Four Rules for Electrical Safety After A Flood

Ensuring electrical safety after a flood must take precedence over salvaging any remains or inspecting the home. The reason: water and electricity do not mix! It is understandable that you are very eager to check on your belongings, to try to get things back to normal as soon as possible. However, there is always a high risk of electrocution after flooding and of course, no material belongings are worth facing any risks and hazards associated with live electricity in your apartment. Here are few practical tips that will help you ensure electrical safety after a flood.

Stay Away from A Flood-Damaged Basement

A flooded basement may have live electrical wires that you are not aware of. While it is easy to think you can really avoid meeting such wires, even the water may not be safe. It would be best to contact an electrician to ensure the home’s electrical meter is removed from the socket to ensure the house is totally disconnected from the grid. This is an ideal way to shut off all power to the house as there can still be an electrocution even if you have lost power – telephone wires, the cable wire or other wires may have electricity due to shorting and contact from outside electricity.

If there is Power Outage, Do Not Assume It Would Remain Off

After flooding, there may be widespread power outage from the municipal electricity supply. However, it is not ideal to rely on the power outage from the general supply for safety after a flood as power may be restored at any time. Never rely on the municipality utility but take steps to shut off the power from your own apartment.

Do not operate the HVAC Equipment until it is inspected

Flooding may sometimes affect the ductwork and could even flow into parts of your air conditioning system or some areas that may appear dry. The HVAC system could be a big electrical risk if powered up without inspection. Ensure a qualified HVAC specialist checks the system before power is restored.

Dispose Electrical Equipment Affected by Flood

After water in your apartment has been pumped out and recovery efforts have begun, you would need to dispose any electrical equipment affected by the flood. Items such as armored cable, fuse boxes, building wire, switches, air conditioners, heaters, circuit panels and breakers and any items that cannot be salvaged must be disposed to avoid any potential risks and dangers while they are in use.

Learn more about J & P Electrical Company and their vast line of new, surplus, and refurbished industrial electrical components including: circuit breakers, bus ducts, bus plugs, disconnects, fuses, panel switches, tap boxes, and transformers at www.jpelectricalcompany.com.  To contact one of our product reconditioning specialists, call 877.844.5514 today.

 

This Slow-Mo Video Will Show You What Happens When Your Circuit Breaker Flips

YouTube channel Warped Perception opens up a common domestic circuit breaker to reveal what is inside.

Most people will have experienced the lights and power going out when a circuit breaker has been tripped. It’s usually pretty easy to simply reset the switch. But what is actually happening inside the break during a trip?

The host of YouTube channel Warped Perception had the same question and so created an episode dedicated to the interior of the common circuit breakers. In his words: “I open up a household circuit breaker and replicate a couple very common household fault scenarios, I film it with the high-speed cameras to reveal exactly what’s going on inside that circuit breaker.”

The first scenario tested is a typical slow blow overload. The second is a complete short circuit. To show exactly how a circuit breaker works Warped Perception opens up a breaker and films it as it does the job it was intended. Watching the breakers work in slow motion is surprisingly mesmerizing. Not only is this video fun to watch it’s highly educational. If you live in a house with electricity it really pays to understand what is going on in the electrical circuits around you.

If you enjoyed this video, spend some time on the Warped Perception channel. The host cuts a fine line between your annoying uncle and your favorite science teacher. His laid-back style makes for educational videos that surprise and delight. Backed up with a 4K camera, the content that he creates always looks good and are often accompanied with some very cinematic soundtracks.

Orignal Source: https://interestingengineering.com/video/this-slow-mo-video-will-show-you-what-happens-when-your-circuit-breaker-flips

 

Different Types of Electrical Switches

We use electrical switches every single day in our lives. Whether they are used to turn on the light or if they are used indirectly while using computers and other appliances, switches are one of the most common electrical accessory around. There are a number of different electrical switches we can use, each having its own unique purpose and use. The type of electrical switch we need to use depends on what we need to use it for. It is a secondary accessory that is highly dependent on the primary accessory it supports. Out of all the switches available in the market, two are highly common and of great use: panel switches and line switches. Let’s have a more detailed look into the two most common types of electrical switches that are in use today.

Panel Switch

Panel switches were developed in the 1910s by Western Electric labs and introduced in the Bell System. Panel switches became used as early types of automatic telephone systems. Known for their huge panel like structure, panel switches are basically very tall strips of layered terminals that are separated by a fine layer of insulation between them. First installed in 1915, the panel switch became the go to method for phone terminals.

That is, however, just one type of panel switch. The second type is far more common and known to almost everyone. Common panel switches are the ones we see on our walls. Most of the switches in our homes are arranged in a panel arrangement. It is basically a plastic panel fitted in the wall with multiple switches embedded in it. This makes it easier for people to switch multiple appliances off or on since the switches are arranged together in the same place.

Line Switch

Much like common panel switches, line switches are very popular as well. In fact, they are perhaps the go to switches to attach to smaller electric appliances. Lamps especially almost always line switches. Line switches carry a relatively smaller load than panel switches and are used for electrical appliances you do not commonly use. An analogy can be drawn with toys that have their own specific switch for use whenever it needs to be used.

