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Reliable signal transmission in confined spaces

The needs of system operators in the water and wastewater industries have changed drastically – there is a trend for higher packing density in control cabinets and consequently ever narrower components. It is a characteristic of the water and wastewater treatment industry to have numerous networked processes – between field level, management level, and subsections that are usually far apart. The requirements on planners, installers, and operators of the systems are increasing steadily. Failsafe concepts are becoming more important due to the increasing implementation of electromechanical and electronic components, systems and solutions, as well as the networking between them.

Overvoltage concepts play an important role. Further, requirements on critical infrastructure have also developed due to the variety of IT security laws enacted over the past five to 10 years. Two major factors are known to be at play here – the high system availability and the resulting security of supply for the population.

As in other infrastructure fields, the trend towards implementing ever smaller and compact components is also noticeable in the field of water and wastewater treatment. To optimise the costs of overall control cabinet manufacturing, the surge protection devices should take up as little space as possible. The goal is to centralise numerous service functions – such as system monitoring – in the control room. To operate the system safely from an EMC perspective, surge protective devices are implemented in large systems.

Numerous channels often have to be housed within a small area in order to transmit analogue or digital signals. Since space is becoming increasingly valuable, Phoenix Contact launched the world’s narrowest surge protection for MCR technology (measurement, control, and regulation), at just 3.5mm  wide.

The components of the device, called Termitrab Complete, are equipped with six terminal points to which two signal lines each and a common reference potential can be connected. With this compact and narrow contactor, up to 572 signal lines can be protected on one meter of DIN rail. The power dissipation has been minimised due to the decoupling resistors in the protective circuits. This feature also aims to satisfy the demand for installing more devices in increasingly smaller spaces.

Lightning protection standards recommend regular inspection of protective devices. This is only possible through visual examination. The Termitrab Complete range features a status indicator that displays an overload of the surge protection directly on the device. Since no additional power is needed for this indicator, the protective device also displays the fault continuously during an overload. If this information is displayed in a control room, the optionally available ‘remote signaling modules’ ensure the necessary data transmission.
Either the PLC (programmable logic controller) can query the potential-free contact directly by wire, or this contact is integrated by interface modules, with, for example, the compact message system TC Mobile I/O X200, which is available from the same distributor. This means that the status of the protective devices in large systems can be monitored not only in the control room, but also sent via SMS to the mobile phone of the service technician. If a contactor is overloaded, trouble-free replacement is possible, in particular with pluggable protective devices.

Classical screw connection technology is still commonly used. If there are many signal lines to be installed however, considerable time can be saved with the quick push-in connection technology. Comparisons with screw connection technology have shown, for example, that the wires can be connected up to 50 per cent quicker. Disconnection is also easily possible by pressing the ‘pusher’. Depending on preference, the installer can choose between screw and push-in connection technology with this new range.

A lightning and surge protection concept is essential because of the higher risk in potentially explosive structural systems, often with far-reaching consequences for people and the environment. In general, observation of lightning protection standard DIN EN 62305, applicable for nearly all structural systems, is sufficient. Part 2 of the standard describes risk management for structural systems, which takes into account the effects of lightning strikes. The standard relates to all structural systems – even systems with explosion risk in accordance with DIN EN 60079-0. The ‘intrinsic safety Ex-i’ type of protection is useful as a secondary protection measure in this environment. This type of protection limits voltages and currents so that a potentially explosive mixture of ignition energy and temperature is not reached. DIN EN 60079-11 is the specific standard for these intrinsically safe circuits – here too, reference is made to the necessity of lightning and surge protection.

For all systems that require high availability, a failure lasting for even a short time is unacceptable. That is why the requirements for surge protection are also more stringent for such systems. The surge protection of the Termitrab complete TTC-Ex product range was designed for such systems. The Ex-i certification of the TTC-Ex components permits the use in field distributors for Ex-zones 1 or 2. Additional approvals attest to the suitability in accordance with Fisco (fieldbus intrinsically safe concept).

In water and wastewater treatment, there is an increased failure risk in large systems due to surge voltages, often severe consequences for both workers and the local environment. A well-planned lightning and surge protection concept is therefore crucial. Using surge protection with telecommunicating status indication ensures quick detection in the control room. Due to the compact design – with only 3.5mm width for the narrowest components – the space needed for surge protection can be reduced significantly. Use in explosion-protected areas is also trouble-free with the available approvals. This product range means that there is a suitable solution for every application in water and wastewater technology.

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