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Is Your Earth Leaking? – Basics of Earth Leakage Circuit Breakers

Earth leakage is an unintended state where electrical current is leaking from an electrical appliance or circuit to earth (ground). Earth Leakage Circuit Breakers are used to protect people and equipment from electrical shocks and against fire risks due to current leakage.

They fall into two types: Current Sensing Breakers and Voltage Sensing Breakers.

Current Sensing Breakers

The most common type of earth leakage circuit breaker in use now is the current sensing breaker or residual current circuit breaker (RCCB). They monitor the difference between current flowing through the phase and neutral wires. An imbalance between phase and neutral causes the breaker to trip, protecting against potential hazards like accidents, fire, or equipment damage.

Current sensing breakers consist of a current transformer with two primary windings and one secondary winding acting as the sensing coil. The primary windings support the phase and neutral wires. When the current flowing through the phase and neutral are equal they create opposing magnetic fields and no current flows through the sensing coil. When there is earth leakage the magnetic fields are not in balance, generating a current through the secondary winding thus causing the breaker to trip.

Advantages of current sensing breakers:

• Can detect any earth fault whereas voltage sensing only detects faults in the main earth connection.
• Can detect changes in phase and neutral currents.
• Are efficient and inexpensive.
• Require fewer connections than voltage sensing breakers.

Current sensing breakers have the disadvantage of nuisance tripping when an electric load suddenly changes and some current goes to earth despite there being no risk of shock.

Voltage Sensing Breakers

Voltage sensing breakers are older and less commonly used now than current sensing breakers. Voltage sensing breakers require a ground connection, unlike current sensing breakers which do not require this connection, to measure earth leakage. They contain a trip coil that senses voltage.

During normal operating conditions, there will not be voltage across the trip coil. When an earth fault occurs, such as line voltage contacts the metal enclosure of the protected device, voltage will cross the trip coil causing the breaker to trip. This protects the equipment and anyone who comes in contact with the electrical devices.

While still in use, voltage sensing earth leakage circuit breakers are generally not used in new projects due to their disadvantages.

Disadvantages of voltage sensing breakers:

• They require extra connections between the source and the breaker.
• Any wiring breaks to earth or live current generates a failure which could result in severe shock hazards to people.
• Other devices connected to the earthing system can generate voltages that cause the breaker to trip.
• They do not provide shock protection if the line conductor is touched.

Explore MISUMI’s selection of earth leakage breakers here .

About the Author

Mike is the Product Manager for Industrial Electronics at MISUMI. He has over 15 years’ combined experience working in Industrial/MRO distribution and Electronic Components distribution. He holds a Bachelor’s Degree from Northern Illinois University.

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Troubleshooting a Tripped Circuit Breaker

Alora Bopray

Staff Writer

Alora Bopray is a digital content producer for the home warranty, HVAC, and plumbing categories at Today's Homeowner. She earned her bachelor's degree in psychology from the University of St. Scholastica and her master's degree from the University of Denver. Before becoming a writer for Today's Homeowner, Alora wrote as a freelance writer for dozens of home improvement clients and informed homeowners about the solar industry as a writer for EcoWatch. When she's not writing, Alora can be found planning her next DIY home improvement project or plotting her next novel.

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Roxanne Downer is a commerce editor at Today’s Homeowner, where she tackles everything from foundation repair to solar panel installation. She brings more than 15 years of writing and editing experience to bear in her meticulous approach to ensuring accurate, up-to-date, and engaging content. She’s previously edited for outlets including MSN, Architectural Digest, and Better Homes & Gardens. An alumna of the University of Pennsylvania, Roxanne is now an Oklahoma homeowner, DIY enthusiast, and the proud parent of a playful pug.

February 12, 2024

If your air conditioner or heat pump unit is the culprit that caused a tripped circuit breaker in your house or office, there are a few possibilities why this happen.

The earth leakage circuit breaker(ELCB) that trips the entire power supply to the house when a lightning strike can easily be restored by switching the lever back to the ON position.

In the case of faulty air conditioner equipment, the ELCB may trip due to earth leakage. In this case, you will need to isolate the cause of the fault or repair the equipment before the power supply can be restored to the entire house.

If the miniature circuit breaker(MCB) trips, the fault could be due to an overcurrent or short circuit. Rectify the problem and power on the MCB.

These circuit breakers are protection devices that protect the electrical circuitry from further damage without which fire hazard and electrical shocks may occurred.

Tripped Circuit Breaker Due To Earth Leakage

Here are some of the possible causes of earth leakage that cause the earth leakage circuit breaker to trip.

The motor wires in the compressor touch the metal enclosure of the compressor. The wires of the motor may come off due to excessive vibration or fault in design.

Once these wires that are connected to the hot circuits touch the metal enclosure which is grounded, current will flow to the ground causing the ELCB to trip.

Disconnect the power and all the circuits to the terminal of the compressor. Use a multimeter and set the scale to measure resistance. Check the resistance between each of the terminals to the enclosure.

If the reading is close to zero, that means that the exposed wire closest to that terminal has touched the metal frame. Repair the fault or replace the compressor before the equipment can be operated again.

Similarly, if the fault is due to the compressor fan motor or indoor blower motor, disconnect the power and isolate the circuits to the motor. Check the resistance of each terminal to the casing(if metal). If it is close to zero, that means that the exposed wire is touching the casing causing it to trip. Remove the motor for repair or replace with a new motor before the equipment can be operational again.

In circuits that have live, neutral and earth wires bundled together, there is a possibility that the insulator of the wires breaks down (due to overheating, faults, under specs or inferior wires) causing the live or neutral conductor to touch the earth conductor. This will cause the circuit breaker to trip too. Troubleshooting this problem is more complicated as it involves not just a particular component but the electrical circuits.

Tripped Circuit Breaker Due To Overcurrent

Sometimes, the miniature circuit breaker tripped after operating the air conditioner for some time due to over-current. This problem will take more time to troubleshoot as the problem does not happen immediately. Here are the possible causes.

Disconnect the mains power before checking the connecting power from the mains to the equipment. For example, if there are 3 terminals that connect the power to the compressor, open up the housing and check the connection.

