PDC-ANALAYSER user's guide
Contents
1. December 1994 pp 1000 1004 Li Y J Rungis The square wave voltage method for the measurement of low level tan of liquid dielectrics 1997 IEEE International Conference on Properties and Applications of Dielectric Materials IEEE Publication 97CH35794 pp 1125 1128 Berger N J C Filippini R Tobaz on Progress in the determination of the dissipation factor tand and or the resistivity p of dielectric Liquids Cigr Journal ELECTRA No 185 August 1999 GIGRE Report on 15 02 Working Group activities on Dielectric Liquids Paris 31 August 1994 IEC Publication 60247 Measurement of relative permittivity dielectric dissipation factor and d c resistivity of insulating liquids 1978 Diabi R J C Filippini C Marteau R Tobaz on On the role of temperature and impurities in the low field conduction of insulating liquids Conference Record of ICDL 96 12 International Conference on Conduction and Breakdown in Dielectric Liquids Rome 1996 IEEE Publication 96CH35981 pp 350 353 Bartnikas R Electrical Insulating Liquids ENGINEERING DIELECTRICS VOLUME III ASTM Publication Code Number PCN 31 002093 21 ISBN 0 803 1 2055 9 1994 Itahashi S H Mitsui T Sato M Sone State of Water in Hydrocarbon Liquids and its Effect on Conductivity IEEE Transaction on Dielectrics and Electrical Insulation Vol 2 No 6 December 1995 pp 1117 1122 IEC Publication 60296 Specification for unused mineral insulating oils for tr2. to disassemble the active part for cleaning purposes The required amount of liquid for a standard test cell LCM 8716 CS is about 210 ml To reach this amount fill in the liquid to be tested up to 23 mm from the top edge of the vessel The temperature of the tested liquid can be determined by introducing the electronic thermometer in the cell through the cover orifice When using a metallic thermometer on the 20 pS m scale the thermometer should be grounded with the grounding clip coming with the instrument to avoid introducing electrostatic noise into the cell The specification of this cell is given in section 9 Copyright ALFF Engineering Switzerland 4 ALFF Engineering 6 LCM calculator The LCM 8716 equipment itself permits the measurement of the volume conductivity o and the relative permittivity r at a temperature T Such a data set of the dielectric properties can be transformed mathematically into various other variables e Resistivity the inverse of the conductivity e Tanod the ratio of the in phase current resistive current and the capacitive displacement current at a given frequency e Power factor the cosine of the phase angle between alternating field strength and current density at a given frequency e Discharge time constant decay time constant of a volume charge density e Volumetric heating heating density at a given electric field strength Although these transformations could be done on a pocket calcu
3. transformers bushings capacitors etc Several investigations have demonstrated that the conductivity of oil is influenced by impurities and ionic components which are introduced or produced in it 8 9 Therefore the oil conductivity characterises well the quality of oil Further it has been shown that the moisture in oil has no significant influence on its conductivity 10 The following values of conductivity given at ambient temperature are typical for a mineral oil in its different states of use New unused oil laboratory quality lt 0 05 pS m New unused oil industrial quality 0 05 0 1 pS m Light used oil in good condition 0 1 1 0 pS m Middle used oil in acceptable condition 1 0 5 0 pS m Heavily used oil in bad condition gt 5 0 pS m Copyright ALFF Engineering Switzerland 8 ALFF Engineering 9 References 1 10 11 12 13 14 15 IEC Publication 61620 Insulating liquids Determination of the dielectric dissipation factor by measurement of conductance and capacitance Test method 1998 Hilaire M C Marteau R Tobaz on Apparatus Developed for Measurement of the Resistivity of Highly Insulating Liquids IEEE Transactions on Electrical Insulation Vol 23 No 4 August 1988 pp 779 787 Tobaz on R J C Filippini C Marteau On the Measurement of the Conductivity of Highly Insulating Liquids IEEE Transactions on Dielectrics and Electrical Insulation Vol 1 No 6
