I think it’s about time we began to know the main contributing factor to how much we pay for electricity. The Power Factor. Some might have heard it before but wouldn’t know what it is. Others will not even have the slightest idea of what it is. I want to use this paper to break this into smaller segments for the layperson to appreciate how significant it is in the power sector from the generation aspect through to the distribution and consumption aspect. This will be recognized only when the major parameters of power factor such as Current, Voltage, power, active power, reactive power, and apparent power are vividly spelled out. These parameters will be expanded further to include capacitive & inductive power factors.
ELECTRIC CURRENT is one of the most basic concepts that exist within electrical and electronic science. It is at the core of the science of electricity, whether it is an electrical heater, television, electrical grid system, transmission line, or whatever the concept, electrical current is central to its operation. It is defined as the flow of ELECTRONS through an electrical circuit and is denoted by the letter “I”. Current cannot normally be seen even though its effect can be seen, heard, and felt all the time and as a result, it is sometimes tough to reach an understanding of what it is.
On the other hand, VOLTAGE is known as the ELECTROMOTIVE FORCE that drives current through an electrical circuit. A perfect analogy that is mostly used is the ‘WATER’ analogy. This analogy considers water flowing through pipes and connected to a pump to make a water circuit. Consider the water to be the current, the pump to be the battery or source of EMF OR VOLTAGE, and pipes to be the wires/cables in the electrical circuit. In this analogy, water can flow through this water circuit even if the water circuit is not connected to the pump.
Nevertheless, if the pump is connected and turned on pressure is being applied to the flow of water through the “Water circuit”. This analogy best depicts the flow of power through an electrical circuit, and the role of voltage in electrical power, and goes further to explain the components of power to a layman.
Both CURRENT and VOLTAGE come together to make ELECTRICAL POWER. No wonder in applied electricity the formula for POWER is the product of VOLTAGE and CURRENT.
Voltage and current are inversely proportional to each other. Therefore, when there is an increase in voltage, there will be a decrease in current and vice versa. As mentioned in the previous paragraphs, both play a significant role in the power factor. Electrical power is the rate at which electrical energy is transferred by an electrical circuit. It is measured in watts (W) and is the product of the voltage and the current in the electrical circuit as mentioned at the beginning of the paragraph. In simplified terms, it refers to the amount of electrical energy delivered by an electrical circuit to operate within a given amount of time. Electrical power is essential for many aspects of modern life, from powering our homes, offices, and hotels to enabling the functioning of technology and machinery in various industries. Three types of power are normally mentioned in electrical engineering namely ACTIVE POWER/, REACTIVE POWER, and APPARENT POWER. All these types of power mentioned would be explained further for clarity. ACTIVE POWER, REAL POWER, and TRUE POWER mean the same thing and can be used interchangeably. It is the type of power that is actually consumed by the electrical device and is measured in watts (W). This is the type of power that puts any device to work. For example, a light bulb comes on and can light a room up as a result of the presence of active power. A fan can rotate because of the presence of active power, our televisions, radio sets, heaters, and other home appliances can work due to ACTIVE POWER. This is also how come we find the ratings of our electrical appliances in watts (W).
REACTIVE POWER also known as PHANTOM POWER is the amount of “unused” power in the circuit. Some also describe it as power that is being consumed by the electrical device but is not actually used. It is instead stored and released as magnetic energy. It is general knowledge in electrical machines that reactive loads do not dissipate power in the sense that is used to power them but measuring the voltage around them indicates the fact that they drop voltage and draw current. The power used up through this voltage drop and current draw is in the form of heat or waste energy. Reactive power is measured in Volts Amps-Reactive (KVARs) and is denoted by the letter “Q”. In inductive loads, such as induction motors, transformers, Air condition systems, and refrigeration systems the reactive power is also beneficial since the magnetic field is necessary to keep these types of loads in service.
APPARENT POWER is the combination of both active power and reactive power. It represents the total power that is being supplied from source to load and is measured in Volt-Amperes (KVA). It is the product of the root mean square (RMS) voltage and root mean square (RMS) current which is denoted by the letter “S” and measured in volts-Amperes (KVA). When the circuit is purely resistive then Active power is equal to apparent power because all the power supplied to the load is used to do useful work. However, in inductive or capacitive (reactive) circuits where Reactance exists then apparent power is greater than real power.
