Introduction to Electrical Breakdown
– Electric current is the flow of charged particles in a material caused by an electric field.
– Charge carriers enable the conduction of electric current.
– Materials with high concentrations of charge carriers are electrical conductors.
– Materials with few charge carriers, like glass or ceramic, are electrical insulators.
– When a high enough electric field is applied to an insulating substance, it undergoes electrical breakdown and becomes a conductor.
Dielectric Strength and Breakdown Voltage
– Dielectric strength is the intrinsic property of an insulating material that determines the electric field strength at which breakdown occurs.
– The breakdown voltage is the applied voltage required to cause breakdown in an insulating object.
– The breakdown voltage depends on factors such as the size, shape, and location of the object.
– In a flat sheet of insulator between two electrodes, the breakdown voltage is proportional to the dielectric strength and the length of insulation.
– The shape of the conductors can also influence the breakdown voltage.
Breakdown Process
– Breakdown occurs when the electric field in an insulator exceeds its local dielectric strength.
– In air or oil, breakdown usually starts at sharp points, edges, or protruding parts of conductors.
– In solid insulators, breakdown often starts at local defects like cracks or bubbles.
– Partial discharge occurs when breakdown is limited to a small region.
– Once breakdown occurs, it rapidly spreads through the insulator, creating a conductive path and allowing current to flow.
Consequences of Electrical Breakdown
– Electrical breakdown in practical circuits is an unwanted occurrence that can cause short circuits.
– It can lead to catastrophic failure of equipment.
– In power circuits, breakdown results in a sudden drop in resistance and a high current flow.
– Electromagnetic waves can also cause temporary breakdown in materials.
– For example, a focused laser beam can cause breakdown and ionization of air.
Other Forms of Breakdown
– Electrical breakdown can occur in solids, liquids, gases, and even in a vacuum.
– Different types of dielectric mediums have different breakdown mechanisms.
– Protective devices are used to interrupt the current in power circuits and prevent continuous electric arcs.
– Failure of protective devices can result in continuous arcs and catastrophic equipment failure.
– Electrical breakdown can also pose fire hazards. Source: https://en.wikipedia.org/wiki/Dielectric_breakdown
In electronics, electrical breakdown or dielectric breakdown is a process that occurs when an electrically insulating material (a dielectric), subjected to a high enough voltage, suddenly becomes a conductor and current flows through it. All insulating materials undergo breakdown when the electric field caused by an applied voltage exceeds the material's dielectric strength. The voltage at which a given insulating object becomes conductive is called its breakdown voltage and, in addition to its dielectric strength, depends on its size and shape, and the location on the object at which the voltage is applied. Under sufficient voltage, electrical breakdown can occur within solids, liquids, or gases (and theoretically even in a vacuum). However, the specific breakdown mechanisms are different for each kind of dielectric medium.
Electrical breakdown may be a momentary event (as in an electrostatic discharge), or may lead to a continuous electric arc if protective devices fail to interrupt the current in a power circuit. In this case electrical breakdown can cause catastrophic failure of electrical equipment, and fire hazards.
