Oct 21, 2019

What is inverter generator? And How It is Different from Conventional Generator?

Many times you may have heard that the inverter generators are fuel-efficient and quieter than conventional generators. Have you wondered why is that so?
Well, today we are going to answer all your queries regarding inverter generators, so keep reading.
But before this you need to understand how alternator works. The alternator is almost the same as generator however there is one big difference. In alternator, the rotor is excited with DC current and thus strong magnetic field is produced by rotor. And when the rotor rotates, the stator cuts these magnetic field and hence the electricity is produced which is collected through the stator.
But in case of generator, armature winding rotates in a fixed magnetic field and the stator produces this magnetic field with the help of excitation winding. The electricity is collected through the rotor with the help of carbon brushes and they wear out quickly so you need to replace them frequently.

Difference between inverter generator and conventional generator

The conventional generator or non-inverter generator produces directly AC current, whereas the inverter generator produces AC current, then converts it to DC current and then again converts it back to AC current, and it has many advantages which we will discuss later. An inverter generator is also fuel-efficient; let’s understand this by this equation.

This is the equation of rotor speed of the generator, and all the generators, including inverter generator, alternator, and the conventional generator, produce the power based on this equation.
Countries like America and Canada use the 60Hz frequency, so here f=60 and P is number poles of any particular generator. Almost all the generators (except for generators used in Hydropower) have two pole arrangement.
Now, as you know, the frequency of the current must be 60Hz, and if the frequency fluctuates even the slightest, let’s say 58Hz or 61Hz, then it may damage your appliances.
If we do the simple math, then to get f=60, the value of n must be 3600 RPM (Rotations per Minute). This means that the rotor of the generator must run at a constant 3600 RPM no matter what. And if this speed increases or decreases, then it may change the frequency of output current.
So now, you know that conventional generator must run at 3600 RPM constantly no matter what amount of power is asked of it.
Let’s understand it by this example. Suppose you have a generator that can supply 1000 watts of continuous power (not peak power), and you want to run a 100-watt bulb. So it will burn some fuel, right? Now let’s say you want to run an electronic device of 500 watts. In both cases the generator will definitely consume fuel, but in both cases the generator must run at 3600 RPM to produce 60Hz current.
So as you can see, there is definitely wastage of fuel; not that high, but some amount of fuel does go to waste.
Well, now let’s understand the inverter generator. As I said earlier, the inverter generator produces power in three stages; first, it produces AC power, then converts it to DC power and then again converts it back to AC power.
This is especially helpful when you need less power from the inverter generator because the generator will rotate at a lower speed (consuming less fuel) and produce power with low frequency. Then the rectifier will convert it to DC power, and then the inverter circuit will convert it to 120V 60Hz power.
Let’s understand it by this example. Suppose you have an inverter generator that can supply 1000 watts continuously, and you want to run a 100-watt bulb. And then you want to run a 500-watt device on it. Now in the case of a 100-watt bulb, the inverter generator will burn less fuel (because it does not need to produce 60Hz supply; hence, the rotating speed will be very low) compared to the conventional generator. And in the case of a 500-watt device, the rotor will rotate accordingly (far less than 3600 RPM) to produce the required power.

[Also Read: Synchronous Generators vs. Induction Generators]

Noise Output

So now you know their difference in fuel efficiency, let’s understand how they differ in terms of noise output.
The generator produces noise mainly due to combustion of fuel, and rotation of mechanical gears. This noise increases when the load demand is increased because in order to cut those intensive magnetic fields of a stator, the rotor needs high torque. And that is why the high amount of fuel is ignited in the chamber and hence, noise production increases too.
The portable generator will make the same amount of noise up to 85% load capacity, but above that, its noise will increase even further. But in the case of an inverter generator, it automatically adjusts its speed according to power demand; thus, it will make less noise at low power requirements.
Moreover, the portable inverter generators are integrated with special mufflers and sound dampening materials, which helps in reducing the noise to a great extent.

So which generator should you use?

Well, the answer is complicated because it depends on your power requirements. As you know, the inverter generators are very expensive and they are designed to be portable and compact; thus, their power output is also low.
If you need a generator for regular use and that too for load demand above 60 or 70%, then you are better off buying a conventional generator because its initial cost is low. But if you need a quiet generator with clean power output, then you should opt-in for an inverter generator.

