Eumir Rizzi ABB Electrification Bergamo, Italy, eumir.rizzi@it.abb.com
Early circuit breakers consisted of a simple thermal-magnetic trip unit that sensed current levels and operated a switch in the event of overheating or a short circuit. In the late 1980s, electronic trip units based on current transformers emerged that measured the current rather than just sensing it. An element of control then entered the picture – delayed tripping, for example.
In recent years, the evolution of monitoring needs in the context of an increasingly connected world and the emergence of sophisticated control needs have forced the pace of circuit-breaker development. For example, air-core current sensors have now replaced the old iron-core current transformers, introducing advantages such as increased accuracy across the entire operating range of the trip unit, which is up to 12 times its rated current, in many cases. Modern electronics also make it possible to integrate the measurement of voltage into the breaker without the need for additional voltage transformers, thus saving space and installation time.
Functional integration has continued apace, eliminating complexity and doing away with many of the transformers, meters, cables, terminal blocks and ducts that competed for the limited space in the switchboard.
From protection device to data source
The integrated metering capability provided by the last generation of trip units offered the chance to build up an extensive metering architecture without increasing the dimensions or complexity of a distribution system. This advance allows more variables to be measured in more places, at kHz sampling rates. Data can then immediately be digitalized and processed onboard the unit. If the trip unit has a data logger, then the values of currents, voltages and other parameters can be stored, analyzed, visualized or downloaded in different formats to other devices.
Although these devices deliver a certain level of sophistication, the functionality and ease-of-use delivered by the new ABB SACE Tmax XT MCCB changes the circuit breaker game significantly →01.
The ABB SACE Tmax XT MCCB
The Tmax XT range of circuit breakers delivers higher performance, better protection and more precise metering than equivalent units – and covers currents from 160 to 1,600 A. The Tmax XT is equipped with ABB’s Ekip Touch protection trip units, which provide preconfigured or customizable digital and analog interfaces. The combination of Tmax XT and Ekip Touch delivers a performance that was traditionally in the realm of the multimeter or network analyzer: voltage, energy, power and harmonics measured with accuracy levels of better than 1 percent; harmonics calculated up to the 50th; and detection thresholds lying under 0.4 percent of the nominal current.
02a Ekip Cartridge, an external accessory that can be installed on a standard 35 mm DIN rail to allow other external accessories to connect to Ekip Touch and Tmax XT. 
02b Ekip Signalling 3T, an accessory that connects via Ekip Cartridge to provide three analog inputs for temperature sensors and one analog input for 4 – 20 mA current loops.
02 Ekip accessories that enhance the power of Tmax XT.
Tmax XT has at its disposal plug-in modules to sense temperature (by means of thermocouples), voltages from a different power line, vibration and pressure. In fact, any 4 – 20 mA sensor can interface to the Tmax XT. Information obtained by these sensors can be immediately processed by the trip unit – to generate alarms, output a command or trip a breaker – rather than being sent to a supervision system on a communication bus for remote handling. All these sensors interface via the Ekip Touch trip unit that is installed in the Tmax XT →02.
Commonality across the range
With the world’s most precise electronic trip units in the smallest frames, the Tmax XT range builds on the Emax 2, the industry’s first smart low-voltage air circuit breaker. In fact, the Tmax XT range has the same logic, features and interfaces as the Emax 2. This commonality, which only ABB can provide on the entire circuit-breaker range, delivers significant time savings and enhances installation quality.
A new way to access information
Tmax XT trip units are equipped with a color touch screen display, which – thanks to an internal battery – can be turned on even when the breaker is de-energized. This availability means that, after a trip, it is possible to navigate through the menu to find the data needed to understand the reason for the trip before reclosing the circuit breaker.
The touch screen utilizes intuitive icons like those found on tablets or cellphones. Complex functionalities are easy to handle – either directly from the touch display or by exploiting the Bluetooth communication capability of the trip unit: Once a cellphone is paired with an Ekip Touch trip unit in a Tmax XT →03, all reading and setting activities can be accomplished via the free Epic cellphone app →04.
Connecting to the TmaxXT
There is much value in the data collected by Tmax XT circuit breakers – especially if data from many breakers in different locations can be gathered, aggregated, compared and analyzed as a whole. To do this, a data transmission means must be provided. The Ekip Touch trip units that fit into Tmax XT enable the potential of ABB Ability™ Electrical Distribution Control System (EDCS) to be opened up, providing over 10 communication protocols. (ABB EDCS is a cloud-based platform that enables a user to monitor and manage a facility’s electrical distribution via smartphone, tablet, or computer in real time to optimize energy use and costs.) Dedicated modules can be snapped onto the breaker to enable these communication capabilities – for example, for field buses such as Modbus RTU, Profibus DP and DeviceNet.
