Aug
27

Methods of Grounding

What is Grounding or Earthing?


To connect the metallic (conductive) Parts of an Electric appliance or installations to the earth (ground) is called Earthing or Grounding.


In other words, to connect the metallic parts of electric machinery and devices to the earth plate or earth electrode (which is buried in the moisture earth) through a thick conductor wire (which has very low resistance) for safety purpose is known as Earthing or grounding.


To earth or earthing rather, means to connect the part of electrical apparatus such as metallic covering of metals, earth terminal of socket cables, stay wires that do not carry current to the earth. Earthing can be said as the connection of the neutral point of a power supply system to the earth so as to avoid or minimize danger during discharge of electrical energy.

Earthing can be done in many ways. The various methods employed in earthing (in house wiring or factory and other connected electrical equipment and machines) are discussed as follows:

1) Plate Earthing:


In plate earthing system, a plate made up of either copper with dimensions 60cm x 60cm x 3.18mm (i.e. 2ft x 2ft x 1/8 in) or galvanized iron (GI) of dimensions 60cm x 60cm x 6.35 mm (2ft x 2ft x ¼ in) is buried vertical in the earth (earth pit) which should not be less than 3m (10ft) from the ground level.


For proper earthing system, follow the above mentioned steps in the (Earth Plate introduction) to maintain the moisture condition around the earth electrode or earth plate.plate earthing, plate grounding.

Plate Earthing

2) Pipe Earthing:


A galvanized steel and a perforated pipe of approved length and diameter is placed vertically in a wet soil in this kind of system of earthing. It is the most common system of earthing.

The size of pipe to use depends on the magnitude of current and the type of soil. The dimension of the pipe is usually 40mm (1.5in) in diameter and 2.75m (9ft) in length for ordinary soil or greater for dry and rocky soil. The moisture of the soil will determine the length of the pipe to be buried but usually it should be 4.75m (15.5ft).Pipe Earthing and Grounding

Pipe Earthing and Grounding

3) Rod Earthing:


It is the same method as pipe earthing. A copper rod of 12.5mm (1/2 inch) diameter or 16mm (0.6in) diameter of galvanized steel or hollow section 25mm (1inch) of GI pipe of length above 2.5m (8.2 ft) are buried upright in the earth manually or with the help of a pneumatic hammer. The length of embedded electrodes in the soil reduces earth resistance to a desired value.

Copper Rod Electrode Earthing System

4) Earthing through the Waterman:


In this method of earthing, the waterman (Galvanized GI) pipes are used for earthing purpose. Make sure to check the resistance of GI pipes and use earthing clamps to minimize the resistance for proper earthing connection.


If stranded conductor is used as earth wire, then clean the end of the strands of the wire and make sure it is in the straight and parallel position which is possible then to connect tightly to the waterman pipe.


5) Strip or Wire Earthing:


In this method of earthing, strip electrodes of cross-section not less than 25mm x 1.6mm (1in x 0.06in) is buried in a horizontal trenches of a minimum depth of 0.5m. If copper with a cross-section of 25mm x 4mm (1in x 0.15in) is used and a dimension of 3.0mm2 if it’s a galvanized iron or steel.


If at all round conductors are used, their cross-section area should not be too small, say less than 6.0mm2 if it’s a galvanized iron or steel. The length of the conductor buried in the ground would give a sufficient earth resistance and this length should not be less than 15m.