In that manner, line switches are commonly used for appliances that are rarely turned on. Lamps, decoration pieces, fountain lights, and disco lights are all common appliances that have line switches attached. Line switches are fairly simple and can be fixed or attached by anyone who has an idea about how to. However, panel switches are often very complex since they are attached to wires from all around a room, or even the entire house! This makes them too difficult for common people to understand, and they cannot find and fix faults on their own. Therefore, whenever there’s a fault with a panel switch it is important to hire a professional for repair or replacement.  You can purchase a new one or a refurbished switch, both will have gone through rigorous testing before making it to you the consumer.

Contact Us Today

Learn more about J & P Electrical Company and their vast line of new, surplus, and refurbished industrial electrical components including: circuit breakers, bus ducts, bus plugs, disconnects, fuses, panel switches, tap boxes, and transformers at www.jpelectricalcompany.com.  To contact one of our product reconditioning specialists, call 877.844.5514 today.

Significant Savings Seen Using Refurbished Electrical Components

In order to be successful in business, we need to be a tad prudent with how money is spent or re-invested into the business and purchasing. Is purchasing a new piece of electrical equipment the best investment, or does capitalizing on an opportunity to purchase quality refurbished electrical components at a significant savings make a viable economic sense?

Pros and Cons

Buying refurbished electrical components has its pros and cons. The pros, it is a great way to save money and in most cases the brand name equipment are built to last. Cons, it can mean money down the drain only when you don’t buy the electrical component from a reputable source and you could end up with an item that is even more damaged or missing integral parts.

Surplus electrical components can come from a few locations:

  • Assets are recovered from manufacturing plants that are closing. The surplus electrical components are then refurbished and sold at a discount.
  • Assets can be recovered from machines that are being disposed of but still have working components. Resulting in one of two situations, the components are refurbished and resold or the entire machine is refurbished.

While one of the benefits of buying reconditioned electrical components is that the items are generally set at a significantly lower price and some equipment contractors will accept returns if an item is ‘defective,’ the down side to this is that you will not get a manufacturer’s warranty.

What Does Reconditioned Mean?

Reconditioned electrical are components that are being repurposed.  They can’t be passed or sold as brand-new products but are instead reconditioned. Whether they are damaged or not, reconditioned electrical components also known as ‘remanufactured’ electrical components are completely disassembled and restored if need be in order to ensure that they perform as expected.

Therefore, before bidding on refurbished electrical components online, there are a few things to keep in mind and if possible ask questions about the item on sale. If it’s a refurbished electrical component be sure to ask about the companies return policies.

Be Cautious Where You Get Refurb Parts From

For a refurbished electrical component, beware of as it may arrive in worse conditions than the actual online photos however you are guaranteed of its safety and reliability. With most resellers and reconditioning companies, you will not be stuck with a defective refurbished electrical component if it is in fact not the right component to fix your machines issue.  An ad may give you all the specifics about the item you are about to purchase and check the seller’s feedback and buyers’ recommendations.  It is important to buy from reputable companies.  This helps to ensure that the reconditioned components that you are purchasing are as good as brand-new OEM electrical parts.

Learn more about J & P Electrical Company and their vast line of new, surplus, and refurbished industrial electrical components including: circuit breakers, bus ducts, bus plugs, disconnects, fuses, panel switches, tap boxes, and transformers at www.jpelectricalcompany.com.  To contact one of our product reconditioning specialists, call 877.844.5514 today.

 

What is the Difference Between a Fuse and a Circuit Breaker?

Large power overloads may potentially destroy electrical equipment, or in more serious cases, cause a fire. A fuse and circuit breaker both serve to protect an overloaded electrical circuit by interrupting the continuity, or the flow of electricity. How they interrupt the flow of electricity is very different, however. A fuse is made up of a piece of metal that melts when overheated; a circuit breaker has an internal switch mechanism that is tripped by an unsafe surge of electricity. Fuses tend to be quicker to interrupt the flow of power, but must be replaced after they melt, while circuit breakers can usually simply be reset.

How Fuses Work

There are many different types of fuses for residential and commercial use, but the most common type is made up of a metal wire or filament that is enclosed in a glass or ceramic and metal casing. In a home, the fuse is typically plugged into a central fuse box where all the building’s wiring passes through. When the electricity is flowing normally, the fuse permits the power to pass unobstructed across its filament, between circuits. If an overload occurs, the filament melts, stopping the flow of electricity.

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It generally takes very little time for the filament in the type of fuse used in a home to melt, so any power surge is quickly stopped. Once a fuse is blown, however, it must be discarded and replaced with a new one. There are many different voltage and ratings available that handle different capacities of electricity, and the best fuse for a circuit is typically one that is rated for slightly higher than the normal operating current.

How Circuit Breakers Work

A circuit breaker works in one of two ways, with an electromagnet (or solenoid) or a bi-metal strip. In either case, the basic design is the same: when turned on, the breaker allows electrical current to pass from a bottom to an upper terminal across the solenoid or strip. When the current reaches unsafe levels, the magnetic force of the solenoid becomes so strong that a metal lever within the switch mechanism is thrown, and the current is broken. Alternately, the metal strip bends, throwing the switch and breaking the connection.