Apr 5, 2019

What is Community Solar? - Everything You Need To Know

Community Solar

Solar energy and especially community solar is something that we are starting to hear very often. If you are confused about what community solar is then let’s try to help you understand what it is. Consider a community garden, where anyone can come to grow vegetables, fruits or even flowers and plants. Basically, a shared local space that provides the people within the community organically produced food. Now just imagine this same scenario with the vegetables and fruit produce replaced with solar panels. This is what is known as community solar, wherein the solar panels generate clean energy to power nearby houses as well as equipment (oven, lights, computers etc.) within a community.

community solar energy system

This concept was popularised by The United States of America, as more than fifteen states in the country have passed legislation acts to develop community solar in order to be able to power residential, commercial and industrial buildings. The reason that this development is efficient is that many times people are not able to adopt this clean energy, as they are either renting a house or their rooftops cannot support the solar panels or they simply do not have the funds required to install the solar panels. With the help of community solar, anyone can be a part of the famous “clean energy revolution” because this community solar makes it easy to share solar energy to everyone within a community. Through this article you will be able to understand:
  • The benefits of community solar
  • How to be a part of community solar
    • Ownership project
    • Subscription project

The benefits of community solar

Now that you have understood what community solar is, it is important to understand the benefits of being part of the community solar. As mentioned before, the major benefit lies within the fact that anyone can be a part of the clean energy revolution by adopting community solar. Apart from this, another major advantage is in terms of finance. With the help of the Virtual Net Metering (VNM), the community solar option seems feasible to people who otherwise cannot afford a solar farm or have funds required for installation. Virtual Net Metering system allows people or businesses to receive Net Metering Credits that is directly related to any renewable energy project. These net metering credits are worth as much as or are equal to the cost of energy utilized from the utility company.
This concept can be a little confusing and so I am going to explain with the help of an example. Imagine you are a participant in the community solar and a share of your solar farm is 5 kWh (kilowatt/hour). This means that you will receive net metering credits worth 5 kWh and this will reduce your energy bill by 5 kWh on a one-on-one basis. The excess energy in any case of underutilization of the energy is fed back to the solar farm.

community solar virtual net metering
Image Source: https://www.letsgosolar.com/consumer-education/community-solar/

As you can see in the image above, it is very evident that Virtual Net Metering system provides obvious financial benefits to the participants of the community solar.
Apart from finance, the other benefits of community solar include environmentally friendly, as if more people start adopting renewable energy it will help sustain the world’s resources. It is indeed promising support for low-income households, as they will now be able to be a part of sustaining the earth, and the costs associated with using this energy is relatively low. Other than this, it is also a good investment as now, due to the low cost of solar farms, small local governments as well as powerhouses can be a part of this program and generate revenue.

How to be a part of the community solar program?

After understanding the benefits associated with community solar, the next question people generally have is “how do I become a part of this program?” There are two types of participation plans for the community solar program, which is explained in detail in this section.

Ownership Project

In this participation plan, you will be able to purchase the panels and enjoy the benefits of the power generated from the panels that belong to you. This plan is very similar to owning a rooftop solar panel system, as you will own a set of panels in the farm and not just a certain number of kWh out of the panel. It is quite common for a solar farm to be co-owned by the participants within a community, some examples of this plan are:
  • Not-for-profit: donors support a renewable energy farm that is owned by a not-for-profit organization by purchasing the energy generated from one or more panel.
  • Special purpose entity: in order to benefit from tax incentives, individual participants come together to launch a business endeavor wherein the share a renewable energy project.
This is a popularly adopted plan by affluent customers, as it makes it easier for people who cannot otherwise install rooftop solar to now have a solar farm of their own, provided they have the funds required. Though this model seems attractive, it sometimes hinders people from low-income households to be a part of the program, as owners tend to block out the panels.

Subscription Project

In this participation plan, once a utility company builds a solar farm, they offer members a chance to participate and gain benefits from renewable energy. This model does not require any upfront fees to be paid in order to be a part of the program, but it requires that participants must reside within the third party utility company’s area. This program, however, allows free and easy entry of participants unlike in the case of ownership project. In the case where a participant decides to leave the program, his/her spot will be open and available for another interested participant. This is the program that is most popularly requested by members as it holds economic as well as environmental benefits for the community.

