Symbol of short circuit (or termination) with an Earth

Question

Can someone explain to me why the symbol of the valve arrester has a short circuit, if it is already earth? I don't understand why it is depicted like this.

Why does the valve arrester have the symbol of a short circuit joined with earth? Does it mean that it is a short circuit to earth?

Note: The CD symbol is a streamer, equipment which measures current.

Context: I posted a previous question: Meaning of this power system line diagram symbol. That question was to ask what the termination symbol was. Now I understand that. This question is asking why in a valve symbol, with a streamer, there IS a termination symbol or a short circuit symbol as in the link cited above, and why is this symbol followed by the earth symbol and not only the valve, streamer and the earth?

Summary: I would like to know why they put a termination symbol and an earth symbol.

Answer 1

Perhaps it shows a connection to its own case (chassis) which is then connected to earth by a wire (or other type of conductor) that is separate to it's own case. Kind of a "feed-through" connection.

Do you have a photo of the item in question?

Edit: added the following below:

I would like to know why they put a termination symbol and an earth symbol.

Reason: to ensure the reader understands that a separate conductor is required to complete the connection to earth. This is important in situations such as sub-stations, where the details of earthing conductors become very important for both functional and safety reasons, as compared to PCB design where a net-name (such as GND or OV) can be used to indicate a connection to a ground plane, so that a separate earthing conductor is not required.