The GFCI Breaker

A ground-fault circuit interrupter (GFCI) is used to prevent electrocution.It installed where electrical circuits are exposed to contact with water. These can be found in kitchens, bathrooms, laundry and such places where electric equipments and water is used together.

Electricity always wants to find a path to the ground. Ground fault means a conducting connection between any electric conductor and any conducting material that is grounded. Ina ground fault, electricity has found a path to ground, but causing a danger through a person’s body.

To save human from this shock, GFCI breaker protection is used. Other circuit breakers and fuses only protect equipment—they will not protect people.When a human body is receiving a shock; the GFCI senses this and cuts off the power before any injury is caused.

It is advised that GFC breaker be installed in areas where appliances and power tools are used in close exposure to water. Tap water or wet objects are able to conduct electricity very easily and can connect your body to a ground potential.This increases your chances of receiving a shock from a ground fault. Appliances that have built-in GFCI breaker protection, as now required for hair dryers, may not need additional GFCI protection, but there are still many appliances not equipped with GFCI protection.The GFCI will recognize the difference in the amount of electricity flowing into the circuit to that flowing out, even in amounts of current as small as 4 or 5 milli amps. As soon as this is identified, The GFCI reacts quickly (less than one-tenth of a second) to trip or shut off the circuit.

It is very important to check the functioning of these circuits every month. Being electronic devises, they can wear out. Using the test button on Fixed GFCI it is easy to test whether it is working or not. However, the portable GFCIs should be tested every time before using them. 

The trouble with GFCI is it takes only 5 mA (0.005 A) of current leakage from the hot wire to the ground to cause a GFCI to trip. A small amount of leakage current may be difficult to avoid in some normal circuits. Hand-held power tools maintained in good condition do not cause a tripping problem. Also permanently installed motors or fluorescent lighting fixtures can produce sufficient leakage to cause nuisance tripping. Another problem may be a long circuit with many splices. It is suggested to consider the effects of loss of power to a circuit before installing GFCI protection.

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Vacuum Circuit Breaker

A vacuum circuit breaker is an electrical switch which makes or breaks an electrical circuit during a short circuit fault or overload condition. It comes under the protection of the power system where large amount of fault current hampers the system. In case a fault occurs in any electrical system, the relay senses the fault and sends the message to the circuit breaker which disconnects the circuit from the fault circuit thus protecting the electrical equipments. A circuit breaker can resume its normal operation after the fault has been cleared. A circuit breaker is an important protection device used for the timely disconnection and reconnection of the electrical circuit after the clearance of the large magnitude fault current.

Based on the arc quenching media, circuit breakers are divided into 4 types:

·         Gas filled type

·         Oil filled type

·         Vacuum type

·         SF₆  type

We are here to discuss about the vacuum circuit breaker.

Operating principle:

 It is a type of circuit breaker in which the arc quenching is done in the vacuum medium of the breaker. This type of breakers is generally used in medium voltage power transmission. The basic principle of operation of such a breaker is the vacuum interrupter which consists of ceramic insulators surrounded by steel arc chambers on either side. The performance of this breaker depends hugely on the type of material used for the current carrying contacts. Any circuit breaker aims to quench the arc with minimum power loss. As the dielectric strength of vacuum is much more than that of air or SF₆ it is far more advantageous than any other type of circuit breaker. It quenches the arc with its high dielectric strength with a very small contact gap.

Whenever the arc is initiated, the de-touching of the contact creates a hot spot in the gap between the contacts. Being vacuum the metals touching the contact vaporises due to the presence of the hot spot and it creates a conducting medium for the arc to flow. Once the arc is completely extinguished, the conducting metal plate re-condenses and by that time the contacts are already disconnected from each other. This prevents the reestablishment of the arc and hence reduces arc quenching by this process.

Uses of vacuum circuit breaker:

Vacuum circuit breakers have a wide range of application for the industrial and commercial medium voltage transmission in a power system.

-          Vacuum contactor for switching of motors

-          Use in transformer

-          Applicable in motor circuits

-          In substations and switchyards 

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CIRCUIT BREAKER TYPES

A circuit breaker is an electrical switch which makes or breaks an electrical circuit during a short circuit fault or overload condition. It comes under the protection of the power system where large amount of fault current hampers the system. In case a fault occurs in any electrical system, the relay senses the fault and sends the message to the circuit breaker which disconnects the circuit from the fault circuit thus protecting the electrical equipments. A circuit breaker can resume its normal operation after the fault has been cleared. A circuit breaker is an important protection device used for the timely disconnection and reconnection of the electrical circuit after the clearance of the large magnitude fault current.

