The selection of RCCB
Selection of RCCB should consider many factors.
Among them, the first is the correct choice of RCCB leakage current. In the bathroom, swimming pools, tunnels and other places with great risk of electric shock, should be used high sensitivity, fast RCCB (the operating current should not exceed 10mA). If the place of installation electric shock accident, get the help of others in a timely manner from the power, the leakage current protection device can be greater than the current to get rid of current; such as fast-type protection device, the operating current can be selected according to ventricular fibrillation current. If it is the first level of protection, that is, points in front of the total protection, the action current can exceed the ventricular fibrillation current. If the workplace can not get the help of others in a timely manner from the power supply, the RCCB operating current should not exceed the current. In the event of an electric shock that may lead to serious secondary accidents, a quick-leakage protective device with an operating current of 6mA should be used.
In order to protect children or patients, quick-leakage protection devices with an operating current of 10 mA or less should also be used. For Class I hand-held power tools, they should be regarded as dangerous in the workplace, the size of the installation of current 10 ~ 30mA fast-type RCCB. Select the action current should also consider the possibility of malfunction. RCCB should be able to avoid unbalanced line leakage current without action; should also be installed at the possible electromagnetic interference does not malfunction. Select the operating current should also consider the actual conditions of the protector. For example, due to the purely electromagnetic operating current is difficult to achieve below 40mA and should not pursue too high sensitivity of the electromagnetic leakage protection device. In the case of multi-level protection, the choice of operating current should also consider the need for multi-level protection selectivity, the total protection should be installed with less sensitivity or a little delay leakage protection device.
Leakage alarm devices used to prevent leakage fire should be used in the sensitivity of RCCB. Its operating current can be selected within 25 ~ 1000mA. Electrical equipment connected to outdoor overhead lines should be equipped with impulse voltage non-operating type leakage protection device.
For the motor, the RCCB should be able to avoid the motor starting leakage current (100kW motor up to 15mA) without action. Protector should have better balance characteristics, in order to avoid the number of times the rated current of the stall current under the impact of malfunction. For not allowed to stall the motor leakage alarm method should be used, and should not be used to cut off leakage.
For lighting lines, should be based on the size and distribution of leakage current, the use of hierarchical protection approach. Branch of the selection of high-sensitivity protector, trunk selection sensitivity protector.
In construction sites, metal structures and other electric shocks on the occasion of a large risk, Ⅰ type portable devices or mobile devices should be equipped with high sensitivity RCCB.
Insulation resistance of electric equipment fluctuates with a wide range of temperature changes. For example, the insulation resistance of a polyethylene insulating material at 60 ° C is only a few tenths of that at 20 ° C. Therefore, the state should be based on thermal leakage protection current selection action.
For the welding machine, should consider the normal operation of the protector from short-term impact welding current, current rapid changes in power supply voltage fluctuations. For high-frequency welding machine, protector should also have good anti-electromagnetic interference performance.
For the non-linear parts and produce high harmonics have rectified parts of the device should be used zero sequence current transformer secondary side connected with a filter capacitor protection, and the transformer core should use low residual magnetism soft magnetic material production. Leakage protection device poles should be selected according to the characteristics of the line. Single-phase line selection of two-pole protection, only with three-phase load three-phase line or three-phase equipment can be used three-pole protection, power and lighting applications of three-phase four-wire lines and three-phase lighting circuit must use quadrupole protector .
Leakage switch rated voltage, rated current, breaking capacity and other performance indicators should be compatible with the line conditions. Leakage protection device type and power supply lines, power supply, the type of system grounding and electrical equipment features to adapt.