1. Adopt protection circuit to prevent the failure of external circuit powered by distribution board. Select the intelligent phase loss protector with small volume. For example, da88cm-ii motor phase loss protection module (Shanghai Product) can be installed in the distribution board to prevent the motor from burning out due to low-voltage phase loss operation.

2. For the distribution board with the capacity of distribution transformer of 100kV · A and above, the temperature control relay (ju-3 or ju-4 ultra small temperature relay) and axial flow fan shall be installed on the box on the left side above the control electrical board at the side wall of the cooling window in the box, so that the exhaust fan can be started automatically when the temperature in the box reaches a certain value (such as 40 ℃), Forcibly expel heat to dissipate heat from the box.

3. The incoming and outgoing lines of the distribution board shall be low-voltage cables, and the selection of cables shall meet the technical requirements. For example, the incoming line of the distribution board of 30KVA and 50KVA transformers uses vv22-35 × 4. Vlv22-35 of the same specification shall be used for shunt outgoing line × 4 cable; The incoming lines of the distribution board of 80KVA and 100kVA transformers use vv22-50 respectively × 4、VV22-70 × 4. Vlv22-50 is used for cable and shunt outgoing line respectively × 4、VLV22-70 × 4 cable. After the cable is crimped with the copper aluminum wiring nose, it is connected with the wiring pile head in the distribution board with bolts.

4. Improve the wiring mode of the low-voltage capacitor bank of the original distribution board, and change its installation position from the pile head on the AC contactor to between the low-voltage incoming line of the distribution board and the meter. Prevent inaccurate measurement of the metering device due to phase failure of the capacitor circuit or capacitor damage during operation. In addition, the selected model of capacitor shall be bsmj series products to ensure reliable component quality and an full operation.

5. Selection of residual current action protector. It is necessary to select products that meet the standard of GB 6829 General requirements for residual current operated protectors and are certified by China Electrotechnical Product Certification Commission. The time delay protector with low sensitivity similar to LJM (J) series can be selected. The mode of protector device shall comply with the national jiagb13955-2005 installation and operation of residual current operated protection device. The breaking time of leakage protector, when the leakage current is rated leakage current, its action time shall not be greater than 0.5 s。

6. Select energy-saving AC contactor (similar to cj20si), and pay attention to the connection between the coil voltage of AC contactor and the corresponding terminal selected as current action protector, and pay attention to correct load matching. When selecting AC contactor, products with insulation grade of class A or above shall be selected. It is necessary to ensure that the rated current of its main circuit contact shall be greater than or equal to the load current of the controlled line. The rated voltage of the electromagnetic coil of the contactor is 380V or 220V.