To reset the flow of electricity after the problem is resolved, the switch can simply be turned back on, reconnecting the circuit. Circuit breakers are often found in a cabinet of individual switches, called a breaker box. The simple switch action of a circuit breaker also makes it easy to turn off an individual circuit in a house if it’s necessary to work on the wiring in that location.

Another use of the circuit breaker is a ground fault circuit interrupter (GFCI) outlet, which functions to prevent electric shock instead of overheating. It works by breaking the circuit in an outlet if the current becomes unbalanced, and can be reset by the push of a button. This technology is particularly useful in bathrooms or kitchens where electrocution is a risk due to the frequent use of electric appliances near a source of water.

Advantages and Disadvantages

The fuse and circuit breaker both have advantages and disadvantages, each of which can depend on the situation in which they are used. Fuses are inexpensive and can be purchased from any hardware store. They also tend to react very quickly to overloading, which means that they can offer more protection to sensitive electronic devices. This quick reaction can be a disadvantage, however, if the circuit is prone to surges that regularly cause fuses to blow.

Fuses must always be replaced once they are blown, which can be challenging in a darkened room or if the appropriate replacement is not immediately available. Another issue is that a do-it-yourselfer can mistakenly select a fuse that has a voltage or current rating that is too high for his needs, which can result in an overheated circuit. In addition, there may be exposed electrical connections in a fuse box, which can pose a danger to someone who does not follow the proper safety precautions.

Circuit breakers have many advantages, not the least of which is how quickly they can be reset. It is usually clear which switch has tripped, and it can be easily reset in most cases. For the average homeowner, it is also safer because there is no question about choosing the right fuse rating and all of the electrical connections are hidden in a breaker box.

A drawback to using a circuit breaker is that it is usually more expensive to install and repair. A circuit breaker also typically does not react as quickly as a fuse to surges in power, meaning that it is possible that electronics connected to the circuit could be damaged by “let-through” energy. It also is more sensitive to vibration and movement, which can cause a switch to trip for reasons unrelated to an electricity overload.

A fuse and circuit breaker are not interchangeable for all power applications. For example, a fuse cannot be used in situations that require a GFCI. Electricians are best qualified to determine whether a fuse or circuit breaker system is better for a particular electrical installation or upgrade.

Original Source: http://www.wisegeek.com/what-is-the-difference-between-a-fuse-and-a-circuit-breaker.htm

 

The Importance of Using Refurbished Electrical Components

Most of the industry experts these days are looking forward to being able to use refurbished electrical equipment and replacement components on their manufacturing lines. Although many people have misconceptions about using refurbished components such as transformers, bus ducts, panel switches, circuit breakers, and such however the truth is that reconditioned machines and components offer a variety of benefits for your workplace.

Importance of using refurbished electrical components can be highlighted from below points:

Reduced cost:

One of the biggest benefits of using refurbished electrical component at industrial processing is that they are cheaper as compared to other identical solutions. The components that come after refurbishing process usually have low selling price irrespective of the reason why manufacturer renewed it. It will help you to save somewhere between 25 to 50 percent on your component purchase.

They come out of rigorous inspection process:

Components that are available at lower price range does not mean to present lower quality. Instead, the refurbished components undergo the more careful testing process. It doesn’t matter what wrong happened to the product before refurbishing process, manufacturers always prefer to follow careful inspection to ensure the best performance. It means you will be able to buy many superior components at the lower price range.

Ease in availability:

Most of the components get obsolete from the market with time and if some specific product lines need them it becomes a challenging task to find the lot again. But the surplus components are the best choice to find components of such limited lots. On time availability of these difficult to find components will help you to avoid downtimes at your workplace. Most of the refurbished products are generally available with same day shipping service.

They come with a warranty:

Just because you are buying Surplus Electrical Components for your product assembly lines, it doesn’t mean that they will not last long. As per market reviews, the refurbished components usually have more life and they also come with a warranty. Most of the manufacturers offer around 12 months warranty on their refurbished component collections so you can find them a trustworthy solution for your industry. Most of these components are certified that they will work safely and same as original ones.

The biggest benefit of buying refurbished components is that you can get services for parts that are outdated, and their production is stopped by the original manufacturer. If you are planning to repair your old pieces of electrical equipment and need same components for replacement, the surplus collection is the best choice to keep working without facing any trouble.

To ensure safe purchase of refurbished components, you must check the policy of the company. It is important to look for a vendor that ensures quality refurbishing of components with safe cleaning process including proper analysis, testing and rigorous inspections. The price range of refurbished components also varies company to company, so it is good to check with various vendors and compare their prices to ensure the best buy services. Once you can find a right seller that guarantees safe operation of refurbished components, you can use them safely at your manufacturing lines.

Learn more about J & P Electrical Company and their vast line of new, surplus, and refurbished industrial electrical components including: circuit breakers, bus ducts, bus plugs, disconnects, fuses, panel switches, tap boxes, and transformers at https://www.jpelectricalcompany.com/products.php.  To contact one of our product reconditioning specialists call 877.844.5514 today.