Look out for darkend or black spots on the terminal indicating that overcurrent had occurred. A loose connection will cause arching hence drawing excessive supply and damaging the wires and the parts that are connected to it.

Tightened the connection after removing and reconnecting the wire that has been damaged due to overheating.

A qualify technician will usually be able to troubleshoot this problem by using a tong clamp ammeter to measure the current of that particular conductor.

If the compressor has a mechanical part that malfunction causing it to lock, the current to operate it will be a few times more than the normal operation. When this happen continuously, the possibility of over-current to happen will occurred causing the circuit breaker to eventually tripped after a certain period of operation.

If the compressor or fan motor uses a 3-phase induction motor, a loss of one phase will cause overheating to occur when operating at full load. If the thermal overload protection does not trip, the circuit breaker will trip if the current exceeds its specification. A good design will usually has a phase loss protector built into the circuit to prevent the motor from running in the first place.

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18th Edition: Earth leakage explained

Do you need to know if your cables are leaky? According to the 18 th Edition, the answer is ‘yes’, as Dave Sweetman, Marketing & Business Development Director at Di-LOG Group explains.

How often have you spent hours fault-finding nuisance tripping issues for free, wishing you’d have known there was a problem before quoting for this particular DB upgrade?

There is a new 18 th Edition regulation identifying the requirement for you to measure Earth Leakage, as stated in BS7671 Reg 531.33.2.

In a nutshell, each electrician must check that each install completed does not have excessive leakage to earth on each of the RCDs or RCBOs.

The maximum permitted value per RCD has been set at 30% of the nominal value, i.e. a 30mA RCD would be no more than 9mA, 100mA would be 30mA, and so on.

Nonetheless, I’m sure you’d find it useful to know if there is a potential issue on an installation before you quote for your next DB change.

The only way to indicate the presence of Earth Leakage would be to use an Earth Leakage Current Clamp Meter.

The Di-LOG DL6518 Earth Leakage Clamp is a low-cost solution that works on differential leakage measurement, which involves simultaneously clamping around the live and neutral conductors together.

You can check any installation by simply clamping around your meter tails on the supply.

The DL6518 has a measurement resolution of 100µA (0.1mA), making measurement very accurate when measuring minimal AC currents.

Domestic installations tend to have dual 30mA RCDs fitted or are even made up entirely of RCBOs.

If the installation shows a combined differential leakage current above 30% of each RCD/RCBO value (in this case 9mA) you may need to take action to manage the leakage to earth and minimise the likelihood of nuisance tripping.

We all know how costly call-outs are to any business to reset or investigate a tripping RCD!

Where possible, you will need to have the day-to-day electrical appliances in operation to accurately determine potential issues.

If excessive leakage is then identified on the tails, you would then need to clamp around the live and neutral conductors of each of the RCDs to determine if the leakage on that RCD is above the 30% threshold, ideally looking for a current considerably less than 9mA. You then repeat for each RCD.

Intentional or unintentional leakage

If the Earth Leakage detected on each RCD is excessive, the user will need to ask: “Is this intentional or unintentional?”

Intentional Earth Leakage tends to be found in electrical appliances in the form of a functioning earth, where a small amount of earth leakage is required for the appliance to function.

Unintentional Earth Leakage tends to occur in poor installations where there could be a breakdown in the conductor insulation or moisture ingress, amongst many other causes.

Identification

Switching each individual circuit off, one-by-one, is a good area to start.Here you can easily identify which circuit you may need to investigate further.

Once a circuit is identified, eliminate the ‘intentional leakage’ first by switching off each individual appliance, one-by-one, to see if this changes the result.

Every electrical appliance has a ‘Protective Earth Conductor current’ limit – you should refer to the In-Service Inspection and Testing Code of Practice for more information on these limits.

If the isolating of electrical appliances does not change the result it may well be ‘unintentional leakage’, and a check of the insulation of the conductors will be required in the form of an Insulation Test.

Leakage management

There are an array of options available to manage your Earth Leakage: balancing circuits between RCDs to fall below the 30% threshold, fitting RCBOs, testing the electrical appliances, or even a complete re-wire… all are critical when you price your next job!

Di-LOG has created a dedicated web page for readers of this article, containing all of the details you need to know about the DL6518 Earth Leakage Clamp, including special offers and technical specs. To visit the page go to: http://www.dilog.co.uk/pe-nov-2019-dl6518-earth-leakage-current-meter/

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What is Earth Fault? It’s Causes, Effects and Protection

Table of Contents

What is Earthing and Grounding?

Earthing and grounding both are processes to connect electrical systems to the ground to protect people against electrical shock. The earthing  process means connecting the dead part of the electrical system (parts that don’t carry current under normal conditions such as the motor body, Transformer body, electrical panels, etc.) to the earth. Whereas the Grounding process means connecting the live part of the electrical system (parts that carry current under normal conditions such as neutral of star connected Transformer and loads ) to the earth. Now coming to our main topic of discussion:

What is Earth Fault?

Earth fault is an open circuit ground fault in which any live conductor or power-carrying cable is detached from its place or breaks and falls on the earth’s surface. In other words, We can say that ln earth-fault current-carrying conductor comes directly in contact with the earth’s surface. So because of the direct contact between a live conductor and the earth’s surface, a huge amount of current starts flowing to the earth due to the conducting nature of the earth.

Causes of Earth Fault

The main cause of earth fault in an overhead transmission and distribution line is the failure or puncture of the insulator. Insulators are used in overhead transmission lines to provide insulation between live conductors and metallic towers that are already connected with the earth’s surface. So if the insulation of insulator fails or in other words if the insulator is punctured then the fault current will flow through the live conductor and metallic tower to the earth creating an earth fault.

Another reason for earth fault is that sometimes overhead transmission lines break due to any unusual loads on line and hence fall to the ground. So in this case also live conductor gets in direct contact with the ground and creates a major earth fault in the electrical system. Whereas in the case of an underground PV cabling system, Earth fault may arise due to insulation damage during installation, abrasion damage to cable sheath, and damage to module back sheet during installation.

