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Overcurrent is a destructive fault that can damage small, as well as, large motors, electric devices, and home appliances.

In this article, I will discuss the current increase (overcurrent) and answer the most important questions about it. let’s get started.

what is overcurrent?

Overcurrent refers to an electrical condition in a circuit where the current flowing through the conductors exceeds the rated or designed current-carrying capacity of the components, such as wires, fuses, circuit breakers, and other protective devices.

Overcurrent can occur due to various factors and can have different consequences, including overheating, component damage, fires, or circuit malfunction.

Overcurrent example

A clear overcurrent example is, when a motor with a rated current of 35A, you can find rated current on the motor nameplate, draws 55A for any reason, it can be a mechanical loading as I discussed in the article Motor Overcurrent, this motor is an overcurrent situation.

Another example is if a current of 167A passes through a cable with a current ampacity of 135A, this cable is over the current situation.

In general, any electrical equipment has a rated current, whenever the current exceeds this value, it’s an overcurrent situation.

Overcurrent effects

Uncontrolled electric overcurrent leads to excessive heat generation and can damage or burn equipment.

A circuit wiring overheats when an overcurrent occurs. There is a possibility that the insulation could melt, and fire can break out as a result.

Circuit overload causes the breaker to trip, opening up and shutting off the power supply. The overload could cause the wiring to overheat and melt, causing a short circuit and leading to a house fire.

In addition to the heat loss from increasing current,  the rising current can also:

• Damage the circuit
• Burn resistors and electronic components
• Damage to electric equipment and home appliances
• And even cause fire to break out around the circuit.

What causes overcurrent in a circuit?

How can you prevent over-current?

Electrical circuits have circuit breakers, surge protectors, and electrical fuses to prevent potential disasters.

The concept of preventing a power outage due to an overcurrent is quite straightforward: you should avoid overloading a circuit in the first place.

There are typically separate circuits for each room of the house, with heavy-duty appliances like an electric dryer or oven requiring a separate dedicated line.

In order to prevent your circuits from overcurrent, let us take a look at how you can do it.

Your circuit load should be calculated

For the workplace, never run any power tool or electrical equipment before you check its power rating, and verify the power source is suitable for it.

Only authorized persons are allowed to add new loads to any power source.

All authorized departments should participate when choosing new equipment. For example, when choosing a new pump, electrical and mechanical engineers should cooperate to make sure the pump and the motor ratings are the same, to prevent motor overloading.

For home circuits, the majority of circuits are rated for 15 to 20 amps, and if you understand how much current your lights and appliances use, you can roughly estimate how much current is safe to put in.

It may be necessary to move the light strand to another room if your load is approaching 80% before plugging in the next strand to avoid overcurrent.

• Never use extension cords without asking an authorized electrician.
• Never overload the outlet with a lot of appliances.
• Ask for advice before connecting any new appliance.
• If you buy a new house, hire an authorized electrician to check its circuits and wiring.

Use large appliances with caution

When searching for a location to plug your lights in, it’s a good idea to stay away from spaces that already include a lot of equipment, such as the kitchen.

To make more current available for those priceless decorations, you may disconnect any equipment or devices you don’t intend to use to avoid overcurrent.

Make LED lighting a priority

Investing in LED lights is one method to make your current setup considerably more festive.

LED lights consume significantly less power than conventional bulbs, saving you money on your electricity bill and easing the pressure on your wiring to avoid overcurrent.

Use Protection devices

The built-in defense against overcurrent in your home is the circuit breaker. They are housed in your electrical panels and turn off electricity to particular areas of the structure if they detect erratic electrical currents.

You may protect yourself against short circuits, when necessary, by doing routine circuit breaker maintenance to make sure it is operating correctly.

Why does the current increase when the load increases?

Each load requires its own current, the more connected loads, the higher the current they draw. To explain it to you, suppose the electrical circuit is a pipeline, the loads are faucets, and the more faucets you open the more water you draw.

In the case of electrical Motors

In case we have a motor (the load), this motor requires electric current depending on its power rating.

