Megohmmeter models and specifications, how to choose the main principles should be in accordance with the test voltage level, the user can choose according to test product features and test instruction for high-voltage megohmmeter, output short circuit current and the range of scope should comply with the code requirements, the high field interference ability and dynamic measuring accuracy, easy to use security, high cost performance.
According to the different requirements of the test object, megohmmeter can be roughly divided into universal type, dominant type, and type three, according to the prevention and handover test rules of electric power equipment, used to measure the insulation resistance of the universal megohmmeter test voltage grade 500V, 1000V.
The leading megohmmeter mainly measures the insulation resistance, absorption ratio or polarization index of the test product. The voltage level is generally 2500V. The 5000V megohmmeter is used to measure the insulation resistance, absorption ratio and polarization index of the winding of synchronous generator, DC motor and AC motor. Sometimes it is necessary to measure or measure the true insulation resistance. For the sample with large capacitive load, the megohm meter with appropriate voltage level and large enough output short-circuit current, large range of insulation value and automatic discharge of the tested product is generally selected. Otherwise, R15S resistance value will have a great influence on the absorption ratio test results, resulting in large errors.
For the test site with strong interference, pointer megohmmeter should be selected, because the measurement data of digital display megohmmeter has a large jump, so the real resistance value cannot be confirmed, and the pointer megohmmeter itself is slow to strong magnetic field interference (damping effect of mechanical meter head). Even if there is an impact, the pointer header display is only a slight swing, the value range is also very intuitive.
1. Insulation resistance test should be carried out for electrical lines, equipment and appliances before or after installation according to the specific situation, and power test can be carried out only after passing the test.
2. Measure insulation resistance. When there is no special requirement, the voltage grade of megohm meter is:
(1) For electrical equipment or circuit below 100V, 250V megohm meter is used.
(2) Below 500V to 100V electrical equipment or circuit, using 500V high voltage megohm meter.
(3) 1000V high voltage megohm meter is used for electrical equipment or circuit from 3KV to 500V.
(4) Below 10KV to 3KV electrical equipment or circuit, using 2500V high voltage megohmmeter.
(5) electrical equipment or circuit of 10KV and above, using 2500V or 5000V high voltage megohmmeter.
3. Project name: Fill in the project name according to the project.
4. Instrument model: Fill in according to the actual megohm meter.
5. Voltage: refers to the output voltage of megohm meter.
6. Power distribution cabinet, screen, box, panel, and equipment: Fill in the numbers according to the construction drawings.
7. Location: Fill in the installation location of the tested device. Route type: fill in according to the construction system drawing number.
Megohm meter voltage level selection
The test voltage of megohmmeter (MEgohmmeter) is related to the rated working voltage of the tested product, but much lower than the working voltage of the tested product.
1, according to the test voltage grade can be divided: low voltage: 50V, 100V, 250V, 500V, 1000V; High voltage: 2500V, 5000V, 10KV;
2, power equipment commonly used megohmmeter (megohmmeter) voltage grade: 100V, 2500V, 5000V;
3, the selection of test voltage is based on the rated working voltage and capacity of the test product, divided into:
(1) Low-voltage electrical equipment and household appliances, the test voltage grade is often higher than the working voltage;
(2) The working voltage of power equipment is higher, and the grade of the test voltage is often lower than the working voltage of the tested products. It is specified by the insulation test code and corresponding standards.
In the absence of special provisions in the test procedures, the following voltage levels are recommended for insulation measurement of electrical equipment or auxiliary and control circuits:
(3) the general provisions of the test voltage level in 2500V and above, to test the absorption ratio or polarization index measurement;
(4) The test voltage is different, the internal medium relaxation polarization strength is different, the insulation resistance value is also different.
However, the insulation resistance index is not very sensitive to small range changes of test voltage.
1. For the samples with large capacitive load, the megohm meter with appropriate voltage level and large enough output short-circuit current, large range of insulation value and automatic discharge of the tested product is generally selected. Otherwise, the insulation resistance value will have a great influence, and the absorption ratio test results will have a large error.
2, to interfere with the stronger test site, should choose pointer megohmmeter, because if choose digital megohmmeter, its measuring data have bigger beating, to confirm the real value, and pointer megohmmeter itself is lagging for strong magnetic field interference (mechanical damping function header), even if there is influence, the motion of the pointer to the header is slightly, value range is also very intuitive.
3, for small interference, the requirement of measuring insulation resistance value of the occasion, should choose the digital megohm meter, because the digital megohm meter display intuitive, high precision.
4, to measure the absorption ratio and polarization index and other large capacity test occasions, should choose to automatically measure the absorption ratio and polarization index of intelligent megohmmeter.
Wuhan Xinshengneng is a professional electric power testing equipment manufacturer, with a professional technical team, the production of a variety of instruments and equipment, a variety of models to choose from. Xinshengneng service for you: 0312-3188565, to learn more visit xinshengneng official website: www.whxsn.com.
