Overcurrent Protection and Why It is Important
Be it low voltage, or an industrial lightning protection getting up close and personal with high voltage, overcurrent protection is one of the most important arrangements to get right. Today we break down the basics of overcurrent protection and its importance to prevent system failure and protect both people and equipment from hazardous situations!
What is Overcurrent Protection?
Simply put, over current protection uses devices that are designed to interrupt the flow of current in a circuit automatically when the current becomes greater than the rated current value due to a short circuit, overload, or fault in the system. Overcurrent proection is found in all electrical installations; from our residential systems to a national grid!
The Importance of Overcurrent Protection
Left un-interrupted, overcurrent events can go a nasty number on electrical systems – overheating, equipment failure, and possibly fires! The overcurrent protection device will respond by disconnection before damage can occur. Not just improving the safety of installations in the immediate sense, these devices can also help extend the life of electrical equipment, minimising maintenance issues and saving cost on repairs.
Types of Overcurrent Protection Devices
There are different types of overcurrent protection devices,Fuses.These consist of fine wires or strips of metal, which melt if the current flowing through them gets too great; if any portion of the circuit is overloaded these wires melt, and the circuit is broken and remains so. For work at a low voltage, and where it is desired to cut off the electric current very rapidly should it rise above a certain value, such fuses are present. The fuse has the following advantages, and disadvantages:
Advantages: Its construction is simple; its action is practically instantaneous.
Disadvantages: A fuse when once blown cannot by any means be used again, but must be replaced.
- Circuit Breakers.
Description of Circuits
The fuse just described is extremely simple; it is quite evident that in some cases it would be very inconvenient to have to stop work and replace the fuse every time this occurred. The principle of circuit breakers is to have means for making the circuit noncontinuous. This is done in two ways:
Thermal circuit breaker. In this a heat is generated by the excessive current; in such an idea the bimettalic strip becomes heated and bending starts up the mechanism in such a way that the circuit opens up,
A magnetic circuit breaker uses an electromagnet, and becomes active when the current flowing in it becomes of a certain value; another action of this magnet is to trip the breaker, i.e., open the circuit.
Advantages: This kind of fuse cannot by any means be ruptured; it may be used over and over again if desired.Disadvantages. The circuit is not broken quite so instantaneously. It does however protect very well in the case of an overload.
Overload Relays. As their name suggests, overload relays are used for protecting motors. They sense the current being drawn to motors and trip the circuit if it is too much and for too long an amount of time. These are often used in conjunction with circuit breakers to give extra protection from overloads.
Pros
Protect motors from long term damage
Easily adjustable for various types
Cons
Only used in regard to specific use motors
Must be very carefully adjusted or you are going to nuisance trip
How to Choose the Right Overcurrent Protection Device Choosing the right overcurrent protection for your system is depend on several things, including how much current is flowing, what kind of load is applied to the circuit, voltage level, and what kind of fault conditions could arise:
Current rating. Make sure the rated protection can take the maximum current that is meant to run through it and surge the circuit.
Response time. Depending on the situation, response time might be very important, as in industrial plants and electrical grids for example.
Type of fault. Different protection devices cope better with different types of fault.Usually, shortcircuit must be managed more quickly than overload, which may lend itself to a slower acting (delayed) device.
Reusability. You may want your protection device to be reusable. If that is so, you will undoubtedly be looking at circuit breakers or overload relays.
Common Uses of Overcurrent Protection
Overcurrent protection is very much a part of some industries from the power distribution to the manufacturing plant itself to the renewables being distributed.
Industrial Equipment Protection
Large machinery and electrical used in industrial environments are particularly vulnerable to the effects of overcurrent. Protecting these large electrical systems with overcurrent devices such as fuses and circuit breakers is critical.
Residential Electric Systems
Although the residential system is typically dealing with much much smaller currents overall than other systems, the same basic principles apply, and overcurrent protection is necessary to help guard against an overloaded appliance or wiring. Fuses and breakers in the appliance or in circuit panel help protect against overload occurrences and short circuit, typically of the kind that could become dangerous or possibly cause a fire.
Power Distribution
Power distribution systems supplying entire cities and towns are heavily reliant on overcurrent equipment. Switchgear, transformers, and protection relays defend the distribution system from faults detected, and from overloading of any kind from getting out of hand or causing widespread damage.
Electric Vehicles (EVs)
With EV and popularity on the rise, protection is important in the charging systems and battery management, keeping them safe in the event of overcurrent. Overload relays and fuses are necessary in EV charging stations and battery packs from being damaged by drawing too much current.
Overcurrent Protection in Silicon Carbide (SiC) Systems
For sophisticated applications such as power electronics with silicon carbide (SiC), overcurrent is important all over again. SiC devices such as SiC MOSFETs and diodes are use for high-performance, high-efficiency systems and because of the greater temperatures and voltages that they’re reasonably intended to operate at, these devices require some extra care to protect them from overload. SiC devices take advantage of bigger thermal conductivity and faster switch speed to make the system better, but precision and responsiveness of overcurrent protection is all the more crucial of the same to ensure reliability and avoid damage by careless application.