General method of Earthing / Proper Grounding Installation (Step by Step)


The usual method of earthing of electric equipments, devices and appliances are as follow:
1. First of all, dig a 5x5ft (1.5×1.5m) pit about 20-30ft (6-9 meters) in the ground. (Note that, depth and width depends on the nature and structure of the ground)
2. Bury an appropriate (usually 2’ x 2’ x 1/8” (600x600x300 mm) copper plate in that pit in vertical position.
3. Tight earth lead through nut bolts from two different places on earth plate.
4. Use two earth leads with each earth plate (in case of two earth plates) and tight them.
5. To protect the joints from corrosion, put grease around it.
6. Collect all the wires in a metallic pipe from the earth electrode(s). Make sure the pipe is 1ft (30cm) above the surface of the ground.
7. To maintain the moisture condition around the earth plate, put a 1ft (30cm) layer of powdered charcoal (powdered wood coal) and lime mixture around the earth plate of around the earth plate.
8. Use thimble and nut bolts to connect tightly wires to the bed plates of machines. Each machine should be earthed from two different places. The minimum distance between two earth electrodes should be 10 ft (3m).
9. Earth continuity conductor which is connected to the body and metallic parts of all installation should be tightly connected to earth lead.
10. At last (but not least), test the overall earthing system through earth tester. If everything is going about the planning, then fill the pit with soil. The maximum allowable resistance for earthing is 1Ω. If it is more than 1 ohm, then increase the size (not length) of earth lead and earth continuity conductors. Keep the external ends of the pipes open and put the water time to time to maintain the moisture condition around the earth electrode which is important for the better earthing system.

 

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27

Separate Fact from Fiction about Lightning Protection

lightning photography

Myths abound about lightning and lightning protection, so it’s important to separate fact from fiction. Thunderstorm season is a perfect time for an up-close look at a few frequently asked questions about lightning protection systems.


Myths continue to abound about lightning and the science of lightning protection. It’s not always easy to know the facts when misinformation is circulated on the internet and through social media. Now that thunderstorm season is in full swing, home and business owners can benefit from accurate information and reality reminders about lightning protection. Here are four answers to frequently asked questions to help separate fact from fiction about lightning protection systems.

lightning_pole

Q. Aren’t lightning rods a thing of the past?

Lightning protection systems are installed more today than ever before. According to Underwriters Laboratories, lightning accounts for more than one billion dollars annually in structural damage to buildings in the U.S. This statistic does not include costs due to loss of business, downtime and repairs. Since today’s homes and buildings are equipped with a variety of sensitive electronics, lightning protection systems serve an important purpose. Protecting occupants, structures and critical systems is an important part of the building design phase, which is why construction planners are specifying more systems. Lightning protection systems increase a structure’s sustainability against a common and often costly, weather threat.


Q. Don’t trees protect a structure against lightning?


No, trees don’t provide protection from lightning striking your home or business. Actually, lightning can side-flash from a tree and hit a nearby structure, so sometimes trees around a structure and provide an easy entry for lightning’s destructive electricity. Lightning traveling along tree roots can enter a structure by jumping onto nearby telephone, cable and electrical lines, introducing harmful surges. Lightning can also injure a tree from a direct strike that can cause heavy limbs to split and fall onto a nearby structure. Lightning kills and damages more trees than we can account for in the U.S., so unless a tree is equipped with a lightning protection system, it can be extremely vulnerable to damage—with the nearby structure vulnerable, as well.


Q. Isn’t a whole-house surge arrester enough protection against lightning?


Surge protection is only one element of a complete lightning protection system. Since lightning can pack 100 million volts of electricity, a strike to an unprotected structure can be disastrous and a single incident can cost thousands of dollars, with losses ranging from damage to expensive electronics to fires that destroy entire buildings. Unfortunately, no surge protection device or “whole-house” arrester alone can protect a structure from a direct strike packing lightning’s mega electricity. A grounding network for lightning (lightning protection system) must be implemented to provide a safe, conductive path to discharge lightning’s electricity. Surge protection + the grounding network = a complete lightning protection system.


Q. Can’t I install the lightning protection myself?


This is not an experiment you want to attempt! Lightning protection is a highly specialized trade that is governed by industry safety Standards. Design and installation is typically not within the scope of expertise held by general contractors, roofers or even electricians, which is why the work is typically subcontracted out to specialists. Trained experts like LPI-certified contractors that specialize in lightning protection and utilize UL-listed components and equipment should be hired to design and install these systems. The highly conductive copper and aluminum materials used are not readily available in hardware stores and design and installation for systems is not a do-it-yourself project.