[Also Read: Solar Photovoltaic street lighting system]

Community solar has definite pros and cons, cons such as the fact that it requires an appropriate area for the farm to be installed. The solar farm cannot be installed in a place where the sun does not shine, and the land space required is quite expansive as well. Apart from this, it also requires a lot of money and time to be built, making it a little tricky for companies as well as participants to consider investing in. However, as mentioned above the benefits of adopting this renewable energy source will definitely prove to be healthy as well as help in sustaining the earth. It is growing in popularity because people and companies are willing to take a step in adopting renewable energy and avail the benefits associated with it.

Author: Amit Bajpayee is a Solar Energy Adviser and nature lover, currently working with Agni Solar. He is a passionate writer and love to write on topics related to renewable energy and solar industry to help people improve their solar energy knowledge and stay update continues.

Feb 2, 2019

How do solar and hydropower drive electricity?

Solar power and hydroelectric power have been under man’s use for a decade to produce electricity. With the growing need of time for smart production of electricity, these processes have become very reliable. Solar power is debatably the cleanest and the most dependable form of energy. As for the benefits of hydroelectric power, it drives 20% of the world’s energy requirements already.
Below is the description of how both of these sources are proving to be a benefit for humankind:

Hydroelectric Energy:

It can be defined as the form of hydropower where the wave of running water (kinetic energy) is transformed into electricity. Working on this cycle is dependent on solar energy as well. The sun plays a major role in driving the water cycle and keeping the natural process in its uniformity. Hydro-energy is potentially converted to kinetic energy under gravitation, which initiates it around.

How do hydroelectric power plants work?

By placing turbines on the way of a natural flow of water, we can easily convert the hydro-energy into kinetic energy. This, in turn, is used in producing electricity. The head and flow will determine the potential energy of the source. The whole process revolves around fast communication between the inlet, power station and turbine wheel, that water passes through. An opening in the dam is used to make gravity drop water through the penstock.

hydroelectric power plant

Similarly, the moving water makes the turbine spin fast which in turn cause the generator magnets to rotate. This proves out to be the source of generation of electricity. These hydropower plants can be run without the help of dams as well by a process known as run-of-the-river. The process is very similar to the one mentioned above; the difference lies in the natural source of water, that are the rivers.

Tidal power:

Tidal power is also a form of hydroelectricity. It is also a very promising source to generate electricity nowadays. It results from the sun’s and the moon’s gravitational influence on the ocean tides. The height differences between the tides serve a strong force to function turbines.

Solar Energy:

The solar-powered photovoltaic cells are used to convert sunrays into electricity. You can also calculate solar power in your house using a solar installation calculator. This process is done by the excitation of electrons present in silicon cells that consume the photons coming from the sun. This electricity can then be used in your homes and businesses. Here’s how you can use solar power to generate electricity:

rooftop solar energy system

Roof system:

In most of the areas, solar energy systems are planted at the roofs, under no shade to catch sunlight in the prime hours between 9 am to 3 pm. Energy potential is at its max if the installation is made facing south. However, other orientations can still be helpful. In a solar panel, if only one of the 36 cells is shaded, that can reduce the energy production to up to 50%. Some systems are designed with pivots. These pivots track the sunray journey from amidst the sky. However, if the panel is non-pivoting, it should mimic the latitude of the inclination of the land that it is placed upon. Alternations in the inclinations and orientations can be made to adjust weather changes and times of the day.

Solar Panels:

Solar panels, also called modules, work on the principle of the photovoltaic photon capture system. They consist of a positive and negative film of silicon placed under a thin glass. As soon as the photons reach this part of the panel, they remove the electrons from the silicon surface. No sooner, the negative charge of the electrons is attracted by one end of the silicon surface only, which produces voltage. Which in cycles, drives the whole process simultaneously.
The current produced is collected by wiring the solar panels with wire in series to form a solar photovoltaic array. Multiple loops of solar photovoltaic array terminate into a single electrical box, known as the fused array combiner. Within the solar o&m, the fuses work to protect the module cables individually. The electricity produced through the panel is in Direct form, which has to be converted to Alternating form to supply your needs.

Net Meter:

In an electric system run by solar power, the DC power is converted to 120/240 volt AC power. This is then fed to the utility power of the building through which it travels ahead. This power is under a net meter. This works to reduce the demand of power from the utility during the generation of the solar energy by the array. If the utility power offline, the grid system completely shuts off. These solar powered systems are known as ‘battery-less’ or ‘on-grid.’ They also account for 98% of solar installments being made nowadays.