The Modbus module ensures fast integration of new products into existing systems. At 12 Mbps, Profibus DP is the perfect choice in automation switchboards if a high-speed data exchange rate is required. Solutions for connecting the circuit breakers to Ethernet networks are also available: Modbus TCP/IP communication modules run at up to 100 Mbps and can be used as a Webservers, allowing browser access to the data stored inside the trip unit.
Interfacing to the outside world
The IEC 61850 standard is becoming widespread as a communication protocol for protection and control systems in electrical plants. Circuit breakers need to handle fault conditions very quickly and for this reason, the two types of low-latency communication services described by IEC 61850 are implemented on Tmax XT: MMS (Manufacturing Message Specification) for vertical communication, and GOOSE (Generic Object Oriented Substation Event) for horizontal communication.
The Tmax XT’s connectivity paves the way to move from a reactive maintenance or repair approach to a predictive approach. Rather than having the breaker trip in the first place, analysis of data from the breaker, or a network of breakers, can help prevent faults from happening in the first place.
The breaker’s connectivity also allows real-time control of plants via remote monitoring and control. When the Ekip trip units are equipped with specific modules →05, control logic can be implemented, networks reconfigured, or generators controlled, to name just a few examples related to smart grids. Finally, by adding an Ekip Com Hub module to a trip unit it is possible to concentrate data from multiple breakers and connect the network to an ABB-managed cloud space.
Tmax XT for a greener world
Control of power consumption at every level in a plant is a prerequisite for energy efficiency optimization, electricity bill reduction and the avoidance of fines for excess demand. Further, a comparison of similar facilities in different locations can help identify best practices across a company.
A further incentive for careful power control comes from Green Building certification, which is becoming essential in many countries for new residential construction and infrastructure such as hospitals, shopping malls and data centers. Green Mark Platinum certification, denoting the highest level of building energy efficiency, is becoming a common stipulation in construction specifications.
The TmaxXT is ideal for this type of extensive power monitoring. The breaker’s built-in connectivity links smartphones, tablets and PCs to data analysis tools on the ABB Ability™ EDCS cloud-computing platform to monitor, optimize, control and predict the condition of the electrical system →06. The extreme precision of the data measured means users have ready access to accurate information, making it easier to monitor resources and identify opportunities for savings. Using the embedded smart power controller can help reduce energy consumption, allow efficient assessment for Green Mark Certification purposes and effectively reduce external auditing costs.
Cyber security
Cloud technology can significantly increase the scalability of architectures, improve the flexibility of interconnection to both new- and previous-generation devices and help to protect investments. However, modern distributed systems involve a significant increase in the perimeter of exposure to cyber threats, both intentional and involuntary. ABB Ability™ cloud architecture has been developed together with Microsoft in order to enhance performance and guarantee the highest reliability and security →07. There are three different modes of cloud operation, each with its own special security considerations:
• Device to cloud scenario. In this case, a “whitelist” for unique identification is established and only local commission is permitted. An encrypted communication channel, exploiting the same protocol as banking systems, is used. No commands can be sent from the cloud to the plant.
• “In the cloud” refers to communication between data centers. ABB/client data is stored exclusively in certified data centers with state-of-the-art cyber security standards, relying on Microsoft Azure cloud platform security policy.
• Browser to the cloud scenario. Here, access to data requires first an authentication via ABB single sign-on (SSO) and a specific authorization. Communication runs via an encrypted channel and no commands can be sent from the cloud to the plant.
All these security implementations are designed according to potential threat analysis and are developed according to security guidelines and recurring code review. Furthermore, cyber security is continuously under assessment and validated by penetration tests to verify robustness.
A future-facing intelligent breaker
The TmaxXT family evolved to face and overcome increasingly complex and broad challenges in the world of electrical protection. The breaker’s rich selection of features has made it into an intelligent multifunctional and modular platform that is light years removed from the humble breaker technology of the 1980s. Precise measurement, comprehensive data acquisition, extensive communications, cloud capability and cyber security are just some of the strengths of a product family set to create the future of electrical systems and to give customers the chance to create whole new levels of sophistication in their electrical installations.
