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Conductivity Meter for Liquids LCM-8716

Conductivity Meter for Liquids LCM-8716. A quick introduction how to perform easy and accurate measurements of conductivity and tan d on insulating liquids. The equipment. The electronic measuring device The cell Two cables A thermometer. Determination of

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Conductivity Meter for Liquids LCM-8716

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  1. Conductivity Meter for Liquids LCM-8716 A quick introduction how to perform easy and accurate measurements of conductivity and tand on insulating liquids

  2. The equipment The electronic measuring device The cell Two cables A thermometer

  3. Determination of Permittivity r,Conductivity  and Dissipation factor, tan = /2for According to IEC 61620 standard*) *) Insulating liquids – Determination of the dielectric factor by measurement of the conductance and capacitance – Test method Measurement based on so called „low amplitude, low frequency“ method, applying an alternate square wave voltage Amplitude of applied voltage: 30 V Frequency of applied voltage: 0.5 Hz

  4. Applied voltage u(t) +V Time TF -V • IR: resistive current • IC: capacitive current Generated current i(t) IR=V/R=GV IC=C V/TF Time Conductance: G=IR/V=(/o) Co Capacitance: C=ICTF/V=or Co Principle of operation applying an alternate square wave voltage

  5. Determination of Dissipation Factor, tan According to IEC 61620 Standard Measured quantities: Resistive Current: IR and Capacitive Current: IC Derived quantities: Conductance: G=IR/V and Capacitance: C=ICTF/V Derived and displayed quantities: Conductivity: =oG/Co and Relative Permittivity: r=C/oCo where, Co: vacuum capacitance of measuring cello: permittivity of vacuum equal to 8.854110-12 As/Vm Derived quantity: Dissipation Factor, tan=G/2fC=/2for where, f: main frequency i.e. 50 Hz or 60 Hz

  6. Conformity and compatibility of standards • The LCM-8716 is developed according to IEC 61620 Standard*) and works with so called “low amplitude, low frequency, alternate square wave method”. • The classic measurement of dissipation factor with an AC voltage is based on IEC 60247 Standard**). • The IEC 61620 Standard is a complement to the IEC 60247 one. • The measured dissipation factors according both standards are identical. *) Insulating liquids – Determination of the dielectric factor by measurement of the conductance and capacitance – Test method **) Insulating liquids – measurement of relative permittivity, dielectric dissipation factor (tan) and d.c. resistivity

  7. Characterisation of electrical insulating liquids with conductivity, permittivity and dissipation factor These quantities are very sensitive to the presence of soluble polar contaminants and aging products. For the recommended limits see the following standards: • IEC 60296 Standard: Fluids for electrotechnical applications – Unused mineral insulating oils for transformers and switchgear • IEC 60422 Standard: Mineral insulating oils in eletrical equipment – Supervision and maintenance guidance • IEC 61099 Standard: Specifications for unused synthetic organic esters for electrical purposes

  8. Advantages of the „low amplitude, low frequency“ method in comparison to the classic method with AC excitation voltage: • Accurate measurement of conductivity (respectively dissipation) factor • Simple design of test cell, low excitation voltage of only 30 V • No influence onto the properties of the liquid proprieties during the measurement (from charge injection into the liquid tested from measuring electrodes). • Comparatively cheap price of cell and measurement instrumentation. • Portable, low weight, no mains required, easy to clean

  9. Test cells • Simple design without guarding electrodes • Easy to clean • Low ratio “electrode surface”/ “liquid volume” minimising the contamination effects from the surface in contact with the liquid. • Comparatively cheap cell price Standard cell (160 ml) disassembled Flow cell

  10. Heater The heater with PID controller permits accurate measurements in function of temperature from ambient temperature to 90°C (optionally 120°C) Heater with cell in receptacle Heater only

  11. Evaluation software “LCM-8716 calculator” Generation of reports Input quantities equal to measured quantities Computed quantities e.g. tan in function of temperature (extrapolation) Characterisation of temperature dependency from measurement of liquid tested at two different temperatures

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