Safely Refurbishing Manufacturing Equipment after a Flood

Flooding can cause much devastation.  One of them being the ability to ruin the workability of electrical equipment. Manufacturing equipment is much like any other electrical equipment in the way it reacts to water flooding inside its circuits. If you are the owner of such machinery, and it has been hit by a flood or any other water spill, then you don’t need to worry because you have an option to refurbish these electrical components.

Reconditioned electrical components can save you from spending extra money on buying new equipment. Also, it can save your time because installation of new equipment and getting it working just like the previous one can be hard.

However, manufacturing equipment requires prudent considerations in order to safely refurbish them. Let us go through these considerations.

  • Assess the damage

The first thing before even considering repairing or refurbishing any electrical component is to check the extent of the water damage that it has received. In order to do that, you would need to gather all the information that you have about the equipment. That information can include all the pertinent drawings and documentation that had come with the instrument.

Once you have that information, you can either yourself do the inspection or have a specialized team to do it. Too often, an electrical component is well insulated by the manufacturers against any water intrusions. Thus, through valuable knowledge about the machinery and the assessment of the damage, one can get an idea if it needs to be repaired.

  • Never try plugging the equipment

Water has electrical properties. When it seeps inside an electrical component, it floods all the circuits therein. If the component is running when it experiences water seepage, then it can result in short circuits. Alternatively speaking, if equipment is turned on after it has received water seepage, then it can still cause short circuits. Either way, the machinery is damaged, and thus, whether equipment is on or off before the flood, you should never plug them into the electrical socket to see if they are working.

  • Leave the equipment for drying

As we said before, you should never plug in the manufacturing equipment in electricity socket. What you should do is let them get dried. Nobody should be allowed to get near to it unless some decision is reached on whether the equipment should be completely removed or its individual parts are taken out for refurbishing.

  • Hire refurbishing professionals

What we talked about in the above paragraphs are main considerations on the part of the owner and the operators of the manufacturing equipment. However, when it comes to repairing the equipment after flooding, proper refurbishing professionals should be hired.

These professionals know the working of equipment and also the makeup of its complex circuits. They can guide you better regarding whether the components should be completely renewed or repaired.

Refurbished electrical components can work just like they used to when they weren’t damaged. Some people have a fear in their hearts regarding these reconditioned electrical components. However, they should know that the repairers are there to bring a damage component to life without compromising its workability.

Learn more about J & P Electrical Company and their vast line of new, surplus, and refurbished industrial electrical components including: circuit breakers, bus ducts, bus plugs, disconnects, fuses, panel switches, tap boxes, and transformers at https://www.jpelectricalcompany.com/assetmanagement.php.  To contact one of our product reconditioning specialists call 877.844.5514 today.

 

Purchasing Reconditioned Electrical Components over New Surplus

Whether you are having your electrical devices fixed or giving them a whole new state-of-the-art facelift, knowing where to look and what to look out for can make all the difference because buying refurbished equipment may be not only a cost-effective alternative in the short-term but also a secure long-term financial solution.

You may have a machine that has replacement parts that are becoming obsolete, but you don’t want to get rid of it or a need to preserve the equipment because it is that is no longer being produced. With a little research, there are certified refurbished experts, licensed distributors, or original equipment manufacturers available out there who are more than capable of offering you solutions that are specific to your needs.

Refurbished Does Not Mean Not As Good

Common misconceptions about purchasing refurbished electrical components are that people believe that because components are often sold at reduced prices, it means they are reduced in performance. This is in fact not the case at all. An electrical component that has undergone comprehensive re-manufacturing and testing process according to all OEM specifications can be restored to a perfect working condition enough that an untrained eye would believe it is brand new. This ensures that refurbished electrical components can continue to function without any hiccups and failure rates that are significantly reduced since it has been tested.

It’s not to mean that those with an inclination toward newer technology than what is currently available in the refurbished equipment market shouldn’t go for the surplus electrical components. In fact, buying new is ideal for those who do not have any financial constraints for this type of purchase.

On the other hand, reconditioning electrical components, otherwise known as refurbishing, electrical components, does indeed, save money, time, and it also extends the components lifespan. In addition to that, by giving electrical components an update, electronics manufacturers reduce e-waste and can keep electronic waste out of landfills. Electronic waste has become a growing concern over the recent past following the exponential growth of the global market of electrical and electronic equipment.

Testing Procedures

It is also important to mention that while original equipment manufacturers OEM are only obligated to batch test their products, reconditioning or refurbishing standards require 100% device testing, a process that follows the following stringent procedures:

  • Conduct an initial test
  • Strip, inspect, and clean the electrical device
  • Replace and recondition worn or damaged electrical components
  • Reassemble
  • Perform verification test
  • Document and finally certify

Saving Money When Possible

If you intend on buying new, more expensive equipment but cannot afford it, purchasing a refurbished electrical component or a piece of newly refurbished equipment may be your best bet.

Learn more about J & P Electrical Company and their vast line of new, surplus, and refurbished industrial electrical components including: circuit breakers, bus ducts, bus plugs, disconnects, fuses, panel switches, tap boxes, and transformers at https://www.jpelectricalcompany.com/products.php.  To contact one of our product reconditioning specialists call 877.844.5514 today.