The inverter is placed in an easily accessible location from the module surrounding. In a residential setup, the inverter is usually paced exteriorly near the sub-panels or the main switches. The main reason to put it according to your comfort it the noise it makes during the process. They work to convert the DC power to a 120 volt AC that can be consumed immediately by a dedicated circuit breaking device. The electricity production meter, electricity net meter, and the inverter are connected. This way the power produced by the solar energy will be first taken up by the electrical loads. There’s a balance kept between the electricity produced and the much that passes out the grid. Whenever there’s more energy production than the net requirement, the utility meter will automatically turn it backward.


Cities that have been in the process of using the sources above for the generation of electricity have seen a massive decrement in their overall cost of electricity. Not only this, but the pollution rates and the rates of diseases dependent on such environmental assaults have also declined. At the present day, there’s a very good rate of consumption of healthier and cleaner ways to generate electricity. If the remaining assaults to the environment are taken into account as well, the results can aid the future generations as well.

Author Bio: Michelle Joe is a blogger by choice. She loves to discover the world around her. She likes to share her discoveries, experiences, and express herself through her blogs. You can find her on twitter: @michellejoe524

Jan 8, 2019

Information on Solar Photovoltaic Street Lighting System & Working Principle

Solar Photovoltaic street lighting system works on photovoltaic cells or batteries, that convert sunlight or solar energy into electricity. If you come across a solar lighting system, note the dark panel on top of the light. That is the panel of the photovoltaic cells, which will convert sunlight into electricity. This electricity will then be stored in the batteries. This power can be used as and when needed. The batteries being connected to solar cells, charge themselves continuously while the solar panel is being exposed to available Sunlight. These batteries are inbuilt into these lighting systems. Hence the lamps are capable of drawing light from them. This consequently negates the solar lighting systems from any kind of need to be attached to wires, for power transmission. Hence solar street lighting systems are always wireless.

[Also Read: Solar Power System]

Being a lighting system, meant for the outdoors, solar lighting comes in many shapes and styles, which are aesthetically appealing.

solar photovoltaic street lighting system

How does a Solar lighting system work?

The working principle of these lights is fundamentally simple. During daytime, the PV cells absorb light. As the Sun goes down, an automated switch, which is a photoreceptor too, sensitive to the intensity of available light, deciphers the low Sunlight. This triggers the system to switch on the solar street lights. At this point in time, many would wonder about how will this receptor work, when the sky becomes overcast with clouds? This is a tad tricky to answer.
If the days have been cloudy, most of the time, it is unlikely that the solar cells have charged themselves abundantly. This will mean weak electricity production from these batteries, which in turn, will imply that the lights will not sustain through the night. However, if the sky becomes overcast suddenly, the photoreceptors will kick in to switch on the lights.
Here is a list of information on solar street lighting systems, for a better understanding.
  • Reach into difficult terrain: Since these lighting systems are without any hassle of wires, the installation of solar lighting systems is easy. Perhaps this is one of the reasons why these lighting systems make for an ideal system in difficult terrains. Hence it is these lighting systems are the ones reaching the most remote areas of rural India today.
  • Ideal for parks and dark places: Solar lighting systems are efficient and powerful. They are cost efficient also which makes these systems a great choice for lighting parks, playgrounds and other darker areas for security.
  • Resistant to blowouts and power outages: Solar lighting system is not dependent on any kind of external source for electricity production, like thermal electricity production. It is therefore unlikely that a storm or bad weather can get these lights to stop working due to a power outage. This is probably one of the reasons why is Solar lighting systems are preferred in areas which experience storms and power outrage often.
  • Low Maintenance: Solar lighting systems are low on maintenance cost. Most of the systems come to with a warranty of 25 years. With hardly any disturbance or human manipulation needed to get the solar lighting system going, these systems are perfectly capable of running flawlessly for years.
  • Once in a year or six months check up: Solar lighting systems need an unobstructed reception of sunlight. However, these light systems, are exposed to outside world 24*7. Hence collection of dust and grim on the surface of the PV cells surface is not surprising. This said, the outdoor lighting systems should be regularly checked to ensure that the panels are free of any accumulation of dust that may form a film of obstruction on the PV panel. Attention must also be paid to the batteries that need to be changed once in a while.
  • Enhances landscape and aesthetic lighting: Whenever it is about the lighting systems, meant for the outdoors, the stress in the aesthetic appeal is always more. This is because the normal solar lamps have a bluish hue to it, which makes it a perfect aesthetic enhancement. This creates an amazing essence of night lights.
[Also Read: The future of solar energy in India]
The solar photovoltaic lighting systems are the stepping stones towards making outdoor solar lighting a reality. The pros of these systems are many, yet much is left to be explored.

