NETA Level 2 Surge Arrester question

[yllelhjuvier]

1. What is the main difference in construction between older surge arresters and metal oxide surge arresters?
Your Answer: Metal oxide arresters have a resistive component, while older surge arresters are purely capacitive.
Correct Answer: Metal oxide arresters contain blocks of zinc oxide and air gaps, while older arresters consist of silicon carbide resistor blocks.
Help: Surge Arresters Applications and Testing

In the provided link the following is stated.

@TestGuy

Older surge arresters generally consist of silicon carbide resistor blocks in series with air gaps. These arresters normally carry no current and have a single voltage rating. Aside from a few exceptions, the selection of these arresters is fairly simple:

Metal oxide surge arresters contain blocks of variable resistance material, usually zinc oxide, with no air gaps. Line-to-ground voltage is applied continuously between the line and ground terminals of the arrester. These arresters do carry a minimal leakage current that can be withstood on a continuing basis.

Therefore the answer is wrong.

[SeaburyNC]

Actually, I’d say that the link is wrong too. Metal oxide surge arrestors can be gapless, or they can have gaps. Just google gapped MOV arresters and you’ll get lots of results for how they are designed, why you might prefer them to gapless arresters, etc. That said, I have no idea how common they are, because I’m pretty sure all the MOV arresters I’ve tested have been gapless.

[TestingPro2B]

Same things have happened to me. Sometimes test guys gets it wrong. There is a way to tell them about it and they will review it but I have never done it so I can’t be of help there.
Most everything I have read on the site is great but there are totally quit a few errors.
Happy hunting!