If the diesel generator set has voltage when idling but no voltage when loaded, it must be because of a short circuit. Generally speaking, it is the short circuit in the electrical equipment, not the fault in the diesel generator set.
There are many reasons for the short circuit in the system, mainly the following:
1. Damage to electrical equipment and components
If the insulation part of the equipment ages naturally or has defects and is broken down during normal power-on operation, a short circuit will occur. Due to improper design, installation, and maintenance, the equipment defects eventually develop into short circuits, etc.
2. Natural environmental reasons
For example, when using diesel generator sets in harsh climate environments, the overhead lines will fall and break due to strong winds and ice on low-temperature wires; short circuit faults will also occur due to direct lightning or lightning induction, equipment overvoltage, insulation breakdown, etc.
3. Man-made accidents
For example, staff violated the operating procedures and switched off the load, causing an arc short circuit between phases; violated the electrical safety work regulations and closed the grounding knife switch, causing a metal dust short circuit; human negligence caused the wrong line to cause a short circuit, or poor operation and management caused small animals to enter the live equipment and cause short circuit accidents.
From the perspective of the chances of various short-circuit faults, the actual operation of the system shows that: single-phase short circuits occur most frequently, followed by two-phase short circuits, and three-phase short circuits have the least chance. However, in general, the system has taken measures, and the single-phase short-circuit current value does not exceed the three-phase short-circuit current. The two-phase short-circuit current value is usually smaller than the three-phase short-circuit current value.
Therefore, the consequences of three-phase short circuits are generally the most serious and should be given enough attention and sufficient research in normal times. At the same time, when the symmetrical component method is used for the analysis and calculation of various asymmetric short circuits, they will eventually be attributed to symmetrical short-circuit calculations.
Therefore, the study of symmetrical three-phase short circuits is the basis for asymmetric short circuit calculations.