Operating principle:

There are two operating principles under which a circuit breaker works.

Mechanical principle:

There are two contacts present in any circuit breaker- fixed contact and movable contact. Under normal operating condition when the circuit breaker is switched “on”, both the contacts remain connected to each other. There is a stored potential energy in between the contacts in form of any pressure or compressed air which is released only when the switching signal is given. On occurrence of a fault, the contact gets disconnected and this stored potential energy is released in form of kinetic energy thus disconnecting the fault circuit from the healthy one with a greater force.

Electrical principle:

On account of the high faulty power that is carried by the circuit breaker there is a possibility of a dangerously high arc taking place between the fixed and movable contacts during its operation. In order to eliminate this arcing sufficient dielectric strength has to be provided in between the contacts by cooling or compressing the air between the contacts.

Types of circuit breakers, Based on their arc quenching media

·         Oil circuit breaker

·         Gas filled circuit breaker

·         Vacuum circuit breaker

·         SF₆ circuit breaker

Types of circuit breakers Based on their services offered

·         Outdoor circuit breaker

·         Indoor circuit breaker

Types of circuit breakers Based on their mechanism of operation

·         Pneumatic controlled circuit breaker

·         Spring operated circuit breaker

·         Hydraulic circuit breaker

Based on their installation voltage

·         Low voltage circuit breaker

·         Medium voltage circuit breaker

·         High level circuit breaker

Uses of circuit breakers:

Circuit breakers have a vast application in field of power system. They are used in both indoor and outdoor power transfer circuits.

-          Used as plug-in breakers directly connected to the main bus bar for emergency power supply

-          Fire resistance breakers used in the switchboards

-          Used as DSN switches for higher operating capacity in case of high fault power

-          Motor circuit breakers for the reliable operation and protection of motors

-          Circuit breakers are also installed in the panel boards.

-          Used in the switchyards where transmission and distribution of power plays an important role

-          Generally used in lines with high current and voltage ratings

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Air Circuit Breaker

At home or work place we are often surrounded by different types of electric equipments. Therefore it is very important to know about how to protect these from any kind of damage and thus enhance their work life. Air Circuit Breaker comes handy when it is about hazardous damage due to unstable voltage or frequency trouble.

Air circuit breaker, popularly known as ACB, is an electrical safety device. It is used to safeguard the machine when the fault occurs. Faults can be of various types – inconsistent voltage, disturbance in frequency, short circuit, reverse power, earth fault etc. Air circuit breaker identifies when the equipment is at risk of being exposed to any of these faults. When a system is at risk of damage because of this, the contacts within the circuit break open and stop electricity from flowing though the electrical system. The energy thus generated is stored by compressing a large powerful coil springs which are attached to the contact assembly of a circuit breaker. Once these springs are compressed, the latch may be operated to release the springs, and spring pressure then shuts the circuit breaker.

This type of circuit breakers works in air at atmospheric pressure. Compressed air extinguishes the arc when the connection opens. Their most common application is in electrical distribution systems.

Air circuit-breakers can be used both as circuit-breakers for general protection (of plants, of user complexes, of electric lines) and as protection circuit-breakers of electrical machines (generators, motors, transformers, capacitors).This can be controlled electronically, and in some models are even controlled though microprocessor.

ACBs can be either fixed or movable. A fixed circuit breaker is installed between the power source and a load.The load is the item receiving power, such as house. A movable circuit breaker can be removedfrom a power source and loaded when necessary.

Aircircuit breakers larger than these are used in large commercial as well as industrial distribution systems. These circuit breakers are installed in much higher continuous current and interrupting ratings than the molded case circuit breaker. Most of these large ACBs use a closing device, known as a “stored energy mechanism,” for fast, positive closing action.

An important characteristic of air circuit breakers is that they should be set up to facilitate easy maintenance. It is also important to test the functioning of ACB regularly. This is the best way to ensure safety of all these instruments and create a non-dangerous work environment for you.

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Miniature Circuit Breakers- What Are They?

