Leading the Way in Electrical Safety & Protection
Electrical Industry Trends
The following are some of the most recent trends in electrical safety and protection;
- RCD Testing
- Self Testing RCDs
- Electric Vehicles & RCD Technology
- Electric Vehicle Charging & Insulation Breakdown
- RCD Technology & Solar Panels
- ARC Fault Protection
RCDs are fitted with a test button to enable the user to test the performance of the RCD from time to time. However, in practice this test functionality is not utilised for a number of reasons. Lack of awareness by the user of the product or in many cases the RCD is not easily accessible. Testing can also be somewhat of an inconvenience because every time the RCD is tested power is removed from the protected circuits and it may be necessary to reset equipment such as clocks or TVs or recording equipment, etc.
Self Testing RCDs
Probably the biggest development in the RCD industry in recent years has been the emergence of self-testing RCDs. In addition to Self Testing, the RCD can also indicate “End Of Life” if it fails the Self Test. These two functions are known as STEOL. Western Automation is at the forefront of this technological advance and we have developed STEOL capability that enables the RCD to perform a Self-Test every two to three seconds throughout the life of the product. When the RCD finally reaches its end of life it will fail the self-test and the user is instantly notified of the EOL state. There are various methods of notification and these are very much dependent on the customer needs. These might include an automatic trip of the RCD to render it out of use or an LED may be lit or an audible alarm may be activated, or a combination of these may be employed. In any event the User will be aware that the RCD is no longer functioning and should be replaced.
Electric Vehicles & RCD Technology
The emergence of Electric Vehicles (EVs) in recent years has given rise to demands for technology that can provide effective solutions to new types of problems. It is important to say at the outset that EVs are very safe, but unfortunately they do carry some risks for the user. The most obvious problem relates to charging of the EV. This involves the connection of a cable to provide an AC supply to the charging system in the EV, with inherent electric shock risks. It is vitally important that during the charging process all reasonable steps are taken to safeguard the user from electric shock. Such protection can be provided within the cable itself, known as Mode 2 charging protection, or protection within a charging station or a wall mounted box, known as Mode 3 charging protection. However, there are other potential hazards that are less obvious. What many people do not realise is that the voltages generated within an electric vehicle can be as high as 600 volts DC. The AC supply is initially converted into DC to charge the battery to a very high level, and in most cases the DC voltage is subsequently converted to AC to drive a single or three phase motor to power the vehicle. The potential voltages in the electric vehicle could therefore be in the region of 400 – 600 volts. While this is extremely dangerous if touched, the insulation levels in the vehicles are very high and the risk of a user ever touching voltages at this high level is very low. Nonetheless, manufacturers and international standards bodies responsible for electrical safety have to look at the risk of electric shock arising from electric vehicles.
Electric Vehicle Charging & Insulation Breakdown
Experts in IEC considered the risks associated with possible insulation breakdown between the EV voltages and ground during charging and found that in such a case a DC current could flow from the electric vehicle through the ground and back to the AC supply charging the EV, thus forming a DC current loop. If the AC supply is protected by an AC or A Type RCD, the DC current will flow through the RCD. This creates a situation where a DC current is flowing through an RCD intended to detect AC fault currents and pulsating DC currents but not pure DC. If the pure DC current is above a certain magnitude it could present a shock risk, but the AC detecting RCD may not be able to provide protection because DC currents passing through the current transformer in the RCD may cause desensitisation or even blinding of the RCD such that it is no longer able to provide shock protection at its rated AC residual operating current, e.g. 30mA. EVs may be in the charging mode for several hours, and in the event of an insulation fault as described above occurring during the charging period, the RCD may no longer be able to provide protection against AC residual fault currents. The RCD may be intended to protect an entire house but such protection may be seriously compromised due to blinding. The IEC concluded that this risk was unacceptably high and introduced requirements to protect against this potentially deadly problem. There are two ways of providing protection against this fault condition.
The first is to use a Type B RCD which is designed specifically to detect DC fault currents. This can be installed anywhere on the installation and will provide protection against AC and DC residual fault currents without being blinded.
The second option is to have a specific detector that detects the dangerous DC current that could blind a conventional RCD. When the current gets above a safe level the DC monitor can be used to activate a circuit breaker to disconnect the electric vehicle while the rest of the installation continues to be provided with electrical supply. Once the EV has been disconnected the AC RCD will no longer be blinded and will provide protection against AC fault currents as intended.
The supply to the EV will continue to be interrupted if the user tries to reconnect the vehicle and resume charging under such a fault condition.
Western Automation has invested a lot of resources to develop RCD technology specifically intended for EV charging systems. Such solutions include Type B RCD technology and DC fault current detection from as low as 6mA. We continue to develop new solutions in advancing electrical safety in the area of EV charging systems.
RCD Technology & Solar Panels
Another area that is becoming very important is photovoltaic (PV) solar panels. PV solar panels generate DC electricity which must be converted into AC to be fed into the AC main supply or back into the grid. Insulation breakdowns may occur due to the solar panel exposure to the elements and harsh environments.
In such an event, the insulation breakdown should be detected as soon as possible so as to minimise the risk of shock or electrical damage. DC or Type B RCDs can provide protection against DC currents on such systems. Furthermore, there may be a risk of DC current flowing on the AC supply and compromising the effectiveness of an AC operated RCD, so detection of DC currents would be required to mitigate such a risk.
ARC Fault Protection
Until recent years ARC Fault detection technology was in its infancy and rarely used, however considerable advances have been made over recent years, that enable providers to offer effective solutions to ARC Fault currents and thereby mitigate fire risks arising from ARC Fault Currents. It is expected that the use of ARC Fault Current Detectors will grow rapidly over the next few years.