Which fault is severe and why?

Severity of faults:

Among the given faults, LLLG or 3 phase faults are most severe. LG or line to ground fault is least severe. Line to line fault is more severe than line to ground fault while double line to ground fault is one level severe than LL. The order of Severity of faults is given below.

Which fault is most severe and why?

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.

Why is a three phase fault most severe?

Three-phase symmetrical faults are known to be the most severe in a power system due to large fault currents. However, single phase phase to ground faults are more common faults that occurs. If not checked in due time, these faults may grow to symmeterical fault which is uncommon but most severe.

Which type of fault is severe in power system?

Short Circuit Faults

These are the most common and severe kind of faults, resulting in the flow of abnormal high currents through the equipment or transmission lines. If these faults are allowed to persist even for a short period, it leads to the extensive damage to the equipment.

Why symmetrical fault is most severe?

Symmetrical faults are interesting one, which means all three phase line shorted with ground and the magnitude of the load current is same in all three phases with 120 deg phase displacement each other. It is the most severe type of fault involving largest current, but it occurs rarely.

Fault Analysis in Power Systems part 1a

Which fault is most severe?

Severity of faults:

Among the given faults, LLLG or 3 phase faults are most severe. LG or line to ground fault is least severe. Line to line fault is more severe than line to ground fault while double line to ground fault is one level severe than LL. The order of Severity of faults is given below.

Is symmetrical or unsymmetrical fault more severe?

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 LG fault is most severe in generator?

Most recent answer

@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.

What is 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 series and shunt fault?

Open circuit faults are also called as series faults. These are unsymmetrical or unbalanced type of faults except three phase open fault. Shunt faults: The shunt fault involves short circuit between conductor and ground or short circuit between two or more conductors.

Which fault is most severe and imposes more heavy duty on the circuit breaker?

Ans: As the symmetrical fault is most severe in a three phase line and imposes the heavy duty on the control gear, therefore, the circuit breaker is rated on the basis of symmetrical short circuit currents.

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.

What is balanced fault?

The balanced (or three phase) fault is the one when all three lines are shorted to ground. It is usually rare, but can happen. When a fault occurs it is important to isolate it by opening protec- tive breakers. To properly set the breakers, the magnitude of the fault currents need to be known.

What is an unbalanced fault?

If the fault involves only one or two of the three possible phases, then the fault is said to be an unbalanced or asymmetrical fault. Due to these faults, the system loses symmetry or balanced condition. Fault calculations can be easily performed by the use of a tool known as the “symmetrical component”.

Which faults symmetrical or unsymmetrical are more frequent in power system and why?

Unsymmetrical faults

These are very common and less severe than symmetrical faults. There are mainly three types namely line to ground (L-G), line to line (L-L) and double line to ground (LL-G) faults. Line to ground fault (L-G) is most common fault and 65-70 percent of faults are of this type.

Which is unsymmetrical type fault?

An unsymmetrical or asymmetrical fault is defined as a fault that affects one or two phases of a three-phase system in contrast with the previously studied balanced or symmetrical faults which equally affect each of the three phases.

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 solid fault?

A three-phase balanced fault can be defined as a short circuit with fault impedance called Zf between the ground and each phase. The short circuit will be called a solid fault when Zf is equal to zero. This type of fault is considered the most sever short circuit which can affect any electrical system.

What is bolted fault?

A bolted fault is an extreme fault where the fault has zero impedance, thus giving the maximum prospective short-circuit current in the faulted circuit. A symmetrical fault is a balanced fault that affects all three phases equally, as opposed to an asymmetrical fault that does not.

What is asymmetrical fault current?

Asymmetrical current is defined as the combination of the symmetrical component and the direct current component of the current. The dc component in the asymmetrical current is controlled by the X/R ratio of the circuit and the contact parting time of the interrupter.

Which surge is more harmful?

1/50 µs is more harmful. 4/50 µs is more harmful.

What is the most common type of fault?

Normal Faults: This is the most common type of fault. It forms when rock above an inclined fracture plane moves downward, sliding along the rock on the other side of the fracture. Normal faults are often found along divergent plate boundaries, such as under the ocean where new crust is forming.

What is metallic fault?

Metallic cable faults

Faults in metallic cables include cross (short-circuit) faults, insulation faults, and ground faults due to factors such as humidity or cable submersion in water (Photo 1). Such faults can cause circuit malfunctions such as noise and interrupted communications (Fig. 1).

What is open circuit fault?

An open-circuit fault occurs if a circuit is interrupted by a failure of a current-carrying wire (phase or neutral) or a blown fuse or circuit breaker. In three-phase systems, a fault may involve one or more phases and ground, or may occur only between phases.