The Circuit Breakers

A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by excess current, typically resulting from an overload or short circuit. Its basic function is to interrupt current flow after a fault is detected. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Circuit breakers are made in varying sizes, from small devices that protect low-current circuits or individual household appliance, up to large switchgear designed to protect high voltage circuits feeding an entire city. The generic function of a circuit breaker, RCD or a fuses as an automatic means of removing power from a faulty system is often abbreviated as ADS (Automatic Disconnection of Supply).

Contents

Origins

An early form of circuit breaker was described by Thomas Edison in an 1879 patent application, although his commercial power distribution system used fuses.[1] Its purpose was to protect lighting circuit wiring from accidental short circuits and overloads. A modern miniature circuit breaker similar to the ones now in use was patented by Brown, Boveri & Cie in 1924. Hugo Stotz, an engineer who had sold his company to BBC, was credited as the inventor on DRP (Deutsches Reichspatent) 458392.[2] Stotz’s invention was the forerunner of the modern thermal-magnetic breaker commonly used in household load centers to this day. Interconnection of multiple generator sources into an electrical grid required development of circuit breakers with increasing voltage ratings and increased ability to safely interrupt the increasing short-circuit currents produced by networks. Simple air-break manual switches produced hazardous arcs when interrupting high voltages; these gave way to oil-enclosed contacts, and various forms using directed flow of pressurized air, or of pressurized oil, to cool and interrupt the arc. By 1935, the specially constructed circuit breakers used at the Boulder Dam project use eight series breaks and pressurized oil flow to interrupt faults of up to 2,500 MVA, in three cycles of the AC power frequency.[3]

Operation

All circuit breaker systems have common features in their operation, but details vary substantially depending on the voltage class, current rating and type of the circuit breaker.

The circuit breaker must firstly detect a fault condition. In small mains and low voltage circuit breakers, this is usually done within the device itself. Typically, the heating or magnetic effects of electric current are employed. Circuit breakers for large currents or high voltages are usually arranged with protective relay pilot devices to sense a fault condition and to operate the opening mechanism. These typically require a separate power source, such as a battery, although some high-voltage circuit breakers are self-contained with current transformers, protective relays, and an internal control power source.

Once a fault is detected, the circuit breaker contacts must open to interrupt the circuit; This is commonly done using mechanically stored energy contained within the breaker, such as a spring or compressed air to separate the contacts. Circuit breakers may also use the higher current caused by the fault to separate the contacts, such as thermal expansion or a magnetic field. Small circuit breakers typically have a manual control lever to switch off the load or reset a tripped breaker, while larger units use solenoids to trip the mechanism, and electric motors to restore energy to the springs.

The circuit breaker contacts must carry the load current without excessive heating, and must also withstand the heat of the arc produced when interrupting (opening) the circuit. Contacts are made of copper or copper alloys, silver alloys and other highly conductive materials. Service life of the contacts is limited by the erosion of contact material due to arcing while interrupting the current. Miniature and molded-case circuit breakers are usually discarded when the contacts have worn, but power circuit breakers and high-voltage circuit breakers have replaceable contacts.

When a high current or voltage is interrupted, an arc is generated. The length of the arc is generally proportional to the voltage while the intensity (or heat) is proportional to the current. This arc must be contained, cooled and extinguished in a controlled way, so that the gap between the contacts can again withstand the voltage in the circuit. Different circuit breakers use vacuum, air, insulating gas, or oil as the medium the arc forms in. Different techniques are used to extinguish the arc including:

  • Lengthening or deflecting the arc
  • Intensive cooling (in jet chambers)
  • Division into partial arcs
  • Zero point quenching (contacts open at the zero current time crossing of the AC waveform, effectively breaking no load current at the time of opening. The zero crossing occurs at twice the line frequency; i.e., 100 times per second for 50 Hz and 120 times per second for 60 Hz AC.)
  • Connecting capacitors in parallel with contacts in DC circuits.

Finally, once the fault condition has been cleared, the contacts must again be closed to restore power to the interrupted circuit.

Arc interruption

Low-voltage miniature circuit breakers (MCB) use air alone to extinguish the arc. These circuit breakers contain so-called arc chutes, a stack of mutually insulated parallel metal plates which divide and cool the arc. By splitting the arc into smaller arcs the arc is cooled down while the arc voltage is increased and serves as an additional impedance which limits the current through the circuit breaker. The current-carrying parts near the contacts provide easy deflection of the arc into the arc chutes by a magnetic force of a current path, although magnetic blowout coils or permanent magnets could also deflect the arc into the arc chute (used on circuit breakers for higher ratings).So The number of plates in the arc chute is dependent on the short-circuit rating and nominal voltage of the circuit breaker.

In larger ratings, oil circuit breakers rely upon vaporization of some of the oil to blast a jet of oil through the arc.[4]

Gas (usually sulfur hexafluoride) circuit breakers sometimes stretch the arc using a magnetic field, and then rely upon the dielectric strength of the sulfur hexafluoride (SF6) to quench the stretched arc.

Vacuum circuit breakers have minimal arcing (as there is nothing to ionize other than the contact material).the arc quenches when it is stretched a very small amount (less than 2–3 mm (0.079–0.118 in)). Vacuum circuit breakers are frequently used in modern medium-voltage switchgear to 38,000 volts.

