One of the main reasons why the electricity bill of a facility, for example a hotel, often seems to keep going up, is due to reactive energy.
What is reactive energy exactly?
If we ask an electrical technician, they will almost certainly tell us about different electrical and physical magnitudes such as the joule effect …, but there’s a good chance a lot of us might not really understand what that means.
Active energy must be produced and is transformed into other forms of energy, producing work or heat. Reactive energy is necessary for the operation of certain electrical appliances and machines that use coils for their operation. For example:Transformers
Reactive energy does not have to be produced, but it does have to be transported, so the networks and electrical installation of a facility must be designed appropriately for it.
That is why the electricity companies penalise us if their consumption exceeds certain values. In the following figure we have a graph giving an example to make this easier to understand.
The electrical frequency in Europe is 50Hz (Hertz), so reactive energy comes and goes from our consumption to the grid 50 times per second, causing variations in the electrical intensity of circuits, triggering overloads in transformer and generator cable lines . That means that reactive energy does not produce useful work for systems and must be either neutralised or compensated for. In the following graph we can see a representation of the Power Triangle.
Active power P is measured in watts (W), reactive Q in volt reactive amps (VAR), and apparent power in S in volt amps (VA)
It is the angle whose cosine gives us the highest or lowest value (and consumption) of Q in our installation. Given that the value of a cosine can only vary between 0 and 1, the higher the value of that cosine, the lower the Reactive Energy present in our facility or installation. For this reason, in reactive energy compensation, the closest value of cosΦ to 1 will always be the one that is sought.
In the figure we can see the angle formed by P and S, it is designated by Φ (fi). It is the angle whose cosine gives us the highest or lowest value (and consumption) of Q in our installation. Given that the value of a cosine can only vary between 0 and 1, the higher the value of that cosine, the lower the Reactive Energy present in our facility or installation. For this reason, in reactive energy compensation, the closest value of cosΦ to 1 will always be the one that is sought.
SO, IF WE HAVE TO PRODUCE IT, WHY ON EARTH DO WE HAVE TO PAY FOR IT?
We have to pay for it because it has to be transported, in addition to oversizing the facilities.
HOW CAN WE COMPENSATE FOR REACTIVE ENERGY?
The way to compensate the reactive energy of an installation is through the use of capacitor banks.
TYPES OF CAPACITOR BANK
AUTOMATIC CAPACITOR BANKS: INSTALLATION AND OPERATION
They are pieces of equipment that provide the necessary kVAr value to keep the cosΦ of the installation close to a value that we have defined in a given situation and as close to 1 as possible.
CAPACITOR PACK CONNECTION TYPES
1): Connection of capacitors by contactors.
2) Connection of the capacitors by thyristors.
THEY ARE FORMED BY THREE KEY ELEMENTS:
Regulator: measures the cosΦ of the installation and gives the necessary order to vary the kVAr delivered to the installation and reach the cosΦ target.
Contactors: elements that operate the capacitors that form the battery to provide the necessary kVAr.
Capacitors: elements that provide the necessary reactive energy to the installation.
“Special attention should be paid to battery calculation, as well as to the selection of the capacitor power selection and the configuration of the system steps.”
In a next article we’re going to talk about the details you need to take into account when calculating the battery, and the configuration of power steps.
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