Digital power: a new safety frontier — Part 2
Reflecting on where technology has taken us, even over the past few years, tells us that change is inevitable. As industry professionals, we have a responsibility not only to keep up with these changes, but to keep up with the risks that emerge with them, as well as the strategies to mitigate them.
This article, the second in a two-part series, addresses the risks and mitigation strategies for digital power — an alternative to mains electricity in safely delivering power to devices over telecommunications cabling. Part 1 outlined the risks of remote powering (aka PoE or Power over Ethernet), what the ICT standards said about the risks and suggested steps we could take to diminish these risks.
Let’s put it simply to help distinguish the two technologies:
- Remote powering 'adds power to data transmission'; and
- Digital power 'adds data to power transmission'.
You may be more familiar with the term ‘Digital Electricity’, a name trademarked by VoltServer, the company that pioneered the technology, but we’ll use the term ‘digital power’ to remain generic.
Digital power typically involves transmitting energy in data packets, with each packet being verified at the receiver. So when there’s a short circuit, or someone touches live conductors, the transmitter recognises the fault condition within a few milliseconds and immediately stops sending any more energy packets — faster than conventional safety switches and with a wider scope of fault conditions. This enables ‘touch-safe’ electrical transmission at high, even hazardous, power levels.
VoltServer succinctly outlines the intent of digital power on its website, stating: “Digital Electricity™ solutions deliver touch-safe electricity where and how it is needed. Digital Electricity™ can be delivered using off-the-shelf data cable, at significantly reduced cost, and with greater speed…and flexibility, when compared to electrical installations.”
So it’s positioned as an alternative to conventional mains cabling, using data cables. And it’s gaining support. For example, property developer Sinclair Holdings recently deployed both digital power and remote powering in a luxury 165-room Marriott hotel in Texas to help improve customer experience, while optimising energy conservation.
“We installed the VoltServer transmitter in the basement next to the electrical switchgear and then ran digital power throughout our 10-storey building using 18/2 speaker wiring,” said Sinclair Holdings CEO Farukh Aslam, who presented a case study on this project at the BICSI Conference in January 2019.
“This feeds power to Cisco PoE switches, which then powers all the devices in the rooms using ‘category’ data cable. Because it was all Class 2 power, we didn’t need any electricians.
“On top of that, we’re aiming to save more than 50% energy, compared to traditional methods, by centrally monitoring and managing everything through the IP network, capturing consumption patterns and optimising everything.”
This is just one example of a growing trend in utilising digital power instead of mains power. But can this technology be safely deployed? After all, buildings that size and complexity must consume huge amounts of power and therefore present dangers to installers, maintainers and users.
ICT digital power safety standards
Let’s start with the AS/NZS 62368.1:2018 standard — a localised version of IEC 62368.1:2018, currently being adopted globally as the electrical and electronic safety standard for AV, ICT and business equipment. It introduces a hazards-based safety engineering approach using a three-stage risk model against potentially increasing risks from rising energy levels. It classifies energy sources, prescribes safeguards against those energy sources, and provides guidance on the application of, and requirements for, those safeguards — all intended to reduce the likelihood of pain, injury and property damage.
AS/NZS 62368.1:2018 classifies energy sources ES1, ES2, ES3 and their controls to safely deliver digital power:
ES1 – Class 1 electrical energy source:
- Touch-current or prospective touch-voltage levels don’t exceed ES1 voltage limits (60 VDC or 30 VAC RMS with no current limit) or ES1 current limits (2 mA DC or 0.5 mA AC with no voltage limit) under normal and abnormal operating conditions and single-fault conditions of elements not serving as safeguards.
- Doesn’t exceed ES2 limits under single-fault conditions of safeguards.
- Accessible to ‘ordinary person’.
ES2 – Class 2 electrical energy source:
- Both touch-current and prospective touch-voltage exceed ES1 limits but don’t exceed ES2 voltage limit (120 VDC or 50 VAC RMS with no current limit) or ES2 current limit (25 mA DC and 5 mA RMS with no voltage limit) under normal and abnormal operating conditions and single-fault conditions.
- Accessible to ‘instructed person’ and ‘skilled person’, but at least one basic safeguard required between ES2 and an ordinary person.
- A circuit with telephone ringing signals as defined in AS/NZS 62368.1 is an example of ES2.
ES3 – Class 3 electrical energy source:
- Hazardous, where both touch-current and prospective touch-voltage exceed ES2 limits.
- ES3 generic circuit defined as a metallic circuit utilised for communications or remote-powering, or both, that exceeds ES2 voltage and touch-current limits, but doesn’t exceed 400 VDC between conductors and 750 mA per conductor.
- ES3 special application circuit defined as a circuit intended to support ES3 service over special application cable that is not generic cabling.
- Accessible only to suitably qualified skilled persons.
- RFT-C and RFT-V circuits are examples of ES3.
