General knowledge about wire and cable construction(1)

1.What are the requirements for the positive sequence impedance measurement of cable lines?
The positive sequence impedance refers to the resistance of the cable conductor under AC voltage and the phasor sum of three adjacent inductive reactances in the cable connected in series.
The positive-sequence impedance of the cable line can generally be directly measured on the cable tray. Generally, lower voltages are used in the measurement. Therefore, a step-down transformer is required to reduce the voltage. The step-down transformer uses a star connection. The capacity is generally above 10kVA. Wide voltage adjustment range. The AC power supply should be stable during the measurement to ensure that the current reaches the specified requirements during the measurement. The reading value of the actual voltmeter must be the voltage at the cable end. The test current should preferably be close to the long-term current carrying capacity of the cable. For each meter, read the values ​​of three meters at the same time after closing the current.
2. According to the "Regulations on Electricity Production Safety", what are the requirements for electrical workers?
(1) After being examined by the hospital, he is in good health and has no symptoms affecting normal work;
(2) Possess relevant knowledge required by the electrical industry, necessary electrical knowledge, master relevant regulations, professional technology and safe operation technology according to their duties and job nature, and pass the exam;
(3) Be proficient in electric shock first aid.