4. 10 2 43 34 10 2 108 3 935 10 3 935 10 808 9 102 2 307 10 use F1 for help exit Figure 2 Screen shot of the main window of the LCM calculator Copyright ALFF Engineering Switzerland 5 ALFF Engineering For most insulating liquids the temperature dependency of volume conductivity can be described with an exponential law according to the equation Or Or exp E k 1 T2 1 T1 6 where o7 and or are the values of volume conductivity at temperatures T1 and T2 expressed in Kelvin K Es is the activation energy in eV and k is the Boltzmann constant equal to 8 62x10 eV K For most of presently available dielectric liquids the variation of relative permittivity in dependency of temperature around 20 C is mainly due to the variation of their volume in function of temperature This variation can be described with the linear equation ErTm 120 1 Vep Tm 20 7 where 1m and no are respectively the values of relative permittivity measured at temperatures Tm C and 20 Vep is the variation coefficient of permittivity at 20 C expressed in 1 C If the parameters E and Vep and their validity ranges are known for a liquid it is possible to perform temperature conversions of all above mentioned quantities with high accuracy It is recommended to customize the LCM calculator according your needs by clicking on P x activation energy compute activation ener
5. 10 S m for conductivity up to 199 9 pS m 10 S m for conductivity up to 1 999 nS m 10 S m for conductivity up to 19 99 nS m 1 digit 1 of indicated value up to 5 00 0 001 for relative permittivity up to 1 999 0 01 for relative permittivity from 2 00 to 5 00 1 digit 0 2 of indicated value simple on site adjustment for test cells from 50 to 70 pF 0 5 Hz 30 V square wave with no dc part one for conductivity one for relative permittivity 0 2 V for 0 to 100 of chosen range short circuit proof 2 6 kg 260 x 283 x 115 width x depth x height in mm six batteries type AA alkaline for several hours of operation universal mains adapter 100 240 Vac 50 60 Hz delivering 6 V DC 0 35 C 10 50 C 70 106 kPa 5 80 non condensing lt 2g 210 ml 60 pF lt 50 ppm C 1 5mm stainless steel two standard 50 Q BNC plugs glass thermometer or electronic thermometer 1 2kg 125 x 82 height x diameter in mm one BNC BNC cable 1m red for application of the excitation one BNC BNC cable 1m black ultra low noise for current measurement 10 ALFF Engineering Appendix A Cleaning procedures of the test cell Two cleaning procedures have been proposed in the IEC 61620 Standard 1 an exhaustive and a simplified procedure I Exhaustive cleaning procedure for the test cells a Empty the cell and drain off the liquid from electrodes and vessel b Boil the complete cell for at least 5 min in a solut
6. Conductivity Meter For Liquids LCM 8716 Manual ALFF Engineering Content DSTA OAC eenn inne amnGaaaenuadannenE 3 2 Measuring 10 ise a cree eect tper spear orale re sean eaiom nunneneneemuaioms 3 3 Conformity and compatibility of standards ceccccccsseeesssssssssssssensssscccessssmsseecesssssssesseceessssnaeeeeeees 4 4 Measuring instrument aa cctancahs cane ossctna es teesieun is ecaate sete ayacete diese asses eect elo ke 4 S Lest Cell ccccictscsssasceaarsadsst rates T al ea eacaea EE 4 OCMC a lO Ol cece eaters eee eae oes 5 7 Performing a measurement See ee eee ee kets oe eee went ee Cee aera een ee Mere ere ar ane 8 8 A Tl I A Oca sponser rescatatamconep eee eeasoenessaieesae idee te teem pease mngmacnel 8 FMR Se STN TEE O TE AEE esos teagan EE gues Roatan asec SRA uate 9 MS Cte ONS seas ee Aer asec decent AE E AEO 10 Appendix A Cleaning procedures of the test Cell ccccessssssssssssssssnnnnmnmnnsesseeeeececeesesnnnnnunnnmmnnseses 11 Appendix B Part list of LCM 8716 ou cccccccscssssssssssssumssessessesesccesssssssssusuumsssessesseceeceesssssssssssununsneneesee 12 Copyright ALFF Engineering Switzerland 2 ALFF Engineering 1 Introduction The Conductivity Meter For liquids LCM 8716 conforms to the new IEC 61620 standard 1 This instrument is based on the so called low amplitude low frequency alternate square wave method and permits accurate measurement of volume conductivity and relative permittivity over a wide range withou