Effect of Earth Fault

Whenever an earth fault occurs in the electrical system than during earth fault, the System gets short, and hence huge amount of short-circuit current flows through the system. That huge current damages electrical equipment which comes in contact with a loop of earth fault circuits and also it interrupts the continuity of the power supply. Due to such a large amount of current flowing to the earth, a large voltage drop occurs that affects the other loads and it may cause the burning of phase or line.

How to check Earth Fault?

To identify the earth leakage fault in cables, megger is used. One terminal of the megger is connected to the live conductor and the other terminal is connected to the earth. If the merger indicates zero reading, it means the conductor is earthed. The same procedure is repeated for other conductors of the high-voltage cables.

Difference between Earth Fault and Ground Fault

Earth Fault  vs Ground Fault :

Earth fault is an open-circuit fault where a power-carrying cable or conductor breaks and gets into contact with Earth or any conductor capability material in contact with Earth. In this fault, the system at the load side is disconnected from the source in case of radial power flow.

Whereas a ground  fault is a short-circuit fault (such as L-G, L-L-G, L-L-L-G) where the power-carrying cable or conductor is not broken but gets into contact with the earth or any conductor capability material in contact with the earth. In this fault, the system at the fault point experiences the flow of a large amount of current into the ground.

Ground fault is more severe than earth fault due to flow of huge current to ground. That can dimage verious electrical equipments of power system, if fault is not cleared within specified time limits.

Earth Fault Protection

Well, after discussing the earth’s fault, its causes, and effects, one of the important questions that arises in our mind is.. ok, then what is the solution to minimize Earth-fault? Does it mean what protective equipment we can use to protect the earth fault? So let’s discuss the protection used to minimize earth faults in detail.

What are  Earth Fault Protection Devices?

The electrical equipment that   provides protection against earth fault is known as earth fault protection devices. These are normally Earth fault relay (EFR) , Earth leakage circuit breaker (ELCB) , and ground fault circuit interrupter, which are used to restrict the fault current. In these devices, the fault current is restricted and the fault is dispersed by the Restricted Earth Fault Protection (REFP) scheme. Now first let’s discuss both earth fault protection devices such as:

• Earth fault relay (EFR)
• Earth leakage circuit breaker (ELCB)

After that, we will see what is Restricted Earth Fault Protection (REFP) schemes.

Earth Fault Relay (EFR)

An earth fault relay (EFR) is a protection device used in electrical installation that can sense a fault between phase and earth.

The  main function of an earth fault relay (EFR) is to operate the CB for leakage current to the earth. RCCB also does the same function but RCCB gives protection to the human body, Whereas EFR provides protection to electrical equipment from earth fault . EFR deals with high voltage and high current.

Hence we can conclude that an earth fault relay (EFR) is an earth fault monitoring device that works on the principle of Kirchhoff’s law.

Earth Leakage Circuit Breaker (ELCB)

ELCB or earth leakage circuit breaker is a safety device used in electrical installation with high earth impedance to prevent electrical shock. In other words, we can say that ELCB is a special type of circuit breaker that is used for protection against earth leakage current. It is voltage voltage-sensing device that works on the concept of stray voltage. Whereas current sensing ELCB is also known as RCCB .

Whenever any earth leakage fault occurs in the system then a stray voltage appears across metal enclosures of electrical equipment ELCB interrupts the circuit if a dangerous voltage is detected. Then it disconnects the rest of the healthy system from the main supply. Once it tripped then it requires a manual reset process to work again normally.

Hence simply we can assume that ELCB is a safety device whose main function is to provide protection against electrical shock. It can’t assure protection against overloading and short-circuit faults.

What is the Restricted Earth Fault Protection (REFP) Scheme?

The restricted earth fault protection (REFP) scheme is very sensitive to internal earth faults for high-rating power transformers, alternators, etc. This scheme is comparatively cheaper than the differential protection scheme.

In this scheme, the common terminal of phase CTs is connected together with the secondary of neutral CT in such a manner that the secondary unbalanced current of phase CTs, and the secondary content of neutral CT will oppose each other.

When an external fault F 1 occurs in the system then the resultant of current I 1 and I 2 flowing through phase CTs and neutral CT respectively will be zero. But whenever an internal fault F 1 occurs inside the protective zone then only I 2 current will flow through the secondary of neutral CT and the resultant current will not be zero.

Hence earth fault relay will sense non-zero current and then it will operate the CB to protect the system with earth leakage fault . The fault current becomes 15% more than the rated current of each winding. To avoid magnetic inrush current, a stabilizing resistor is connected in series with an earth fault relay.

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Earth leakage explained

Earth leakage is electric current that finds its way to earth via an unintended path. There are two categories: unintentional earth leakage, which results from faulty insulation or equipment, and intentional earth leakage, which is a consequence of the way equipment is designed. It seems strange to “design in” earth leakage, but it’s sometimes unavoidable – IT equipment, for example, often produces some earth leakage, even when it’s working properly.

Whatever the source of earth leakage, it must be prevented from causing electric shocks. This is usually done by using either RCDs (residual current devices) or RCBOs (residual current circuit breakers with overcurrent protection). These measure the current in the line conductor and compare it with the current in the neutral conductor. If the difference exceeds the mA rating of the RCD or RCBO, it will trip.

Most of the time, earth leakage works as intended, but sometimes an RCD or RCBO keeps tripping for no apparent reason – this is “nuisance tripping”. The best way to tackle this is with an earth leakage clamp meter, such as the Megger DCM305E. This is clamped around the line and neutral conductors together (but NOT the protective conductor!) and it measures the earth leakage current.

To decide which circuit is causing nuisance tripping, turn off all the MCBs in the consumer unit and position the earth leakage clamp around the mains cables. Turn on each circuit in turn. If one causes the earth leakage to increase significantly, this is likely to be the problem circuit. Next decide whether the leakage is intentional. If it is, some form of load spreading or circuit splitting will be needed. If it’s unintentional leakage – the result of a fault  – the fault must be found and repaired.

Don’t forget the problem might be a faulty RCD or RCBO. To check, do an RCD ramp test. If it’s a 30 mA device – the most common rating – it should trip somewhere between 24 and 28 mA. If it trips at a lower current, it probably needs replacing.