Considering that most of the key parameters have been explained it is safe to go ahead to explain the main parameter, the POWER FACTOR. However, for clarity purposes I will not plunge into the technical explanations directly, instead, I will start with an analogy that is widely used to demonstrate the power factor. “The beer analogy”. Let’s assume you are at a bar on a sunny day to order a mug of your favorite beer. The thirst-quenching portion of your beer will be known as the ACTIVE POWER and will be represented with (KW). Unfortunately, life isn’t perfect so along with the thirst-quenching portion comes a bit of foam. (And let’s face it, that foam just doesn’t quench your thirst.) This foam will be known as the REACTIVE POWER and will be represented by VOLT-AMPS REACTIVE (KVAR). The total contents of your mug will also be known as the APPARENT POWER and will be represented by VOLT-AMPERES (KVA) which will be the summation of the thirst-quenching portion and the foam. From this analogy, the power factor will be known as the ratio of the thirst-quenching portion of beer (KW) to the total contents in the mug (KVA). (Please note that the letter “K” within the units of measurement stands for “Kilo” and can change to “M” or “Mega” based on the quantity of what is been measured.)
I will now go straight to the technical explanations of the power factor. From the “beer analogy”, the power factor can be technically defined as the ratio of the ACTIVE POWER (KW)to the APPARENT power (KVA) consumed by an alternating current (A.C.) electrical equipment or a complete electrical installation. This is a measure of how effectively electrical power is converted into useful work output. Graphically it can be represented as the cosine of the phase angle between the (KW) and (KVA). Any industrial process that uses electric motors to drive pumps, conveyors, refrigeration plants, Air conditioning systems E.T.C. introduces
inefficiencies into the electricity network by consuming or drawing excessive current called “inductive Reactive current”. Let’s not be misled, this inductive reactive current is also beneficial to inductive loads to keep them in service. However, excess of it is harmful to our systems as it also increases our electricity bills. Although this current produces no useful work output, it increases the current on the supplier’s switchgear & distribution network. Moreover, it also increases the current on the consumer’s switchgear and cabling. This has to be corrected for effective power consumption. To correct this, you must first measure and understand the type of power factor in the system with the use of a clamp-on power factor meter. Whether it’s a lagging/inductive power factor OR leading / capacitive power factor. (Always remember the code Capacitance is to voltage as inductance is to current) this is how to remember if a power factor is inductive or capacitive. In the case of the inductive power factor, the current LEADS the
VOLTAGE in an A.C waveform at an angle of 90 (Ninety degrees) whereas in the capacitive power factor, the CURRENT LAGS the voltage at an angle of 90 (Ninety degrees). Breweries, refineries, textile factories, hospitals, steel works, bottling companies, cold stores, paint factories, offices, and even homes are examples of industries and buildings that suffer from bad power factor. (Also note that the best power factor that can be obtained is “1” which is known as the “Unity power factor” and the power factor has no unit) The foremost step in exploring the solution to any problem is to identify the problem at hand.
Similarly, to first correct power factor problems you must be familiar with the type of power factor in the system. Whether it’s inductive or capacitive. Secondly, you must be familiar with the methods of correcting power factor. Always remember what I usually call the correction code (inductive is to capacitive while capacitive is to inductive). This code simply means an inductive power factor is corrected by the use of capacitive equipment such as phase advancers, capacitor banks, and Static Var Compensators (SVC) whereas a capacitive power factor is corrected by the use of inductive equipment such as synchronous motors, and even the use of SVC’s as well. Some of the power factor correction equipment mentioned is not the equipment that the layperson is familiar with and will find it difficult to appreciate what it is and how it does its work. Given the fact, they have been mentioned in this write-up, an abridged description of two power factor correction equipment will be expounded to give readers the transparency of the work this equipment does in the system.