If the motor starts with no load, it draws a no-load current, it’s smaller than the full-load current.

By increasing the mechanical load, the motor needs to provide more torque to overcome this load, and of course, it will draw more current.

In case of home loads

In case of connecting more loads on home or a building outlet. Electrical loads are typically connected in parallel.

If you have a load raised, it means the added load is connected in parallel with the existing load.

Parallel connections always decrease the equivalent impedance. Therefore, the current increases.

When loads are connected in parallel, each load draws its own currency from the circuit according to the requirements of that load. Therefore, the current increases when the load is increased.

How can I tell if my electrical panel is overloaded?

If your panel main circuit breaker trips, and when you turn it on again it works for a while and then trips again, it’s a clear sign of a possible overloaded panel.

But, keep in mind that there are other reasons for circuit breaker tripping, you can hire an electrician to measure the currents of the panel, check the man circuit breaker rating, and make sure it’s overloaded.

If you know how to use a current clamp, you can measure the current by it, check the circuit breaker rating, and make sure the CB rating is greater than the measured one.

Make sure to switch on all loads during the measuring process, this is the only way to have a clear idea about the panel load.

One more thing, an electrical engineer can calculate the panel loads, check the circuit breaker’s ratings, and make sure it’s not overloaded.

It’s crucial to watch out for clues that your electrical panel could be generating an excessively high level of electricity when you start putting in more and more appliances for any reason.

To assist you in recognizing when this could be happening, we’ve listed a few telling indications.

Panel Overheating, the overheating that might result from excessive current flowing through your breakers or cables is also a sign of an overloaded panel.

In my workplace, we use thermal imaging to check that panels are not overloaded.

What happens when an electric current increases?

When the electric current increases, the following points can happen:

In the case of electric motors

The higher the current, the higher it temperature rise. This temperature increase can cause the motor insulation to fail, and lead to an internal short circuit between windings and complete damage if the protection device fails to trip the circuit.

In the case of home wiring

Excessive current trips the circuit breaker of your home panel. Of course, it will increase the temperature of the wiring, the panel, and the circuit breaker.

If the increased current is caused by an appliance, the appliance will get damaged if the CB fails to trip.

Ready to dive in? Check out my comprehensive article Avoiding Overcurrent Situations: Tips to Keep Your Circuits and Devices Safe now

In the case of electric cables

Cable temperature rise can cause the insulation to get damaged. When the insulation gets damaged, the live phase and the neutral or another phase will get in touch and a short circuit happens.

In the case of an electric generator

The generator will heat up, its winding insulation will melt and a short circuit occur between its phases. Yep, it’s complete damage.

We can say, that an overcurrent could cause the circuit wiring, as well as the electrical equipment to overheat. This could lead to, equipment damage or melting of the insulation and a possible fire.

The heat loss from increasing current can cause damage to the circuit, burn resistors, damage electrical equipment and home appliances, or even cause fire to the surroundings.

Circuits are designed to work with a particular voltage and resistance. If the excessive current flows in a conductor, the results will be very bad if the protection device fails to trip the circuit.

Why does the current increase in temperature?

From a physics point of view

Electric current is the flow of electrons in a conductor. As the current increases, the electron flow will increase.

Due to the increased flow of electrons, the collision of electrons will intensify generating heat energy and power losses. This is why the electric current increases the temperature.

From an electricity point of view,

any conductor has a resistance, when current flows through the conductor it faces its resistance.

From the power equation we have, Power = I² *R, which means that increasing ‘I’ and the ‘R’ increases the power loss in the shape of heat and raises the temperature.

The temperature rise beyond the allowed limits on any device is directly linked to the fact that you have exceeded power consumption higher than the rated value.

Any equipment is designed to meet a specific power consumption, if the limit is exceeded its power, gets heated.

ِAny electric current value causes produce temperature, the more current the higher the temperature rise.

Starting from the equipment-rated current to the overcurrent and ending at the short circuit current. All these currents produce heat, and the value of the temperature rise differs from one currency to another. 

