18th Edition practice exam question help

[Bob Geldoff1234]

Hi guys,I am currently revising for the 18th Edition exam a week on Friday and have come across a practice question that I cannot find any reference to in the BBB.
Here is the question they ask:-
If a fault occurs in the HV system,and a magnitude of fault voltage of 430 volts occurs between exposed conductive parts and earth on the LV installation.What is the maximum tolerable duration of the fault?

The answer is evidently 300ms.

I cannot find where they get this info from?
Any guidance would be most helpful.

 

[Charlie_]

442.2.2

 

[Deleted member 26818]

I’d get that wrong then, thought it was 5s.

 

[Charlie_]

I would have said >5 s

If mock is saying 300mS then it is wrong

 

[Bob Geldoff1234]

Does seem to read as <5 seconds in the book.I have found another answer in the online mock to be possibly wrong.
The quiz is here:-
18th Edition Exam Simulator | -----------.co.uk - http://www.-----------.co.uk/18thedition/18th-edition-exam-simulator.php

 

[Charlie_]

I read it as >5s for 250v to 1200v

 

[Bob Geldoff1234]

The options were 100ms,10ms,300ms or 200ms.
No wonder I am confused

 

[Charlie_]

Sounds like they have got some questions mixed up..
if this was a game of jeopardy my answer would be...
When testing RCBOs to bs en 61009.
With a leakage current flowing equivalent to 100% of the rcd tripping current, what is the maximum disconnection time?