A CAPACITOR is a semiconductor device that stores electrical charge. Capacitors vary in shapes and sizes but the basic construction of capacitors are two conducting plates made from Aluminum, held parallel to each other and separated by dielectric insulating materials like ceramic. A capacitor acts like a storage tank for water. When there is a continuous supply of water to the tank it will get full. However, when there is an interruption in the supply of water to the tank it will still have some water stored for later use. Likewise, in circuits, when there is increased or excess current in the system the capacitor has the capability of storing that excess current for future use. They are compact, reliable, convenient to install, and highly efficient. For these reasons, engineers choose it for their power factor correction. A CAPACITOR BANK is a collection of capacitors connected in parallel that can be switched “on” OR “off” to provide the required amount of reactive power for power factor correction.
Besides power factor correction, capacitors have supplementary applications in various circuits such as a temporary battery that maintains power supply while power is cut off, used in the telecommunication industry along with other devices in filtering signals, and also used in computers in cases of an emergency shutdown, it can also be used in commercial appliances like cameras, fans, electronic chargers, LED lights E.T.C. Another power factor correction device that will be highlighted is the Static Var Compensator which possesses the potentials of a capacitor and an inductor So have the ability to inject and absorb reactive power.
STATIC VAR COMPENSATOR (SVC) which is also known as a static reactive compensator is a device used to improve the power factor of an electrical power system. It consists of a bank of capacitors and reactors, so they can be used to inject or absorb reactive power into or out of the system to maintain a desired voltage level. The control system of the SVC monitors the system voltage and current and adjusts the reactive power output of the device accordingly. SVCs are very instrumental in power factor correction because of the capabilities they possess.
Power factor correction has quite several advantages affiliated with It. These advantages range from technical to economical and occasionally some environmental advantages. I will go further to open up on some of the advantages associated with power factor correction/improvement.
- In some places where there is a penalty for a low power factor incorporated in the utility’s power rate structure, a high-power factor will call for a fine or penalty. Aside from the penalty, you will be paying more for electricity since your (KVA) APPARENT POWER will be increased. Therefore, a reduced system KVAR (Reactive power) improves the power factor and reduces the power bills by reducing the KVA (Apparent power).
- Reduction of power generated due to improved system efficiency. Reduced power generation means less greenhouse gas emissions and fossil fuel depletion by Thermal power plants.
- Increase System Capacity. Power factor improvement boosts system capacity and allows additional loads (motors, lighting, etc.) to be added without overburdening the system. For example, in a typical system, a transformer of 1000KVA with a PF of 0.80 will only supply 800KW of active power to the load to do useful work. Correcting the system to a P.F. of 0.95 increases the active power to 950KW. This is an increase of an additional 150KW of active power to do useful work.
- Improve System Operating Characteristics (Reduce Line Losses). An upgraded power factor at the load points shall ease the system of transmitting reactive current. Less current in the system shall reduce losses in the distribution system of the facility since losses are proportional to the square of the current. Therefore, fewer kilowatts (KWH) of electricity will be purchased from the utility.
- IMPROVED VOLTAGE. A low power factor causes an increase in current flow for a given load. When there is a surge in line current, there will be a drop-in voltage, which results in a lower voltage at the equipment. With an improved power factor, the voltage drop in the conductor is minimized, improving the voltage of the equipment and ultimately preserving the life span of the equipment.
Most people are oblivious to the effects or inefficiencies associated with bad power factor and run their systems with major inefficiencies and increased bills to pay when they have not consumed a significant amount of that power. Sometimes you may be wondering why your equipment goes bad in no time or does not function to its maximum capacity. Having read this write up I wish you speak to a professional to help you correct it. As a Power system engineer and energy management consultant who understands how this inefficiency affects your electrical systems in your industrial and domestic properties, I will always advise clients to monitor their electrical systems properly for any inefficiencies and fix them before the worst occurs. A healthy system is a healthy business and a healthy mind. If your systems are performing properly and effectively, excessive money is not spent on the system, and the life span of equipment or components of the system is preserved then productivity will be high. This eventually increases revenue and makes business owners happy.
I together with other electrical engineers will be very delighted to see industries operate at a very good power factor and will carry on with championing the advantages of an improved power factor since we are aware of the technical and economic benefits that have on the electricity network in the country. I also hope this paper influences people to look out for any inefficiencies that hinder their systems from functioning effectively. Consistently keep in mind that “A healthy system is a healthy business and a healthy mind”