7. ansformers and switchgear 1982 IEC Publication 60963 Specifications for unused polybutenes 1988 IEC Publication 60867 nsulating liquids Specifications for unused liquids based on synthetic aromatic hydrocarbons 1993 IEC Publication 61099 Specification for unused synthetic organic esters for electrical purposes 1992 IEC Publication 60836 Specification for silicon liquids for electrical purposes 1988 Copyright ALFF Engineering Switzerland 9 10 Specifications Conductivity Meter For Liquids LCM 8716 Electronic measuring instrument conductivity measurement range resolution of the conductivity measurements uncertainty of conductivity measurements relative permittivity measurement range resolution of permittivity measurements uncertainty of permittivity measurements calibration of the test cell frequency of the measurement voltage amplitude of the measurement voltage optional analogue outputs analogue output voltage span weight size power supply in the field power supply in the lab temperature use temperature stock pressure humidity acceleration Test cell required amount of liquid vacuum capacitance capacitance drift with temperature electrode gap material electrical connection temperature measurement weight size cables Copyright ALFF Engineering Switzerland ALFF Engineering 104 2x10 S m on four ranges 104 S m for conductivity up to 19 99 pS m
8. e application as specified in the old IEC 60247 standard can disturb the thermodynamic equilibrium of highly insulating liquids and generate unrepresentative results of conductivity and tand The specification of IEC 60247 are only acceptable for tan measurements of moderately insulating liquids This was the main trigger to work out the new IEC 61620 standard as complement to IEC 60247 standard describing an adequate measuring method for investigations on highly insulating liquids 4 Measuring instrument This instrument works with low voltage and low current levels and represents no danger at all for its operators To avoid possible damage do not short circuit the electrodes of test cell when these are connected to instrument and the instrument is turned on The specification of this measuring instrument is given in section 9 5 Test cell The application of a square wave excitation voltage with low amplitude of only 30 V permits the development of a test cell with simple design easy to use and to clean The compact test cell of the LCM 8716 is composed of only two parts a container and an active part Two coaxial electrodes stainless steel are attached on a cap also stainless steel This cap also supports two BNC connectors coupled to the two electrodes The electrodes possess a clean polished surface The vessel and the active part can be cleaned according to procedures described in the appendix A It is not possible and not necessary
9. gy and permittivity var coeff typ new oil typ used oil first measurement 2nd measurement at low temperature at high temperature fo 389 ev 2 0 temperature C E 0 C permittivity var coeff 0 85 conductivity pS m fi 1 63 typical 2 21 1 relative permittivity 24 34 00 0005804 12C Compute frequency properties of interest temperatures of interest only for tan delta and ee power factor computation I conductivity 1 jo _typical_ Bo Hz V resistivity 2 20 JV relative permittivity 3 ja 0 M field strength jy ee i 60 only o rt heating J power factor 5 ls 0 computation J J discharge time constant 6 g 0 fi 0 kuzan J volumetric heating 7 1100 C Use F1 for help Load Save Cancel Figure 3 Screen shot of the Setup window of the LCM calculator Copyright ALFF Engineering Switzerland 6 ALFF Engineering The LCM calculator accepts freely set values for E and vep All the same specific values of E and Vep for new and used mineral oil have been implemented according to references 8 9 to make simpler a first assessment Using preset values for E and Vep is astonishing precise for small extrapolations as measuring at 22 9 C and extrapolating to 25 C However making extrapolations without precise knowledge about E for large temperature differences like measuring at 15 C and extrapolating to
10. ion of about 5 trisodium phosphate diluted in de ionised water Afterward rinse the cell several time with de ionised water c Rinse for 5 min under running tap water d Boil the complete cell in de ionised water for minimum half an hour e Dry the cell in a clean oven at 105 C for 2 hours f Let the cell cool down to ambient temperature in a desiccator without touching the surface of electrodes with bare hands g Fill the cell with the insulating liquid to be measured h Empty the first filling and perform the measurement on the second filling If the cleaned cell is not used immediately store it in a desiccator avoiding any contamination II Simplified cleaning procedure for test cells used for only