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Earth Leakage Relay (ELR)

An earth leakage can represent a danger to life or property if it is not located and mitigated. Studies have revealed that at least 500 people experience electrocution every year in the US alone. Earth leakage relays can be helpful in sensing and mitigating such incidents.

What is earth leakage?

What is an earth leakage relay, working principle, elr wiring diagram.

Earth leakage is an unindented situation in which a conductor carrying current comes in contact with the earth or chassis of equipment, either directly or indirectly, causing a current flow to the earth. Earth leakages can be a result of insulation failure or electric shock (current flows through the human body to the ground).

An earth leakage relay is a device used to sense earth leakages and open a circuit breaker when the leakage current exceeds the preset value. It can protect human beings from electrocution and prevent fire hazards . Earth leakage relays are used in combination with Core balance current transformers(CBCT) or Zero phase current transformer (ZCT) .

During an earth fault, the current flows directly to the earth by bypassing the load. This happens when a live conductor touches the earth directly or through the human body. This can be the result of insulation failures, wet surfaces or improper wiring.

Under normal conditions, the vector sum of the current flow in phase and neutral will be zero. Earth faults cause an imbalance in the current flow in the phase and neutral conductors (vector sum of the current would not be zero). Core balance current transformers or zero-phase current transformers are used to sense this current imbalance.

The earth fault relay continuously monitors the output of the CBCT. When its output exceeds the present limit (leakage current limits can be set) , the relay contacts operates. These relay contacts are used in the activate the trip contacts of the circuit breaker and trips it.

A typical wiring diagram of an earth leakage relay is shown below. Operational power is applied to the terminal A 1 and A 2 of the ELR and the CBCT is connected to the terminals T 1 and T 2 . The normally closed terminals of the fault signalling contacts are connected to the Undervoltage release coil of the circuit breaker. So when the leakage current sensed by the CBCT exceeds the set value, the ELR interrupts the power to the Undervoltage release and breaker trips immediately.

Earth leakage relays can detect leakage before potential damage is caused. The leakage current limit needs to be adjusted between 10mA and 3A based on the application. IEC/EN 60755 defines general rules for residual-current protection devices.

11 thoughts on “Earth Leakage Relay (ELR)”

Good Morning Kindly quote the following 1.RELAY EARTH LEAKAGE CORE BALANCE CURRENT: 500mA VOLTAGE: 550V PN: Ms2-A1-500

Regards Mwaka Nachilombe

How the elr function in 3 phase supply without neutral if leakage happened?

For 3 phase three-wire system, the vector sum of currents in all three phases is zero. Any imbalance will induce a current in the CBCT. If the current exceeds the preset value, the ELR trips.

it is working phase unbalancing detected and operated relay earth fault.

How ug series cbct trip mccb when when neuttraland all phases (4 cables) passing inside cbct ? and how to solve this issues ?

Kindly refer the drawing shown above. https://www.electricalclassroom.com/earth-leakage-relay-elr/#3-elr-wiring-diagram- .The contacts of the earth leakage relay is connected to the shunt trip coil of the MCCB.

Thanks for the Imformation team. Please send me the drawings of different types of electrical connection of earth leakage relays

I want power panel board wiring diagram

How does Zero pottential transfomer pick up when a person is elctricuted to protect him/her.

When netrual pass through CT where does it go to the field?

Because if only 3 lines passes through CT it will only measure imbalance so I want to know that when neutral passes through CT where does it go to the field.

All the four lines must pass through the CBCT.

This is a useful article to refresh my knowledge on this key electrical component. Thanks for sharing.

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What Causes Earth Leakage Circuit Breaker To Trip

Electricity is an integral part of our everyday lives, providing us with the power to cook food, heat our homes, and even listen to music. Unfortunately, electricity can also be dangerous if it isn't properly managed. That's why having a functioning Earth Leakage Circuit Breaker (ELCB) is so important. But what exactly is an ELCB, and what causes these devices to trip? An ELCB is a device that helps protect electrical circuits from overloading and short-circuiting. It works by detecting any leakage of current to ground, and then cutting off the electricity supply. This prevents an overload or short-circuit, which can cause significant damage to both the electrical wiring and appliances in your home. Of course, there are several different factors that can cause an ELCB to trip. The most common of these is an overloaded circuit. If too much electrical current is flowing through a wire, the circuit breaker will sense the excess load and shut off the power to prevent a fire or other hazardous situation. Another common cause of ELCB tripping is a short-circuit. A short-circuit occurs when two wires touch each other, causing a large amount of current to pass through the circuit. Again, the ELCB will detect this high current level and shut off the power to protect the wiring. Finally, an ELCB can also trip if there is an electricity fault. This is usually caused by a loose wire or a faulty appliance, and the ELCB will detect the fault and shut off the power to prevent it from causing further damage. Although an ELCB can be a lifesaver, it's important to remember that these devices are only intended to provide basic protection from overloaded and short-circuited circuits. If you suspect that your ELCB has tripped due to a more serious problem such as a faulty appliance, it's important to call a qualified electrician to inspect and repair the issue. In conclusion, an ELCB is an essential part of any electrical system, providing vital protection against unsafe electrical conditions. Common causes of ELCB tripping include overloaded circuits, short-circuits, and electricity faults. If you ever notice that your ELCB has tripped, it's important to call a qualified electrician right away to inspect the issue.

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Earth-Leakage Relay

An earth-leakage relay is a safety device that detects and isolates leakage currents in electrical systems, protecting equipment and personnel.

Earth-Leakage Relay: An Essential Protection Device for Electrical Systems

Earth-leakage relays are crucial safety devices designed to protect electrical systems and equipment from dangerous leakage currents that could potentially cause hazardous situations or even fatal incidents. In this article, we will discuss the fundamentals of earth-leakage relays, their working principles, and their importance in maintaining the safety and integrity of electrical systems.

What is an Earth-Leakage Relay?

