As of July last year, new measures have been introduced for dealing with dangerous earth faults in Australian rooftop solar PV systems. The most important among them is a requirement for all systems to be equipped with an ‘earth fault alarm’ that is triggered when a fault occurs.
Shocks and fires are two of the main potential hazards associated with any electrical system. Frequently, these hazards are associated with earth faults – situations where electrical current may run to ground through paths other than an earth wire due to a problem in the electrical circuit. These paths could include parts of the home itself – which could ignite a fire – or through a human being – which could result in electrocution.
Without proper design, engineering and safeguards, as with any electrical system, solar PV systems may also be susceptible to earth faults. Unfortunately, Australia has something of a fraught history on this topic. Some in the solar industry blame solar-related safety issues to date on rooftop DC isolators, which were made mandatory for new PV systems in 2012.
The peculiar Australian issue of DC isolators
In theory, rooftop DC isolators make solar PV systems safer by enabling firefighters to turn them off in the event of a fire. It would appear, however, that some brands of these isolators have conversely resulted in an increase in the number of PV system fires: Their location on the roof, exposed to the elements, means that in some instances they may malfunction and become a ‘weak link’ in the system – resulting in earth faults. A number of models from several brands of DC isolator manufacturers have been recalled – with one company alone accounting for over 27,000 recalled devices. (The Queensland government’s Work & Safety website has a page devoted to advice on identifying and dealing with these isolators.)
DC isolators are not the only cause of earth faults, but it seems clear that they’re the main culprit: as Mark Williamson of the Clean Energy Regulator noted at Energy Storage Australia 2015, over 80% of serious electrical safety issues with home solar systems in Australia have to do with DC isolators. Fortunately, to date none of the fires or failures associated with the isolators have resulted in human injury.
Updated standard requirements for identifying earth faults
Although SolarSafe – a company that specialises in post-installation services for solar systems – published an argument against the mandatory use of rooftop DC isolators in solar arrays and even started a campaign to petition Standards Australia to change it, the requirement will not be going away anytime soon. In fact, as of July of 2015, instead of eliminating the isolators, the new standard requirements have been brought in to mitigate the problems that they can potentially cause – not to mention possible earth faults elsewhere in the system.
What makes earth faults especially dangerous is that they can happen quietly and easily go unnoticed. Although owners of existing systems have hitherto been encouraged to proactively check that their isolators are in working order,updates to the standard (AS/NZS 5033:2014) will make such measures obsolete for new system owners by mandating the inclusion of an earth fault alarm in every system.
As per the updates to the standard:
- an earth fault alarm system shall be installed.
- the system shall, in the event of an earth fault, initiate action to correct the fault by means of an alarm.
- the alarm can be either audible, visual or another form of communication (e.g. email).
- the alarm shall operate at least hourly until the fault is rectified.
- if using an audible or visual alarm, it shall be installed in a place where the system owner will be aware of the alarm signal.
A number of companies are moving forward with products suited to these requirements. Inverter manufacturer SMA and Fronius, for example, have both integrated earth fault alarms into at least some of their inverters, and a quick Google search reveals a number of other products available for this purpose.
Additionally, home energy management system developer carbonTRACK has recently announced that it has built earth fault alarm functionality into its software platform (they also released a white paper on the topic). carbonTRACK’s earth fault alarm system goes above and beyond the updated standard requirements in the following ways:
- It immediately activates the safety trip, thereby removing any immediate danger.
- It immediately notifies both the system owner and the installer (via SMS or email) that a fault has occurred.
- It continues to send notifications every 15 minutes until the fault has been fixed.
Regardless of what product is used in the end, anyone who is contemplating having a solar system installed should speak to their installer about what form the earth fault alarm will take (e.g. audio? visual? SMS? email?) and what they should do in the event that the alarm goes off.
Should you be worried about earth faults in your solar system?
Here we should emphasise that standards are in place to make sure that solar PV systems are not inherently dangerous to solar homeowners: Properly designed and installed solar PV systems using good-quality components should pose no danger to a home or its occupants. Indeed, Australia’s DC isolator debacle has resulted in the tightening of safety measures in Australia – namely, the new requirement for earth fault alarms. In this respect, new solar systems are safer than ever.
If you are the owner of a solar PV system installed before the earth fault alarm requirement was instated (July of 2015) and you have concerns about its safety, please refer to the Queensland Workplace Health & Safety Electrical Safety Office’s website (here) for information about recalled DC isolators. Additionally, there are a number of companies that specialise in helping solar system owners resolve safety (or other) problems with existing solar PV systems. SolarSafe is one such company, but a Google search is likely to reveal a number of operators local to your area.
© 2016 Solar Choice Pty Ltd