Dec 27, 2018

Electrical Safety Inspection: Importance and Checklist

No one hesitates to call an electrician whenever a fault is seen. However, most people will take their electrical wiring safety for granted.

Importance of home electrical safety inspection

All electrical installations/wiring will deteriorate with age and use. However, most home owners often overlook the wiring condition. At the most, an electrical safety inspection will only be called when a breaker has already been tripped or a fuse has already been blown. It is not surprising that an electrical fault is a common cause for house fires.
Having your electrical wiring inspected is one of the most important things to keep your home safe from electrical hazards. You don't want to risk the lives of your loved ones, nor getting your property damaged due to electrical fires. Therefore, electrical safety should be a top priority in your home.

home electrical safety inspection

A proper electrical safety inspection will:
  • Identify electrical wiring and components that may have degraded over time.
  • Reveal if any electrical circuits are overloaded.
  • Reveal if any lack of earthing.
  • Identify any defective wiring or other mistakes made by non-certified electricians or DIY home-owners.
  • Spot oversized fuses or breakers that may cause an electrical fire hazard.
  • Find any potential electric shock risks.

When to do home electrical safety inspection?

  • When purchasing a home. It is better to ensure that your new home is electrically safe before moving in.
  • If your home is more than 25 years old and has not had an electrical inspection.
  • If you have had a major renovation to your home.
  • If you observe an electrical appliance that is operating erratically, especially if it is much older.
Periodic safety checks are also important and should be carried out every 10 years or while adding a new appliance.

[Also Read: Electrical Safety for manufacturers]

Home electrical safety inspection checklist

  • All light fixtures, sockets, switches are in good condition and working.
  • All wires are in good condition without any signs of deterioration, wear and tear.
  • All circuit breakers, RCDs etc. are operating properly and fuse elements are appropriately installed.
  • Suitability of all switchgear (MCBs, RCDs etc).
  • Proper grouping and labeling inside the distribution panel.
  • Earthing/grounding system is proper.
  • Wiring method is up to date to ensure that it is suitable for current use.
  • All wires of a circuit are grouped together.
  • Proper insulation of electrical system near wet and damp locations.
  • Wires or sockets are not being overloaded.
  • Reducing the necessity of extension cords by adding permanent fittings if required.
This is a general checklist while inspecting a home electrical system. Adding to these, Portable Appliance Testing (PAT) should also be carried out periodically. This testing includes examination of electrical appliances and equipment. Visual examination, earth continuity testing, insulation test between current carrying parts and the outside metal etc. tests are carried out in PAT testing by a certified electrician or someone who has sound knowledge in electrical testing. Portable Appliance Testers for carrying out this testing can be available on rent or for buying.
A certified professional electrician will inspect thoroughly to ensure the safety. It is important to call only a licensed electrician for safety inspection or for any major electrical work. You may be able to easily find a licensed electrician in your local area by searching on the internet. For example, these electricians in Perth provide electrical safety inspection and recommend you what can be done based on their inspection.
Electrical safety inspection is must for every household to ensure safety from electrical hazards. Worrying about electrical inspection costs? Well, you may actually save more by preventing repair costs by calling an electrician after a fault has occurred. And it's not just about costs, it could be about lives.

Sep 17, 2018

What to do when your RCD or Circuit breaker trips

When it comes to electrical safety, it is extremely important to have various safety devices installed, such as RCD and Circuit Breakers. These devices, when properly installed, protect from electrocution and fire hazards caused by electrical faults. An RCD or Residual Current Device is also called as Safety switch.

switchboard, RCD, Safety switch, circuit breaker

Is an RCD same as a Circuit Breaker?

