Power Generation, Power Plants, Transmission, Distribution & Protection

Electrical Power Generation:

First Law of thermodynamics states that energy cannot be created or destroyed; However, power can be converted from one form of energy to another form of energy. This is especially important in power generation because power production in almost all types of power plants depends on the use of a generator. Generators are used to convert mechanical energy into electrical energy.  

Second law of thermodynamics conceptualizes that the entropy of a closed system can never decrease. As the law relates to power plants, it dictates that heat must flow from a high-temperature body to a low-temperature body (the device in which electricity is generated). 

Types of power plants    

Hydroelectric plants generate energy by using the power of water to turn generators.     

Thermal power plants are divided into two different categories; those that create electricity by burning fuel and those that create electricity through a prime mover.

A common example of a thermal power plant that produces electricity by consuming fuel is the nuclear power plant.

Nuclear power plants use heat from a nuclear reactor to convert water into steam.

Solar power plants obtain their energy from sunlight, which can be accessed by photovoltaics (PV).

Wind power plants, also known as wind turbines, obtain their energy from the wind by connecting a generator to the fan blades and using the rotational motion caused by the wind to power the generator.

Electrical Power Transmission

Energy transmission is the movement of energy from its place of generation to a place where it is applied to do useful work.

Power is formally defined as units of energy per unit of time. In SI units:

Alternating current is normally preferred, as a transformer can easily step up its voltage to minimize resistive loss in conductors used to transmit power over long distances; Another set of transformers is required to step it down to safer or usable voltage levels at the destination.

Power transmission is usually done through overhead lines, as it is the most economical way to do so.

Underground transmission using high-voltage cables is chosen in highly populated urban areas and in underwater high-voltage direct current (HVDC) connections.

Energy could also be transmitted through changing electromagnetic fields or through radio waves; Microwave energy can be efficiently transported over short distances using a waveguide or in free space using wireless energy transfer.

Thermal energy can be transported in pipes containing a high heat capacity fluid, such as oil or water, such as those used in district heating systems.

Power (and energy) can be transmitted through the physical transport of chemical or nuclear fuels.

Electrical Power Distribution & Use

Power Transformers Used in a substation to step up or step down voltage. Except for the central station, all subsequent substations use step-down transformers to gradually reduce the voltage.

Instrument transformers operate at high voltages and carry current of thousands of amperes. Measuring instruments and protection devices are designed for low voltages (generally 110 V) and currents (approximately 5 A). Therefore, they will not operate satisfactorily if mounted directly on power lines.

This difficulty is overcome by installing instrument transformers on the power lines. a)Current transformer (C.T) b)Potential transformer (P.T)

Current Transformers (C.T) A current transformer is essentially a step-up transformer that steps down current by a known ratio. The primary of this transformer consists of one or more turns of thick wire connected in series with the line.

The secondary consists of a large number of turns of line wire and serves for measuring instruments and relays. Potential Transformers (C.T) It is essentially a step down transformer and reduces the voltage by a known ratio.

The primary of this transformer consists of a large number of turns of fine wire connected along the line. The secondary winding consists of a few turns and provides the measuring instruments and relays with a voltage that is a known fraction of the line voltage.

Electrical Power Protection

Protection of electrical power systems against failures by disconnecting failed parts from the rest of the electrical network. Devices used to protect power systems from failure are called protective devices. 

Protection devices:• Current and voltage transformers to reduce high voltages and currents in the electrical power system to levels suitable for relief. • Protection relays to detect the fault and initiate a trip or disconnection order.

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, which relied on coils operating on moving parts to detect abnormal operating conditions, like surges. Current, surge, reverse power flow. 

• Circuit breakers to open/close the system based on relay commands and automatic recloser.

A circuit breaker is a self-operating electrical switch designed to protect an electrical circuit from damage caused by excess current due to overload or short circuit. Its basic function is to interrupt the flow of current after a fault is detected.

• Batteries to provide power in the event of a power outage in the system.

 • Fuses are capable of detecting and disconnecting faults. A fuse is an electrical safety device that functions to provide overcurrent protection of an electrical circuit. Its essential component is a wire or strip of metal that melts when too much current flows through it, thus interrupting the current.

Power System

The majority of these systems rely upon three-phase AC power.

SCADA systems

In large electric power systems, supervisory control and data acquisition (SCADA) is used for tasks such as switching on generators, controlling generator output and switching in or out system elements for maintenance.