Learn more about lightning protection system installation by viewing LPI’s short video at: http://lightning.org/learn-more/watch-learn/#video-6

Public Reminded about Dangers of Lightning and Surge Protection Limitations

During National Electrical Safety Month, LPI raises awareness for lightning, an overlooked electrical hazard


HARTFORD, Conn., May 14, 2015 /PRNewswire-USNewswire/ — May is National Electrical Safety Month and the Lightning Protection Institute (LPI) is joining the Electrical Safety Foundation International (ESFI) to raise awareness about the importance of electrical safety—including lightning, an underrated and often forgotten electrical hazard.


Lightning is the rapid discharge of atmospheric electricity that can pack up to 200 kA of electric energy (100 million volts of power). A lightning strike to an unprotected structure can be disastrous and a single incident can cost thousands of dollars, with losses ranging from damage to expensive electronics to fires that destroy entire buildings. A single surge protection device or “whole-house” arrester is not sufficient to protect a structure from a direct lightning strike packing extreme electric energy. A grounding network, commonly known as a “lightning protection system” must be implemented, as well to provide safe and effective protection against lightning.


“The electrical ground installed by the electrician for your structure is there to protect the internal workings of the electrical system for everyday electricity—it’s not designed to handle the mega electricity that lightning can pack,” said Bud VanSickle, executive director for the Lightning Protection Institute (LPI). “Even though the majority of surges are created from large appliances switching on and offwithin a structure or power grid switching from the electric utility company, lightning is typically responsible for the most powerful and destructive types of surges.”

Prior to the age of electronics, the threat to structures from lightning was primarily fire-related. Enhanced communications lines, power and generation systems and gas and water piping have since created induction problems for today’s structures, allowing lightning’s access through energized lines or system grounds. Decades ago, the introduction of low voltage wiring and electronically controlled building components presented a new vulnerability to lightning. To address these concerns, lightning protection codes and standards were updated in the 1990’s; adding more provisions for grounding and new criteria for lightning arresters and surge protection devices (SPD’s).

“Today’s lightning protection network takes a total package approach which includes a system to ground the structure, a primary SPD (or SPD’s) for the service entrance and sometimes secondary protection at the point of use for high-end equipment or appliances,” said VanSickle. “It’s important that the lightning protection system complies with national safety Standards of NFPA 780 and UL 96A to address requirements for full protection.”

The NFPA and UL safety Standards for lightning protection systems employ practical and tested solutions to protect a structure, its occupants, contents, equipment and operations. A complete system includes: strike termination devices, conductors, ground terminals, interconnecting bonding to minimize side flashing, and surge protection devices for incoming power, data and communication lines to prevent harmful electrical surges. Additional connectors, fittings or bonding for CSST gas piping may be required and surge protection devices for vulnerable appliances may be needed, as well.

Lightning protection is also not a “do-it-yourself” project. Only experienced and reputable UL-listed and LPI-certified lightning protection contractors should install these systems to ensure materials and methods comply with safety Standards.

The Electrical Safety Foundation International (ESFI) sponsors National Electrical Safety Month each May to increase public awareness of electrical hazards. For more information about ESFI and electrical safety, visit www.esfi.org.

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27

Protect Your Gadgets: Why You Need a Surge Protector

Do you have your PC, television, or other expensive electronics plugged directly into a power outlet? You shouldn’t. You should plug your gadgets into a surge protector, which isn’t necessarily the same thing as a power strip.


Sure, we all might forget about surge protection because everything seems to be going fine, but it only takes one power surge or spike and your expensive electronics could become useless.

water_damage

Power Surges and Strikes

Electrical sockets are supposed to provide a consistent voltage of electricity, and devices you plug into your power outlets depend on this. In some cases, a power spike can occur when the voltage suddenly increases. This can often be caused by lightning strikes, power outages, or malfunctions in the grid the power company is responsible for. A spike is a short increase in voltage, while a surge is one that lasts more than a few seconds. Surges are usually caused by problems with the electrical grid.

voltage spike

Whatever the cause, a sudden increase in current can damage electronics that are drawing power from the surging or spiking outlet. It could even render them completely inoperable, the increase in current having damaged them beyond repair.