RCD or Safety Switches are often confused with circuit breakers. While both of these devices protect us from electrical hazards, they are not the same thing.
A safety switch constantly monitors the current flowing through the live and neutral wires. Under normal conditions, the current through live and neutral wires is equal, that means the circuit is balanced. However, if returning current through the neutral wire is not equal to the current going through the live wire, it means a part of the current is going somewhere else. This could just be a current leakage or maybe someone is being electrocuted. Whenever an RCD (Safety switch) detects such an imbalance in live and neutral current, it breaks the circuit almost instantly (within 0.03 of a second).
A circuit breaker basically protects circuits from short-circuit and overcurrent conditions. It detects when the current flowing through is greater than the rated value and cuts off of the circuit. A circuit breaker is not designed to protect an individual from electrocution. So it is important to have safety switches installed in addition with circuit breakers.

What causes an RCD or Circuit Breaker to trip?

When something is seriously wrong with electrical wiring or circuit, the RCD and/or circuit breaker trips disconnecting the circuit from power supply. There are various reasons that can trip a safety switch or circuit breaker.
  • Circuit overload: Overloading of a circuit is the most common reason for tripping your circuit breaker. When a circuit is overloaded it consumes more current. When this increased current reaches beyond the rated limit, the circuit breaker "trips". A safety switch may not trip in case of overload as the circuit still might be balanced.
  • Short circuit: This occurs when the live wire touches neutral wire directly. In this case, a large amount of current flows producing a large amount of heat and may cause a fire hazard. A circuit breaker trips almost instantly in case of short circuits.
  • Ground fault: Similar to short circuit, a ground fault occurs when a hot wire or live wire touches the ground. In this case also, current increases rapidly causing the circuit breaker to trip.
  • Faulty appliance Damaged or faulty appliances can leak excess current. When this leakage current is detected by an RCD or safety switch, it trips and disconnects the circuit.
  • Damaged wiring: Damaged wiring may cause current leakage, ground fault or even short-circuits.
  • Moisture: Current leakage can also occur due to moisture present in electrical switchboards, sockets etc. Wet appliances also produce electrical faults when switched on.
Along with these, there are various other reasons that can produce electrical faults and trip your RCD or circuit breaker.

What to do when your RCD or Circuit Breaker trips?

Resetting a tripped RCD or Circuit Breaker is pretty easy. You just need to flip back the toggle switch to "ON" position. However, it is not a good idea to directly reset the tripped RCD or Circuit breaker without knowing what may have caused it to trip. Following are the steps to figure out the cause of tripping of an RCD or Circuit breaker.
  1. Turn off all the lights and unplug as many appliances as you can. The circuit breaker may have tripped due to overloading of the circuit. So if you directly reset it without disconnecting appliances, there is a good chance of causing the same problem again. Also, if you have recently added and switched on an appliance, make sure to disconnect it before resetting the breaker.
  2. CAUTION! Working with electricity can be dangerous. Never try to touch an electrical panel or any electrical equipment with wet hands. Also, make sure to stand on dry surface with rubber shoes at all times while working with an electrical panel.
  3. Go to your electrical panel and find out which RCD or Circuit Breaker has tripped. This may be easy as you just need to find out which toggle switch has flipped from ON position to OFF position. Once you figure our the tripped device, follow the below steps.
    • First, move the toggle switch to full OFF position (Tripped position is half-way between ON an OFF position).
    • Then move the toggle switch to full ON position. This will restore the power to the circuit.
  4. If the device does not trip again immediately and the power is restored, you can skip to the next step. But if the device trips immediately again, it may be a sign of a fault in wiring or a serious electrical problem. In this case, you need to call a certified electrician to get it checked properly.
  5. After restoring the power, plug in the required appliances one by one and check if the RCD or Circuit breaker trips again. If you plug in a faulty appliance, the device will trip again. Make sure not to overload with too many appliances.

This article is sponsored by:
Westline Electrical Services is a proudly WA owned and operated family business. Their professional Electricians serve residential, commercial, and industrial customers.

