absolutely, in laymans terms

an isolating transformer is exactly that, it isolates either side of the transformer through an air gap. the primary doesnt touch the secondary side.

a RCD is a residual current device which detects a current leakage in and then will trip the circuit if it exceeds that current.

Advantage depends on what you are trying to do.

Normally, an isolation transformer protects against casual contact with the phase conductor. However, if you touch the phase and neutral conductors at the same time, you get no protection at all.

An expert can comment on the behaviour of an RCD in the same situation, especially in the case of a double insulated appliance.

Jase2985:

 

absolutely, in laymans terms

 

an isolating transformer is exactly that, it isolates either side of the transformer through an air gap. the primary doesnt touch the secondary side.

 

ill just add to this, there is no earth on the secondary (load) side so if you were to touch the live wire there is no path to earth for the current, so there is no shock (note: there could be a mild tickle as there could be some capacitance there)

Yes, but isn't the main concern avoiding an unintended return path to earth? If you use your heart to complete a circuit between phase and neutral, an RCD also won't know if it is you and not a light bulb providing the load.

Rikkitic:

 

Yes, but isn't the main concern avoiding an unintended return path to earth? If you use your heart to complete a circuit between phase and neutral, an RCD also won't know if it is you and not a light bulb providing the load.

 

  

 

I think your heart will normally leak some current away to earth so an RCD will protect you even if you're 'only' connected to phase and neutral.

But if you stand on polystyrene with your gumboots and repeat the experiment, I don't know if an RCD will help you either.

Rikkitic:

 

Yes, but isn't the main concern avoiding an unintended return path to earth? If you use your heart to complete a circuit between phase and neutral, an RCD also won't know if it is you and not a light bulb providing the load.

 

  

 

an RCD measures the phase and neutral and compares them if there is an imbalance in the current then it trips, the imbalance wouldnt happen from the load

Rikkitic:

 

As per the title. From a practical safety point of view, is there any real difference between the two? What is the advantage, if any, of one over the other? 

 

 

 

 

 

 

 

When isolation transformers became available in the 1960's-70's it was the only available means of safety (by 1970's standards) RCD were unheard of or way beyond the price of practical use.

With the common use of microprocessors and micro electronics, the size, price and reliability of RCD's are well affordable. There are situations for both isolating transformers and RCD's where they won't provide personal protection, but with out going into the technical reasons it could develop in to a very long story.

My opinion is if you want to lug a 20kg brick of an isolating transformer around go for it, you will more than likely hurt yourself when you trip over it or repeatably trip the built in circuit breaker as they won't run high power gear for very long.

Get an RCD, buy a good one, don't get a el-chepo Bunnings or M10 house brand one, remember you are using this to save your life. If you are in doubt get your electrician to check it with his/her RCD tester to prove it trips within the prescribed mA range and the trip time.

Rikkitic:

 

Yes, but isn't the main concern avoiding an unintended return path to earth? If you use your heart to complete a circuit between phase and neutral, an RCD also won't know if it is you and not a light bulb providing the load.

 

  

 

your right an RCD would not know, and neither would a isolating transformer, but it is unlikely that with an RCD you could touch both phase and neutral without some sort of earth return which would trip the RCD.

Many years ago I worked at Telecom and knew the electrical engineer who dealt with all this sort of stuff and he was also on some governmental board which dealt with electrical regulations.

He told me that several times there had been RCD salesmen coming in to try and convince Telecom to change from isolating transformers to RCDs.

He would challenge them to hold the phase wire and earth wire out of their RCD while he did the same on his isolating transformer.

None of them took him up on his challenge.  (I can personally testify to getting a belt through an RCD - at home and unrelated to the afore mentioned challenge.)

Needless to say, today I live in a house full of RCDs and wouldn't have it any other way.

Both protect against earth faults. 

An Isolation transformer does this by preventing a circuit being created between earth and phase. 

An RCD cuts the power supply once the current flow to earth exceeds what has been deemed as safe for that situation. There are different type of RCD for different situations. 

Plugging in multiple appliances into the one isolating transformer can negate the protection it offers depending on the appliances plugged in

Pluging in multiple appliances into an RCD still gives you the protection it offers.

You'll certainly still feel it with an RCD but hopefully for no longer than 30ms.

gregmcc:

 

With the common use of microprocessors and micro electronics, the size, price and reliability of RCD's are well affordable.

 

They are not 'that' cheap, and a pain in the ***** if poorly installed (why do electricians check their own work!!).   We had regular RCD trips in the house, largely caused by cumulative circuit leaks rather than any specific fault. Had a different but really good electrician install an RCD on every circuit to spread the load better.  I think the switchboard RCD's were around $100 each or so? And 20 or so circuits in the house.  Total cost was around $2500 from memory.  

But, safety is important...electricity is just super dangerous. Read some of the plug safety certifications....impressive engineering goes into a simple plug. 

decibel:

He would challenge them to hold the phase wire and earth wire out of their RCD while he did the same on his isolating transformer.

Poor horse.