3 Extreme Conditions that Put Low Voltage Circuit Breaker Reliability at Risk

August 30, 2018 Eric Quesnot

When it comes to protecting people and equipment in low voltage (LV) environments, nothing is more important than having reliable circuit breakers in place. Over time, circuit breaker technology has advanced in many different ways, including becoming more intelligent and more flexible. This has allowed them to increase performance and meet a broader range of applications.

However, in extremely harsh environments, circuit breakers are faced with conditions that are especially challenging. These conditions can cause false trips or other kinds of breaker failures. In this post we’ll have a quick look at some of these situations, and the types of circuit breaker features you should look for to make sure they’re robust enough to survive any hazard. Circuit breakers that operate reliably will keep people and electrical installations protected, while operations run continuously and efficiently.

Extreme vibration risks

There are many applications where circuit breakers face high vibration profiles. This can include wind turbines, marine environments in proximity of thrusters or anchor positioning systems, or installations near emergency generators or power frequency converters.

Most air circuit breakers (ACBs) are required to withstand vibration to category 3M2 of the IEC 60721 standard, which are classed as ‘vibrations of low significance’. But consider the intense environment of a wind turbine, where circuit breakers are installed in the turbine nacelle several dozen meters high, with exposure to high winds and in close vicinity of heavy moving parts and power converters. Circuit breakers can take a real beating in this kind of environment. As wind turbines now supply more than 5% of global electricity demand – in the double-digits in many countries (43% of Denmark’s power comes from wind) – it’s become increasingly critical that every electrical component is exceptionally robust. Circuit breakers chosen for such environments need to be designed to greatly exceed the 3M2 vibration class.

The connectors used inside circuit breakers have often been one of the failure modes under high vibrational stress. Where internal parts are connected, repeated vibration can produce fretting corrosion which can cause false signal transmissions and, in turn, false tripping. Look for circuit breakers with internal ‘flexible’ connector designs that help avoid this problem.

Electromagnetic interference

With digitization spreading throughout all aspects of business, industry, and personal life, it’s important that immunity to electromagnetic disturbances is reinforced in all types of devices, including circuit breakers. Radiated waves from mobile devices like cell phones can potentially cause misoperations, such as false measurements, disturbed data transmissions, and nuisance trips. It’s also important that any activity within a circuit breaker, such as switching powerful currents, isn’t causing emitted disturbances that can affect other devices like analog sensors.

Voltage spikes conducted through the power infrastructure can also interfere with the reliable operation of a circuit breaker. These can come from sources like capacitor bank switching, welding machines, and power converters. Of course, they can also come from lightning strikes, which can damage the breaker’s control unit or other electronics.

These are all good reasons to ensure that you choose a circuit breaker that’s been tested for high immunity to all three dimensions of radiated, emitted, and conducted disturbances.

Intense hot and cold

There are many indoor and outdoor applications where circuit breakers must endure extreme temperatures while maintaining reliable performance. Once again, wind turbines are a good example. Make sure the operating range specification of the breaker will easily cover temperatures expected in such environments.

In addition, consider the rigors of transportation. What is often not considered is that electrical equipment shipped by long sea or air voyages can often experience far greater temperature extremes, not to mention potentially high levels of salt in the atmosphere. So it’s important to choose circuit breakers that will only operate reliably in extreme applications, but also can survive any kind of transport conditions to arrive without their performance being compromised.

The Masterpact™ MTZ smart circuit breaker from Schneider Electric is designed for harsh environments, thanks to many new innovations. It’s the first circuit breaker to reach and exceed the IEC60721 vibration category 3M4 – classed as ‘vibrations of high level’ – raising the bar from 0.5 g to 1 g intensity. This performance is enabled by flexible internal connector designs and solid connections with multilayer gold and nickel coatings.

Masterpact MTZ also offers improved electromagnetic compatibility in all three dimensions defined by the IEC61000-4 standard. It withstands radiated disturbances up to 20 V/m and conducted disturbances up to 4 kV. And Masterpact MTZ is the first circuit breaker to withstand 25 kA and 6 kV surges, protecting it from direct and indirect lightning strikes. It is also rated for a very wide storage and transportation temperature rating of -40 °C to +85 °C, with an operating range of -25 °C to +70 °C.

This has been the sixth post in our series on how the newest smart circuit breakers are helping improve operational efficiency and reliability. To learn more about our circuit breakers, please visit the dedicated website.

The post 3 Extreme Conditions that Put Low Voltage Circuit Breaker Reliability at Risk appeared first on Schneider Electric Blog.

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