Air circuit breakers may use compressed air to blow out the arc, or alternatively, the contacts are rapidly swung into a small sealed chamber, the escaping of the displaced air thus blowing out the arc.

Circuit breakers are usually able to terminate all current very quickly: typically the arc is extinguished between 30 ms and 150 ms after the mechanism has been tripped, depending upon age and construction of the device. The maximum current value and let-through energy determine the quality of the circuit breakers.

Short-circuit

Circuit breakers are rated both by the normal current that they are expected to carry, and the maximum short-circuit current that they can safely interrupt. This latter figure is the ampere interrupting capacity (AIC) of the breaker.

Under short-circuit conditions, the calculated maximum prospective short-circuit current may be many times the normal, rated current of the circuit. When electrical contacts open to interrupt a large current, there is a tendency for an arc to form between the opened contacts, which would allow the current to continue. This condition can create conductive ionized gases and molten or vaporized metal, which can cause further continuation of the arc, or creation of additional short circuits, potentially resulting in the explosion of the circuit breaker and the equipment that it is installed in. Therefore, circuit breakers must incorporate various features to divide and extinguish the arc.

The maximum short-circuit current that a breaker can interrupt is determined by testing. Application of a breaker in a circuit with a prospective short-circuit current higher than the breaker’s interrupting capacity rating may result in failure of the breaker to safely interrupt a fault. In a worst-case scenario the breaker may successfully interrupt the fault, only to explode when reset.

Typical domestic panel circuit breakers are rated to interrupt 10 kA (10000 A) short-circuit current.

Miniature circuit breakers used to protect control circuits or small appliances may not have sufficient interrupting capacity to use at a panel board; these circuit breakers are called “supplemental circuit protectors” to distinguish them from distribution-type circuit breakers.

Standard current ratings

Time till trip versus current as multiple of nominal current

Circuit breakers are manufactured in standard sizes, using a system of preferred numbers to cover a range of ratings. Miniature circuit breakers have a fixed trip setting; changing the operating current value requires changing the whole circuit breaker. Larger circuit breakers can have adjustable trip settings, allowing standardized elements to be applied but with a setting intended to improve protection. For example, a circuit breaker with a 400 ampere “frame size” might have its overcurrent detection set to operate at only 300 amperes, to protect a feeder cable.

International Standards, IEC 60898-1 and European Standard EN 60898-1, define the rated current In of a circuit breaker for low voltage distribution applications as the maximum current that the breaker is designed to carry continuously (at an ambient air temperature of 30 °C). The commonly available preferred values for the rated current are 6 A, 10 A, 13 A, 16 A, 20 A, 25 A, 32 A, 40 A, 50 A, 63 A, 80 A, 100 A,[5] and 125 A (similar to the R10 Renard series, but using 6, 13, and 32 instead of 6.3, 12.5, and 31.5 – it includes the 13 A current limit of British BS 1363 sockets). The circuit breaker is labeled with the rated current in amperes, but excluding the unit symbol, A. Instead, the ampere figure is preceded by a letter, B, C, or D, which indicates the instantaneous tripping current — that is, the minimum value of current that causes the circuit breaker to trip without intentional time delay (i.e., in less than 100 ms), expressed in terms of In:

Type Instantaneous tripping current
B Above 3 In
C Above 5 In up to and including 10 In
D Above 10 In up to and including 20 In
K Above 8 In up to and including 12 InFor the protection of loads that cause frequent short duration (approximately 400 ms to 2 s) current peaks in normal operation.
Z Above 2 In up to and including 3 In for periods in the order of tens of seconds.For the protection of loads such as semiconductor devices or measuring circuits using current transformers.

Circuit breakers are also rated by the maximum fault current that they can interrupt; this allows use of more economical devices on systems unlikely to develop the high short-circuit current found on, for example, a large commercial building distribution system.

In the United States, Underwriters Laboratories (UL) certifies equipment ratings, called Series Ratings (or “integrated equipment ratings”) for circuit breaker equipment used for buildings. Power circuit breakers and medium- and high-voltage circuit breakers used for industrial or electric power systems are designed and tested to ANSI or IEEE standards in the C37 series.

Types of circuit breakers

Front panel of a 1250 A air circuit breaker manufactured by ABB. This low voltage power circuit breaker can be withdrawn from its housing for servicing. Trip characteristics are configurable via DIP switches on the front panel.

Many classifications of circuit breakers can be made, based on their features such as voltage class, construction type, interrupting type, and structural features.

Low-voltage circuit breakers

Low-voltage (less than 1,000 VAC) types are common in domestic, commercial and industrial application, and include:

  • Miniature circuit breaker (MCB)—rated current not more than 100 A. Trip characteristics normally not adjustable. Thermal or thermal-magnetic operation. Breakers illustrated above are in this category.
  • Molded Case Circuit Breaker (MCCB)—rated current up to 2,500 A. Thermal or thermal-magnetic operation. Trip current may be adjustable in larger ratings.
  • Low-voltage power circuit breakers can be mounted in multi-tiers in low-voltage switchboards or switchgear cabinets.

