Is 690vac dangerous?

rorymcgrory

Hi there, doing some work in a terminal and there a lot of cable carrying 690v. These cables are fairly exposed too. Is this voltage dangerous?

The tax man

Whose cables are they?

dunworth1

if unsure stay away

Kensington

Most likely three phase mains power, each carrying ~240V you'd have a p.d. of almost 690V between the first and third phase.

To answer your question, treat it as live mains

Red Alert

You've 380 V between any two phases in Ireland at distribution level.

icdg

OP you might clarify what the situation is so I might move this to the correct forum.

This forum is for discussion of cable television and related platforms.

Solair

Generally, yes anything above about 50V is potentially dangerous (even lower than that if it manages to pass through your heart)

690V is a very odd voltage in Ireland. Although, I think it might be used in some unusual applications like wind turbines and off-shore rigs for driving huge motors and avoiding extra copper cabling

Normally three phase here is 400V (used to be 380V).

110V - US domestic power can kill you.
230V - European/Irish domestic power can kill you.
400V - European/Irish 3-phase can kill you.
690V - Can definitely kill you!

Stay well clear!

There should not be any exposed cables / terminals / bus bars that are accessible by members of the public / normal workers.

It would be a serious breech of the Health and Safety at Work Act and electrical wiring regulations.

2011

Solair wrote: »

690V is a very odd voltage in Ireland. Although, I think it might be used in some unusual applications like wind turbines and off-shore rigs for driving huge motors and avoiding extra copper cabling

Normally three phase here is 400V (used to be 380V).

110V - US domestic power can kill you.
230V - European/Irish domestic power can kill you.
400V - European/Irish 3-phase can kill you.
690V - Can definitely kill you!

I would agree. However I think thta the OP might have been measuring a voltage that appers across a capicitor or inductor. In an AC circuit when capacitive and inductive devices are installed in series individual components can have a higher voltage appear aacross them than the supply voltage.

Take a series R-L-C circuit:

When the circuit is at or near resonance, the voltages across the capacitor and inductor can be larger than the supply voltage.

In theory a pure inductor's voltage will lead the resistor's voltage by 90 while a pure capacitor's voltage lags the resistor's voltage by 90 degrees. The inductor voltage is 180 degrees out of phase with the capacitor's voltage. At resonance they cancel each other out.

Solair

690V is used industrially for some unusual setups. It would be sourced from an on site transformer.

larger industrial sites are connected to the ESB network at medium voltage, usually 10kV or 20kV. It's up to them to step down their own power locally. So, they can quite easily use 690V for certain specialised equipment.

It's just not very common. However,690V is a standard voltage.

icdg

I'm really not sure where this thread should go and the OP hasn't answered my earlier request. Engineering might be the best place for it but having looked at that board I'm not sure it fits in.

If the OP wants to PM me with a move request I will consider it, otherwise I am going on the view that it isn't a cable television issue.