INTRODUCTION:

Miniature Circuit Breakers are electromechanical devices used to protect the electrical circuits from over current. Miniature

Circuit Breakers are also called as MCB in short form. Over current in the electrical circuits are majorly caused by the following three things, short circuit, overload and faulty design. Miniature Circuit Breakers are better alternate to Fuse, because once an overload is detected, MCB does not require replacement. MCB offers most improved safety operation and it can be easily reset. It has also a greater convenience without incurring larger operating cost.

OPERATION:

The function of MCB is too simple. Once a fault in circuit is detected, MCB interrupts the flow of continuity current through the circuit. In simple terms, MCB operates like a switch, when the current flowing through it reaches a maximum fixed limit, it automatically turns off.  MCB are designed generally to protect against over current and over temperature faults which means in the sense of overheating.

There are two contacts available in the circuit, one is fixed and the other moveable. When the current reaches or exceeds the predefined limit a solenoid will give force to the moveable contact to open (At that time the fixed contact will be disconnected) and the MCB turns off by stopping the current to flow in the circuit. Therefore to restart the flow of current the MCB will be manually turned on. This is the mechanism used to protect the circuits from the faults arising due to over current or over load. A bi-metallic strip is used to protect against the fault arising due to over heating or increase in temperature. Generally MCBs are designed to trip within 2.5 millisecond when an over current fault arises. In case of overheating and temperature rise it will take for the MCB to trip 2 seconds to even 2 minutes.

 ADVANTAGES OF MCB COMPARED TO FUSE:

1. MCBs automatically switch off the electrical circuit when it meets faulty condition. MCB is more sensitive to over current than fuse.

2. When the switch operating knob comes to off position during tripping, the faulty portion of the electrical circuit can be easily identified. But in case of fuse, it is not possible.

3. In MCB fast restoration of supply is possible by switching operation and it is not possible in Fuse.

4. Electrically it is more safety in MCB than Fuse.

The only one disadvantage is MCB is bitwise costlier than Fuse.

APPLICATIONS:

MCBs are majorly used in Home electrical panels to protect from overload. Also used in lighting systems such as lamp lights, fluorescent lights etc, MCBs are more beneficial when we use heaters. It also used in many industrial appliances.

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When do the Nuisance Trips Happen with the Earth Leakage Circuit Breakers?

Nuisance trips can take place when there is an installation with two connections to the earth. Whenever there is any high current striking near by it can cause a voltage gradient in the soil which in turn provides the ELCB with enough voltage causing it to trip.

Whenever the rod used in the installation is placed close to any earth rod of adjoining building, the leakage in the earth in the neighbouring building can also raise the ground potential and in turn cause a huge difference in voltage between the two earths. This also causes the ELCB to trip. Such occurrences do not happen often but are encountered at times which close earth rods which are unsuitable for the ELCBs are used of the installations.

Nuisance trips are at times caused even from normal and harmless currents or earth leakage happens to an extent. Nuisance trip are more often seen in the RCDs rather than in the Earth Leakage Circuit Breakers.

One of the major causes of nuisance trips is due to the accumulated currents which are caused by the installations which have a low insulation resistance. This can happen if the equipment is older or can also take place in equipments which have heating elements or can also occur in the wiring in the buildings which are longer damp as well as rainy climatic conditions. The resistance can lower in such cases due to the tracking of the moisture. If the device which is used is 30 mA and if the burden from the various sources is 10 mA then the ELCB unit would trip at 20 mA. The individual appliances in this case are safe and out of risk but such occurrences will reduce the tripping level of the unit. Such problems were majorly seen in the old installations where a single Earth Leakage Circuit Breaker was used for the protection of multiple circuits. Many of such are now replaced with the RCDs as they provide more protection to the appliances but the RCDs are more often seen to suffer in cases of false trips. 

There are also occurrences when there is a passage of fault current which is not sensed by the Earth Leakage Circuit Breaker, but the operation of the ELCB is never compromised. The ELCB just does the same by preventing the earth metal work to rise due to the dangerous voltage conditions.

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Pros And Cons Of Earth Leakage Circuit Breakers

The Advantages of Earth Leakage Circuit Breakers:

·        There is one major advantage of the Earth Leakage Circuit Breakers over the RCDs. The ELCBs have not very sensitive towards the fault conditions and hence have less nuisance trips.

