Electrical Protection
This is no less of an importance to every industrial system, as a fault not only may wreck the machinery and systems concerned, but may endanger the lives of personnel. The protection devices learning of which almost so decreases the chances of these difficulties occurring that it permits the system to work for very much longer periods without the overt action of supervising aids. Let us now see something of the more familiar of the electric protection devices encountered in industrial systems.
Fuses
A simple electrical protection device still in use in production, indeed even in commerce, is that of the fuse. A thin bar of wire takes the current when it is being ‘over’ loaded, but fuses if too great a current passes through in normal operation thus break (and interrupt) the circuit. They are relatively cheap and easy to store and are therefore afforded, to a fair extent, protection by large numbers of devices. Main features of fuses.
Overload Protection – The protecting device will interrupt the circuit if the limit of current is exceeded.Speed – fuses come into action quite satisfactorily very rapidly indeed that the damaging action of a damaging current may come first in a series of “taking scenes” to the switches which we are to operate to secure protection for the equipment, Not a reuseable device – when the fuse blows the protection device is condemned.Uses of fuses would have to include all devices often of quite low voltage for use in industrial and commercial equipment, from motors to power distribution.
1980 – Current Resettable Fuses – Fast-Paced, Economical Reboot
Expanding on a theme of protecting our devices, let’s now add some “fun” to our devices with a current-resettable fuse!These “resettable” fuses reset after you stop the flow of excessive current, which is super handy! Plus, you could cut down on costs on industrial systems since you don’t have to worry about replacing fuse!
How does it work, I hear you ask? Well, say current is flowing through that fuse of yours and the level rises,. That current level creates enough heat to melt the fuse filament. So far, so good. The differences come when that heat dissipates. Do the high-tech thing and touch it with your finger. Ta da! You reset it by allowing the fuse a moment to cool and it is working again!
These handy fuses are used for many situations, such as motor starters, industrial equipment safety systems and whenever frequent resetting occurs.Circuit Breakers – Take a Break
Current-sensitive circuit breakers do just what they say they do: trip out before a fault occurs in the electrical system. Why is this handy? For one thing, you do not need to worry about replacing, “tripping out” fuses, just flip a switch and keep the electronic device alive and happy in all sorts of conditions!Probably the ones we’re most familiar with are thermal circuit breakers that break the circuit when there’s too much heat, that is too much current: an overload! The second are magnetic circuit breakers which use an electromagnet action against a switch. Where can we find them amongst us? Power distribution panel, electrical panel, and of course the big fellows still in industrial systems where failure of electronic equipment could cost plenty.
Surge protectors – Shoosh Away the Spikes
Surge protectors do just that; protect the device from “spikes” or power surges that can come from a lightning strike, “surging” of the power lines turning on and off, etc. How do they do this? They “lock down” the voltage and re-route? Are they handy? You bet! Every single device plugged into our outlets is protected by them, and businesses, of course, use them widely, protecting everything from essentially very sensitive microprocessors in the communication networks to as tough HVAC units.Overload Relays: Preventing Motors from Burning Out
Overload relays are electrical protection devices that protect the motor from pain in case of prolonged overcurrent or overload.These motors are used in big heavy industry, and the load relay saves them from burning up.
How do they work?
Continuous Current
As the current is drawn it is monitored and if it goes over the rated value it trips and breaks the motors connection with the supply, saving it from burning up. Where are the overload relays used?
Industries utilising big machines motor driven, like HVAC, pumps, conveyors, etc.Yup necessary that so the chap don’t go and kill himself out in the field!
Residual current devices (RCDs): For human safety
Residual current devices (or circuit-breaker) are safety devices protecting you from losing it all by sensing a leak of current. With an electrical fault should it go unnoticed, this leakage of current could lead to you joining the late priority list of madmen. The RCD makes sure that it disconnects the supply before anyone gets hurt.
How do RCDs work?
Sensing Leakage
Basically the device senses live and neutral being different. If it senses a leakage current e.g. owing to faulty insulation it disconnects the circuit immediately.
Immediate Disconnect
Should a leakage be sensed it cuts off the circuit in a fraction of a second to make you less likely to be electrocuted or injured. contact, e.g. on building sites, industrial locations, electrical substations, etc.
Lightning Protection Systems: protecting the building from lightning strike
Wherever it is possible for dark clouds to precipitate thunderstorms and lightning a lightning protection system is suitably fitted to a building to protect the people and equipment within from the threat of lightning. These are designed to conduct the strike safely to earth whereupon it can be let safely dispersed to ground. This system depends upon lightning rods (air terminals) and upon grounding systems and surge protectors.
Air terminals lightning rods: These captors are positioned so as to render themselves liable to be struck by the bolt, and in so doing offers a path to earth for the strike.
Down Conductors: The lightning is grabbed by the rod, so to speak, and travels by way of the down conductor to earth.
Grounding systems: allow arresting of the bolt in safe fashion in the ground.
Industries where there is risk of lightning strike damaging the sensitive apparatus and operation being jeopardised and indeed destroyed may be afforded protection of lightning protection systems.
7: Silicon carbide (SiC) in electrical protection devices
Silicon carbide (SiC), in form or another and indeed in a different driving age, was in excess of silicon, employed in the manufacture of some electrical protection devices quite some time ago.The hallmarks of the technology are:
Fast thermal conductivity of the devices and proximity voltage levels, and great reliability in use.
The following aspects of protection devices may be SiC.
SiC?MOSFETs (metal-oxide semiconductor field-effect transistors): With speed of protection of the electrical kind of the essence this can provided by means of SiC?MOSFET technology producing often a much higher switching speed and, as silicon devices possess, and surge protection and overload relay device protection devices may well contain SiC.
SiC?diodes: A power conversion system, and high voltage applications using the SiC power diode to further enhance the electrical protection for an industrial system. Ancillary parameters such as electrical performance will ?of course be improved by the incorporation of SiC in these devices and especially help in the safeguarding of delicate sensitive apparatus items. Also the overall efficiency of the whole industrial system may be greatly improved using SiC, particularly involved in harsh environments and high performance, challenging situations in the matters of temperature and voltages.
Conclusion
We sincerely hope that you have enjoyed this very, very brief overview and introduction to just a few of the electrical protection devices in use today, and the way they play their part in the smooth and orderly running of your industrial systems, and protecting your people and equipment. We really have only scratched the surface and the mountain of further electrical protection and control devices in industrial use today could fill a library. But to have some measure of understanding of how the fuses and circuit breakers “really” work and what else may be going on in the sophisticated guards such as surge protectors, and also SiC, will get you ahead in your knowledge and understanding of the workings and performance of the devices. In the future, the incorporation of SiC technology in these devices will provide performance, application, heart start, and value for money.