G"B'T48*H function using the soft 9ey. f. Press the test button in the insulation tester to inect voltage to the calibrator. #ecord the measured value in the transmille &2 and the applied value from the tester. #ecord the error. ?.)Insulation "oltage 3easurement ; 3ethod 2 a. To measure voltages above 1 " the following method shall be used. b. The insulation Tester is to be connected to 1 8< load5-D 116. 4cross the load a mulimeter will be connected through a high voltage probe as the voltage rating for multimeters cannot e%ceed 1". c. Start applying the voltage across the load and measure the voltage across the load using the mulimeter. d. -hec9 the error between the insulation tester voltage and the voltage measured by the reference multimeter. ?.0Insulation current 3easurement (Figure 3) e. Select the reuired voltage range to be measured using either the digital -ontrol or the up > down arrow 9eys in Transmille &2 *lectrical Test -alibrator. #anges include 0", 1", 20", 0" and 1".The impedance of each range is automatically set to give the correct load 1m4 > .0m4 5see test current below6 at the applied nominal voltage range.

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Figure 2


Screenshot of transmille &2 display

Figure 3

g. Select the reuired measurement current using the Soft Jeys. The default setting for current load is .0m4 nominal which is thecorrect load>test current for the 1=th *dition euipment ;e.g. must be able to supply .0m4 at the speci!ed test voltage.Blder insulation testers 51:th *dition6 produced 1m4 current at the speci!ed test voltage. The &24 should be set to 1m4 current for these instruments. "ery old testers may only produce a very small current and the voltage will collapse under any loadK these should be tested using additional euipment. ?.:Insulation Tester with -ontinuity function a. -alibrate the low value ohms>continuity ranges by applying at least two low ohm resistance values. b. Lote that insulation testers are 2;terminal and are often calibrated with the leads supplied. This shall be reported on the calibration certi!cate. ?.="oltage 3easurement 4ccuracy a. -alibrate the voltage measuring ranges at a minimum of two points along the range using transmille &)1 following accredited procedure 54->MSP>2N6.

?.?8uard Terminal function -hec9ing Page 5 of 13



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a. @here a guard terminal is incorporated on an insulation tester, the functionality of this terminal shall be veri!ed. This can be done in the following way by connecting two suitable series resistors in parallel with the resistance being measured. 5See !gure 1 below6.

(igure+ Step 1 ; 3easure without the guard terminal connected 51=& 3< e%pected6 Step 2; 3easure with the guard terminal connected 51 8< e%pected6 N. 4ccuracy -riteria a.

If the $$T reading e%ceeds and adustment of the same is not possible to ma9e it within the manufacturer recommended tolerance limit,then the instrument need to be reected without calculating the uncertainty limits.

b. If the $$T reading e%ceeds the manufacturer recommended tolerance limit and adustment is possible to ma9e it within tolernace limit as spec!ed by the manufacturer, then the same need to be approved, certi!ed.The uncertainty *stimation needs to be done and given in the certi!cate. c. If the $$T is within the manufacturer tolerance limit without any adustment, then the instrument is approved,certi!ed. The uncertainty *stimation needs to be done and given in the certi!cate.

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1. Intermediate -hec9 for the #eference Instrument a. Intermediate chec9 of the reference instrument shall be done every 6 months. The reference instrument is used for calibrating an Insulation Tester O18< load under diAerent voltages 50", 1", 20", 0", 1"6. The results would be recorded in a wor9 sheet. b. The same nsulation Tester is calibrated again with the 3egger -alibration bo%; -D11 O18< load under same voltages 50", 1", 20", 0", 1"6. c. Doth the calibration results shall not have a variation of more than 1 from each other at any of the points. d. If a varaition is found more than the acceptable limit, a corrective action form will be raised by the concerned technician and investigation to be done to !nd out the root cause of the problem. 4 corrective action will have to be ta9en to rectify the error. $ntil the case is resolved the calibration would be stopped using the instrument in uestion. 11. $ncertainty Dudgeting (or Insulation Tester -alibration 11.1 Type 4 $ncertainty 5u46 a. Type 4 uncertainty is determined by the statistical analysis of a series of measurements. Ten measuremnts are ta9en to !nd this random uncertainty. 11.2 Type D uncertainty 5uD1, uD2, uD&, uD)6 a. 4ll the other uncertainties that cannot be determined statistically, during the measurement process. They fall in to the category of Type D uncertainties ; ; ; ; ;

