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Sahithyan's S1

Introduction to Electrical Installations

An assembly (connected as a complete set) of associated electrical equipment to fulfill a specific purpose and having certain coordinated characteristics.

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

Current that exceeds the rated value. Includes overload and fault current.

Current carrying capacity

The rated value of current, for conductors.

Faulty current

Can be subdivided into:

  • short-circuit current
  • earth fault current

Most common types of faults

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

Fault between phase conductor and non-current carrying metallic parts. High voltages may appear on the frames of electrical equipment.

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

  • 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