How Surge Protectors Help

Standard electrical outlets don’t have any protection against power surges and spikes. Surge protectors are generally made and sold in the form of power strips, although you can also buy single-outlet surge protectors that sit against the socket and provide a single, protected outlet. You can also pick up travel surge protectors, which are small, offer fewer outlets, and will fit in a laptop bag.
Surge protectors use a variety of different methods to do this, but they generally boil down to a system that diverts energy over the safe threshold to a protective component in the surge protector itself. The surge protector ensures that only the normal, safe amount of electricity passes through to your devices.

surge protector in use

Power Strips Are Not Necessarily Surge Protectors

Some people are confused about this and call every power bar a “surge protector,” but this isn’t true. The cheapest power strips are often not surge protectors and only provide additional power outlets for you. When using a power strip for your expensive electronics, be sure its specifications say it has a surge protector. Below, you’ll see a type of power bar that probably isn’t a surge protector.

power strip not surge protector

You should also consider sticking with a surge protector from a reputable company. The cheapest surge protector from an obscure manufacturer may not provide much protection when it’s actually needed. Reputable surge protectors will also offer warranties, promising to replace any electronics connected to the surge protector if a surge occurs and they become damaged. Look for this before you buy a surge protector.

surge protector lights

How Often Do You Need to Replace a Surge Protector?

Surge protectors don’t last forever. The components they use to divert energy can wear down as a result of power surges. This means that your surge protector’s life depends on how frequently power surges occur in your area. A surge protector can only absorb a limited amount of additional power.


Some surge protectors have lights that go off (or on) to let you know when they can no longer provide any protection, while some of the more expensive surge protectors may even have an audible alarm that goes off to let you know of this. Keep an eye on your surge protector and replace it when the surge protector asks you to.


Surge protectors are easy to forget about when everything seems to be going fine, and they would be completely useless in a perfect world where the electrical system never malfunctioned. However, surge protectors are a fairly inexpensive and important way of protecting your expensive gadgets. You probably want a power strip for your gadgets, anyway — so you might as well get a surge protector that provides one.

Source: How-To Geek

 

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15

Troubleshooting Power Factor Correction Capacitors

By Bennie Kennedy

Power factor correction capacitors reduce energy costs by avoiding the premium rates that utilities charge when power factor falls below specified values. Facilities typically install these capacitors when inductive loads cause power factor problems. Capacitor banks normally provide years of service, but they need to be inspected on a regular basis to make sure they are working properly. Problems such as loose connections, blown fuses or failing capacitors can reduce the amount of power correction available and, in extreme cases, even cause a total system failure or a fire. This article describes how to inspect power factor correction capacitors and avoid these problems.

Safety first!

Capacitors are energy storage devices that can deliver a lethal shock long after the power to them is disconnected. Most capacitors are equipped with a discharge circuit but, when the circuit fails, a shock hazard will exist for an extended period of time. When testing is required with the voltage applied, you must take extreme care. Capacitor bank maintenance requires training specific to the equipment, its application, and the task you are expected to perform. In addition, the proper personal protective equipment (PPE) per NFPA 70E is required.

Additional hazards are involved in working with current transformer (CT) circuits, including the wiring and shorting block. The CT itself is normally located in the switchboard, not in the capacitor bank enclosure. Even after the capacitor bank has been de-energized, there is a danger of electrical shock from the CT wiring. If the CT circuit is opened when there is a load on the switchboard, the CT can develop a lethal voltage across its terminals.

What is power factor?

Power factor is defined as the percentage ratio between the true power, measured in kilowatts (kW), and apparent power, measured in kilovolt amperes (kVA). The apparent power is the total requirement that a facility places upon the utility to deliver voltage and current, without regard to whether or not it does actual work. Utilities usually charge a higher rate when power factor falls below a certain level, often 90%.

