Digital RCDs usher in new era of preventative maintenance
Chris Pack of Eaton explains why it is vital for machine builders, especially for those who export worldwide, to work with partners that know the international requirements to save both time and money.
Maximising uptime is vital for companies to remain competitive in today’s market. For example the cost of downtime on a machine can easily run in to tens of thousands of pounds. Many businesses operate with minimal reserve stock, while processes typically run at over 95% uptime to meet demand. For these reasons, downtime can quickly lead to loss of shipments impacting turnover and customer confidence.
Circuit protection and in particular digital residual current devices (RCDs) can help machine builders offer their manufacturing customers improved uptime as they provide local and remote monitoring and pre-warning capabilities. This technology provides information about the machine’s health to maintenance personnel and therefore facilitates preventive maintenance, ultimately leading to less machine downtime. And further increases to a machine’s reliability can be made by installing the right technology according to appropriate standards and safety requirements.
RCDs protect against damaging electrical faults, where residual and leakage currents caused by fault conditions occur within an electrical circuit. These can have devastating effects on the human body, causing cardiac arrest or worse, and lead to machine failure affecting the bottom-line. They can also lead to fires. RCDs have been available for decades, reliably protecting man and machine. The first patents were received by Professor Biegelmeier in 1957, and further development ensued with the first permanent magnet tripping unit being developed in 1965 – this is the heart of the modern RCD. The first digital RCD Type B and B+ technology was available in 2014. The advantages of RCDs are widely known, but digital RCDs are heralding a new era in preventative maintenance.
The IEC 60364 and the respective national standards or the NEC (National Electrical Standard) for North America provide the base for the installation of low voltage electrical systems worldwide. Beyond that, the IEC 60204-Series has fundamental significance for industrial installations because it addresses the electrical safety of machines. According to the standard, the electrical equipment of a machine must fulfil the safety requirements that are identified during the risk assessment of the machine. Based on practical experience, it is proven that RCDs help to reduce the hazard potential. Another aspect recommended by the IEC 60204 is preventative maintenance. Through using the latest digital RCD technology, machine builders can implement these measures.
Digital RCDs combine protection functionality with digital features – unique within the circuit protection market – that work together to provide maximum circuit status information and increase the protected system or machine’s availability. The digital technology is applied to both RCCBs and RCBOs. These devices continuously measure the residual current value, using their real-time results to drive local pre-warning LEDs and remote pre-warning potential-free outputs. These pre-warnings allow maintenance staff to resolve creeping problems before they lead to interruptions or failures. System status is always available at a glance, and cost savings accrue due to the reduction in unscheduled service callouts. Further savings arise because test intervals can now be performed annually.
System availability is further enhanced, as the digital protection devices have short time delays and optimised tripping thresholds that ensure malfunctions of a brief duration do not cause nuisance tripping and loss of system availability.
Types of RCDs
Eaton recommends using at least a Type A RCD to provide the necessary protection level for industrial applications. Beyond that, Type B RCDs are recommended for fire hazard and additional protection in connection with speed controlled machines or rather frequency inverter applications in general. The occurring smooth DC current negatively influences or incapacitates the detection of Type AC or A RCDs, so in the worst case their protection is disabled.
Type B residual protective devices can detect sinusoidal AC and pulsating DC as well as smooth DC fault currents, making them suitable for all kinds of applications and occurring waveforms according to IEC/EN 62423. Trigger conditions for fault currents with different frequencies up to 1kHz are defined for Type B residual current devices.
Type Bfq RCDs comply with Type B requirements (IEC/EN 62423) while being designed for use in circuits that include frequency converters for speed-controlled drives. They have specially-adapted tripping curves, defined up to 50kHz which are designed to avoid nuisance tripping.
Type B+ RCDs comply with the requirements of VDE 0664-400 and have a frequency tripping response defined up to 20kHz. Their maximum tripping current at higher frequencies is limited to 420mA. This provides superior protection from fire risk caused by ground fault currents in applications with electronic drives. This is especially requested in agricultural applications to avoid any fires caused by high frequent earth leakage currents.
Intelligent wiring solutions
RCDs are an important component for reducing downtime, but machine builders and installers can increase uptime further and make savings by integrating them within an ‘intelligent wiring’ environment. For example, devices such as MCBs, RCCBs and RCBOs can be quickly and easily connected to intelligent wiring and communications technology through Eaton’s SmartWire-DT MCB/RCD module. This makes additional I/O level and wiring redundant, enabling machine builders to reduce installation and upgrade time and costs.
Using this system, the status (on, off, tripped) of the protection devices is made available within the machine’s control/monitoring system or to the power distribution network. This continuously provides the service and maintenance teams with information about the system, helping them to react immediately to problems.
Machine builders specifying circuit protection equipment (in particular RCDs) and seeking to minimise costs while offering high performing, reliable machines have a number of possible strategies. These relate to the equipment’s technical features along with a wider range of equally important factors. An ability to specify and receive exactly the same products anywhere in the world simplifies exporting, maintenance and operations.
Not only is operational efficiency and productivity increased through the improved diagnostics available with today’s digital technology, but with the right circuit protection technologies, the safety and protection of both man and the machine is also increased.
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