The characteristics of low-voltage circuit breakers are given by international standards such as IEC 947. These circuit breakers are often installed in draw-out enclosures that allow removal and interchange without dismantling the switchgear.

Large low-voltage molded case and power circuit breakers may have electric motor operators so they can open and close under remote control. These may form part of an automatic transfer switch system for standby power.

Low-voltage circuit breakers are also made for direct-current (DC) applications, such as DC for subway lines. Direct current requires special breakers because the arc is continuous—unlike an AC arc, which tends to go out on each half cycle. A direct current circuit breaker has blow-out coils that generate a magnetic field that rapidly stretches the arc. Small circuit breakers are either installed directly in equipment, or are arranged in a breaker panel.

Inside of a circuit breaker

The DIN rail-mounted thermal-magnetic miniature circuit breaker is the most common style in modern domestic consumer units and commercial electrical distribution boards throughout Europe. The design includes the following components:

  1. Actuator lever – used to manually trip and reset the circuit breaker. Also indicates the status of the circuit breaker (On or Off/tripped). Most breakers are designed so they can still trip even if the lever is held or locked in the “on” position. This is sometimes referred to as “free trip” or “positive trip” operation.
  2. Actuator mechanism – forces the contacts together or apart.
  3. Contacts – allow current when touching and break the current when moved apart.
  4. Terminals
  5. Bimetallic strip – separates contacts in response to smaller, longer-term overcurrents
  6. Calibration screw – allows the manufacturer to precisely adjust the trip current of the device after assembly.
  7. Solenoid – separates contacts rapidly in response to high overcurrents
  8. Arc divider/extinguisher

Magnetic circuit breakers

Magnetic circuit breakers use a solenoid (electromagnet) whose pulling force increases with the current. Certain designs utilize electromagnetic forces in addition to those of the solenoid. The circuit breaker contacts are held closed by a latch. As the current in the solenoid increases beyond the rating of the circuit breaker, the solenoid’s pull releases the latch, which lets the contacts open by spring action.

Thermal magnetic circuit breakers

Shihlin Electric MCCB with SHT

Thermal magnetic circuit breakers, which are the type found in most distribution boards, incorporate both techniques with the electromagnet responding instantaneously to large surges in current (short circuits) and the bimetallic strip responding to less extreme but longer-term over-current conditions. The thermal portion of the circuit breaker provides a time response feature, that trips the circuit breaker sooner for larger overcurrents but allows smaller overloads to persist for a longer time. This allows short current spikes such as are produced when a motor or other non-resistive load is switched on. With very large over-currents during a short-circuit, the magnetic element trips the circuit breaker with no intentional additional delay.[6]

Magnetic-hydraulic circuit breakers

A magnetic-hydraulic circuit breaker uses a solenoid coil to provide operating force to open the contacts. Magnetic-hydraulic breakers incorporate a hydraulic time delay feature using a viscous fluid. A spring restrains the core until the current exceeds the breaker rating. During an overload, the speed of the solenoid motion is restricted by the fluid. The delay permits brief current surges beyond normal running current for motor starting, energizing equipment, etc. Short-circuit currents provide sufficient solenoid force to release the latch regardless of core position thus bypassing the delay feature. Ambient temperature affects the time delay but does not affect the current rating of a magnetic breaker. [7]

Large power circuit breakers, applied in circuits of more than 1000 volts, may incorporate hydraulic elements in the contact operating mechanism. Hydraulic energy may be supplied by a pump, or stored in accumulators. These form a distinct type from oil-filled circuit breakers where oil is the arc extinguishing medium. [8]

Common trip breakers

Three-pole common trip breaker for supplying a three-phase device. This breaker has a 2 A rating.

When supplying a branch circuit with more than one live conductor, each live conductor must be protected by a breaker pole. To ensure that all live conductors are interrupted when any pole trips, a “common trip” breaker must be used. These may either contain two or three tripping mechanisms within one case, or for small breakers, may externally tie the poles together via their operating handles. Two-pole common trip breakers are common on 120/240-volt systems where 240 volt loads (including major appliances or further distribution boards) span the two live wires. Three-pole common trip breakers are typically used to supply three-phase electric power to large motors or further distribution boards.

Two- and four-pole breakers are used when there is a need to disconnect multiple phase AC, or to disconnect the neutral wire to ensure that no current flows through the neutral wire from other loads connected to the same network when workers may touch the wires during maintenance. Separate circuit breakers must never be used for live and neutral, because if the neutral is disconnected while the live conductor stays connected, a dangerous condition arises: the circuit appears de-energized (appliances don’t work), but wires remain live and some residual-current devices (RCDs) may not trip if someone touches the live wire (because some RCDs need power to trip). This is why only common trip breakers must be used when neutral wire switching is needed.

Medium-voltage circuit breakers

Medium-voltage circuit breakers rated between 1 and 72 kV may be assembled into metal-enclosed switchgear line ups for indoor use, or may be individual components installed outdoors in a substation. Air-break circuit breakers replaced oil-filled units for indoor applications, but are now themselves being replaced by vacuum circuit breakers (up to about 40.5 kV). Like the high voltage circuit breakers described below, these are also operated by current sensing protective relays operated through current transformers. The characteristics of MV breakers are given by international standards such as IEC 62271. Medium-voltage circuit breakers nearly always use separate current sensors and protective relays, instead of relying on built-in thermal or magnetic overcurrent sensors.

