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Any similarity between an EVC point and a socket for a refrigerated cargo container?

AncientMariner
Unless things have changed since I retired in 2002, I am curious regarding the similarity between an EVC point and a socket for a refrigerated cargo container.


On board ship, refrigerated cargo containers were simply plugged in to the ships electrical system. 3-phase, 3-wire plus earth, so a 4-pole plug and socket. The acceptable voltage being 380 to 460v 60 or 50 Hz. Most ships being 60 Hz, but some I sailed on had been designed for possible MOD charter and were 50 Hz. (there were some dual voltage containers, ie for 3-phase 230 volt supplies which some ships had.)


The lowest power consumption was for frozen cargo, whereas cargo which was carried chilled or even warm, due to fresh air requirements rather than recirculation, resulted in higher power consumption.


Considering that the container was connected via 10 metre or so cable, this looks similar to an EVC connection?  In rough weather, I have experienced heavy seas over the deck causing cables to be ripped out at the container end and when the weather subsided, I found that the doors of a container full of French Fries were having some cooked on deck by a fizzing broken cable.


Circuit protection either three cartridge fuses or a MCB, never came across any RCDs. Some ships fed the sockets directly off the main 440v bus, so an earth fault on a container, usually the defrost heater, would show as an earth on the ship's main 440v bus, other ships had the luxury of a number of isolating transformers. A quick Google tells me that some ships can carry 500 refrigerated containers, some more. This explains why my last ship generated at 6.6 kV.


Containers held on the quay side were plugged into pillars and I guess the same for when containers were at their destination, or awaiting stuffing. I never saw one of these in those days https://catalog.eslpwr.com/wp-content/pdfs/s_3500-02.pdf but certainly looks serious.


Yet the requirements suggested in  http://digitalfizz.com/cargostore/wp-content/uploads/Reefer_Power.pdf of RCD protection and under volt release, seems less stringent to that for a EVC point?


Clive

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    Certainly when a refrigerated container in onboard the ship, I would expect it to connected to the ships hull by the earth core in the cable and hopefully by contact through the container's mounting points. Although most of the ships that I sailed on had hatch lids. so say 9 containers stacked down guides below the hatch lid and perhaps 5 or 6 on top. The reason I said hopefully, is that the hatch lid sits on a rubber strip around the hold, so perhaps a single container on a lid could conceivably not have a connection via contact between the lid and hatch coaming. Thinking back, I have actually seen a single container on a hatch lid; this on a ship where the below deck containers were either general of if refrigerated, they used a blown air system from air chillers in each hatch. 


    Actually what I was trying to get discussion on was when the container is off the ship and sitting on the quayside. Many container yards where they would be plugged in are surfaced with brick paviors, just like my driveway! OK the container is metal to brick rather than rubber tyre to brick, so if we have two containers not touching but close enough for a person to place a hand on each, should due to rough handling the earth core have pulled out of one of the plug terminals and there is also an earth fault we would seem to be relying 100% on an RCD somewhere?  


    So going back to an EVC, if the supply to the house where the EVC point is mounted, is TN-S is anything more than an RCD required for shock protection? 

    Clive

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    Certainly when a refrigerated container in onboard the ship, I would expect it to connected to the ships hull by the earth core in the cable and hopefully by contact through the container's mounting points. Although most of the ships that I sailed on had hatch lids. so say 9 containers stacked down guides below the hatch lid and perhaps 5 or 6 on top. The reason I said hopefully, is that the hatch lid sits on a rubber strip around the hold, so perhaps a single container on a lid could conceivably not have a connection via contact between the lid and hatch coaming. Thinking back, I have actually seen a single container on a hatch lid; this on a ship where the below deck containers were either general of if refrigerated, they used a blown air system from air chillers in each hatch. 


    Actually what I was trying to get discussion on was when the container is off the ship and sitting on the quayside. Many container yards where they would be plugged in are surfaced with brick paviors, just like my driveway! OK the container is metal to brick rather than rubber tyre to brick, so if we have two containers not touching but close enough for a person to place a hand on each, should due to rough handling the earth core have pulled out of one of the plug terminals and there is also an earth fault we would seem to be relying 100% on an RCD somewhere?  


    So going back to an EVC, if the supply to the house where the EVC point is mounted, is TN-S is anything more than an RCD required for shock protection? 

    Clive

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