What is an earth fault?
DC Voltage is not generally referenced to earth, so earth fault risk is commonly overlooked by electricians. However, when DC voltage is connected to an operating transformer-less inverter, the potential difference between the DC and earth can be over 400 Vdc. This means that the cable tied to the rail (often with sharp stainless steel cable ties) has a 400 Vdc potential to the rail, all day every day. A breakdown in this insulation, wherever it occurs on the solar installation, is an earth fault.
The potential risk
At best, an earth fault will cause your system to stop operating. At worse it can cause a worker on the roof a shock. If multiple faults occur at the same time, then a person working on a roof could receive a shock big enough to throw them off the roof. It is both the risk of lost revenue and personal injury that has prompted the regulators to introduce mandatory earth fault alarms.
While there are rudimentary ways of activating an appropriate alarm, the best way is to combine it with online inverter monitoring. When an earth fault occurs, an email alert is sent to the owner every hour, hopefully causing them to take action. The advantage of online monitoring should not be understated. It’s not just a gimmick for geeks, but a clever way of using technology so that both you and your electrician can automatically and remotely monitor your solar system’s performance for years to come. If you are in the greater Brisbane area and are looking into solar or need advice on your current system, contact Mark or Ryan on 3268 3836, or send us a request to call you back.