Read also my article about Electric transformer temperature rise.  and the other one, Motor temperature rise causes and limits.

Why does an increase in current increase power losses?

Power loss is a result of the conductor resistance that the current faces while passing through the conductor.

As you can see, from the below power loss equation, the power is proportional to the square of the current. So, if the current increases, the power losses will increase much faster.

As we know, Power = I² × R, This means, the higher the current the higher energy loss in the conductor in the form of heat. As I mentioned above.

The increase of power loss in the conductor increases the conductor’s temperature. We don’t have an ideal conductor with zero resistance, if we do its power loss will be zero.

What is Overcurrent Protection?

Over-current protection importance

In order to keep yourself and others safe from many risky situations, overcurrent protection is important.

Every electric circuit must have circuit overcurrent protection. If the current levels of an electric circuit exceed the safe limits for which they were built, the circuit may be harmed or even destroyed.

Circuit wires may become too hot if there is an overcurrent. In turn, fire and insulation melting might result due to this situation.

There may be serious consequences if a circuit is not equipped with overcurrent protection. An electrical shock, fire, or electrocution can result from overcurrent, which can destroy unprotected electronic devices and cause human injury and fatality.

The purpose of an overcurrent protection device is to protect against dangerously high temperatures in conductors or their insulation. It is crucial to match the conductor size and current rating of the protection device.

We can say, that overcurrent protection is essential because it protects humans and equipment as well against destructive and fatal accidents.

Is current protection and surge protection the same?

No, it’s different; overcurrent protection protects the excessive current flow in the circuit, and surge protection protects against excessive voltage or spikes of voltage to the circuit.

Overcurrent protection is the protection against excessive currents beyond the acceptable current rating of the equipment. It generally operates instantly.

Magnetic circuit breakers, fuses, and overcurrent relays commonly provide overcurrent protection.

High and low-voltage power distribution systems, as well as control systems, frequently incorporate overcurrent protectors.

On the other hand, Surge protection protects equipment against power surges and voltage spikes while blocking voltage over a safe threshold.

When a threshold is an overrated voltage, a surge protector shorts to ground voltage or blocks the voltage.

Low-voltage power distribution systems frequently utilize SPD, sometimes referred to as surge protector, lightning protector, and lightning arrester, as a lightning protection device.

It is often linked to the line in parallel or series to discharge the wave.

Difference Between Overcurrent and Overload Protection

Overloading equipment causes it to draw an overcurrent. We, electrical engineers, usually use the word overload in case the equipment gets more load, electrical or mechanical, than it’s designed to handle.

For example, a motor is overloaded means its mechanical load is greater than the motor-rated power so, it draws an overcurrent.

Another example is when a cable is overloaded, it means the cable load, electrical load, draws current greater than the cable current carrying capacity, so the cable has over current passing through it.

Overcurrent protection is the protection against excessive currents beyond the acceptable designed current rating of equipment or an electric device. Short circuits, arc faults,s, and earth faults are overcurrent types.

On the other hand, overload protection is protection against overloading equipment that causes it to face an overcurrent situation, and would cause the equipment to overheat.

A well-designed circuit and periodical inspection of loads can help prevent overload

Hence, an overload is also some kind of overcurrent. Slow-acting fuses and overload relays are commonly used for overload protection devices.

A thermal-magnetic CB as well as the dual element fuse has both thermal and magnetic elements which means that it could provide both overcurrent and overload protection.

How does overcurrent protection work?

According to the circuit current rating of equipment or circuit, overcurrent protection devices have a current rating.

In case of any fault, when the circuit current exceeds the rating current of protection devices, it cuts the circuit’s supply, by the thermal or magnetic effect of the overcurrent. As you know, current has both thermal effects, and if the current passes through a coil it will produce a magnetic effect.

The thermal effect can melt a fuse to protect the circuit and can trigger the mechanical mechanism of a circuit breaker to trip the circuit.

The magnetic effect also can trigger the circuit breaker faster than the thermal effect. By using this working principle, overcurrent protection devices protect equipment or circuits.

