Breaking new ground for circuit breakers

Operators are keen to control energy costs and react to the opportunities offered by the changing face of power and energy due to renewable energy, data centres, smart buildings and electric vehicles.

So, what are the priorities for facilities managers? Conventionally, operators want electrical power distribution equipment that works reliably, is affordable to buy and to run and that is small enough to fit comfortably in their electrical cabinet or plant room. However, times are changing and today’s operators are now reacting to changing priorities. What they all have in common is that they want to reduce energy costs and deploy remote monitoring so that they can keep an eye on assets and reduce maintenance bills.

In practice, one operator might want to maximise use of energy generated on-site, whereas operators that sublet units inside their site may want accurate sub-metering of the feeds to each unit. Alternatively, another site manager may want to integrate equipment that is capable of remote control and communication to participate in a Demand Side Response (DSR) scheme. Or they may want to avoid penalty tariffs that can apply when drawing more power than agreed in their utility contract.

The latest moulded case circuit breaker (MCCB) technology can help respond to these issues.

How have MCCBs improved?

Traditional MCCBs are straightforward devices that protect the distribution of electricity in a commercial or industrial building. The latest generation of MCCB, such as ABB’s Tmax XT, has been developed to be more compact than previous units. The latest breakers can provide up to 1600 A in a smaller footprint. As a result, panels can be smaller and more circuits can be controlled in an existing envelope. That’s ideal for operators who want to stick with tried and tested technology with a straightforward and affordable MCCB that works with their existing infrastructure.

What new features have been added?

Accurate metering and communication are both required for advanced functions. Therefore, an important new feature embedded in the latest generation of MCCB is measuring of current and voltage to an accuracy of less than one percent, as well as monitoring of frequency, power and energy based on the latest digital technology. This eliminates the need for external meters.

From a communication perspective, it’s vital that the MCCB should be able to work seamlessly as part of an operator’s overall facility. In practice, this means that a device may need to be compatible with communication protocols such as Modbus RTU, Profibus, DeviceNet, Modbus TCP, Profinet and EtherNet/IP, as well as the IEC 61850 smart grid communication standard that is being adopted widely in medium-voltage systems. 

Combining metering and communication opens up potential for integration with a SCADA or building management system, as well as remote monitoring via the web on a computer, tablet or even a smart phone.

This will provide a benefit for some operators who need to provide sub-metering for tenants of units on their site. They will be able to download consumption and billing data rather than needing to send a meter reader.  

What advanced functions are possible?

With the communication and metering in place, it’s possible to add decision-making capabilities to enable advanced functions that can improve productivity and reduce energy consumption. For example, by integrating a network analyser and data logger, a facility owner will gain comprehensive data to help them identify the root cause of issues and also feed into a preventive maintenance programme.

Another example is where a circuit breaker is equipped with measurement, network analyser, power protection and a power controller. These can be combined to maintain the balance of supply and demand in a self-sufficient grid-edge facility, for example by switching to island mode in the case of a disturbance on the grid. It’s even possible to integrate advanced protection and control required for specific applications.

For example, a circuit breaker that controls the flow of power from a wind turbine or solar photovoltaic panels can integrate advanced measurement, diagnostics and act as interface for a grid connection.

Another example is for operators of motors and generators, rotating equipment that can be sensitive to damage from voltage sags or surges. Traditionally, operators have had to implement sophisticated controls such as dedicated relays and wiring to ensure safe shutdown in the event of an issue. However, the latest MCCBs can be ordered with a trip unit that is programmed to provide dedicated protection for motors and generators.

How can an MCCB reduce energy bills?

Power management is another advanced function that is possible with the latest MCCBs. This is the technique of automatically switching off low priority loads to keep a site’s overall energy consumption below a maximum threshold.

This is helpful for site managers who want to do avoid penalty tariffs that their utility can charge under the DCP161 regulation for exceeding the maximum half-hourly consumption agreed in their contract.

It’s often possible to switch off HVAC or other services temporarily without a significant impact on building occupants. Traditionally, power management has required dedicated load control devices for each individual load. However, this can become complex and costly to engineer and maintain.

Instead, the latest MCCBs can be supplied with a power management module. This uses an algorithm that monitors the consumption from the loads and automatically switches off low priority loads before consumption can exceed the maximum half-hourly threshold. Once consumption drops off again, the controller will bring loads back into operation.

An important consideration is that the algorithm in the controller will consider the ‘respect time’ of each load. This is the minimum time that a piece of equipment must remain connected or powered down and therefore is vital to avoid damaging sensitive equipment and minimising maintenance requirements.  

With all of these digital capabilities built in, MCCBs can help operators to reduce costs and future-proof their sites.

Sean Massey is product marketing manager at ABB

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