27.—(1) Before commencing a supply to a consumer’s installation, or when the existing supply characteristics have been modified, the supplier shall ascertain from the distributor and then declare to the consumer—
(a)the number of phases;
(b)the frequency; and
(c)the voltage,
at which it is proposed to supply electricity and the extent of the permitted variations thereto.
(2) Unless otherwise agreed in writing between the distributor, the supplier and the consumer (and if necessary between the distributor and any other distributor likely to be affected) the frequency declared pursuant to paragraph (1) shall be 50 hertz and the voltage declared in respect of a low voltage supply shall be 230 volts between the phase and neutral conductors at the supply terminals.
(3) For the purposes of this regulation, unless otherwise agreed in writing by those persons specified in paragraph (2), the permitted variations are—
(a)a variation not exceeding 1 per cent above or below the declared frequency;
(b)in the case of a low voltage supply, a variation not exceeding 10 per cent above or 6 per cent below the declared voltage at the declared frequency;
(c)in the case of a high voltage supply operating at a voltage below 132,000 volts, a variation not exceeding 6 per cent above or below the declared voltage at the declared frequency; and
(d)in the case of a high voltage supply operating at a voltage of 132,000 volts or above, a variation not exceeding 10 per cent above or below the declared voltage at the declared frequency.
(4) The Secretary of State may, following an application by any distributor affected by a declaration made pursuant to paragraph (1), authorise the variation of any of the values or permitted variations contained in a declaration provided that the applicant has previously given notice of his application to such persons and in such terms as the Secretary of State may require.
(5) Where the Secretary of State has authorised a variation under paragraph (4) the distributor shall forthwith serve notice of any such variation on every supplier, other distributor referred to in paragraph (2), and consumer to whom it may apply.
(6) Every distributor shall ensure that, save in exceptional circumstances, the characteristics of the supplies to consumer’s installations connected to his network comply with the declarations made under paragraph (1).
(7) The number and rotation of phases in any supply shall not be varied by the distributor except with the agreement of the consumer or, in the absence of such agreement, the consent of the Secretary of State who may impose such conditions, if any, as she thinks appropriate.