Intelligent circuit breaker

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Rob McCaskie, product manager for power circuit breakers at ABB Low Voltage Products, explains how the new generation Emax 2 circuit breaker is also a power manager.

Maintaining close control of electric power consumption is an increasingly important element of building services, both in order to reduce the energy costs related to consumption and to improve environmental sustainability. Automatic control of the building loads, based on the power they demand, is an optimum solution for effective cost reduction. The aim of these control systems is to moderate the demand for electric energy by avoiding non-coordinated operation of the loads.

For example, during a hot summer day, building air conditioning systems might start working all at the same time, resulting in peaks in consumption and possible problems with energy supply. The building operator may need to increase the contracted level of power with consequent increase of fixed costs. And in the worst cases, to prevent the overload protection from tripping, the plant must be over-dimensioned.

A traditional dedicated load control system normally requires the installation of a large number of dedicated control devices, with increasing costs and complexity as the number of loads increases.

Whereas low voltage circuit breakers have traditionally switched loads, new communication standards such as IEC 61850 have created a framework for smart grid communication that includes large users of low voltage power such as industrial and commercial buildings and ships.

This has opened up the potential for a new generation of low voltage circuit breaker that not only switches loads but manages power consumption. That was the reason that ABB developed a new generation low voltage circuit breaker called Emax 2 that has taken a major step forward in the principles of control, connectivity, performance and ease of use.

Control
Control over loads is a high priority for large consumers of low voltage power. By prioritising the switching off and on of loads, an operator can limit the power consumption to a maximum level and limit energy bills and reduce the risk of blackout.

The conventional method for switchboard control is to equip circuit breakers with complex communication systems and programme the supervision software. However, expectations are changing and today’s operators want flexibility at low cost. The key is to include monitoring, instrumentation and communication in a single unit, even down to a power supply that can be connected to any AC or DC voltage. By removing external and add-on units, the cost, engineering and space required for these are eliminated.

Equipment with touch screen technology and web-based applications can be accessed locally or via smartphones, tablets or desktop computers – all without the need for specific programming. This means that a modern circuit breaker provides an economic way for a small plant to increase its monitoring capabilities or for a large plant to simplify local supervision and maintenance. 
By using an inbuilt algorithm that monitors power usage over time and determines the average, a smart circuit breaker will control a built-in load list and limit the power consumption to a maximum level set by the operator. This means that the breaker will automatically take low priority loads offline, saving utility bills without the need for additional monitoring systems.
And by building measurement of voltage, current, power, energy and power quality, an operator can identify the root cause of increased power outages or reduced service life of cables and capacitors without installing additional instrumentation.

Connectivity
Since the introduction of IEC 61850 for smart grids, operators have been upgrading their installations on a piecemeal basis to avoid the cost and disruption of a step change. Circuit breakers introduced today now need to be compatible with the existing legacy system at the facility where they will be installed but also with the new standard, so it’s vital that new technology is compatible with the seven most popular global communication protocols.

Another aspect of connectivity is the compatibility of a new unit with the existing infrastructure. Common bus configurations can be vertical or horizontal with anything from one to four bus runs and operators like the flexibility of choosing the location of the neutral position. Minimising the length of copper bus is an important consideration. As a result, the new circuit breaker is designed to fit the most common bus configurations for simplicity, its terminals can be rotated from horizontal to vertical in the field for maximum flexibility and each terminal is sized to fit the standard width of bus bar for that current. Plus, it’s possible to choose the neutral position and the largest model is available with a choice of neutral conductor sizes to allow for the correct sizing of bus bar and the opportunity to reduce construction costs.

At the rear of the units, the terminals can be rotated from horizontal to vertical in the field for maximum flexibility, but they have been designed to fit the most common bus configurations for simplicity. Each terminal is dimensioned to fit the standard width of bus bar for that current. One, two or three terminal stabs ensure easy connection of up to four bus runs, ensuring easy connection and installation while minimizing bus bar stock.

Performance
A challenge in many installations is how to deliver high performance while using limited space and materials. ABB’s new Emax 2 has four frame sizes, each of which is only as wide as required by its current rating. This gives operators the opportunity to optimise their use of space and materials. Rated at 1,600 A to 6,300 A, the breakers’ design and use of quality materials allows for high performance in a small size from 210 mm to 762 mm wide.

With increased current-carrying capacity in a small size, the units overcome the potential issue of overheating with a built-in module that activates cooling fans.
By using new generation Rogowski sensors, the circuit breaker measures performance to high precision to 1 percent accuracy for current, 0.5 percent for voltage and 2 percent of power and energy.

Ease of use
The smartphone and mobile communications revolution has transformed expectations of control systems. Today, operators can purchase web-operated security systems that send audio visual alerts when movement is detected. Tablets are now out-selling laptops and new ways of working are seeing industrial touch screens introduced across many industries, including oil and gas, utilities and elsewhere.

By introducing touch screen technology and web-based apps that allow intuitive access to information and programming in ten languages that enable control from remote locations, the new generation of control technology is simpler to use and more intuitive than previous generations.

Safety is a primary consideration too and by creating a circuit breaker that keeps personnel separate from the operating parts and is lockable to prevent unwanted operation during maintenance, ABB has ensured that the Emax 2 units are inherently safe. The withdrawable version even has guide rails for simple and accurate positioning. And building on the safety aspects, the breaker is significantly smaller and lighter than previous models, which means simpler handling during installation and maintenance. For example, a unit rated for an uninterrupted current of 1,250 A has weight of 32 kg versus around 60 kg of the original design.

Managing large quantities of low voltage power
By introducing the Emax 2, ABB has created the world’s first low-voltage circuit breaker that can be used for energy management and smart grid communications. It is designed for facilities that use large amounts of low voltage power. Applications include industrial and commercial buildings, data centres and on board ships.

The breaker integrates energy management and off the supply to non-essential equipment at times of peak demand. This not only saves energy but also helps prevent blackouts, which are often caused by peak demand exceeding supply. Intelligent decision making is achieved through an in-built controller using complex algorithms to decide when to switch power on and off.

For an individual building, using Emax 2 in place of traditional breakers can lead to a reduction in peak power demand of up to 15 percent. Replacing an existing breaker with the Emax 2 is technically simple and due to energy savings, it will typically pay for itself within a year.

A compact and flexible installationOne installation where the Emax 2 is proving its worth is on board a state-of-the-art diesel-electric ferryboat equipped by Italian electromechanical construction specialist IMESA. It was the only switchgear that would deliver selective circuit breaking capability with short circuit breaking capacity of 50 kA at 600 V AC as well as fit within an extremely compact space and a horizontal bussing distribution system.

Thanks to the unit’s compact size and ability to be mounted in the horizontal position, it was possible to fit five circuit breakers in a single column, saving 45% of the footprint of a conventional distribution switchboard.



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