Ex Royal Signals Command and Control Bunker

https://www.blakley.co.uk/wp-content/uploads/PDS052_ECM_Series.pdf

https://www.dmp.wa.gov.au/Safety/Guidance-about-trailing-and-6364.aspx

ECM is earth continuity monitoring by making a current loop comprising of cpc/earth between supply to load and a pilot wire from load end of cpc/earth back to supply end.

Pilot Earth loop continuity monitoring is to ensure integrity and low resistance of cpc/earth and action ads in the event of loss or too high resistance of cpc/earth.

As an aside I remember as a lad in 70s an electrician explaining PE loop monitoring of earth/cpc for industrial and construction site power tools and equipment. PE loop operating at 25V IIRC with special extra pin plugs and sockets for the system (Reyrolle?).

marconi said:

https://www.blakley.co.uk/wp-content/uploads/PDS052_ECM_Series.pdf

https://www.dmp.wa.gov.au/Safety/Guidance-about-trailing-and-6364.aspx

ECM is earth continuity monitoring by making a current loop comprising of cpc/earth between supply to load and a pilot wire from load end of cpc/earth back to supply end.

Pilot Earth loop continuity monitoring is to ensure integrity and low resistance of cpc/earth and action ads in the event of loss or too high resistance of cpc/earth.

As an aside I remember as a lad in 70s an electrician explaining PE loop monitoring of earth/cpc for industrial and construction site power tools and equipment. PE loop operating at 25V IIRC with special extra pin plugs and sockets for the system (Reyrolle?).

Click to expand...

Thanks for that, really helpful.

Any ideas on a Terminator 5 ?

Term/D terminator - http://www.fdb.uk.com/project/termd/

At the load end one could simply connect the pilot conductor and the cpc/earth together. Such a connection would have zero impedance. All well and good unless upstream there is a cable fault and for some reason the pilot and cpc/earth conductor are connecting together: the ELCM would not be able to detect a fault downstream of this point. What to do?

If one placed a very low value resistance at the load end say 2 Ohms, then using a Wheatsone bridge method of resistance measurement one could accurately confirm at the supply end the existence of the 2 Ohms bridging pilot and cpc/earth at the load end.. If the measurement is 'too high' or 'too low' this could be detected and used to trip the supply for ads.

Another way is to put just a diode between pilot and cpc/earth at the load. With an ac test voltage the current with be unidirectional. However, if the pilot and earth are shorted upstream the current will be bi-directional. The good state is unidirectional and the faulty state is when a bi-directional current is detected so this enables ads to be implemented.

Term/D terminator - http://www.fdb.uk.com/project/termd/

You would have to measure the dc resistance of the terminator 5 first connected one way and then reversed to see if it is a resistor or a diode.

Of course - teaching you to suck eggs ;-) , you will supply the cabin and provide earthing and bonding as required by UK wiring regulations. You do not use the ECM/ELCM/PLEM system. This may require some disconnection or stripping out of wiring and such. And the cabin is 'expecting' a 3P + N supply which you will have to modify for SP + N. Plenty of advice on the EF should you need it.

PS: ads = automatic disconnection of supply.

An ECM (earth continuity monitor) can operate in one of two directions: downstream, making sure that a connected load is getting an earth from the installation, or upstream, making sure that the installation has an earth. We seem to have both elements here. The ECM in the unit is looking for upstream earth continuity via the insulated pilot earth spike, before allowing the main contactor to energise the distribution board. This would be relevant if the container were supplied as a stand-alone from a generator parked next to it, for example. If the container is not able to maintain the same potential as the surrounding earth via the spike, the main contactor goes off.

Then we also have the PCLM terminator that forms the end of the line for an ECM elsewhere, part of a larger site-wide distribution system, that needs to see continuity of the earthing to the container before allowing it to have power. If the cable is broken or improperly connected, power would not even be distributed to it from the main switchgear cabin. My guess would be that this uses a diode in its pilot circuit to distinguish between a pilot fault and a valid connection, whereas the on-board ECM possibly uses resistance thresholds.