Residual current operation protection, commonly known as leakage protection, residual current operation protection device consists of residual current operation relay, low-voltage circuit breaker or AC contactor.
1, the role of residual current action protection device
In the neutral grounded low-voltage power grid, the accidental electric shock and death caused by the leakage of electricity is prevented.
2. Operation principle of residual current operation protection device
Three-phase residual current operation protection device consists of zero-sequence current mutual TA0, amplification part, actuator Q and other components. When there is a leakage or personal electric shock on the protected circuit, the secondary side of the zero-sequence current transformer induces a current I. When the current I reaches the setting value, the amplifier circuit is started and the trip unit in the actuator is actuated.
3, residual current action protector classification
3.1. Classified by operating mode
(1) RCDs that do not require an auxiliary current.
(2) RCDs that require auxiliary power,
3.2, classified by number of poles
(1) Unipolar two-wire RCD.
(2) Bipolar RCD.
(3) Bipolar three-wire RCD.
(4) Tripolar RCD.
(5) Three-pole four-wire RCD.
(6) Quadrupole RCD.
The above-mentioned unipolar two-wire, two-pole three-wire, and three-pole four-wire RCD all have a neutral line N that can pass through the zero-sequence current transformer and cannot be disconnected.
3.3, classified by protection function
(1) RCD without overload protection.
(2) RCD with overload protection.
(3) RCD with short circuit protection.
(4) RCD with overload and short circuit protection.
(5) The rated current of the RCD is ln: 6, 10, 16, 20, 25, 32, 40, 50, 63, 80, 100, 125, 160, 200A.
(6) The rated residual operating current I of the RCD is: 0.006, 0.01, 0.03, 0.05, 0.1, 0.3, 0.5, 1, 3, 5, 10, 20A.
4, residual current action protection
(1) The residual current operation protection device is suitable for three-stage protection.
The distribution transformer of the low-voltage power grid must be equipped with total protection. The total protection is installed in the distribution box (cabinet) of the distribution transformer so that the whole network of the low-voltage network of the distribution transformer is within the protection scope. The secondary protection is installed on the branch line of the low voltage line (in the distribution box). The tertiary protection is installed on the switching power supply side of the customer's line, and the temporary power equipment must be installed with the final protection.
(2) The rated residual current of the total protection should be adjustable. The adjustment range is generally between 50~200mA, and the maximum can reach 300mA.
For the grid with small leakage current, the rated residual current of non-rainy weather is 50mA, and the rainy season is 200mA.
For the grid with large leakage current, the rated residual current of non-rainy weather is 100mA, and the rainy weather is 300mA.
After achieving perfect hierarchical protection, it is allowed to increase the operating current to 500mA.
(3) The secondary protection operating current is generally 50~100mA.
(4) The operating current value of the three-stage protection residual current operating switch is generally not more than 30mA. Its operating time generally does not exceed 0.1s.
The rated residual operating current of a hand-held motorized appliance is 10mA, and 6mA is a particularly humid place.
(5) When the low-voltage power grid carries out graded protection, the superior protection should use a time delay protector, and the breaking time should be increased by 0.2 s compared with the operation time of the first stage protection and electrical engineering protection device of the following figure 1114. (0.5; 0.3; three levels less than 0.1)
5, the installation of residual current protection device
(1) The residual current operation protection device should be installed in a ventilated, dry place to avoid the erosion of dust and harmful gases. The installation location should be kept at a distance of 20cm from the AC contactor and should avoid magnetic interference from nearby wires and electrical equipment.
(2) When wiring, special attention should be paid to the fact that the wiring of the protection device should not be connected incorrectly. The protected circuit should be wrapped with yarn or tape and passed through the center of the zero-sequence current transformer before and after the hole of the zero-sequence current transformer. The harness should not be scattered within 20cm and the enclosure should be properly grounded to ensure safety.
(3) The residual current operation protection device must use products that meet the national standards and be qualified for inspection by the superior competent authority before use.
(4) The main circuit control switch of the combined protector is an air switch with a shunt release, and an AC contactor can also be used.
Stop valve is usually used for or connecting the medium flow and is not recommended for throttling.
The maximum permissible leakage of the Stop Valve with non-metal elastic seals is zero, and that of the stop valve with meal seals is 0.1xDNmm3/s. Therefore, acceptable stop valves with metal seals possibly have slight leakage. Hence, in the applications where there must not be any leakage,especially at the pipeline ends,stop valves with soft seals should be used,and shutoff valves with metal seals should not be used.
Nominal Pressure of Brass Stop Valve is 1.6MPa. Medium temperature for metal seal is -20℃~150℃, and medium temperature for non-metal elastic seal is -20℃~120℃. When the stop valve is used for saturated steam, the pressure of the saturated steam should be ≤0.6MPa.
Stop Valve
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Ningbo Jiekelong Precision Manufacturing Co., Ltd. , http://www.jklvalve.com