(1) Measurement of insulation resistance.
    (2) Leakage current test at DC 1mA voltage (U 1mA ) and 0.75U 1mA .
    (3) Test of AC leakage current at operating voltage.
    (4) Test of the power frequency reference voltage under the power frequency reference current.
    (5) Measurement of the insulation resistance of the base.
    (6) Check the operation of the discharge counter.
First, the measurement of insulation resistance
    Metal oxide arresters are made up of metal oxide valve plates in series with no spark gap and shunt resistance (see section 7 of Chapter 1). By measuring the insulation resistance, it is possible to initially understand whether the interior is damp and has defects such as porcelain cracks. It can also be found whether the internal fuse of the low-voltage metal oxide arrester is broken. Measurements should be made using a 2500V and above megger. The requirements are: for those above 35kV, not less than 2500MΩ; for those of 35kV and below, not less than 1000MΩ;
    The base insulation resistance is measured by a 2500V and above megohmmeter. The "pre-regulation" requires self-regulation of the insulation resistance value. In some local grid pre-regulations, the requirement is not less than 5MΩ.
Second, measure the leakage current of DC 1mA voltage U 1mA and 75% U 1mA
    The purpose of this test is to check whether the valve plate of the metal oxide arrester is damp, aging or cracked in porcelain; determine whether its operating performance meets the requirements.
    The wiring of this test can be a single-phase half-wave rectifier circuit, as shown in Figure 13-3. The parameters of the components in the figure vary depending on the voltage level of the metal oxide arrester of the test.
    It should be noted that:
    (1) Record the ambient temperature and relative humidity at the time of the test. Generally , the temperature coefficient of U 1mA of the metal oxide arrester valve plate is about 0.05%-0.17% (that is, the U 1mA is reduced by about 1% for every 10°C increase in temperature ), and can be converted if necessary. The relative humidity also affects the measurement results. The surface of the porcelain sleeve should be wiped clean before measurement.
    (2) Shielded wires should be used for wires that measure current.
    (3) The test should be carefully boosted. When the current reaches 1 mA, the corresponding voltage value is accurately read.
Third, the measured operating voltage and the AC leakage current
    The metal oxide arrester has a total leakage current including a resistive current and a capacitive current under the action of an alternating current voltage. In normal operation, it is mainly capacitive current, and the resistive current only accounts for 10% -20%. When the valve is aging, the arrester is damp, the internal insulation is damaged, and the surface is seriously dirty, the capacitive current does not change much, and the resistance is not good. The current is greatly increased. Therefore, by measuring the AC leakage current and its active component (ie, resistive current) at the operating voltage, it is possible to judge the defect of the arrester.
    This test can be measured by a resistive current detector. The commonly used LCD-4 type resistive current detector made in Japan, the Swedish TXL type MOA leakage current analyzer and the domestic BFJ-1 type, FLC-1 type leakage Current tester, etc. Figure 13-4 shows the wiring of the resistive current component measurement loop using the compensation method.
    When the movable terminal of the variable resistor R is at the ground side zero value, the meter M measures the full current value (or the capacitor current value); appropriately moves the R upward, the movable terminal, and the capacitive current on the R1. The voltage drop compensates for the voltage drop across the capacitive current R2 in the arrester. Meter M shows the lowest value, which is the resistive current component (peak). M can use two-channel electronic oscilloscope. Before the test, the input terminals of the two channels of M are connected to the output voltage of the voltage divider at the same time, and the horizontal displacement of the two channels is adjusted to make the two voltage waveforms completely coincide. Then keep the horizontal displacement does not move, to return to normal wiring, began formal testing.
    Press the "pre-regulation" requires: full current, resistive current or the power loss in the voltage measurement operation, the measurement value is compared with the initial value, increased surveillance should change significantly; when I-fold increase in resistive current, power should be checked.
    Should be recording the measured ambient temperature, relative humidity, and operating voltage, measurements should be carried out when the porcelain surface and dried, to be noted that the influence of the interference phase.
Fourth, measure the power frequency reference voltage under the power frequency reference current
    Frequency reference voltage is an important parameter MOA without gaps, which indicates the position of the excitation curve of the saturation point of the valve. After a certain period of operation, the frequency change of the reference voltage can directly reflect the aging of the arrester, the degree of deterioration.
    The test method is to express the power frequency reference current specified by the manufacturer as the peak value of the resistive current component, usually 1.20 mA), applied to the metal oxide arrester, and the peak voltage measured at the two ends of the arrester is the power frequency reference voltage. .
    When there is a suspicious indication of the resistive current, the power frequency reference voltage should be measured. It can further determine whether the arrester is suitable for continued use. The criterion for judging is to compare with the initial value and the previous measured values. When there is a significant decrease, the surge arrester should be strengthened. When the reference voltage is reduced by more than 10% for the arrester of 110kV and above, the cause should be ascertained. Should quit running.
    The measured ambient temperature is 20 °C ± 15 °C, and the measurement should be carried out separately for each section. If the whole phase arrester has an unqualified arrester section, the arrester should be replaced (or the whole phase should be replaced), so that the phase arrester is qualified.
Five, check the discharge counter action
This check can be found in the relevant part of the valve arrester.
Residual Current Circuit Breaker With Over Load Protection
TWO FUNCTION : MCB AND RCCB FUNCTIONS
leakage breaker is suitable for the leakage protection of the line of AC 50/60Hz, rated voltage single phase 240V, rated current up to 63A. When there is human electricity shock or if the leakage current of the line exceeds the prescribed value, it will automatically cut off the power within 0.1s to protect human safety and prevent the accident due to the current leakage.
leakage breaker can protect against overload and short-circuit. It can be used to protect the line from being overloaded and short-circuited as wellas infrequent changeover of the line in normal situation. It complies with standard of IEC/EN61009-1 and GB16917.1.
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