-alibrator $ncertainty , uD1 3easurement error due to limitations of the $$THs resolution uD2 $ncertainty due to thermal emf of test leads , uD& 5Bnly ta9en in "oltage measurement 6 I year speci!cations of the reference instrument, uD) $ncertainty due to 7rift, uD0

11.& -ombined $ncertainty 5uc6 a. It is a summation of Type 4 and Type D uncertainties 5 $1$D1$D2$D&$D)Q.Q6 using law of error propagation. 11.) *%panded uncertainty 5$6 Page 7 of 13

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a. *%panded measurement uncertainty 5or e%panded uncertainty6 is de!ned as the product of a combined standard measurement uncertainty and a factor larger than one to provide a certain level of con!dence. It is combined uncertainty multiplied by 2 5coverage factor 96 to provide a level of con!dence of N0. 12.

3odel *uation

Yi = Ym +Ymc §UB1+§UB2+§UB3+§UB4

Rm "alue from the master instrument Ri  Indicated value in the $$T Rmc -orrection from the master instrument $D1 -alibration of the reference meter $D2 #esolution of The $$T $D& Thermal *3( in the 'eads 5Bnly applicable if a "oltage measurement fearure is available in the unit6 $D) 7rift in the master instrument. 1&.

(ormula used for estimating uncertainty

1&.1 Type 4 $ncertainty 5u46 Stanard deviation 5S6 @here n K Total Lumber of 3easurements S n measurements

2

Ui K value of individual Ua K 4verage of total

number of measurement Ui ; Ua i1 nK1 *stimated standard uncertainty

u4 

S

;;;;;;;;;;;;;;;;;;; *516 Page 8 of 13

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n where S K estimated standard deviation. Probability 7istribution is Normal 1&.2 Type D uncertainties a. $ncertainty from 3aster *uipment -erti!cate 5 uD16

uD1



*%panded $ncertainty 2

;;;;;;;;;;;;;;;;;;; *526 Probability 7istribution is Normal

b. $ncertainty due to $$THs resolution 5uD26 #esolution

;;;;;;;;;;;;;;;;;;;

*u5&6

uD2 

2U &

Probability 7istribution is ectangular c. $ncertainty due to thermal emf of test leads 5uD&6

uD& 

4verage of ive and Kive voltage of test leads

;;;;;;;;;;;;;;;;;;;

*u5)6 2

This uncertainty contribution will be considered only in voltage measurement function in the Insulation tester. Probability 7istribution is ectangular d. $ncertainty 7ue to 7rift 5uD)6 Page 9 of 13



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7rift in direct reading instruments is de!ned for a speci!c time interval of interest. The standard uncertainty for drift is

uD)

VR;RtV>W& ;;;;;;;;;;;;;;;;;;;;;; *u506 R; 3easurement at Time GH Rt; 3esaurement at Time GtH Probability 7istribution is ectangular

1&.& (ormula used for *stimation of standard combined uncertainty

uD12

Standard combined uncertainty, ;;;;;;;;;;*u5:6

uc 

u4  uD12 uD12 uD12 uD12

1&.) (ormula used for calculating e%panded uncertainty $ uc % 2 59 is the coverage factor which is 26 ;;;;;;;;;;*u5=6 !roce"ure 1). 1).1 Type 4 $ncertainty 5#andom *rrors6 a. *stimation of Type 4 uncertainty limit

1. *nsure the indicated reading of $$T is within the tolerance limit given by the manufacturer 2. Ta9e minimum 0 readings on each parameter and range. &. -alculate the average value for the series of measurement for all ranges and parameter ). Dy using the above mentioned formula,calculate the standard deviation 5 # 6. 0. 4pply estimated standard deviation to $%(1) above to calculate the Type 4 uncertainty limit 5 U1 6. 1).2 Type D $ncertainties 5Systematic *rrors6 a. *stimation of Imported $ncertainty 5uD16 Page 10 of 13



