Electrical Fault: An electrical line or electrical equipment fault is when the current flows instead of in the desired direction due to some fault or defect in the electrical circuit.
Most faults in power systems are usually caused by line short circuits. Faults occur due to sudden line or equipment damage, insulation failure due to lightning, etc. Faults cause serious damage to machinery, lines, and equipment attached to the line. The value of fault current and power depends on the voltage at the fault point of the system and the total impedance or reactance to the fault.
Definition of Electrical Faults
A fault in an electrical line or electrical equipment is any defect or defect in an electrical circuit that causes the current to flow in a different direction rather than in the desired direction and to a much higher than the desired value.
Or, when two or more conductors come into contact together while operating at a normal voltage difference, an electrical fault is said to have occurred.
Different types of faults in electrical power system
Short circuit faults are one of the faults that occur in electrical power systems. Short circuit faults are mainly of two types, namely-
- Symmetrical Fault
- Unsymmetrical Fault
What is symmetrical fault?
A fault in a system where an equal amount of fault current flows in each phase of the three phases, and the angular distance between the fault currents in each phase is 120°, is called a symmetrical fault.
To find the fault current of each phase, the fault current of any one phase can be found.
For example,
(i) Short circuit of three phases together (L-L-L) and
(ii) Three phases together are short circuited to earth (L-L-L-G).
These two types of fault symmetrical font. Symmetrical faults are the most severe faults in power systems.
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What is Unsymmetrical Fault?
A fault in a system causes an unequal amount of current to flow instead of an equal amount of current in each phase of the three phases. Or a fault that causes unequal fault currents to flow at unequal angular distances. It is called an unsymmetrical fault.
Unsymmetrical faults are as follows:
(i) Single line to ground fault (L-G)
(ii) Line to Line Fault (L-L)
(iii) Double Line to Ground Fault (L-L-G)
Causes of electrical faults in electrical power systems
The reasons for the electrical fault are as follows:
1. Insulation failure
2. Sudden loss of line
3. Lightning surge
4. voltage drop
5. Imbalance and collapse of stability etc.
The reasons for the fault are discussed in detail below- content_copy share
1. What is insulation failure fault?
High voltage or over voltage is generated due to a switching surge or lightning strike. These high voltages weaken the insulation of system equipment and lines. Moreover, the insulation of overhead line insulators is damaged due to stress and distortion caused by overheating or overheating. Due to these reasons, the predetermined insulation strength of an electrical system is degraded and at one time a fatal accident like a short circuit occurs. It is called an insulation failure fault.
2. Sudden loss of line
High voltage transmission lines can be downed by wind or fallen trees causing short circuits between conductors and earth or between conductors.
3. Lightning surge
A lightning strike on a transmission line during a lightning storm causes a sudden increase in line voltage, which can damage equipment connected to the system.
4. Voltage drop
Unexpected voltage drops in feeders, busbars and lines are detrimental to the system.
5. Imbalance and collapse of stability
Such faults can occur due to earth fault or inter-turn fault in the alternator or sudden load changes. If the value of the fault current or short circuit current is known, the following advantages are available.
(a) Circuit breakers with correct ratings can be selected very easily.
(b) Determine the size and capacity of the protective relay.
(c) The value of reactance of the current limiting reactor can be determined.
Different types of electrical short circuit
Short circuits that commonly occur in electrical systems. Their names and pictures are given below.
1. Short circuit between single phase and earth
2. Short circuit between any two phases of three phases (Between phase and Phase)
3. Short circuit between any two phases and earth
5. Short circuit between three phases together with earth (Between all the three phases and ground)
6. Short circuit between all the three phases:
The first four faults (1, 2, 3, 4) are called unsymmetrical faults and the last two faults (5, 6) are called symmetrical faults.
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