one type of liquids The following procedure can be applied to clean cells which are devoted to only one type of liquid a Empty the cell and drain off the liquid from electrodes and vessel b Rinse for 5 min the electrodes and the vessel of the cell with an analytical grade solvent appropriate to the previously tested liquid c Rinse the different parts with analytical grade ethanol d Dry the cell in a clean oven at 80 C for 3 hours and let the cell cool down to ambient temperature in a desiccator e Fill the cell with the insulating liquid to be measured f Empty the first filling and perform the measurement on the second filling Recommended analytical grade solvents Cyclohexane for hydrocarbon liquids
11. lator ALFF ENGINEERING offers a software LCM calculator which can be downloaded as freeware at www alff engineering ch PDF LCM3 zip and www alff engineering ch downloads htm This LCM calculator permits also to extrapolate all these variables to other temperatures Depending on the temperature gap and on the accuracy of the temperature dependancy coefficients for the extrapolation the uncertainty caused by the extrapolation could be very low to extremely large This extrapolation feature must be used with care and professionalism 4 gLcm Calculator v3 0 by ALFF ENGINEERING Oo x New Examples Print Save Setup About input measured values temperature C conductivity pSm relative permittivity TER 28 3 fi 3 2 2 computation results m optional description of liquid under investigation for printout purposes example of used transformer oil still in good condition m computation results temp C cond S m resist p O m permittivity r tand power factor dis time s heat W m 0 0 275 7 10 5 3 627 10 2 2 236 44 32 10 44 32 10 71 83 27 57 20 0 850 9 10 15 1 175 10 2 2 211 1384 104 138 4 104 23 00 85 09 40 0 2 274 10 12 439 7 10 2 185 374 2 10 374 2 104 8 507 227 4 60 0 5402 10 12 185 1 10 2 159 899 3 10 899 3 10 3 539 540 2 80 0 11 63 10 2 85 97 10 2 134 1 960 107 1 960 10 1 624 1 163 10 90 0 1654 10 12 60 47 10 2 121 2 803 10 2 803 10 1 135 1 654 10 100 0 23 07
12. like mineral oil IEC 60296 11 polybutenes IEC 60963 12 alkylbenzene mono dibenzyltoluene phenylxylylethane and isopropylnaphthalene IEC 60867 13 Ethanol for organic esters like dioctylphthalate tetrahydricalcohol esters IEC 61099 14 Toluene for silicone liquids IEC 60836 15 Copyright ALFF Engineering Switzerland 11 ALFF Engineering Appendix B Part list of LCM 8716 1 piece 1 piece 1 piece 1 piece 1 piece 1 piece 1 piece 6 pieces 1 piece 1 piece 1 piece measuring device test cell stainless steel electrodes test cell stainless steel vessel test cell electronic thermometer with adapter black BNC BNC low noise cable measurement red BNC BNC cable test signal power supply delivering 6 V DC from 100 Ver to 240 Ver 50 60 Hz EURO plug primary cells type AA alkali manganese for about 15 hours of operation CDROM LCM calculator for PC s with Windows 95 98 ME 2000 XP clip for grounding metallic thermometers this manual Copyright ALFF Engineering Switzerland 12
13. lp and to find computation details like the formulas used Copyright ALFF Engineering Switzerland 7 ALFF Engineering 7 Performing a measurement Clean the test cell according IEC61620 1 see also Appendix A Before filling in any liquid to be tested connect the test cell to the measuring device by means of the two BNC cables As the test cell now contains air the relative permittivity is 1 000 and the conductivity is too low to be seen by this device Turn on the instrument and choose the range of relative permittivity to lt 2 So the relative permittivity can now be calibrated to 1 000 by making use of the adjustment knob located under the permittivity display The conductivity display is supposed to show 0 on all ranges Calibrating the relative permittivity means calibrating also the conductivity measurement as this adjustment influences both displays by the same factor Turn off the instrument remove the BNC cables from the test cell plugs and open the test cell Fill in the liquid to be tested up to 23 mm from the top edge of the stainless steel vessel or fill in about 210 ml of liquid Connect the BNC cables turn on the instrument and insert the thermometer if necessary switch the relative permittivity range to 2 and find the appropriate range for the conductivity 8 A typical application A typical application of LCM 8716 is the quality assessment of mineral oil used in high voltage apparatus e g power and instrument
