Here are Protection Elements You Find in Power Distribution Networks


Protection Elements You Find in Power Distribution Networks

  1. Fuse

  2. Relay

  3. Lightning arrester

  4. Circuit breakers

  5. Line sectionalizer

  6. Circuit reclosers

  7. Load-break switch


In electronics and electrical engineering, a fuse is an electrical safety device that operates to provide overcurrent protection of an electrical circuit. Its essential component is a metal wire or strip that melts when too much current flows through it, thereby stopping or interrupting the current. It is a sacrificial device; once a fuse has operated it is an open circuit, and must be replaced or rewired, depending on its type.

Fuses have been used as essential safety devices from the early days of electrical engineering. Today there are thousands of different fuse designs which have specific current and voltage ratings, breaking capacity, and response times, depending on the application. The time and current operating characteristics of fuses are chosen to provide adequate protection without needless interruption. Wiring regulations usually define a maximum fuse current rating for particular circuits. Short circuits, overloading, mismatched loads, or device failure are the prime or some of the reasons for fuse operation. When a damaged live wire makes contact with a metal case that is connected to ground, a short circuit will form and the fuse will blow.

A fuse is an automatic means of removing power from a faulty system; often abbreviated to ADS (Automatic Disconnection of Supply). Circuit breakers can be used as an alternative to fuses, but have significantly different characteristics.

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In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected. The first protective relays were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as over-current, overvoltage, reverse power flow, over-frequency, and under-frequency.

Microprocessor-based digital protection relays now emulate the original devices, as well as providing types of protection and supervision impractical with electromechanical relays. Electromechanical relays provide only rudimentary indication of the location and origin of a fault. In many cases a single microprocessor relay provides functions that would take two or more electromechanical devices. By combining several functions in one case, numerical relays also save capital cost and maintenance cost over electromechanical relays. However, due to their very long life span, tens of thousands of these “silent sentinels” are still protecting transmission lines and electrical apparatus all over the world. Important transmission lines and generators have cubicles dedicated to protection, with many individual electromechanical devices, or one or two microprocessor relays.

Lightning arrester

Electric power transmission is the bulk movement of electrical energy from a generating site, such as a power plant, to an electrical substation. The interconnected lines which facilitate this movement are known as a transmission network. This is distinct from the local wiring between high-voltage substations and customers, which is typically referred to as electric power distribution. The combined transmission and distribution network is part of electricity delivery, known as the electrical grid.

Circuit breakers

circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by excess current from an overload or short circuit. Its basic function is to interrupt current flow after a fault is detected. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.

Line sectionalizer

A sectionalizer is a protective device that automatically isolates a faulted section of line from the rest of the distribution system. … Line reclosers and sectionalizers work together on distribution circuits to insure greater reliability. Although they look almost identical, their functions are quite different!

Circuit reclosers

A recloser is an automatic, high-voltage electric switch. Like a circuit breaker on household electric lines, it shuts off electric power when trouble occurs, such as a short circuit. Where a household circuit breaker remains shut off until it is manually reset, a recloser automatically tests the electrical line to determine whether the trouble has been removed. If the problem was only temporary, then the recloser automatically resets itself and restores the electric power.

Reclosers are used throughout the power distribution system, from the substation to residential utility poles. They range from small reclosers for use on single-phase power lines, to larger three-phase reclosers used in substations and on high-voltage power lines up to 38,000 volts.

Load-break switch

Ascending changes in the way we generate, transmit and use of electricity in developed economy or highly industrialised society, prioritised the maintenance of continuity of supply to consumers. With the goal to be integrated in smart cities, the safety of electrical equipment by fast disconnection of the power supply in case of fault events like leakage current, electrical arc, over current or overvoltage is taken care through switchgear such as disconnecting switches, circuit breakers, etc. For the systems up to 33kV, the more costly circuit breakers are getting replaced with load break switches. A load break switch is a type of switching device used for voltages in the range of 12 to 36 kV and must have the following capabilities:

-Interruption of current equal to its continuous current rating at the system voltage and the power factor of the normal load
-Designed to possess enough insulation to isolate the circuit in closed position.
-Interrupting small capacitive and inductive currents which is essential for disconnecting the unloaded overhead lines, transformers, cables, etc.
-Carrying the maximum fault current for the duration required by the interrupting device to clear the fault.
-Making on the terminal fault at rated voltage.


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