w_tom wrote:

If RCDs do not provide human safety to UK bathrooms, they why? Why
is electricity at 230 volts in UK bathrooms not a threat when
electricity in Canada and US at 120 volts has been considered dangerous
since 1970s. Why is UK electricity not dangerous in UK bathrooms -
especially when RCDs are so inexpensive?

The "hair-dryer picture" referred to in the NIC article is there only as
an an illustration of why mains-voltage socket-outlets are still not
permitted in UK bath & shower rooms.

Hand-held appliances are now allowed if hard-wired and are in Zone 3 or
beyond ( 0.6 m from the bath or shower tray). The supply to a portable
appliance in Zone 3 must be protected by a 30 mA RCD. The RCD in this
case is providing supplementary protection against electric shock by
direct contact. Other than this, RCD protection is not required for
direct contact protection - this being ensured by requirements for
adequate insulation and for the use of equipment with suitable IP ratings.

Protection against shock by indirect contact (i.e. contact with parts
which are live as the result of a fault) is achieved by means of earthed
equipotential bonding and automatic disconnection of supply ('EEBADS').
The regulations give design principles which are based on the IEC
touch-voltage curve, and seek to prevent the appearance of dangerous
voltages between accessible metal parts for an excessively long time.
Automatic disconnection of supply here is preferably (and usually)
achieved by an overcurrent device - i.e. the rupture of a fuse or
tripping of an MCB. However the standard does recognise the use of RCDs
for this purpose when the earth fault loop impedance is too high to
ensure operation of the overcurrent device - such as where there is no
metallic earth path to the earthed point of the substation transformer
(TT-system).

In bathrooms and other areas of high shock risk local supplementary
equipotential bonding is required to reduce touch voltages further.

--
Andy