·        The ELCB can have a nuisance trip in situations where the voltage as well as the current in the earth line is a fault current which occurs from a live wire.

The Dis-Advantages of Earth Leakage Circuit Breakers:

·        The ELCBs do not indentify faults which do not pass current via the CPC into the earth rod.

·        A single building system cannot be split into multiple sections using the ELCBs the independent fault protection as most of the earthing systems are bonded towards a pipe work.

·        The Earth Leakage Circuit Breakers can be easily tripped by the external voltages from the things which are connected to the earthing system. For example, metal pipes, a TN-C-S combined neutral or earth.

·        The ELCBs are also much different from the RCDs as the ELCBs when connected to the leaky appliances like water heaters or washing machines or at times electric cookers can make them trip.

·        Most of the ELCBs also add some extra resistance which acts as an additional point of failure and thus affects the earthing system badly.

There are some of the Earth Leakage Circuit Breakers which do not respond towards a fault current which is rectified. There are also similar issues with the ELCBS as well as RCDs but ELCBs being much older and with some good improvements over the years, any old Earth Leakage Circuit Breaker can have little and uncommon fault current to which it might not respond to. As failures are much common with any electrical and mechanical device, the Earth Leakage Circuit Breakers which are used for them have to be properly and periodically tested to confirm that they still function properly. The Earth Leakage Circuit Breakers do not function properly if any of the earth wires get disconnected from them and they will no longer trip. Hence such installations do not function properly. 

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The History and Types of Earth Leakage Circuit Breakers

The Earth Leakage Circuit Breakers were initially used on the TT earthing systems, but now these are replaced by the residual current devices. There are few systems which still use the Earth Leakage Circuit Breakers.

The ELCBs which were used earlier help in detecting the sine wave currents but were not useful for the rectified fault current. As time passed by, the filtering capacity over the nuisance trips has also seen some improvement. These Earth Leakage Circuit Breakers used to offer very little safety and also the risk of a nuisance trip was always high. Some of the major companies which manufacture the Earth Leakage Circuit Breakers are Major Tech, Fuji Electric, Schneider Electric, Legrand, Havells, ABB, Siemens AG, Areva T&D, Camsco, Telemecanique, Orion Italia, Crabtree, MEM, and Terasaki.

The Types of Earth Leakage Circuit Breakers:

There are majorly two types of ELCBs. They are the voltage operated and the current operated.

The voltage operated ELCB s were first seen and invented in the 20^th century and they also provided a major advancement in terms of safety. These were very useful for mains electrical supplies which had inadequate earth impedance. Though there are many voltage operated ELCBs, there are not many new installations. A voltage operated ELCB helps to detect a sudden rise in the potential in between the metal work (which is mostly inter connected) and an isolated electrode. Most of these operate at a potential which is detected at 50 volts.

The voltage operated ELCBs also have a second terminal which is used for the connection of the remote reference earth connection.

The current operated ones are the Residual-current devices or the RCDs which have majorly replaced the voltage operated Earth Leakage Circuit Breakers. They gained popularity as they help in protection of the earth leakage using a different methodology of detection.

Whenever the term Earth Leakage Circuit Breakers is used, it means the usage of the voltage operated ELCB. 

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The Working Principle of Earth Leakage Circuit Breaker

The Earth Leakage Circuit Breaker or the ELCB as it is called is a safety device which is majorly used in the electrical installations. The Earth Leakage Circuit Breakers have high earth impedance which helps to prevent shock. The ELCB helps in detecting small and minute stray voltages on the metal enclosures of the electrical equipment and it also interrupts the circuit if any dangerous or high voltage is detected. These were in wide use in the initial days till they were replaced by the residual circuit breakers as they help in detecting the current leakage directly. The main purpose of the usage of the Earth Leakage Circuit Breaker is to prevent any sudden damage to humans or any animals due to the occurrence of electric shock. 

The Operation of Earth Leakage Circuit Breakers:

Any Earth Leakage Circuit Breakers can be stated as a special type of latching relay which has the main of the buildings incoming power connected to it. This is connected through the process of switching contacts as the ELCB automatically disconnects the power which there is an earth leakage.  The Earth Leakage Circuit Breakers also help to detect any fault currents which are from the live to the ground wire and it protects within the installation. This does not take place in the case of a voltage sensing Earth Leakage Circuit Breakers. 

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