The thermal effect is used for overload protection, lower values of overcurrent, while the magnetic effect, the faster, is used for protection against the short circuit over currents.

Fuse and circuit breakers are overcurrent protection devices that contain time/current characteristics (TCC) that specify how long it takes to clear the fault for a specific value of fault current. The higher the overcurrent value, the faster the tripping time of the circuit breaker.

The fuse’s metal strip or wire melts when too much current flows across it, cutting off the current flow. Fuses are sacrificial components, which means an overcurrent destroys them.

On the other hand, circuit breakers turn off when they face any fault or a short circuit, unlike fuses, which melt to break the circuit. Circuit breakers can therefore be reused.

Can overcurrent damage an overcurrent protection device?

Yes, overcurrent can potentially damage an overcurrent protection device, such as a fuse or a circuit breaker, if the device is subjected to current levels exceeding its rated capacity for an extended period.

While these protection devices are designed to withstand short-term overcurrent conditions and perform their protective function, they are not invulnerable and can be damaged under certain circumstances:

1. Sustained Overloads: If a circuit experiences a sustained overload, where the current exceeds the device’s rated capacity for an extended period, it can cause overheating of the protection device. Prolonged overheating may damage the device, affecting its ability to function properly in the future. For example, a fuse may blow or a circuit breaker may trip due to overheating.
2. Fault Currents: In the case of a short circuit or a severe fault current event, the magnitude of the current can be extremely high. While protection devices are designed to handle these situations and quickly interrupt the fault current, the stress from such high current levels can potentially damage the internal components of the device.
3. Inadequate Device Rating: Using a protection device with an inadequate current rating for the circuit it is intended to protect can result in the device being damaged during an overcurrent event. For instance, if a lower-rated fuse or circuit breaker is used in a circuit with a consistently high current load, it may trip or blow repeatedly, leading to damage.
4. Device Wear and Tear: Like any mechanical or electrical component, overcurrent protection devices can experience wear and tear over time. Frequent tripping, exposure to adverse environmental conditions, or improper handling can contribute to device degradation and reduce their effectiveness.

It’s essential to select protection devices with appropriate current ratings for the circuits they are intended to protect.

Regular maintenance and inspection of protection devices are also important to ensure their continued reliability and performance.

Damaged or malfunctioning protection devices should be replaced promptly to maintain electrical safety and prevent potential hazards.

Can over-current damage a circuit breaker?

Yes, overcurrent can potentially damage a circuit breaker, but circuit breakers are designed to withstand and interrupt overcurrent conditions within their specified ratings.

However, there are limits to their capacity, and extreme overcurrent events or sustained overloads can lead to damage or failure.

Here are some considerations regarding overcurrent and circuit breaker damage:

To prevent damage to circuit breakers and ensure their reliable operation, it’s important to adhere to the following practices:

• Select circuit breakers with appropriate current ratings for the circuits they protect.
• Avoid overloading circuits beyond their designed capacity.
• Properly maintain and inspect circuit breakers to identify signs of wear or damage.
• Replace damaged or malfunctioning circuit breakers promptly.
• Ensure that circuit breakers are operated within their specified voltage and current ranges.

While circuit breakers are designed to provide overcurrent protection and are more robust than fuses, they are not immune to damage under extreme or improper operating conditions.

Regular maintenance and adherence to electrical safety standards are essential to maintain the integrity and reliability of circuit breakers in electrical systems.

For more information about Why circuit breakers go bad, read my article.

What happens if an over-current protection device is oversized?