An earth-leakage relay is a type of protective relay that detects leakage currents in electrical systems, which can be a sign of insulation failure or equipment damage. Leakage currents are unwanted currents that flow through the earth or other conductive paths, bypassing the intended electrical circuit. When a leakage current is detected, the earth-leakage relay sends a trip signal to the circuit breaker, disconnecting the power supply and preventing further damage to the system and potential harm to personnel.

How Does an Earth-Leakage Relay Work?

Earth-leakage relays typically use a current transformer (CT) to detect leakage currents in the system. The CT is designed to encircle all the phase conductors and the neutral wire of the circuit, providing a zero-sum current when there is no leakage current present. If a leakage current occurs, the CT senses an imbalance in the current flow, which is then processed by the relay to determine if the leakage current exceeds a predetermined threshold. If the threshold is exceeded, the relay sends a trip signal to the circuit breaker, disconnecting the power supply and safeguarding the system from further damage.

Types of Earth-Leakage Relays

There are two main types of earth-leakage relays commonly used in electrical systems:

• Electromechanical Earth-Leakage Relay: These relays use a mechanical element, such as a magnetic core, to detect the leakage current. When the leakage current exceeds the set threshold, the mechanical element moves, causing a set of contacts to close and send a trip signal to the circuit breaker.
• Electronic Earth-Leakage Relay: These relays use electronic components to measure the leakage current and compare it to a predetermined threshold. If the leakage current surpasses the threshold, the relay sends a trip signal to the circuit breaker. Electronic relays are more sensitive and faster in response compared to their electromechanical counterparts, providing improved protection and more accurate fault detection.

Importance of Earth-Leakage Relays

Earth-leakage relays are essential for several reasons:

• Safety: Leakage currents can lead to electrocution, fire hazards, or equipment damage. Earth-leakage relays help minimize these risks by detecting and isolating the faulty circuit.
• Preventive Maintenance: By detecting insulation failure or equipment damage early, earth-leakage relays enable prompt action to address the issue, preventing further damage and potentially costly repairs.
• Regulatory Compliance: Many electrical codes and standards mandate the use of earth-leakage relays to ensure the safe operation of electrical systems.

Applications of Earth-Leakage Relays

Earth-leakage relays are widely used across various industries and applications to ensure the safety and reliability of electrical systems. Some common applications include:

• Industrial Plants: Earth-leakage relays are crucial in factories and manufacturing facilities to protect machinery, equipment, and personnel from potential hazards caused by leakage currents.
• Commercial Buildings: In commercial settings, such as offices, hotels, and shopping centers, earth-leakage relays are employed to maintain the safety and integrity of electrical systems, protecting both people and property.
• Residential Buildings: Earth-leakage relays are also used in residential buildings to safeguard occupants from potential electrical hazards and ensure the reliable operation of home appliances and electrical systems.
• Power Distribution Systems: Utilities and power distribution companies use earth-leakage relays to monitor and protect their networks from insulation failures and other faults that may lead to power outages or damage to electrical infrastructure.

Selecting the Right Earth-Leakage Relay

When choosing an earth-leakage relay for a specific application, several factors must be considered, including:

• Sensitivity: The relay’s sensitivity to leakage currents should be appropriate for the application. Higher sensitivity relays provide better protection but may be prone to nuisance tripping, while lower sensitivity relays may not adequately protect against potential hazards.
• Response Time: The relay’s response time should be fast enough to disconnect the circuit before any damage or harm can occur. Electronic relays generally offer faster response times than electromechanical relays.
• Adjustability: In some cases, it may be necessary to adjust the relay’s sensitivity or trip settings to suit the specific requirements of an application. Selecting a relay with adjustable settings can provide greater flexibility and customization.
• Reliability: The relay should be reliable and durable, with a proven track record of performance in similar applications. It is essential to choose a relay from a reputable manufacturer with a history of producing quality products.

Earth-leakage relays are vital protection devices that safeguard electrical systems, equipment, and personnel from the hazards associated with leakage currents. They help maintain the safety and integrity of electrical installations, preventing potential damage and costly repairs. By understanding the principles of earth-leakage relays, selecting the appropriate type and specifications for a specific application, and adhering to relevant codes and standards, engineers and technicians can ensure the safe and reliable operation of electrical systems across various industries and applications.

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Earth leakage current : Measures & protection

Most of the electrical installations nowadays are having loads that incorporate electronics. These electronic loads influence the electrical installation in various ways:

• They generate harmonic distortion in the current they consume.
• They generate current leakages at the mains frequency, 50Hz, and at higher frequencies under normal operating conditions.
• As soon as they are connected to the electrical power supply they generate a leakage current point.
• During an insulation fault, the leakage current might not be sinusoidal, but rather pulsating, for example.

Computers, washing machines, dishwashers, microwaves, mobile phone chargers, low consumption light bulbs, ceramic hobs, air conditioning units, electric vehicle chargers, dryers, machine tools etc.

Q. What is Leakage Current?

Leakage Current is defined as the current which flows through protective ground conductor to ground. In the absence of grounding or improper grounding connections, it is the current that could flow from any conductive part or the surface of non-conductive parts to ground if any conductive path was available (i.e. human body). There are always extraneous currents flowing in the safety ground conductor.

Q. Why is it important?

Electrical equipment commonly includes a grounding system to provide protection against a shock hazard if there is an insulation failure. The grounding system usually consists of a grounding conductor that bonds the equipment to the service ground (earth). If there is a catastrophic failure of the insulation between the hot (power) line and touchable conductive parts, the voltage is shunted to ground. The resulting current flow will cause a fuse to blow or trip a relay and open a circuit breaker; preventing a shock hazard. Obviously, a possible shock hazard exists if the grounding connection is interrupted, either intentionally or accidentally. The shock hazard may be greater than supposed because of the leakage currents. Even if there is no insulation failure, interruption of the leakage currents flowing through the ground conductor could pose a shock hazard to someone touching the ungrounded equipment and ground (or other grounded equipment) at the same time. This possibility is of much more concern in medical applications, where a patient may be the recipient of the shock. A fatal shock could result if the patient is in a weakened condition or unconscious, or if the leakage current is applied to internal organs through patient contacts. The double insulation provided in non-grounded equipment provides protection by using two separate layers of insulation. The protection in this case is ensured because both layers of insulation are unlikely to fail. However, the condition that produce leakage currents are still present, and must be considered.

