An assembly (connected as a complete set) of associated electrical equipment to fulfill a specific purpose and having certain coordinated characteristics.
Standard colors
Section titled “Standard colors”| Type | Color | Example |
|---|---|---|
| Protective earth | Mixed yellow and green | |
| Neutral | Blue | |
| Single phase line | Black or brown |
Nomenclature
Section titled “Nomenclature”Electrical equipment
Section titled “Electrical equipment”Any item used in generation, transmission, distribution and utilization of electrical energy.
Examples: generators, transformers, measuring instruments, protective devices, wiring materials, etc.
Overcurrent
Section titled “Overcurrent”Current that exceeds the rated value. Includes overload and fault current.
Current carrying capacity
Section titled “Current carrying capacity”The rated value of current, for conductors.
Faulty current
Section titled “Faulty current”Can be subdivided into:
- short-circuit current
- earth fault current
Most common types of faults
Section titled “Most common types of faults”Short-circuit fault
Section titled “Short-circuit fault”Large current will flow. Over heating will occur. Damages may occur to wires, insulators, switches, etc. Aka. phase-neutral fault.
Insulation failure
Section titled “Insulation failure”Fault between phase conductor and non-current carrying metallic parts. High voltages may appear on the frames of electrical equipment.
Protection for safety
Section titled “Protection for safety”Protecting livestock and electrical equipments from electric faults.
- Prevent damage by fire or shock
- Maintain supply continuously
- Minimize the system interruptions under faulty conditions.
- Against direct contact: Relates to live parts.
- Against indirect contact: Relates to exposed parts. Conductive but not normally live. Made live by fault.
Properties of protective equipment
Section titled “Properties of protective equipment”- Certainty and reliability of operation under normal, fault, non-operational conditions
- Discrimination: ability to isolate faulty part from the system
- Rapidity of operation: how fast the equipment responses
- Simplicity
- Low initial and maintenance cost
- Easy adjustment and testing
Protection methods
Section titled “Protection methods”- Earthing of equipment
- Use of circuit breakers/fuses
- Use of residual current circuit breakers