If an over-current protection device (such as a fuse or circuit breaker) is oversized for the circuit it is meant to protect, it can lead to several potential issues and compromises in electrical safety and equipment protection. Here are some consequences of using an over-sized protection device:

1. Reduced Protection: The primary purpose of an over-current protection device is to safeguard the circuit and connected equipment from excessive current levels, which can cause overheating, fires, and equipment damage. When an oversized device is used, it may not trip or open the circuit as intended when overcurrent conditions occur. This means that the circuit and equipment may not be adequately protected from short circuits, overloads, or faults.
2. Increased Fault Energy: An oversized protection device can allow excessive fault currents to flow without tripping or interrupting the circuit. This can result in higher fault energy levels in the event of a short circuit, increasing the potential for electrical arc flash incidents and equipment damage.
3. Equipment Damage: Oversizing protection devices can lead to damage to downstream equipment. For example, if a circuit breaker with a much higher current rating than the circuit’s load capacity is used, the equipment connected to the circuit may not be adequately protected from overcurrents. This can lead to overheating and damage to the equipment, including motors, transformers, and wires.
4. Inefficiency: Oversized protection devices can be less efficient in terms of energy consumption. They may allow unnecessarily high currents to flow for longer periods before tripping, leading to increased energy losses and potentially higher operating costs.
5. Violation of Electrical Codes and Standards: Oversizing protection devices can lead to non-compliance with electrical codes and standards. Electrical codes specify the correct sizing and selection of protection devices based on the characteristics of the circuit and equipment being protected. Using an over-sized device may result in non-compliance and regulatory violations.
6. Misleading Fault Analysis: Oversized protection devices can make it challenging to identify and analyze faults or overcurrent events within a circuit. Since the device does not operate as expected under fault conditions, troubleshooting and diagnosing electrical issues can become more complex.

To ensure proper electrical safety and equipment protection, it is crucial to select and install protection devices with current ratings that match the circuit’s load and characteristics.

The selection of protection devices should be in accordance with electrical codes and standards. Additionally, regular maintenance and testing of protection devices are essential to verify their proper operation and compliance with safety requirements.

Oversized protection devices should be replaced with appropriately sized ones to maintain electrical safety and equipment protection.

What if an overcurrent protective device opens slower than expected?

If an overcurrent protective device, such as a circuit breaker or a fuse, opens slower than expected, it can have several implications and potential consequences, depending on the specific circumstances and the nature of the overcurrent condition:

1. Equipment Damage: Slower tripping of the protective device can allow excessive current to flow through the circuit for a longer duration. This prolonged overcurrent can result in overheating of wiring, equipment, and components, potentially causing damage or degradation.
2. Fire Hazard: Overcurrents can generate heat, and if the protective device does not trip promptly, the prolonged overcurrent can increase the risk of electrical fires. Electrical components and insulation may become damaged due to excessive heat.
3. Safety Hazards: Slower tripping of protective devices can pose safety hazards to individuals in the vicinity. For example, if a fault condition occurs and the circuit breaker does not trip quickly, it may expose people to electrical shock hazards.
4. Compromised Protection: The primary purpose of overcurrent protection is to prevent electrical circuits and equipment from being subjected to current levels that exceed their designed capacity. When a protective device opens slower than expected, it compromises the protection provided by that device.

To address the situation when an overcurrent protective device is not operating as expected, here are some steps to consider:

1. Investigation: Identify the cause of the slow operation. It could be due to a malfunctioning protective device, loose connections, or other issues within the electrical circuit.
2. Immediate Shutdown: If there is an ongoing overcurrent condition and the protective device is not responding as expected, it is essential to de-energize the circuit immediately to prevent further damage or hazards. Disconnect power at the main switch or circuit breaker panel if necessary.
3. Professional Inspection: Seek the assistance of a qualified electrician or technician to inspect the protective device, the circuit, and any associated equipment. They can diagnose the issue and recommend appropriate corrective actions, such as repairing or replacing the protective device.
4. Maintenance and Testing: Regularly maintain and test protective devices to ensure they operate within their specified response times. Periodic testing and maintenance can help identify potential issues before they become critical.
5. Replacement: If the protective device is found to be faulty or not operating correctly, it should be replaced promptly with a properly rated and functioning device to restore adequate protection.

Ensuring that overcurrent protective devices operate correctly and promptly is crucial for electrical safety and equipment protection.

Any signs of malfunction or unexpected behavior should be addressed promptly to prevent potential hazards and equipment damage.

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