True power (KW) / apparent power (KVA) = power factor

50 KW / 52KVA = .96 (a good power factor of 96%)

50 KW / 63 KVA = .79 (a poor power factor of 79%)

Motor inductance is the most typical cause of poor power factor, and the problem only increases when motors are not loaded to their full capacity. Harmonic currents reflected back into the systems also reduce power factor.

Measuring power factor requires a meter that can simultaneously measure voltage, current, power and demand over at least a one-second period. A digital multimeter (DMM) cannot perform these measurements, but a power quality analyzer such as the Fluke 43B used with a current clamp will measure all of these elements over time and build an accurate picture of power consumption. A power logger, another type of power quality tool, can perform a 30-day load study to provide an even better understanding of power factor and other parameters, over time.

Low power factor can be corrected by adding power factor correction capacitors to the facility’s power distribution system. This is best accomplished via an automatic controller that switches capacitors, and sometimes reactors, on and off. The most basic applications use a fixed capacitor bank.

Under normal conditions, capacitors should operate trouble-free for many years. But, conditions such as harmonic currents, high ambient temperatures and poor ventilation can cause premature failures in power correction capacitors and related circuitry. Failures can cause substantial increases in energy expenses, and in extreme cases create the potential for fires or explosion. So, it’s important to inspect power factor correction capacitors on a regular basis to ensure they are working properly. Most manufacturers post the service bulletins on their web sites. Their typical recommended preventative maintenance interval is twice annually.

Inspection with infrared imager

The most valuable tool for evaluating capacitor banks is a thermal imager. The system should be energized for at least an hour prior to testing. To begin, check the controller display to determine if all the stages are connected. Next, verify that the cooling fans are operating properly. Conduct an infrared examination of the enclosure prior to opening the doors. And, based on your arc-flash assessment, wear the required personal protective equipment.

Damage to circuit breaker feeding a capacitor bank. A thermal examination would have detected abnormal heating.

Examine power and control wiring with the thermal imager, looking for loose connections. A thermal evaluation will identify a bad connection by showing a temperature increase due to the additional resistance at the point of connection. A good connection should measure no more than 20 degrees above the ambient temperature. There should be little or no difference in temperature phase-to-phase or bank-to-bank at points of connection.

powerfactor

The difference in temperature indicates that the fuse on the left is blown.

Cap_bank_Fluke

This infrared image indicates that a capacitor has failed.

An infrared evaluation will detect a blown fuse by highlighting temperature differences between blown and intact fuses. A blown fuse in a capacitor bank stage reduces the amount of correction available. Some units are equipped with blown fuse indicators but others are not. If you find a blown fuse, shut down the entire bank and determine what caused the fuse to blow. Some common causes are bad capacitors, reactor problems; and bad connections at line fuse connections, load fuse connections, or fuse clips.

Look for differences in the temperatures of individual capacitors. If a capacitor is not called for or connected at the time of examination then it should be cooler. Also, keep in mind that the temperatures of components might be higher in the upper sections due to convection. But if, according to the controller, all stages are connected, then temperature differences usually indicate a problem. For example, high pressure may cause the capacitor’s internal pressure interrupter to operate before the external fuse, thus removing the capacitor from the circuit without warning.

Current measurements

As part of preventative maintenance, a current measurement on all three phases of each stage should be taken and recorded using a multimeter and a current clamp. Also use the multimeter to measure the current input to the controller from the current transformer in the switchboard, using a current clamp around the CT secondary conductor. A calculation is required to convert the measured current value to the actual current flowing through the switchboard. If the current transformer is rated 3000 A to 5 A, and you measure 2 A, the actual current is . In addition, measure the current through the breaker feeding the capacitor bank for phase imbalance, with all stages connected. Maintain a log of all readings, to provide a benchmark for readings taken at a later date.

