Unsaon nang sugdan ang pag-test sa insulasyon sa mga kasangkapan sa kuryente?

Ang Layunin sa Pagkuha sa Insulation Resistance

Ang pangunahon nga rason sa paghimo og insulation testing sa electrical equipment mao ang siguraduhon ang public ug personal nga seguridad. Tungod sa paghimo og insulation tests tali sa disconnected current-carrying conductors, grounding conductors, ug conductors intended for grounding, mahimong ma-eliminate ang posibilidad sa sunog gikan sa short circuits.

Asa Nagbasehan sa Paghimo og Insulation Testing?

• Safety Ang pinaka importante nga rason sa paghimo og insulation testing mao ang siguraduhon ang public ug personal nga seguridad. Tungod sa paghimo og insulation tests sa disconnected live conductors, grounding conductors, ug conductors to be grounded, mahimong ma-eliminate ang panganak sa sunog gikan sa short circuits.

• Pagpadayon sa Equipment Life Ang insulation testing usab importante para sa proteksyon ug pagpadayon sa service life sa electrical systems ug motors. Ang regular nga maintenance testing maghatag og data para sa analysis ug makaprediksi sa potential system failures. Sa wala pa, ang insulation testing gikinahanglan aron masayri ang cause sa failure kung adunay usa.

• National Standards Requirement Ang materials ug electrical equipment kinahanglan mo-obserbahan sa insulation preventive tests batasan sa corresponding national standards aron masiguro ang kalidad sa manufactured electrical equipment ug sigurohon nga ang equipment nimo-meet sa regulatory ug safety standards.

Principle sa Insulation Testing

Ang insulation testing sama sa paghimo og leaks sa water pipe. Kasagaran, ang high-pressure water gi-inject sa pipe aron masayri ang seepage. Ang pressurized water nagbutang sa leak points mas sayon mosulay. Sa electrical field, ang "pressure" nagrefer sa voltage. Sa panahon sa insulation testing, ang relatively high DC voltage gi-apply sa equipment under test aron mas sayon mosulay ang potential leakage points.

Ang insulation resistance tester measures the leakage current under applied voltage ug calculates the insulation resistance value gamit ang Ohm's Law. Ang design philosophy sa mga instrument niini mao ang apply ug control test voltage sa "non-destructive" manner. Kahit na ang provided voltage mao ang taas, ang current labi ka limited. Kini nagpreventa sa secondary damage sa equipment tungod sa poor insulation ug sigurohon ang safety sa operator.

Asa Nagbasehan Dili Mahimong Gamiton ang Multimeter Para Makuha ang Insulation Resistance?

Kahit na ang multimeter makapagmeasure og resistance, dili siya makapresenta nganong kondisyon sa insulation. Tungod kay ang multimeter gigamit og 9V DC power source para sa measurement, wala kini makapagprovide sa high voltage gikinahanglan sa testing.

Paggili sa Insulation Test Voltage

Batasan sa GB50150-2006 "Electrical Installation Engineering - Handover Test Standard for Electrical Equipment":

• Para sa electrical equipment o circuits nga operating voltage below 100V, gamiton ang 250V test voltage.
• Para sa electrical equipment o circuits nga operating voltage between 100V ug 500V, gamiton ang 500V test voltage.
• Para sa electrical equipment o circuits nga operating voltage between 500V ug 3000V, gamiton ang 1000V test voltage.
• Para sa electrical equipment o circuits nga operating voltage between 3000V ug 10000V, gamiton ang 2500V test voltage.
• Para sa electrical equipment o circuits nga operating voltage above 10000V, gamiton ang 5000V o 10000V test voltage.

Insulation Resistance Testing Procedure (using an insulation resistance tester as an example)

a. Turn off the equipment or system ug disconnect it from all other circuits, switches, capacitors, brushes, surge arresters, ug circuit breakers. b. Fully discharge the system under test to ground. c. Select the appropriate test voltage. d. Connect the leads. If the insulation resistance being measured is large, it is recommended to use shielded leads and add a grounding wire to prevent breakdown.

Test leads should be avoided from being tangled to reduce measurement errors. e. Start the test, read the instrument value after a period of time (usually one minute), and record the data and the ambient temperature at that time. f. At the end of the test, if the object under test is a capacitive device, fully discharge the device. Finally, remove the connecting leads.

Asa Nagbasehan sa Paggamit og Shielded Leads Sa Paghimo og Large Resistances?

Kung ang insulation resistance being measured is very large, ang measurement voltage is fixed, ug ang current through the conductor is relatively small, making it susceptible to external influences. Using shielded leads for testing, where the shielded lead is at the same potential as the negative (-) terminal, can prevent the accuracy of insulation resistance measurement from being reduced due to surface leakage or other unexpected current leakage. Additionally, during testing, apart from the two test probes, adding a grounding wire can prevent breakdown and ensure safety.

Insulation Testing Tools

Ang insulation resistance testing gihimo gamit ang special testing instruments. Ang pinaka commonly used instrument mao ang megohmmeter o insulation resistance tester, pero ang uban pang types of instruments usahay gamiton para sa check sa integrity sa different insulation types.

• Megohmmeter (Hand-Cranked Type) A hand-cranked powered megohmmeter, known as a megohmmeter, originated in the 1950s and 1960s and is the earliest insulation resistance testing instrument. It comes in different specifications, such as 250V, 500V, and 1000V. It generates DC voltage by cranking the handle, features a pointer-type dial, and generally requires two people to operate: one to operate the megohmmeter and another to time and record data.
• Digital Insulation Resistance Tester A battery-powered megohmmeter with multiple adjustable test voltage ranges. The electronic display provides more accurate readings. It usually includes safety protection features such as automatic discharge and leakage current monitoring. With additional testing capabilities like multimeter functions, polarization index, and dielectric absorption ratio, its application range is broader. Its compact design allows a single engineer to complete all testing steps.
• Leakage Current Clamp Meter A leakage current clamp meter can be used to measure the insulation condition of equipment that cannot be de-energized. The magnetic fields generated by load currents cancel each other out. Any unbalanced current comes from current leaking from the conductor to earth or elsewhere. To measure this current, the leakage current clamp meter should be capable of detecting currents less than 0.1mA.

Precautions

• Do not connect the insulation tester to live conductors or energized equipment; ensure compliance with the manufacturer's instructions.
• Use open-type fuses, switches, and circuit breakers to turn off the equipment under test.
• Disconnect branch conductors, grounding conductors, and other equipment connected to the equipment under test.
• Ensure the disconnection of conductor capacitance before and after the test.
• Some equipment may have a discharge function.
• Check for leakage current in fuses, switches, and circuit breakers in de-energized circuits. Leakage current may cause contradictory or erroneous test readings.
• Do not use an insulation tester in environments containing hazardous or explosive gases, as the instrument may produce an arc if the insulation performance is compromised.
• Wear insulated rubber gloves when connecting test leads.