Q. What causes Leakage Current?

There are two types of leakage currents: ac leakage and dc leakage. Dc leakage current usually applies only to end-product equipment, not to power supplies. Ac leakage current is caused by a parallel combination of capacitance and dc resistance between a Voltage source (ac line) and the grounded conductive parts of the equipment. The leakage caused by the dc resistance usually is insignificant compared to the ac impedance of various parallel capacitances. The capacitance may be intentional (such as in EMI filter capacitors) or unintentional. Some examples of unintentional capacitances are spacings on printed wiring boards, insulations between semiconductors and grounded heat sinks, and the primary-to-secondary capacitance of isolating transformers within the power supply. Consequences Earth Leakage current beyond 30mA can be lethal leading to death. 30mA sensitivity is required for protection in domestic applications where the person may come in direct contact with electric equipment in locations such as labs, schools, workshops etc.100mA and 300mA protection is required where there is indirect contact or due to insulation failure in the cables.

Q. How is it measured?

A meter specially designed for measuring leakage currents is used. The current flowing in the ground conductor is measured by connecting the meter in series with the grounding connection. For information processing equipment, the ground connection is opened and the current flowing to the neutral side of the power line is measured. For medical equipment, the current flowing to ground is measured. The meter may also be connected between the outputs of the power supply and ground. The test conditions include swapping the ac line and neutral connections, and turning power switches off and on while monitoring the current. The test is performed after the equipment has warmed to normal operating temperature and, in some cases, following certain test that cause abnormally high temperatures within the equipment. The intent is to identify and measure the worst-case leakage current.For very low leakage currents, the meter is replaced with a network consisting of either a resistor or a resistor and capacitor combination. The voltage drop across the network is then measured using a sensitive ac voltmeter. Ungrounded or double-insulated equipment is checked by connecting the meter between any touchable conductive part and ground. In the case of non-conductive housings, a copper foil of a specific size is placed on the housing, and the current flowing from it to ground is measured.

Q. How can you get your equipments protected from Leakage Currents?

So how can you get your equipments protected from the leakage currents or how can you eliminate the effects of leakage current? Quantify the leakage current and then identify the source. One best way of going about this is to use Earth Leakage Relay (ELR). The Earth Leakage Relay with Core Balanced Current transformer provides protection from earth leakage with advance intimation (Pre-alarm) of impending occurrence of the event. The user can proactively take action to avoid occurrence of any mishaps. Rishabh’s ELR with 4 digit 7 segment LED display with True RMS measurement (as per IEC 60947-2 Annex M) provides the user with benefits that go the extra mile. Rishabh’s ELR is a microcontroller based device designed to measure low level of leakage current and isolate the faulty equipment or circuit from the system. Leakage current is sensed through Rishabh’s Core Balanced Current Transformer. Fixed time trip occurs when Earth Leakage Current exceeds the trip time which is programmable by means of front keys provide on the front panel of the relay or PRKAB software (can be provided optionally with Rishabh’s ELR). The user can program the threshold level ranging from 30mA to 30A. In case of earth leakage the LED indicators will glow depending upon the percentage of programmed threshold value. For e.g. If the set level is 30mA and the leakage current is more than 15mA then green LED will start blinking which will provide a visual alert to the user. This empowers the user to take corrective actions before any accident. Core Balanced Current Transformer (CBCT) uses the technology of residual magnetic flux. All conductors to be protected shall pass through the core balance current transformer. The vector sum of all the currents should be equal to zero.

In case an earth leakage occurs, the zero- sequence fault current which flows is not cancelled by the flux of the other two phases and hence induces current (residual current) in the secondary. The core balance current transformer can be connected to an earth fault / leakage relay which can be used to generate the tripping signal. CBCTs are manufactured with one core and one secondary winding. The number of secondary turns does not need to be related to the cable/feeder rated current because no secondary current would flow under normal balanced conditions. This allows the number of secondary turns to be chosen such as to optimize the effective primary pick up current. The choice of ratio should therefore be left to the manufacturer to obtain the best possible results.

If more than one 3-phase cable are used in parallel, it is recommended that a separate CBCT on each cable be connected across a common relay or a separate relay be provided for each CBCT. The cable on which the CBCT is mounted acts as the primary conductor of the CBCT. Under normal operating conditions, the three line currents are almost 120 degree apart and balance each other. The resultant secondary current is zero. Upon occurrence of an earth fault, the faulted phase is the only one experiencing earth fault current in the primary. The maximum value of current is decided by the system earthing conditions. The CT wires should be placed adequately away from high current carrying conductors or source of strong magnetic field to avoid noise pickup.

Customer shall provide following information while ordering a CBCT :-

• Cable size or minimum ID require for CBCT
• Minimum earth leakage current to be detected by CBCT + Relay combination
• Specifications of the relay to be used including burden & setting range available
• Choice of ratio

Mr. Santosh R. Bhangale Product Manager Rishabh Instruments Pvt. Ltd. Nasik – India

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Random earth leakage trips (And some causes)!

A tripping earth leakage unit can be terribly annoying. The more installations I do, the more I have to deal with tripping earth leakages…

The number one most common reason I find after an Inverter installation, is circuits (Plugs and lights) that was connected before the earth leakage in the original DB, We then split them out to the essential circuit part and when we start commissioning, we run into earth leakage issues and very soon it becomes clear that the original electrician could not find the fault and decided to connect the circuit before the earth leakage to “hide” it and get the system going. For us to be able to then sign off our installation we end up looking for the issues and in one such case it took us a day and a half to find and fix earth faults on 6 circuits in one very big 3 story house.

The second most common reason is Surge arrestor plugs. The electronics in them provides a path from neutral to ground, that lowers the resistance between earth and neutral and that ads a small “ma” reading without a real earth fault. Now use them on the output of an inverter with a NE bonding relay that opens and closes every time the grid falls away or being restored… Its almost certain the El will trip.

Look at one such example I found again this week. I made a little vid for the client, but decided to post it here so that others might see it as well. If you experience similar trips, please be on the lookout for these. (I was trying to remove the audio, but did not succeed)

VID: Earth resistance readings.