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1. -alibratorHs uncertainty is mentioned in the calibration certi!cate of the 3aster instrument as e%panded uncertainty hence divide the value by 2 to get the combined uncertainty. 2. $se the above mentioned formula $%(2) to get $D1 b. *stimation of $ncertainty due to 'imited #esolution of the $$T 5uD26 1. #esolution of the $$T is ta9en into consideration. The limit to the ability of an instrument to indicate small changes in the uantity being measured, referred to as resolution or Xdigital rounding errorY, is treated as a systematic component of uncertainty. /alf scale of the resolution is ta9en and the probability distribution is rectangular, therefore the divisor is W& . 2. $se the euation, 5$%u3) to get uD2. c. *stimation of $ncertainty due to Thermal *3( 5uD&6 1. #efer to the technician guide to get the value of uD&. 2. If an electrical conductor passes through a temperature gradient then a potential diAerence will be generated across that gradient. This is 9nown as the Seebec9 eAect and these unwanted, parasitic voltages can cause errors in some measurement systems K in particular, &here small "c 'oltages are eing measure" &. Ta9e the leads which are used for the calibration. Short circuit one end of the cables and other ends are connected to the voltage terminals. Ta9e readings with the leads connected to the positive and negative of the voltage terminal and readings ta9en with the leads switched at the voltage terminal. ). The probability distribution is rectangular, therefore the divisor is W& . 0. $se the euation, $%u(4) to get uD&. d. *stimation of $ncertainty due to 7rift 5 uD)6 1. #efer to technician guide to get the values of uD). 2. *lectronic instruments are e%pected to have drift. 7rift can be identi!ed from the certi!cates of two consecutive calibration done to the instrument. &. The probability distribution is rectangular, therefore the divisor is W& . ). $se the euation *u506 to get uD) e. *stimation of -ombined $ncertainty 5$ -6 1.

Ta9e the individual uncertainty values of Type 4, uD1, uD2, uD& and Page 11 of 13

uD)



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#-m ol

#ource o. Uncertaint-

!roailitistriution

i'isor

u4

#epeatability -alibration of the 3aster Instrument #esolution of the $$T Thermal *mf5*rror due to leads 7rift

Lormal

1

1

Lormal

2

1

#ectangular

W&

1

#ectangular

W&

1

#ectangular

W&

1

Lormal

1

;

Normal(/=2)

1

7

uD1 uD2 uD& uD) uc

-ombined $ncertainty

U

$,an"e" Uncertaint-

#ensiti'it5oecient(5i)

4dd all

uncertainties above, using the 'aw of *rror propagation. &. The probability distibution is normal because it is a summation of many standard probability distributions. The divisor is 1 ). $se *u5:6 to get the combined $ncertainty f. *stimation of *%panded $ncertainty 1. 4lthough the combined standard uncertainty is used to e%press the uncertainty of many measurements, some commercial, industrial and regulatory applications may reuire a measure of uncertainty that de!nes an interval about which the measurement value will lie with a certain level of statistical certainty. This type of measure is termed e%panded uncertainty, and is determined by multiplying the combined standard uncertainty by a coverage factor, 9. The coverage factor is usually in the range of 2 to &. *hat is the e,an"e" uncertaint- o. the measurement &hich is multi,lie" - a co'erage .actor /=20,ro'i"ing the le'el o. conf"ence o. a,,roimatel- 

e. $ncertainty Dudgeting for Insulation Tester -alibration.

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10. a. b. c. d.


7ocumentation #ecord all calibration points 5includes applied value and measured value6 in the wor9 sheet 54->@(>&6 before and after 5 if reuired 6 adustment. If the instrument is out of tolerance and not possible to adust , it is forwarded to the technical supervisor with a fault report. #eadings are enterd in to the central suystem along with all the details of the instrument 5 if calibration completed 6 -erti!cate of calibration is suued to the customer.

1:.

7ata to be recorded. a. 4pplied readings and indicated readings to be recorded in wor9 sheet. b. 4pplied readings and indicated readings after adustment 5 if need be 6 to be recorded in the same wor9sheet 5 3ay use more than one page as reuired but need to bind together and the assigned certi!cate number to be mentioned in each page6 c. -alculation of tolerance limit and calculation of uncertainty values are to be performed. Prepare calibration certi!cate > service report as per the procedure

1=.

4C%ing the identi!cation mar9 a. The due date of calibration will be mentioned as per the clientHs reuirment or will be mentioned as one year. b. The calibration stic9er must be aC%ed in the instrument in such a way that it doesnHt bloc9 any of operation of the instrument.

1?. #eason for #evision #evision 1 + 1.-hanges in the format. 2.Inclusion of documentation chapter. #evision 2 + 1.Inclusion of #ange #evision & + The whole procedure was revised to meet the reuirements of ISB>I*1=20 standard. Inclusion of $ncertainty procedure. 7ate + 11>7ec>21)

8888$N 9F !95$U$8888

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Insulation Tester 1 CI 02 I2

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