Fault current
Healthy insulation within instruments is exposed to short-term surges caused by direct or indirect switching and lightning strikes. Insulation failures can also occur, which results in very high fault current. This current is also more than ten times the rated current of the instruments.
Insulation aging
Aging of power supply devices can lead to their uniform failure at normal mains frequency voltage.
External causes
External objects such as birds, kite strings or branches are considered external causes of errors. These objects can span either conductor and ground, causing ground faults between individual conductors (phase-to-ground), or span two conductors, causing phase-to-phase faults.
- Consequences of failure
The error must be corrected as soon as possible. Many devices can be damaged if the error is not resolved quickly. The harmfulness of errors depends on the type of error. For example, the three-part short circuit is the most dangerous fault because the short circuit current is the highest. Some of the consequences of a short circuit current are listed below.
- Due to the resulting heating and mechanical forces, electrical devices such as buses, generators and transformers are damaged.
- Due to asymmetric errors, increasing negative sequence currents occur, which result in heating.
- Stress curves are also undesirably compressed due to disturbances. A drop in frequency can lead to instabilities.