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

Difficult to say whether they arrive on board with an electrical test certificate. All containers are supposed to have certificates and if they are reefer containers this will include the electrics, and should be subject to periodic inspection, but......


When you are unloading/loading thousands of containers in a port (in the space of less than a day) who is checking the certification? This is probably eased with modern systems using blockchain tracking of each container but checking each one is still a challenge.


With regard to the use of three wire/four wire distribution for the reefer sockets, some companies insist on it (e.g. Maersk - but their ships have a significant reefer capacity, numbered in the thousands, though they are cagey about just how many) while others don't. The basic deciding factor is how much does it cost to find an earth fault and fix it (during the life of the ship) compared to how much does it cost to install transformers. The fewer reefer sockets the less likely to have transformers.


RCDs are very uncommon on ships since most have IT systems which means the RCD may not provide any protection. Reefer sockets fed via a transformer with an earthed neutral on the secondary side provide an exception, but as Clive says, the most common fault is through sea-water ingress (or more likely green sea damage) resulting in an earth fault. The plugging and unplugging are not carried out live so there should be no danger to personnel. It is further complicated by the fact that you would need the RCDs to be out on deck (or at least in deckhouses) and therefore need to monitor the supplies to make sure an RCD trip didn't result in the cargo being ruined. If you have one RCD per circuit then that is a lot of detection while if you have one RCD per block of sockets I would be surprised if you were able to get it to stay in. The current arrangement, with large MCCBs used to feed multiple sockets having trip detection means that there is some testing to find the faulty circuit on a trip, but it is probably a block of 12 or 24 reefers.


On the whole I think that there is not a great deal of commonality between this and EVC points, since EVC points are accessible to the general public, they are plugged/unplugged with much greater frequency and generally by non-trained personnel (though on a ship the level of training of the personnel may be sometimes questionable), and the earthing is not the same since a container is in direct contact with the ship's metal structure while an EV is sitting on insulating rubber tyres.


Alasdair

Difficult to say whether they arrive on board with an electrical test certificate. All containers are supposed to have certificates and if they are reefer containers this will include the electrics, and should be subject to periodic inspection, but......


When you are unloading/loading thousands of containers in a port (in the space of less than a day) who is checking the certification? This is probably eased with modern systems using blockchain tracking of each container but checking each one is still a challenge.


With regard to the use of three wire/four wire distribution for the reefer sockets, some companies insist on it (e.g. Maersk - but their ships have a significant reefer capacity, numbered in the thousands, though they are cagey about just how many) while others don't. The basic deciding factor is how much does it cost to find an earth fault and fix it (during the life of the ship) compared to how much does it cost to install transformers. The fewer reefer sockets the less likely to have transformers.


RCDs are very uncommon on ships since most have IT systems which means the RCD may not provide any protection. Reefer sockets fed via a transformer with an earthed neutral on the secondary side provide an exception, but as Clive says, the most common fault is through sea-water ingress (or more likely green sea damage) resulting in an earth fault. The plugging and unplugging are not carried out live so there should be no danger to personnel. It is further complicated by the fact that you would need the RCDs to be out on deck (or at least in deckhouses) and therefore need to monitor the supplies to make sure an RCD trip didn't result in the cargo being ruined. If you have one RCD per circuit then that is a lot of detection while if you have one RCD per block of sockets I would be surprised if you were able to get it to stay in. The current arrangement, with large MCCBs used to feed multiple sockets having trip detection means that there is some testing to find the faulty circuit on a trip, but it is probably a block of 12 or 24 reefers.


On the whole I think that there is not a great deal of commonality between this and EVC points, since EVC points are accessible to the general public, they are plugged/unplugged with much greater frequency and generally by non-trained personnel (though on a ship the level of training of the personnel may be sometimes questionable), and the earthing is not the same since a container is in direct contact with the ship's metal structure while an EV is sitting on insulating rubber tyres.


Alasdair