Please add your experiences with earth faults here?

interesting post - I think you might have solved another electrical mystery for me.

Firstly I am in the dark when it comes to electrical things and rely on so called “qualified professionals” and unfortunately that opens me up for exploitation, this post is not a dig at the electrical profession - just to highlight the “fly by night” operators.

Just before covid struck, I hired a recomended “qualified” electrician, “specializing” in inverter installations to do the final wiring up of my 3kw MUST inverter with it’s own DB containing CB for the ceiling lights & light current wall plugs.

All I wanted him to do was to remove both ceiling light circuits (10 x 14w LEDS) & 1 light current wall plug circuit (LCD tv / media player / 1 x 14w LED lounge lamp) a total of 3 live wires & their matching neutrals from the main house DB and reroute them to the newly installed inverter DB. I wanted them completely off eskom and that’s where the crap started! he didn’t even do anything himself - his “helper” did all the wiring while he sat on his ass! the only thing he did was mount the MUST 3kw inverter and the inverter DB.

The result was the earth leakage in the new inverter DB would trip every time the inverter switched over to eskom power, I had to reset the EL manually everytime we tested it - kind of defeats the purpose of an automatic switchover feature. I requested he come back fix the problem, but he never returned and I never paid him except for materials up front.

roll on a few months later and growing tired of having to get out of bed late at night to reset the EL after loadshedding, I got another “qualified” electrician to come and fault find the problem - this one was bragging about his skill and knowledge of inverter installations and he knew “exactly” what the problem was?

I had by that time found out through various solar forums that you need a clean direct - no EL power supply to the inverter, so his brief was to run a clean power supply, bypassing the main house DB EL to the inverter AC input and also to install a 2 pole “DC” disconnect for my 24vdc 105amp battery supply cables to the inverter. He showed up with a 16amp AC 2 pole CB from brights? After he pulled a clean power supply through to the inverter AC input the EL problem still existed?!! paid him for materials (except the 16amp AC CB) and never heard from him again.

So what was the chances of hiring another “qualified” professional electrician that can’t fix the problem - third time lucky I thought, this time after carefully explaining to him the problem on the phone and warning him if he can’t find & fix the problem - I’m not paying him a cent! He repeatedly reassured me he will fix it within an hour or no charge.

15min later he was knocking on my door. Very pleasant chap - ex Zimbabwean - fully kitted out with tool belt with all electrical instruments, ironically with both previous electricians I had to lend them extension leads / ladder & torch etc. first thing he did was to remove ALL appliances from wall plugs and he checked every wall plug for polarity, or something like that - all plugs were correct except my bedroom wall plug that seem to have an earth wire problem.

He then inspected the newly installed “clean” power supply to the inverter and showed me why my El problem still existed. Seems the last “qualified” electrician had wired it wrong!! Once he corrected the wiring - and actually bypassed the main DB EL this time, the inverter worked like charm and is still working perfectly, so much so that I don’t even notice when the power goes off or back on again. He also cleaned up the wiring in the new inverter DB, apparently coiling up excess wire is a no no!?

Then a few weeks back another problem reared it’s ugly head - all of a sudden after many years working perfectly, my washing machine & tumble dryer starts triping the garage EL?

thanks to your post above I think I know the problem now - both machines have one of those ELLIES surge protectors on their individual main power supply. I did this years ago as I lost the MB on the brand new washing machine due to eskom supplying crappy power and a new MB from Defy costs R3500! thank gard for guarantees - I just had to pay for the call out. I have since had a surge protector added to the main house DB so I guess I don’t need the ELLIES anymore.

I will remove them and see if the EL trips again - if they do I’ll replace the EL in the garage DB and see if that solves the problem.

thanks for the post.

Adding to this.

First electrician, after explaining to him and his helper, when fitting the double pole changeover switches, remove both neutral AND live. The helper did not understand fully.

After 4 attempts to switch on, my then 48v APC UPS lost its charger, uneconomical to repair.

Thank sparks for that APC, as it sacrificed itself for all the finer electronics connected to it like routers, PC’s, TV’s etc. If there was no APC, the losses would have been substantially more.

Second round, Plonkster and I learned that the older Multuplus II inverters were extremely sensitive to Surge arrestor plugs. When Eskom comes back on, 2nd DB’s earth leakage trips.

After removing all of them, although better, less tripping, the problem still persisted.

So found new sparkies who have never installed a Victron grid-tied system, we will do this together, came around to get the system properly commissioned for SSEG registration.

After doing the test as per the forms, turned out the earth from the street was faulty al these years, actually never properly working since the house was built. After installing a new earth spike, costs that were unforeseen, the tripping problem was at final last resolved.

Sofar this thread can be summed up in: Removed all surge arrestors everywhere. Problem persists, check each plug / light circuit for Incorrect wiring. And run the SSEG commissioning tests as per the CoCT form.

Oh I’ve had this problem twice now.

The first thing to understand is that a small amount of “standing loss” is normal. There is supposed to be a few milliamps going to earth. Some of it is just due to the fact that no insulation is perfect: A couple microamps will find its way to earth even if everything is perfect. And some of it is due to EMI filters and surge arrestors. EMI filters are way worse. The average al-cheapo surge arrestor consists of a triad of MOVs (metal oxide varistors). These things have capacitances in the low picofarrad, and they pass way below 1mA.

But some surge arrestors and EMI filters can pass several milliamps. And especially those with the neon lamps in the plugs that indicates whether everything is fine… those leak a LOT! Cut that crap off and just put on a normal plug!

In my previous house, the trouble was transients. The standing loss itself was not too bad, but it would spike over 20mA for a split second when the inverter was testing its bonding relay. The result is that every time the power comes back after an outage, the RCD trips. Very very frustrating. I fixed it by fitting a transient resistant RCD. Cost me 4k.

In the new house, I had no transient issues. I also learned that the CBI earth leakages are much more resistant to transients than many of its competitors. Nevertheless, I had a standing loss of 13mA.

The rules says that a 30mA RCD MAY trip at 15mA, and MUST trip at 30mA. A good RCD therefore starts to nuisance trip around 15-20mA. At 13mA, it meant any sort of disturbance would push me over.

