What are the problems in the use of grounding device of automatic vacuum packing machine?

1. What are the problems existing in the use of the grounding device of the automatic vacuum packaging machine? The calculation of ground current is not accurate

  What are the problems in the use of grounding device of automatic vacuum packing machine? For vacuum packaging machine, the short circuit current flowing through the grounding device is directly related to the calculation of the grounding resistance, the thermal stability of the grounding wire, the equipment contact voltage and the calculation of the step voltage, so the correct calculation of the current flowing through the power plant, substation grounding device is very important. "Grounding of ac electrical device" stipulates that the short-circuit current entering the ground through the grounding device shall be calculated. When the grounding device is short-circuited inside and outside, the larger symmetrical component of the short-circuit current flowing into the ground through the grounding device shall be adopted. The current shall be determined according to the larger operation plan of the system after 5-10 years' development, and the distribution of short-circuit current at each neutral point of the system and the diversion of lightning conductor shall be considered. During the calculation, the short-circuit current value of single-phase grounding should be calculated according to the short-circuit impedance of the system in larger operation mode.

What are the problems in the use of grounding device of automatic vacuum packing machine? For the users of packaging machinery and equipment, in actual engineering calculation, some designers directly take the grounding short-circuit current as the ground entry and do not calculate the shunt of the overhead earth wire and the shunt of the transformer neutral point, resulting in the deviation of the grounding design. Large grounding short-circuit current should be adopted in the verification of the thermal stability of the butt ground wire, and the diverging of the lightning conductor should not be considered. Since there are many parallel circuits of the ground network trunk, the cross-sectional area of the ground network trunk can be obtained to be smaller than that of the equipment grounding lead. In practical grounding engineering, the grounding wire of the same power plant and substation can be verified according to the large grounding short-circuit current of the grounding system.

2. What are the problems existing in the use of the grounding device of the automatic vacuum packaging machine? It is difficult to accurately measure the grounding resistance of packaging machinery

What are the problems in the use of grounding device of automatic vacuum packing machine? As the grounding resistance is the main index to characterize the performance of the grounding device, it is an important means to judge whether the grounding device can meet the requirements. The traditional current and voltage method is adopted to measure the grounding resistance. The error sources are mainly from three aspects:

(1) what are the problems existing in the use of grounding device of automatic vacuum packaging machine? Error caused by resistance test method of packing machine

What are the problems in the use of grounding device of automatic vacuum packing machine? The error caused by the resistance test method of the automatic packaging machine mainly includes the test layout and the type of test current. The distance between the auxiliary current and the geodesic grid is chosen to be 4-5 times of the diagonal length of the geodesic grid. The position of the auxiliary current has a great influence on the result. Theoretically, because the distribution line of the tested ground current is affected by the auxiliary current, if the auxiliary current is not arranged far enough, the distribution line of the tested ground current will produce distortion and affect the measurement result. Therefore, in order to reduce the error, the auxiliary current layout should be as far away as possible.

What are the problems in the use of grounding device of automatic vacuum packing machine? For the test current, it is mainly to measure the influence of the frequency of the power supply. From the concept of grounding resistance and the actual situation, only the measured grounding resistance value under the ac power supply of 50Hz power frequency is consistent with the requirements of the procedure.

(2) what are the problems existing in the use of grounding device of automatic vacuum packaging machine? Error caused by interference between lines

In the process of test, the measurement error is caused by mutual inductance between current line and voltage line. The measurement error is related to the distance between the lines and the current in the wire.

(3) what are the problems existing in the use of the grounding device of the automatic vacuum packaging machine? Error caused by power frequency interference

What are the problems in the use of grounding device of automatic vacuum packing machine? The main source of power frequency interference is power frequency induction. Power frequency interference voltage frequency is 50Hz, high amplitude, with the change of power load and change, it is difficult to find out the power frequency interference size rule. As power frequency interference is an important source of interference in field test, it is also a major source of measurement error. Therefore, to reduce the measurement error, this part of interference must be removed. In order to remove power frequency interference, the phase-reversal method is usually adopted at home and abroad, and a test power source different from the industrial frequency can also be used to measure the grounding resistance of the grounding device of live equipment, so as to avoid the measurement error caused by power frequency interference.