Capacitance measurements

Before measuring capacitance, de-energize the capacitor bank and wait for the period specified in the manufacturer’s service bulletin. While wearing the proper personal protective equipment, confirm with a properly rated meter there is no ac present. Follow your facility’s lockout/tagout procedure. Using a dc meter rated for the voltage to be tested and set to 1000 V dc, test each stage phase-to-phase and phase-to-ground. There should be no voltage. The presence of voltage indicates the capacitor may not be discharged. If no voltage is detected, measure capacitance with the meter and compare the reading to the manufacturer’s specifications for each stage.

Visual inspection and cleaning

Also perform a complete visual inspection. Look for discolored components, bulging and/or leaking capacitors, and signs of heating and/or moisture. Clean and/or replace filters for cooling fans. Clean the units using a vacuum – never use compressed air. Prior to re-energizing the capacitors, perform an insulation integrity test from the bus phase-to-phase and phase-to-ground. The control power transformer line side breaker or fuses must be removed to prevent erroneous readings phase-to-phase. Power factor correction capacitors are designed to provide years of service when properly maintained in accordance with the manufacturer’s instructions. Inspecting capacitor banks on a regular basis provides assurance that they are operating safely while delivering the anticipated energy cost savings.

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Lower Bills Using Power Factor Correction

What Is a Power Factor and How Does it Affect Your Utility Bill?

In electrical engineering, Power Factor (PF) is the ratio of real power to the apparent power flowing to the load from the source. From a business standpoint it’s important to understand how having a low Power Factor raises your plant or factory’s power bill. We present this article to help you identify this value and use corrective techniques to raise it for substantial savings and greater equipment efficiency.

Power Factor is measured between 0 and 1.0 (usually given as a percentage, with 100% or 1.0 being unity) and is usually judged as either leading or lagging, depending on the position of the current waveform with respect to the voltage. If your facility’s PF is below a certain level (typically 96%-95% for many power companies), your provider will charge a reactive power fee. This is because a low PF represents an inefficient load source that is drawing reactive, i.e. ‘non-working,’ power which the utility has to make up for. Unless your facility can raise its PF to 96-95% or above, you’ll continue to see this extra charge every month on your bill.

For maximum efficiency, power in an AC circuit is best used when the voltage and current are in alignment. However in the real world much of your electrical equipment is probably delaying as it draws current, meaning that the current and voltage are instead in misalignment. In this case your equipment has a level of inefficiency depending on how misaligned it is, causing it to draw more current to operate. Therefore your PF value reveals how efficiently your AC power system and equipment are using power.

How Is Power Factor Calculated?

An AC circuit’s Power Factor is calculated using three aspects of its electrical power as they relate to one another, these being:

Real power—Power used to run equipment, expressed in kW.

Reactive power —Power which does not produce work, expressed in kVAr. As your reactive power use increases, your electric system loses more energy, hence the reactive power fee.

Apparent power—The combination of real power and reactive power, expressed in kVA.

 

Figure 1–Calculating Power Factor

In an electric power system, a load with a low power factor draws more current than a load with a high power factor (near 100%) for the same amount of useful power transferred. These higher currents increase the energy lost in the distribution system and also require larger wires and other equipment. In other words, your Power Factor percentage shows you how much of the total current is being used to do real work, i.e. a PF of 80% means that a full 20% of the current is non-working power. Again, because of the costs of larger equipment and wasted energy, electrical utilities will usually assign a penalty fee to industrial or commercial customers if they have a low power factor.

A high power factor is generally desirable in a transmission system to reduce transmission losses and improve voltage regulation at the load, so it’s often beneficial to correct the power factor of a system to near 100%. When reactive elements supply or absorb reactive power near the load, the apparent power is reduced.

Motors driven by Variable Speed Drives will use the same power as before, but may draw more current. Note that with reduced stored energy in the DC Bus capacitors, they may be more vulnerable to power dips.

How You Can Benefit From Power Factor Correction:

LOWER ELECTRICITY BILLS: PF correction is an actionable way to lower your utility bills. Savings can range from hundreds to tens of thousands of dollars per year, depending on the size of your facility.