I bought a new laser printer. As you might expect, that has a SMPS, and therefore some kind of EMI filtering. I had to leave the printer unplugged when not in use to prevent nuisance tripping.

I eventually fixed the problem by splitting my essential circuits across two RCDs. The biggest culprit was in the kitchen. My Siemens coffee maker leaks a whole 3mA.

That is just sacrilege, you have to get rid of it right now, throw it out … I’ll come be around tomorrow at 10am and pick it up …

Very useful thread. I’ve had my share of this in the past and it drove me nuts.

I eventually (after months) traced it to a faulty PSU for an old LG monitor that I had, plugged into a particular multiplug. As soon as I threw switched on the screen it tripped. It had gotten progressively worse. After I threw that bastard out all was well.

After Jaco put in my system I had a couple of good months, but at some point the same started happening. At leat at this point the DB was split into essentials and non-essentials and only essentials tripped. Eventually traced it to a faulty, soon-to-go oven element. Replaced it and all was well.

Even a laptop charger does this. Took me weeks to find the problem. The inverter part somehow got stuffed. In any wall socket I plugged it in, earth leakage would trip. Actually stumbled on the problem by accident.

Other then that, never had any such issues but this thread is of great value to search out and destroy potential future issues.

One issue with this is that it is so hard for the average home user to test, since most of them do not have the test equipment. While you can do a lot by trial and error, it is a lot harder when the problem is caused by a cumulative addition of appliances. You may well conclude that the problem is appliance X, but meanwhile appliance X just added the last 2mA on top of appliances A, B, C, etc…

It is stupid how handicapped you can be without the test equipment. Recently I repaired a microwave oven. They show you on youtube how to diagnose it. You measure the heater element of the magnetron, the windings of the transformer, the high voltage fuse, and so on and so forth. But the tricky part is the high voltage diode (quite an ingenuous setup, using a diode to make a voltage doubler circuit). The howtos tell you to use the highest range on your digital multi meter. I can tell you that this doesn’t really work. The best tool for testing the HV diode of a microwave oven is an insulation tester. You cannot properly test it with the low voltage a DMM uses…

(And yes… that turned out to be the issue with mine. It blew the HV fuse because the HV diode had gone faulty, and of course that was the last thing I suspected…).

Also tried the microwave oven fix last year with YouTube guiding me. All good from checking door sensors and other small stuff until it is diode time yes. My cheapish multimeter was of no use there.

Turned out to be the magnetron (which at least I correctly diagnosed) and a transformer part if memory serves - had to take it in because couldn’t sort it myself.

The saying goes, “If you ain’t got the right tools, don’t start the job” - words I seldom live by lol.

Oh yes, and you need to know how the tools / equipment work.

There is a point where it is just easier to buy a new one, especially of the old one has a bit of wear and/or rust on it. This is actually precisely what I did. When it stopped working, I went to a local appliance store and bought a new one. The main reason: The kitchen is transitioning from White to Silver. The second reason: We’re furnishing the flats in the backyard to turn them into AirBnBs (yeah yeah I know… COVID… not much else to do with them), and I was going to need another Microwave anyway.

Also slowly but surely busy with this process. About 1/3rd there. Painfully slow, waiting on utility bill savings…hahahahaha

At least one thing I know for sure that I beat you on fair and square!

This was an infomative read. Thanks @JacoDeJongh My recent experience however was a little different. As i recently installed an inverter and split my loads into a essential and non essential load DBs. All of the equipment in my new non essential DB being brand new and the non essential loads moved to be powered from there. Finished the install. Turned the power on and had immediate earth leakage tripping. Turned off all the loads and it would be fine. As this DB powers the high load items in my house, geyser, oven, we checked wiring and tried again. Then issue was still there. So disconnected all loads and wires a spare plug to the DB for testing. And low and behold it would trip with any load, 700w from the grinder, 20w frok an LED globe. It was returned to the supplier the next day. They tested it and deemed it faulty, swapping it out for another new unit. No issues on the “new new” earth leakage.

Yes C.Potgieter, this is where a R180 plug/EL tester is worth the money over and over. When I di COC inspections I find faulty E/L units fairly often.

Had a bit of a panic attack late yesterday afternoon.

As per the picture, I have this blue light in my db showing that the grid is present.

So I walk past this old tablet that is permanently on and showing the VRM portal and I notice the big red horizontal bar stating grid lost… and I off course immediately glance in the direction of the DB to confirm… but wait, the blue light is on!!!

So panic sets in, as this is around 18h00 and the wife is merrily blasting away on the air fryer and microwave etc, as this is her time to do stuff like that. Glance back towards the tablet to see that the batteries is already down to 94% in less than 20 minutes and gooing those amps!

Run around like an afkop hoender trying to find the problem, looking at all three of the db’s in the house and running to the inverter in the garage which is busy inverting and showing there is no grid input but I cant find the problem.

Shout to the wife to switch all appliances of and I get ready to switch us back to Eskom with the changeover switch installed at the critical load db.

Now during this panic (because you know, my batteries got hurt now and my inverter is probably stuffed as well) I at least recall Plonkster stating that it is best to first switch everything off by sommer testing the earth leakage which is also at the changeover switch.

Remember him saying that those Hager breakers was not really designed to change over directly on full load so trip everything rather.

And then it dawned on me. Earth leakage…

Why I didn’t bother to look there, or even consider it at the time, is because that thing had tripped only once or twice in the entire 6 years we’ve been living in the house. And because you can barely see it against the black background.

Panic is an ugly thing people!

Mamparra!!!

Now if you had the inverter supplied from before the RCD, this sort of thing would not happen. You are allowed to do that, since you are not feeding sockets with it, and the inverter isn’t fitted in a place where kids can get to it (right?). Although in my own home, I have a 300mA RCBO in front of the inverter, so I still get fault protection for gross leakage currents, and it also serves as overcurrent protection at the same time.

RCD? Residual current device is my best guess. What is this? Oh this is the earth leakage?

No the inverter is in the garage which is apart from the house. No kid gets near my garage!