1、 Preparation before operation

1. Confirm equipment suitability
   • Voltage level matchingSelect the appropriate range of insulation tester (such as 500V, 1000V, 2500V, 5000V) based on the voltage of the tested equipment.
   • System type adaptationDistinguish between IT systems (ungrounded) and TT/TN systems (grounded), and select instruments that support corresponding monitoring functions (such as leakage current detection and insulation resistance measurement).
   • Environmental condition verificationEnsure that the testing environment is free from strong electromagnetic interference, high temperatures (>40 ℃), or humidity (relative humidity>80%) to avoid affecting measurement accuracy.
2. Instrument status check
   • Visual inspectionConfirm that the instrument casing is not damaged, the wiring terminals are not loose, and the display screen is not cracked.
   • Functional self-testAfter booting up, execute a self-test program to check the battery level, calibration validity period, and whether the alarm function is normal.
   • Calibration verificationVerify the accuracy of the instrument using a standard resistance box or equipment with known insulation resistance (if tested with a 100M Ω standard resistance, the error should be ≤± 5%).
3. The tested device loses power
   • power outageDisconnect all power sources (including main power, backup power, UPS) of the tested equipment and hang a "Do Not Close" warning sign.
   • Discharge treatmentFully discharge capacitive equipment (such as motors, cables, capacitors) for at least 5 minutes to avoid residual charges damaging instruments or endangering personnel safety.
   • Segregated WitnessUse a multimeter or voltage tester to confirm that there is no voltage in the tested circuit, ensuring the safety of the test.

2、 Precautions during the testing process

1. Correct wiring
   • High voltage end (L)Connect the live parts of the tested equipment (such as phase lines and windings).
   • Grounding terminal (E)Connect the device casing or grounding terminal to ensure good contact (contact resistance<0.1 Ω).
   • Shielded end (G)(Optional): For high-voltage cables or long-distance lines, connect a shielding layer to eliminate surface leakage current interference.
2. Parameter Settings
   • Test voltage selectionSet the test voltage according to the rated voltage of the equipment (such as 500V for low-voltage equipment and 2500V or 5000V for high-voltage equipment).
   • Test time controlThe continuous testing time should not exceed 1 minute (to avoid equipment overheating), or according to standard requirements (such as IEC 60034-1 which specifies a motor testing time of 1 minute).
   • Alarm threshold settingAccording to industry standards (such as GB/T 16927.1), set the qualified insulation resistance value (such as low-voltage equipment ≥ 0.5M Ω, high-voltage equipment ≥ 1M Ω/kV).
3. Environmental interference avoidance
   • Stay away from strong magnetic fieldsAvoid testing near strong electromagnetic sources such as transformers and welding machines to prevent signal distortion.
   • Reduce human interferenceDuring testing, operators should stay away from the tested equipment to avoid human capacitance affecting the measurement results.
   • Avoid damp areasIf it is necessary to test in a humid environment, waterproof instruments should be used or the equipment surface should be dried.
4. Data recording and analysis
   • Multi point testingTest the insulation resistance of each phase to ground for three-phase equipment separately and record the minimum value.
   • Trend comparisonComparing the current data with historical records, if the insulation resistance decreases by more than 30%, further investigation of the cause (such as moisture, aging, mechanical damage) is required.
   • Environmental correctionIf the humidity of the testing environment is greater than 70%, the results need to be humidity corrected according to standards such as IEC 60060-1.

3、 Safety protection measures

1. Personal Protective Equipment (PPE)
   • insulating glovesUse insulated gloves that comply with GB 12014 standard (withstand voltage level ≥ test voltage).
   • insulated shoesWear anti smashing insulated shoes (withstand voltage ≥ 10kV).
   • gogglesTo prevent eye damage from electric arcs or splashes during the testing process.
   • protective clothingWear anti-static and flame-retardant work clothes to avoid sparks caused by static electricity.
2. Emergency preparedness
   • fire extinguisherCO ₂ or dry powder fire extinguishers should be equipped on site, and the use of water-based fire extinguishers (which may conduct electricity) is prohibited.
   • first aid kitInclude insulation tape, tourniquet, etc., and ensure that personnel are familiar with first aid methods for electric shock (such as cardiopulmonary resuscitation).
   • Emergency stop buttonFamiliar with the emergency shutdown process of the tested equipment, ensuring the ability to quickly cut off the power supply.
3. Dangerous area control
   • set up a cordonSet up a cordon around the testing area to prohibit unrelated personnel from entering.
   • Hang warning signsHang a "Testing, No Operation" sign at the control cabinet and power switch.
   • Special person supervisionAssign a dedicated person to monitor the testing process and ensure that the operation complies with safety regulations.

4、 Post maintenance and storage

1. Instrument cleaning
   • Shell cleaningWipe the instrument casing with a dry cloth and avoid using corrosive cleaning agents.
   • Maintenance of wiring terminalsRegularly wipe the wiring terminals with alcohol swabs to remove the oxide layer and ensure good contact.
   • Dust prevention treatmentCover the instrument with a dust cover during storage to prevent dust from entering the internal circuit.
2. Battery Management
   • Regular charging and dischargingIf using lithium batteries, charge and discharge them every 3 months to avoid battery aging.
   • Low-temperature storageWhen stored for a long time, keep the battery level at 40% -60% and store it in a dry, low-temperature environment (<25 ℃).
   • Replacement reminderWhen the battery life is reduced to 50% of its original value, replace it with a new battery in a timely manner.
3. Calibration and verification
   • Periodic calibrationAccording to the instrument manual or standard (such as JJG 690-2014), it is required to be calibrated by a metrology institution every year.
   • Verification labelAfter calibration, paste a qualified label indicating the calibration date, validity period, and verification institution information.
   • Nonconforming product handlingIf the calibration is not qualified, immediately stop using the instrument and contact the manufacturer for repair or replacement.
4. Storage environment requirements
   • temperature controlStorage temperature range -20 ℃~+50 ℃, avoidharshTemperature causes component damage.
   • humidity controlRelative humidity<70%, to prevent condensation or corrosion inside the instrument.
   • Seismic measuresUse specialized packaging boxes for storage to avoid mechanical impact on the instrument during transportation or storage.

5、 Common misconceptions and corrections

1. Misconception 1: Do not discharge before testing
   • riskResidual charges may damage the instrument or cause electric shock to personnel.
   • correctThe tested equipment must be fully discharged with a discharge rod and verified to have no voltage before testing.
2. Misconception 2: The higher the test voltage, the better
   • riskExcessive voltage may break through the insulation of equipment and cause damage.
   • correctStrictly select the testing voltage according to the rated voltage of the equipment to avoid overvoltage testing.
3. Misconception 3: Ignoring the influence of environmental humidity
   • riskA humid environment can lead to low insulation resistance and misjudgment of equipment failure.
   • correctAfter testing in a humid environment, the results need to be humidity corrected or retested.
4. Misconception 4: Failure to restore device status after testing
   • riskMay affect the normal operation of the equipment or pose a risk to subsequent operations.
   • correctAfter the test is completed, remove the wiring, restore the equipment to its original state, and clean up the site.

The correct use of industrial insulation detectors requires strict operating procedures, safety protection, and post maintenance. By following the above precautions, the accuracy of the test results can be ensured, while ensuring the safety of personnel and equipment and extending the service life of the instrument.