compressional forces

Normal dip-slip faults are produced by vertical compression as Earth’s crust lengthens. The hanging wall slides down relative to the footwall. Normal faults are common; they bound many of the mountain ranges of the world and many of the rift valleys found along spreading margins of tectonic plates.

Reverse faults are exactly the opposite of normal faults. If the hanging wall rises relative to the footwall, you have a reverse fault. Reverse faults occur in areas undergoing compression (squishing). Since the beds indicate that the hanging wall has risen relative to the footwall, this is a reverse fault.

In a normal fault, the block down dip of the fault line moves down (D) relative to the opposite block (Figure 3d). In a reverse fault, the block down dip of the fault line moves up (U) relative to the opposite block (Figure 4d).

In a reverse fault, the block above the fault moves up relative to the block below the fault. This fault motion is caused by compressional forces and results in shortening. Other names: thrust fault, reverse-slip fault or compressional fault. Examples: Rocky Mountains, Himalayas.

Dip-slip faults are inclined fractures where the blocks have mostly shifted vertically. If the rock mass above an inclined fault moves down, the fault is termed normal, whereas if the rock above the fault moves up, the fault is termed reverse.

Reverse faults are steeply dipping (more near vertical), thrust faults are closer to horizontal. 45° is a commonly cited cut-off between the two types of faults. A more important difference is that thrust faults allow whole thick slivers of continental crust to override each other.

Three types of faults There are three kinds of faults: strike-slip, normal and thrust (reverse) faults, said Nicholas van der Elst, a seismologist at Columbia University’s Lamont-Doherty Earth Observatory in Palisades, New York.

A fault is formed in the Earth’s crust as a brittle response to stress. Generally, the movement of the tectonic plates provides the stress, and rocks at the surface break in response to this. Faults have no particular length scale.

Past fault movement has brought together rocks that used to be farther apart; Earthquakes on the fault have left surface evidence, such as surface ruptures or fault scarps (cliffs made by earthquakes); Earthquakes recorded by seismographic networks are mapped and indicate the location of a fault.

normal fault – a dip-slip fault in which the block above the fault has moved downward relative to the block below. This type of faulting occurs in response to extension and is often observed in the Western United States Basin and Range Province and along oceanic ridge systems.

Faults are cracks in the earth where sections of a plate (or two plates) are moving in different directions. Faults are caused by all that bumping and sliding the plates do. They are more common near the edges of the plates.

There are four types of faulting — normal, reverse, strike-slip, and oblique. A normal fault is one in which the rocks above the fault plane, or hanging wall, move down relative to the rocks below the fault plane, or footwall.

A fault is a fracture on which the walls have been relatively displaced to a significant degree parallel to the fracture. A fissure is a fracture whose walls have been opened significantly by sepa- ration in a direction normal to the plane of the fracture.

All the Three Phases to Ground Fault – It is the most severe type of the fault and very rarely occurs in the power system. It occurs due to a breakdown of insulation between all the phases as well as to the earth.

A ground fault (earth fault) is any failure that allows unintended connection of power circuit conductors with the earth. Such faults can cause objectionable circulating currents, or may energize the housings of equipment at a dangerous voltage.

Line to ground fault

Line – Line – Line Fault – Such types of faults are balanced, i.e., the system remains symmetrical even after the fault. The L – L – L fault occurs rarely, but it is the most severe type of fault which involves the largest current. This large current is used for determining the rating of the circuit breaker.

Fault currents are caused by very low impedance short circuits. These may be shorts to ground or across phases. The resulting high current flow can result in overheating of equipment and conductors, excesses forces, and at times even serious arcs, blasts, and explosions.

To find the fault current at any point in the network, a sum is made of the impedances in the network between the source of supply (including the source impedance) and the point at which the fault is occurs. To find the fault current Ik, the nominal applied voltage, U0 is divided by the summed impedance Z.

The results obtained show that symmetrical three phase fault is the most severe kind at the transmission lines, while for faults occurring very close to the generating station or synchronous generator, single line to ground fault is the most severe.

A line-to-line fault occurs when two conductors are short circuited. A double line-to-ground fault occurs when two conductors fall on the ground or come in contact with the neutral conductor. LG, LL, and LLG are unsymmetrical fault while LLL and LLLG are the symmetrical faults.

Obviously symmetrical fault is more severe than asymmetrical fault. During symmetrical fault all of the three phase of the transmission line is short circuited with each with other or all them are grounded . During this kind of fault huge short circuit current will flow from all the three phase to ground.

A three-phase fault is a symmetrical fault. The other three fault types (line to ground, line to line, and two- line to ground) are called unsymmetrical or asymmetrical faults. Because symmetrical faults result in balanced conditions, they may be analyzed using per-phase analysis.