theorY applications
Technical overview
insulation
To ensure that electrical equipment and installation operate correctly total safety, all the conductors are insulated: sheathing for cables, varnish for windings.. Carried out applying voltage with smaller amplitude than for dielectric testing, yields result expressed kΩ, MΩ, TΩ. IEC 60364-6), which tolerates initial line-earth insulation fault and only shuts down the installation second fault occurs.
n Verification insulation after powering After powering the installation, the insulation should checked regularly make sure there substantial drift away from the initial values. Deterioration the equipment may occur naturally, but often also accelerated external contaminants such dust, oil, etc. This test often performed applying voltage but can also done with voltage.? Single-function multi-function instrument, for testing installations machines?
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. Furthermore, some particularly sensitive installations (operating theatres hospitals, chemical industries, etc. When the quality these insulating materials diminishes, leakage currents may flow from one conductor the other and, depending the extent the insulation faults (the worst being short-circuit), may cause serious damage. carry out this preventive maintenance effectively, the Chauvin Arnoux range megohmmeters proposes the following functions: - PI, DAR and quality ratios for quick assessment insulation quality, with the added advantage that they are not particularly influenced temperature, making them easy use without requiring correction the results Automatic calculation the insulation resistance reference temperature (C. Whether electrical installations machines, the quality the insulating materials deteriorates time passes due the stresses affecting the equipment. B) Insulation measurement motors, transformers, etc. When measuring insulation relation the earth, you are advised place the positive pole the test voltage the earth prevent earth polarization problems when carrying out multiple tests. Measurements are needed prevent and prepare for the hazards linked insufficient damaged insulation. Then test voltage applied and the insulation resistance value read.). therefore strongly recommended monitor their insulation over time. For this reason, reserved for type tests new reconditioned equipment: only equipment that passes the test will put into service. Two types measurements are required: Verification the conductors: this checks that none the conductors, cut-off devices connection equipment has suffered damage liable cause insulation fault. The main purpose this test ensure that the construction rules concerning leakage paths and clearances have been respected. Dielectric testing may destructive the event fault, depending the test levels and the available energy the instrument. The result obtained voltage value usually expressed kilovolts (kV).
III- insulation measurement Applications
A) Insulation measurement electrical installations Insulation test before powering Before powering new installation, its insulation must tested.
100 M
Criteria for choosing insulation tester Here are few tips help you choose insulation tester that matches your requirements. This measurement performed using insulation tester, also called megohmmeter. both cases, the insulation will considered acceptable the insulation resistance measured greater than the threshold specified the applicable standard for the installation tested (NF C 15-100 France, VDE 100 Germany, European standard IEC 60364, IEEE 43-2000, etc. These measurements concern both the electrical equipment and the installations which connected. Insulation resistance measurement, however, non-destructive under normal test conditions. So, addition the measurements during commissioning new renovated equipment, regular insulation testing installations and equipment helps prevent such incidents organizing preventive maintenance designed detect ageing and therefore prevent premature deterioration the insulation properties before they reach level liable cause the incidents described above. Because the method used the same for testing before powering up, the installations must switched off. All the standards concerning electrical installations equipment specify the measurement conditions and minimum thresholds respected for insulation measurements. The application What type equipment will you testing: electrical installations, switchgear, telephony, etc..? Rated operating voltage, manufacturer recommendations, dedicated standards? Test voltage: 100 250 500 1,000 2,500 5,000 10,000 15,000 VDC? Measurement range: kΩ, MΩ, GΩ, TΩ? User comfort Reading mode: needle display with logarithmic scale, digital LCD, analogue bargraph? User-friendly features: programmable alarm thresholds, backlighting, remote control probe? Operating mode Hand-cranked generator, normal rechargeable batteries? Other measurements required: continuity, current, voltage, etc. This deterioration reduces the electrical resistivity the insulants, leading turn increase the leakage currents and causing incidents which may serious terms the safety people and property, but also terms production stoppage costs industry. This type measurement requires dielectrometer.A 6549) Method based the influence test voltage variation (step voltage measurement)
II- measuring levels insulation
In concrete terms, first all the installation equipment checked ensure that voltage present it. This resistance indicates the quality the insulation between two conductors and provides good idea the risks leakage currents.
I nsulation resistance measurement and dielectric testing I
These two concepts, which characterize the quality insulant, require further explanation they are too frequently confused. This done before commissioning the installation, with all the receivers disconnected.) are built using IT-type neutral system (cf. reality, this voltage surge may due lightning the induction caused fault power transmission line. Because non-destructive, particularly useful for monitoring insulant ageing during the operating life electrical equipment installations. Equipment with faulty insulation may break down, burn cause fault the installation itself, thus triggering protective devices and shutting down the whole installation. These measurements are carried out during commissioning new reconditioned items, and then repeated regularly monitor their evolution over time. Dielectric strength testing, also called "breakdown testing", measures insulant's ability withstand medium-duration voltage surge without sparkover occurring. Verification the whole installation relation the earth