Medium-voltage circuit breakers can be classified by the medium used to extinguish the arc:

  • Vacuum circuit breakers—With rated current up to 6,300 A, and higher for generator circuit breakers. These breakers interrupt the current by creating and extinguishing the arc in a vacuum container – aka “bottle”. Long life bellows are designed to travel the 6–10 mm the contacts must part. These are generally applied for voltages up to about 40,500 V,[9] which corresponds roughly to the medium-voltage range of power systems. Vacuum circuit breakers tend to have longer life expectancies between overhaul than do air circuit breakers.
  • Air circuit breakers—Rated current up to 6,300 A and higher for generator circuit breakers. Trip characteristics are often fully adjustable including configurable trip thresholds and delays. Usually electronically controlled, though some models are microprocessor controlled via an integral electronic trip unit. Often used for main power distribution in large industrial plant, where the breakers are arranged in draw-out enclosures for ease of maintenance.
  • SF6 circuit breakers extinguish the arc in a chamber filled with sulfur hexafluoride gas.

Medium-voltage circuit breakers may be connected into the circuit by bolted connections to bus bars or wires, especially in outdoor switchyards. Medium-voltage circuit breakers in switchgear line-ups are often built with draw-out construction, allowing breaker removal without disturbing power circuit connections, using a motor-operated or hand-cranked mechanism to separate the breaker from its enclosure. Some important manufacturer of VCB from 3.3 kV to 38 kV are ABB, Eaton, Siemens, HHI(Hyundai Heavy Industry), S&C Electric Company, Jyoti and BHEL.

High-voltage circuit breakers

Three single phase Soviet/Russian 110 kV oil circuit breakers

400 kV SF6 live tank circuit breakers

72.5 kV hybrid switchgear module

Electrical power transmission networks are protected and controlled by high-voltage breakers. The definition of high voltage varies but in power transmission work is usually thought to be 72.5 kV or higher, according to a recent definition by the International Electrotechnical Commission (IEC). High-voltage breakers are nearly always solenoid-operated, with current sensing protective relays operated through current transformers. In substations the protective relay scheme can be complex, protecting equipment and buses from various types of overload or ground/earth fault.

High-voltage breakers are broadly classified by the medium used to extinguish the arc:

  • Bulk oil
  • Minimum oil
  • Air blast
  • Vacuum
  • SF6
  • CO2

Due to environmental and cost concerns over insulating oil spills, most new breakers use SF6 gas to quench the arc.

Circuit breakers can be classified as live tank, where the enclosure that contains the breaking mechanism is at line potential, or dead tank with the enclosure at earth potential. High-voltage AC circuit breakers are routinely available with ratings up to 765 kV. 1,200 kV breakers were launched by Siemens in November 2011,[10] followed by ABB in April the following year.[11]

High-voltage circuit breakers used on transmission systems may be arranged to allow a single pole of a three-phase line to trip, instead of tripping all three poles; for some classes of faults this improves the system stability and availability.

High-voltage direct current circuit breakers are still a field of research as of 2015. Such breakers would be useful to interconnect HVDC transmission systems.[12]

Sulfur hexafluoride (SF6) high-voltage circuit breakers

A sulfur hexafluoride circuit breaker uses contacts surrounded by sulfur hexafluoride gas to quench the arc. They are most often used for transmission-level voltages and may be incorporated into compact gas-insulated switchgear. In cold climates, supplemental heating or de-rating of the circuit breakers may be required due to liquefaction of the SF6 gas.

Disconnecting circuit breaker (DCB)

72.5 kV carbon dioxide high-voltage circuit breaker

The disconnecting circuit breaker (DCB) was introduced in 2000[13] and is a high-voltage circuit breaker modeled after the SF6-breaker. It presents a technical solution where the disconnecting function is integrated in the breaking chamber, eliminating the need for separate disconnectors. This increases the availability, since open-air disconnecting switch main contacts need maintenance every 2–6 years, while modern circuit breakers have maintenance intervals of 15 years. Implementing a DCB solution also reduces the space requirements within the substation, and increases the reliability, due to the lack of separate disconnectors.[14][15]

In order to further reduce the required space of substation, as well as simplifying the design and engineering of the substation, a fiber optic current sensor (FOCS) can be integrated with the DCB. A 420 kV DCB with integrated FOCS can reduce a substation’s footprint with over 50% compared to a conventional solution of live tank breakers with disconnectors and current transformers, due to reduced material and no additional insulation medium.[16]

Carbon dioxide (CO2) high-voltage circuit breakers

In 2012 ABB presented a 75 kV high-voltage breaker that uses carbon dioxide as the medium to extinguish the arc. The carbon dioxide breaker works on the same principles as an SF6 breaker and can also be produced as a disconnecting circuit breaker. By switching from SF6 to CO2 it is possible to reduce the CO2 emissions by 10 tons during the product’s life cycle.[17]

Original Source: https://en.wikipedia.org/wiki/Circuit_breaker