14. s the determination of conductivity values down to 0 01 pS m respectively tand values down to 1E 6 at 50 Hz This high sensitivity allows accurate measurements of conductivity and tand at low temperatures and consequently the characterisation of liquids at room temperature can be carried out with confidence 5 6 Applied voltage u t Time C e e Co Generated current i t le V RE i i Ca Vacuum capacitance Principle of operation using the alternate square wave method Figure 1 Measuring method used in LCM 8716 Copyright ALFF Engineering Switzerland 3 ALFF Engineering 3 Conformity and compatibility of standards The LCM 8716 instrument is developed according the new IEC 61620 standard 1 This new standard doesn t substitute the old IEC 60247 standard old nomination IEC 247 7 but it is a complement to it The IEC 61620 standard proposes a new measurement method the so called low amplitude low frequency alternate square wave method permitting an accurate determination of the conductivity relative permittivity and dissipation factor tand of highly insulating liquids at low temperature without disturbing their thermodynamic equilibrium It is well known that the conductivity is a characteristic of a liquid only if it is measured at thermodynamic equilibrium The investigations of Task Force 04 of Cigr WG 15 02 5 6 have demonstrated that the application of high electric stress and or prolonged voltag
15. t disturbing the thermodynamic equilibrium of the liquids investigated 2 3 4 5 The measurement of volume conductivity in the range of 0 01 pS m to 20 000 pS m allows the use of this instrument for quality assessment of high resistive liquids even at ambient temperature 2 Measuring method The liquid in the test cell is excited with a low amplitude 30 V low frequency 0 5 Hz alternate square wave voltage without any dc component see figure 1 By measuring the current through the liquid the capacitance C and the conductance G can be determined and the values of relative permittivity and volume conductivity o are given according to the following equations r C Co 1 amp G C 2 where is the permittivity of vacuum equal to 8 8541x107 As Vm and C is the vacuum capacitance The derived dissipation factor tan for a given frequency f can be determined according to the following equation G C 2af For insulating liquids used in electrical power apparatus the conduction is the sole cause of loss at power frequencies 50 60 Hz which are low frequencies indeed Therefore the dissipation factor tand calculated from the measured amp and o with alternate square wave method is equal to the value of tand measured with the classic bridge method 5 6 tand 3 For determination of conductivity or tan delta the alternate square wave method is by far more sensitive than the classic bridge method It permit
16. the would be properties at 90 C results in a high uncertainty because the uncertainty increases more rapidly than proportional to the temperature bridged There are three alternatives for setting up the activation energy and the permittivity variation coefficient e By making use of two measurement results of the insulating liquid done at temperatures well apart Enter these values in the Setup window and the LCM calculator computes both Es and vep This is the recommended method for more pronounced interpolations and extrapolations and yields good results e By entering manually the figures for the activation energy and the permittivity variation coefficient known by you from previous measurements of this insulating liquid or known from measurements of almost identical samples e If these coefficients are completely unknown the typical values proposed in the setup window can be used These values should be considered guess values and they are useful for modest extrapolations only On the setup window you can also choose the properties of interest ALFF ENGINEERING recommends to check only the properties significant to the actual investigation to keep affairs simple and uncrowded The frequency in the setup window is required exclusively for tand and power factor computation as these properties change with frequency Similarly the field strength is required exclusively for the volumetric heating computation Use F1 to evoke he
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