ELECTRICAL AND POWER SYSTEM MAINTENANCE written by Sunday Abalaka
An electrical system is a utility/facility that provides electricity. Maintenance involves functional checks, servicing, repairs, or replacing necessary devices, equipment, machinery, building infrastructure, and supporting utilities in industries, business, governmental, and residential installations.
Electrical and power system maintenance is defined as carrying out functional checks, servicing, repairs, etc. on a utility that provides electricity. For this article, I will address common faults in electrical systems and how to remedy them. In a circuit, an error occurs when there is an abnormal electric current running through that circuit, and this usually involves an electrical failure of the equipment. Under normal operating conditions, electrical equipment operates at standard current and voltage ratings. Immediately the fault occurs, the current and voltage ratings will deviate from their nominal ranges. Electrical faults can cause unbalance of the phases, over current, voltage surges, under-voltage, etc. this can result in interruption of regular operation in the network, electrical fires, failure of equipment, etc. Electrical systems are usually protected with equipment such as circuit breakers and relays to limit break-downs due to electrical faults.
TYPES OF FAULTS
In a three-phase power system, faults can be categorised into open circuit or short circuit faults. These faults can be symmetrical or unsymmetrical. Let’s discuss these faults in detail.
OPEN CIRCUIT FAULTS
These faults occur due to failure of one or more conductors. Causes include melting fuse or conductor in one or more phases, failure of circuit breakers, failure of cable joints, among others.
Effects of open circuit faults include;
- Danger to personnel
- Abnormal operation of the system
- Over-voltages on certain parts of the network which can further lead to insulation failure that develops to short circuit.
These types of faults can be tolerated for more extended periods as compared to short circuit faults, but this fault should be removed as soon as possible to avoid more significant damage.
SHORT CIRCUITS FAULTS
A short circuit is an abnormal connection that possesses very low impedance between two points of different potential; this may be intentional or accidental. These faults are common and severe, and they result in a flow of abnormally high currents through equipment or transmission lines. Failure to address these faults as soon as they occur will lead to extensive damage to the equipment.
Causes include break-down of transmission lines, deterioration of insulation in electrical equipment, inadequate designs, ageing of insulation, and improper installation.
Effects of short circuit faults
- Abnormal current over-heats the equipment, this reduces the life span of the insulation of that equipment
- Can lead to an explosion in appliances like transformer and circuit breakers
- As long as short circuit faults persist, power flow is restricted or completely blocked
These are faults that occur when all three phases are simultaneously short-circuited. These faults rarely happen. However, if they occur, they cause severe damage to the equipment.
These are the most common types of faults in a power system. They cause an unbalanced current in the network. Some examples are given below.
The line-to-line fault: this occurs when two live conductors come in contact with each other. These happen when the wind causes swinging overhead cables to come in contact with each other.
The line-to-ground fault: this fault forms a short circuit path between the line and ground. These are the most common and least severe of all the defects.
The line-to-line-to-ground fault: this is when two live conductors come in contact with each other as well as the ground. These are very severe faults.
PROTECTION DEVICES AGAINST FAULTS
- Fuse: it consists of a thin copper wire enclosed in a casing with two metallic contacts. Immediately a fault occurs in the system; the fuse opens the circuit.
- Circuit breakers: this is the most common protection device. It breaks contact between the equipment and supply from the system in the event of a fault.
- Protective relay: is used to detect faults and then initiate the circuit breaker to isolate the faulty circuit.
- Lighting arrestor: used to arrest and reduce the effect of surges on transmission lines and equipment that result from lightning strikes.
Great importance should be given to the electrical power systems to ensure that all faults are fixed as soon as they happen to reduce the damage that will result from these faults. These will not only ensure the smooth running of the system but will also guaranty the durability of the equipment.