- Cables intended to carry ES3 must be clearly identified at all access points and separated from other services and telecommunications circuits. Cable route must be marked at regular intervals, noting the potential presence of hazardous energy sources.
This ACMA-mandated standard has introduced significant changes to the soon-to-be-published AS/CA S009:2019 Wiring Rules. The ‘Public Comment Background Paper’ issued with the draft AS/CA S009 standard addresses the impact of AS/NZS 62368.1 and how industry should deal with potential hazards, particularly energy sources and personnel classifications. It states in part:
“ES1, ES2 and ES3 are defined in DR AS/CA S009, while a new Appendix P provides information on the equivalence of these terms and the terms ELV, SELV and TNV used in AS/CA S009:2013.
“ES3 is considered hazardous and represents equivalent hazardous energies in AS/NZS 60950.1. Previously, where voltages exceed TNV limits on customer cabling, LV Telecommunications circuits were used, eg, EWIS, which is classified as a ‘hazardous service’.
“DR AS/CA S009 supports ES3 circuits over generic cabling limited to maximums of 400 V and 750 mA per conductor. Exceeding these on generic cabling is deemed as not fit-for-purpose as it does not provide adequate safeguards to ensure the safety of customers, cabling providers, carrier staff and general public.
“New requirements have been specified for cables that are intended for ES3 generic circuits. In addition to existing requirements in AS/CA S008, these cables now are required to have a maximum conductor resistance (equivalent to 0.5 mm conductor diameter), an identifiable sheath colour (‘Homebush Gold’) and be clearly labelled ‘ES3 circuit’ every 2m in the colour ‘Homebush Red’. ES3 generic cables are not to be used for ES3 special application circuits.
“DR AS/CA S009 [also requires] subducting ES3 circuits when installed with other cables, and preventing access to sockets capable of carrying ES3 circuits.
“Separation of telecommunications and electrical circuits for indoor cabling listed in Appendix G has been revised to reflect ES1, ES2 and ES3 energy levels.”
DR AS/CA S009 has also introduced the terms ‘ordinary’, ‘instructed’ and ‘skilled’ persons to associate risk controls with individuals’ skills and education, relating distinct levels of protection, based upon how much each person understands the relevant risks.
Ordinary person (formerly ‘end-user’) generally applies to equipment users, but can also apply to bystanders. Cablers can be instructed persons or, with additional training, skilled persons.
Instructed persons are trained by a skilled person, so that they know what energy sources in the product may cause pain, and they know how to avoid unintentional contact with them.
Skilled persons may have access to ES3 parts, so they must have the appropriate training, qualifications and experience to be able to recognise where and what hazards exist within the equipment, and be able to apply knowledge and skills to safeguard against pain and injury.
Many argue that the increasing deployment of wireless technologies like Wi-Fi and LTE (ie, 4G/5G) has significantly diminished ICT infrastructure risks. It’s true that wireless isn’t electrically conductive and doesn’t carry current or pose the risk of electrocution in the proximity of mains cabling like copper cabling. But wireless technologies rely heavily on wires.
Wi-Fi 6 Access Points (APs), defined by the yet-to-be-released IEEE 802.11ax standard, typically need two Cat 6A data cables to handle the data bandwidth. And these APs are also mostly PoE enabled, so as Wi-Fi deployment increases, so too will the risks associated with data cables carrying power, particularly on older cabling not designed to do so. A common enterprise trend is overlaying Wi-Fi over wired ICT infrastructure — wireless isn’t replacing wired, it’s augmenting it.
5G — touted by some as the ‘nirvana’ of modern data access — will require a massive increase in the number of antennas for both external carrier-based networks and in-building networks, simply because of the greater attenuation of RF signals at frequencies higher than 4G networks. More antennas mean more wires. 5G will mostly be connected with fibre-to-the-antenna (FTTA) technology, but many in-building networks will likely connect via copper cabling. Again, this increases the number of current-carrying cables in a building, probably in proximity to mains cabling, thereby increasing risks.
These wireless market trends will be eclipsed by the Internet of Things (IoT). Part 1 of this article stated that IoT will introduce billions of low-cost devices in many diverse applications, mostly connected wirelessly. Many of these remote devices will be battery powered, but the complex infrastructure to connect them — millions of Ethernet switches, RF extenders, remote PCs, etc — will need greater power, typically using PoE. Once again, more current-carrying cables.
Put simply, the increase in wireless networks will see a massive increase in remote powering and digital power and their associated safety risks.
The true value of standards
The committees that write these standards are professionals with many years’ experience in ICT. Their collective views are representative of best practice on what to state in standards for the long-term benefit of industries.
So when we see so much emphasis placed on the risks associated with ES1, ES2, ES3 in AS/NZS 62368.1, AS/CA S008 and AS/CA S009, we can be sure that this is important to our industry.
Standards have a big role to play in risk mitigation. Ultimately, adherence to these standards by all will ensure our safety along with the safety of those affected by our work.
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