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Introduction to Substation

  • Introduction to Substation, electrical grid, high voltage conductor, substation, switchgear, power grid,

     

    Electrical Engineering in order that subsequent time you feast your eyes on a substation you'll be ready to appreciate it the maximum amount as I do originally named for smaller power plants were converted for other purposes substation is now a general term for a facility which will serve a good sort of critical roles on the facility grid those roles depend upon which parts of the electrical grid are being connected together and therefore the refore the types number and reliability requirements of the eventual customers downstream and the first and sometimes simplest of those roles is switching the overall layout of a substation consists of some number of electrical lines called conductors if you would like to suit in with the electrical engineers coming into the power these high-voltage conductors hook up with a series of some or many pieces of kit before heading bent their next step within the power system as a junction point within the grid a substation often is the termination of the many individual power lines. This creates redundancy making sure that the substation stays energized even if one transmission line goes down but it also creates complexity the connections to these various devices are called buses often rigid overhead conductors that run along the entire substation the arrangement of the bus is a critical part of the design of any substation because it can have a serious impact on the general reliability like all equipment substations occasionally have malfunctions or things that simply require regular maintenance to avoid shutting down the whole substation.

    We need switches that can isolate equipment transfer load and control the flow of electricity along the bus this may seem obvious but turning on and off high-voltage lines isn't as simple as flipping a light switch at high voltages even air can act like a conductor which means even if you create a break in the line electricity can continue flowing in a phenomenon known as an arc not only does arcing defeat the purpose of the switch it is incredibly dangerous and damaging to equipment so switching in a substation is a carefully controlled procedure with specially designed equipment to handle high voltages disconnect switches are often just called switch gear in addition to the equipment that serves another important role during a substation protection i discussed earlier that much of our electrical infrastructure is exposed and call at the open that's nice for people like me who enjoy having a look but it also means being vulnerable to an endless number of things that can go wrong.


    From lightning strikes to wind storms to squirrels grid operators contend with so many threats to their infrastructure on a day-by-day. When something causes a short-circuit on the power grid also called a fault it can severely damage power lines and other equipment not only that because of the overwhelming complexity of the facility grid faults can and do cascade in unexpected and sometimes uncontrollable ways leaving huge populations without power for hours or days. Many of the ways we protect equipment from faults are handled at a substation one of the most common types of electrical fault is a short circuit to ground this type of fault creates a low resistance path for current to flow and leads to an overload of power lines and equipment the simplest way to protect against this type of fault is with a fuse a device that physically burns out at a certain current threshold fuses are dead simple and don't require much maintenance but they do have some disadvantages to their one-time use and they can't be used to interrupt current for other types of faults on the other hand circuit breakers are a class of device that serves similar roles as fuses but provide more sophistication for dealing with a wide variety of faults like disconnect switches circuit breakers need to be carefully designed to interrupt huge voltages and currents without damage as soon as contacts within a breaker are moved aside from each other an electrical arc forms.

    This arc needs to be extinguished as quickly as possible to prevent damage to the breaker or unsafe conditions for workers extinguishing the art is accomplished by a material called a dielectric that doesn't conduct electricity for lower voltages the circuit breakers can be located in a sealed container under vacuum to avoid electricity conducting in the air between the contacts for higher voltage breakers are often submerged in tanks filled with non conductive oil or dense dielectric gas these breakers give grid operators more control about how and wind current gets interrupted not every fault is that the same and sometimes operators even realize a disturbance before time and may trigger breakers early to stop cascading failures many vaults are temporary like lightning strikes a special kind of circuit breaker called a recloser can interrupt current for a short period of time and re-energized the line to test the default has cleared recloser is usually trip and reclose a few times depending on their programming before deciding that a fault is permanent and locking out if electricity.

    Demand on the grid gets so high that it cannot be met by the utility substations can also be wont to shed load rolling blackouts are wont to lower the total electrical demand to avoid bigger failures on the grid one of the most important parts on the power grid is that different segments flow at different voltages voltage is a measure of electrical potential somewhat equivalent to the pressure of a fluid in a pipe at large power plants electricity is produced at a somewhat low voltage of around ten to thirty kilovolts or kV


    From there the voltages increase much higher so that it can travel along transmission lines using a higher voltage reduces the losses along the way making them more efficient but also much more dangerous this is why overhead transmission lines are so tall to keep them out of the way of trees and human activities but when transmission lines have reached the populated areas which they serve it's not feasible to keep them so high in the air so prior to distribution the voltage of the grid needs to be brought back down using transformers located within a substation a transformer is an extremely simple device that relies on the alternating current of the grid to function it consists of two adjacent coils of wire as the voltage in one coil changes it creates a magnetic field. This field couples with the other coil inducing a voltage the incredible part of a transformer has to do with the number of loops in each coil the induced voltage will be a function of the ratio of the loops for example if the transmission side of a transformer has a thousand loops while the distribution side has a hundred the voltage on the distribution side will be ten times less.

    This simple but incredible fact makes it possible for us to intensify or down voltage as necessary to balance the security and efficiency along each a part of the facility grid the simplicity of transformers is great in a lot of ways but it also means it can be difficult to make fine adjustments to the power leaving the substation because of this many substations include equipment for monitoring and controlling the power on the grid instrument transformers are small transformers used to measure the voltage or current on the grid or provide power to system monitoring devices depending on the varying transmission and distribution losses the voltage on the grid can also swing outside an acceptable range regulators are devices. With multiple taps which will make small adjustments up or right down to the distribution voltage on feeder lines leaving the substation toward customers.

     

    Reference: https://www.dnvgl.com/

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