AVOID UTILITY REACTIVE POWER FEES: Utility companies routinely charge reactive power fees to consumers with low power factors (less than 96%-95%). For example, this can result in your bills increasing by up to 20%, depending on which company is supplying your electricity.

REDUCE CARBON EMISSIONS: By utilizing power factor correction you can also lower the amount of carbon emissions released into the atmosphere. This can be another great source of savings.

REDUCE I2R LOSSES in transformers and electrical distribution equipment.

ACHIEVE HEAT REDUCTION in cables, switchgear, transformers and alternators which in turn prolongs the lifespan of this equipment.

REDUCE VOLTAGE DROP in cables, allowing the same cable to supply a larger motor and improve the starting of motors located at the end of long cable runs. This also helps to avoid motor failure and damage to your equipment.

How Can You Raise Your Power Factor?

To avoid reactive power fees and improve equipment efficiency, you can raise your power factor by applying several different power factor correction techniques. Individual electrical customers who are regularly charged by their utility for a low PF often install correction equipment to reduce or remove these costs. Power factor correction brings the power factor of an AC power circuit closer to 100%, such as by supplying reactive power of the opposite sign by adding capacitors or inductors that act to cancel the inductive or capacitive effects of the load, respectively.

To begin with there are a few simple methods you can use to raise your PF without buying expensive devices. For example, check your existing equipment to see if any pieces are operating above the voltage it’s been rated for. You can also cut back on how often your plant is running motors with a light load and avoid running idling motors for extended periods.

Linear loads with a low power factor such as induction motors can be corrected using a passive network of capacitors or inductors. In the electricity industry, inductors are said to consume reactive power and capacitors are said to supply it, even though the energy is really just moving back and forth on each AC cycle. For example, you can offset the inductive effect of motor loads by using locally-connected capacitors. If a load has a capacitive value, connect inductors (also known as reactors in this context) to correct the power factor.

Capacitors prevent equipment from having to draw reactive power from the grid. Non-linear loads such as rectifiers distort the current drawn from the system. In such cases, you can use active or passive power factor correction to counteract the distortion and raise the power factor. The devices correcting the power factor may be located at a central substation, spread out over a distribution system, or built into power-consuming equipment.

However, reactive elements cannot simply be applied without engineering analysis. The reactive elements can create voltage fluctuations and harmonic noise when switched on or off. They will supply or sink reactive power regardless of whether there is a corresponding load operating nearby, increasing the system’s no-load losses. In the worst-case scenario, reactive elements can interact with the system and with each other to create resonant conditions, resulting in system instability and severe overvoltage fluctuations.

Another option is to use an automatic power factor correction unit, consisting of a number of capacitors that are switched by means of contactors. These contactors are controlled by a regulator that measures power factor in an electrical network. Depending on the load and power factor of the network, the power factor controller will switch the necessary blocks of capacitors in steps to ensure that the power factor stays above a selected value.

Instead of using a set of switched capacitors, you can utilize an unloaded synchronous motor to supply reactive power. The reactive power drawn by the synchronous motor is a function of its field excitation. This is referred to as a synchronous condenser. Started and connected to the electrical network, it operates at a leading power factor and puts vars onto the network as required to support a system’s voltage or to maintain the system PF at a specified level.

For power factor correction of high-voltage power systems or large, fluctuating industrial loads, power electronic devices are seeing increasing use. These systems are able to compensate for the sudden changes of power factor much more rapidly than contactor-switched capacitor banks, and being solid-state they require less maintenance than synchronous condensers.

Summary:

By using a device to identify the Power Factor of your plant or factory’s equipment, you can realize substantial savings, improve the efficiency of your electrical equipment, and help prevent shutdowns or delays due to overheating machinery. It may take some preliminary analysis and/or investment in energy-efficient equipment, but you can realize long-term energy savings by measuring your facility’s power factor and applying suitable PF correction techniques.

 

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