Apr 17, 2018

Methods of voltage control in power system

Before learning the methods of voltage control in power system, we must first understand why do we need to control voltage. In power systems, voltage is supposed to be constant which is obviously not. So we have to control it in such a way that it remains constant. But why does the voltage need to be constant at all? Because, most of the devices, apparatus, electrical machines, consumer appliances etc. are all designed to work at a specified voltage. Wide variations of voltage may cause errors in operation, malfunctioning or performance deterioration. It is desirable that the consumers receive power at substantially constant voltage. In many countries, including India, the statutory limit of voltage variation is ±6% of the declared voltage at consumers' end.
Therefore, it is important to apply certain techniques, certain methods to control the power system voltage to keep it constant. Following are the methods of voltage control in power system.

voltage control in power system

Methods of voltage control in power system

  1. Using excitation control or voltage regulators at generating stations
  2. By using tap changing transformers
  3. Using induction regulators
  4. By using shunt reactors
  5. By using shunt capacitors
  6. Using synchronous condensers

Excitation control or voltage regulators at generating stations

Induced emf (E) of a synchronous generator (alternator) depends on the excitation current (field current). The terminal voltage of an alternator can be given as V = E - IZ. As the load current, and hence the armature current, increases, voltage drop in the armature also increases. The field current must be increased to compensate this voltage drop, such that the terminal voltage is at the target value. For this purpose, alternators are provided with excitation control or automatic voltage regulator systems. There are two main types of automatic voltage regulators (AVR):
  1. Tirril regulator
  2. Brown-Boveri regulator
An automatic voltage regulator detects the terminal voltage and compares it with the reference voltage. The difference between detected voltage and given reference voltage is called as the error voltage. The regulator then controls the excitation voltage of the alternator to cancel out the error voltage. Thus, an automatic voltage regulator controls the voltage by controlling the excitation.
Excitation control method is satisfactory only for short lines. For longer lines, the terminal voltage of alternator has to be varied widely for the voltage at far ends to remain constant. Obviously, this method is not feasible for longer lines.

By using tap changing transformers

The voltage control in transmission and distribution systems is usually obtained by using tap changing transformers. In this method, the voltage in the line is adjusted by changing the secondary EMF of the transformer by varying the number of secondary turns. Secondary voltage of a transformer is directly proportional to the number of secondary turns. Thus, the secondary voltage can be adjusted by changing the turns ratio of the transformer. Secondary number of turns can be varied with the help of tappings provided on the winding. Basically, there are two types of tap changing transformers.
  1. off-load tap changing transformers
  2. on-load tap changing transformers

Voltage control using off-load tap changing transformers

In this method, the transformer is disconnected from the supply before changing the tap. Off load tap changing transformers are relatively cheaper. But the main drawback with them is that the power supply is interrupted while changing the tap.

Voltage control using on-load tap changing transformers

In modern power system, continuity of the supply is important. Therefore, on-load tap changing transformers are preferred to control the voltage.

By using induction voltage regulators

An induction regulator is basically an electrical machine somewhat similar to an induction motor, except that the rotor is not allowed to rotate continuously. The rotor of induction regulator holds primary (excitation) winding which is connected across (parallel) the supply voltage. The stationary secondary winding is connected in series with the line which is to be regulated. From electrical point of view, it is immaterial whether primary winding is rotating or secondary winding is rotating. The magnitude of voltage in the secondary winding depends upon its position with respect to the primary winding. Thus, the secondary voltage can be adjusted by rotating the primary winding. Induction voltage regulators were used to control voltage of electrical network in earlier days, but they are now replaced by tap changing transformers.

Voltage control by using shunt reactors

Shunt reactors are basically inductive elements that are provided at sending end and receiving end of long EHV and UHV transmission lines. When a transmission line is not loaded or lightly loaded, the line capacitance predominates and receiving end voltage becomes greater than the sending end voltage. This effect is known as Ferranti effect. In such situation, shunt reactors are switched in the line. Shunt reactors compensate the line capacitance and, hence, control the voltage.

Voltage control by using shunt capacitors

Shunt capacitors are usually installed at the receiving end substations or near industrial loads. Most of the industrial loads draw inductive current and therefore the power factor is lagging (usually 0.3 to 0.6 lag). The line experiences IXL drop due to this lagging current. Switching in shunt capacitors compensate this inductive reactance, thereby, decreasing the IXL drop. Thus, shunt capacitors can be used to control the line voltage when the load is highly inductive.

Voltage control by using synchronous condenser

A synchronous condenser is basically an over-excited synchronous motor running on no-load. Synchronous condensers are also called as synchronous phase modifiers. A synchronous condenser is located near the load end and can inject or absorb reactive power. And, thus, a synchronous phase modifier improves the voltage profile.