Can an RCD prevent fire?

In the past I have read articles and statements by consumer and safety bodies indicating that Residual Circuit Devices (RCD's) and or Residual-current Circuit Breaker with Overcurrent protection (RCBO's) can prevent fire. 

There are different types of faults within electrical installations which can lead to fire, for an RCD/RCBO to prevent or stop a fire there needs to be a particular type of fault. It may help if I start by explaining how an RCD works.

RCDs operate by measuring the current balance between two conductors, similar to a balanced see saw, for a circuit which is connected to an RCD the Current Out needs to be balanced with the return.

If this changes due to a fault or someone comes into contact with the circuit then a leakage of that current (typically 5–30 mA) causes in imbalance and the RCD disconnects the supply (less than 300 ms) and prevents electrocution.

So, for an RCD to stop or prevent a fire there has to be an imbalance within the circuit as this how an RCD operates and isolates the supply.

Until now the RCD could only protect us, our families and homes from electrocution and a single particular type of live - earth fault which could develop into a fire known as 'Surface Tracking' this is when minerals from detergents or spillages have been deposited on or around cables, for example within a washing machine or dishwasher. Once there are sufficient deposits, arcing can start and this can activate an RCD as it results in the imbalance discussed earlier.

The video shows a demonstration of how this 'Surface Tracking' can develop into a fire and what an RCD is capable of regarding this type of fault.

Most electrical fires are caused by High Resistive Connections (HRC) which lead to the development of excessive heat. Circuit Breakers, RCD's and RCBO's and  are unable to detect HRC as this generally happens externally. The very nature of these faults mean that the connections themselves become very hot, more than 1000oC, which rapidly becomes a fire at which point if the supply is not isolated then the fire will develop beyond our immediate control.

However with Thermarestor we use the RCD or RCBO to isolate the supply when and monitored connection becomes hot, operating in an abnormal manner and well outside its design parameters, around 80oC. With Thermarestor protecting your electrical installations, electrical accessories and appliances and by using the RCD or RCBO protecting the circuit we can isolate the supply before there is any sign of smoke or flame.

So the answer to the question "Can an RCD prevent fire?" is yes but only a certain type of fire when it's on its own, partner it with a Thermarestor System and the possibilities are endless. 

We are not a suppression or alarm system that waits for fire. We monitor connections that shouldn't get hot and do something positive to protect life and property.