What are the types of faults that can occur in a 3 phase line?

Electrical faults in three-phase power system mainly classified into two types, namely open and short circuit faults. Further, these faults can be symmetrical or unsymmetrical faults. Let us discuss these faults in detail.

What is 3phase symmetrical fault?

The symmetrical fault occurs when all the three conductors of a 3-phase line are brought together simultaneously into a short-circuit condition as shown in Fig. … This type of fault gives rise to symmetrical currents L e. equal fault currents with 120° displacement.

Which fault is severe in AC 3 phase system?

LLLG (line to line to line and ground)is the most severe fault for generators and will damaged maximum to generator with same current(fault) level of other types of faults. Three-line fault is the most sever fault.

What are faults types?

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 reverse fault is one in which the hanging wall moves up relative to the footwall.

How many types of faults are there?

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.

What is the difference between symmetrical & unsymmetrical faults?

Answer: Symmetrical faults are those faults which involve with all the three phase. it simply means that symmetrical faults affect all the three phases. On the other side, unsymmetrical faults are those faults in which either one or two phase involve.

What is difference between symmetrical and unsymmetrical fault?

A symmetrical fault is a fault where all phases are affected so that the system remains balanced. 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.

What is LLLG fault?

One interesting type of electrical fault in a 3-phase system is an LLLG fault (line-line-line-ground). This type of fault is among the least common, simply because all wires in the system must be bridged to create such a fault.

What are the causes of faults?

Faults are generally caused under the influence of stresses acting upon the rocks of the crust of the earth from within. Any rock on or below the crust may withstand all the operating stresses up to a limit, which depends upon its cohesive strength and internal friction.

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How many types of electrical faults are there?

There are mainly two types of faults in the electrical power system. Those are symmetrical and unsymmetrical faults.

What causes fault current?

A fault current is an unintended, uncontrolled, high current flow through an electrical system. Fault currents are caused by very low impedance short circuits. … Causes of faults include things such as lightning strikes, animals, dirt and debris, dropped tools, corrosion, and human error.

What are the three types of faults explain each type?

There are three different types of faults: Normal, Reverse, and Transcurrent (Strike-Slip). Normal faults form when the hanging wall drops down. … Reverse faults form when the hanging wall moves up. The forces creating reverse faults are compressional, pushing the sides together.

What are normal faults?

Normal, or 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 a Reverse fault.

How do you identify faults?

To correctly identify a fault, you must first figure out which block is the footwall and which is the hanging wall. Then you determine the relative motion between the hanging wall and footwall. Every fault tilted from the vertical has a hanging wall and footwall.

What are types of unsymmetrical faults?

The unsymmetrical faults are classified as single line to ground faults (SLG), double line to ground faults (DLG) and line to line faults (LL). More than 90 % faults occur in a power system are single line to ground faults. The connection diagrams of different types of unsymmetrical faults are shown in Fig.

What are earth faults?

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.

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What are unsymmetrical faults?

Unsymmetrical faults are the faults which leads unequal currents with unequal phase shifts in a three phase system. The unsymmetrical fault occurs in a system due to presence of an open circuit or short circuit of transmission or distribution line. It can occur either by natural disturbances or by manual errors.

What is Llg fault?

Double Line to Ground Fault (LLG): Figure 11.9 shows a Double Line to Ground Fault at F in a power system. The fault may in general have an impedance Zf as shown. The current and voltage (to ground) conditions at the fault are expressed as. The symmetrical components of voltages are given by. from which it follows that.

What is bolted fault or solid?

A bolted fault is a short circuit fault with no fault resistance. Bolted faults deliver the highest possible fault cur-rent for a given location and system configuration, and are used in selecting equipment withstand and interrupting ratings and in the setting of protective relays.

What is the feeder reactor?

Feeders Reactors Reactors, which is connected in series with the feeder is called feeders reactor. When the fault occurs on any one feeder, then the voltage drops occur only in its reactors and the bus bar is not affected much. Hence the machines continue to supply the load.

What is symmetrical and unsymmetrical alkene?

The key difference between symmetrical and unsymmetrical alkenes is that symmetrical alkenes have doubly bonded carbon atoms bearing the same ligands, whereas unsymmetrical alkenes have doubly bonded carbon atoms bearing different ligands. … Often, we call them olefins.

What causes zero sequence current?

The zero sequence currents are produced due to the existence of zero sequence voltage. The above equation shows that there is no zero sequence current present in the delta connection, because of the absence of the return paths of these current.

Why symmetrical fault is severe than unsymmetrical fault?

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.

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How do you find symmetrical fault current?

For example, if the percentage impedance up to point of fault is 10% and full load current is 40 A then short circuit current will be [40 x (100 / 10)] = 400 A. Example: Consider the figure below and calculate the symmetrical fault current considering three phase short circuit at the HV terminal of Transformer.

Why is LG fault severe at Generator?

@Uneet, the zero sequence reactance at the generator terminal is very low, so faults such as (LG, LLG and LLLG) will be severe at the generator terminals.

Which is the most severe fault in transmission line?

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.

Why do faults move?

Faults are fractures in Earth’s crust where movement has occurred. Sometimes faults move when energy is released from a sudden slip of the rocks on either side. … It forms when rock above an inclined fracture plane moves downward, sliding along the rock on the other side of the fracture.

What is the importance of faults?

The faulting patterns can have enormous economic importance. Faults can control the movement of groundwater, they can exert a strong influence on the distribution of mineralisation and the subsurface accumulations of hydrocarbons. And they can have a major influence on the shaping of the landscape.

What are the nature and causes of faults?

Causes of Faults

  • Overvoltage due to switching surges.
  • Severe lightning strokes.
  • Aging of conductor.
  • Heavy wind, rains, and snowfall.
  • Falling trees on the transmission line.
  • Excessive internal and external stresses on the conductors.
  • High changes in atmospheric temperatures.
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