{
  "url": "https://openlegislation.uk/electricity-supply-regulations-1988/regulation-30",
  "json_url": "https://openlegislation.uk/electricity-supply-regulations-1988/regulation-30.json",
  "legislation": "uksi/1988/1057",
  "legislation_title": "The Electricity Supply Regulations 1988",
  "legislation_url": "https://openlegislation.uk/electricity-supply-regulations-1988",
  "path": "regulation/30",
  "kind": "regulation",
  "number": "30",
  "heading": "Declaration of phases, frequency and voltage at supply terminals",
  "text": "(1) Before commencing to give a supply to a consumer, the supplier shall declare to the consumer—\n(a) the number and rotation of phases;\n(b) the frequency; and\n(c) the voltage,\nat which it proposes to deliver the supply and the extent of the permitted variations of those values:\nProvided that, unless otherwise agreed between the supplier and the consumer, the frequency to be declared shall be 50 hertz and the voltage to be declared in respect of a low voltage supply shall be 240 volts between the phase and neutral conductors at the supply terminals.\n(2) For the purposes of this regulation, and unless otherwise agreed by the consumer, the permitted variations are—\n(a) a variation not exceeding one per cent above or below the declared frequency; and\n(b) a variation not exceeding six per cent above or below the declared voltage at that frequency where that voltage is below 132 kV, and not exceeding 10 per cent above or below the declared voltage where that voltage is 132 kV or above,\nor the variation which may have been authorised by the Secretary of State under paragraph (3).\n(3) The Secretary of State may, on application by a supplier, authorise him to alter any of the declared values or any permitted variation if he gives such notice of his application as the Secretary of State may require.\n(4) The supplier shall forthwith give notice of any authorisation under paragraph (3) to every consumer to whose supply it may apply.\n(5) The supplier shall ensure that, save in exceptional circumstances, any supply he gives complies with the declaration under paragraph (1).\n(6) The polarity of direct current and the number and rotation of phases in any supply shall not be varied without 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 he thinks appropriate.",
  "extent": null,
  "status": null,
  "version": "current",
  "annotations": [],
  "outstanding_effects": [
    {
      "type": "amended",
      "affecting": "uksi/1990/390",
      "affecting_title": "The Electricity Supply (Amendment) Regulations 1990"
    },
    {
      "type": "amended",
      "affecting": "uksi/1994/3021",
      "affecting_title": "The Electricity Supply (Amendment) (No. 2) Regulations 1994"
    },
    {
      "type": "substituted",
      "affecting": "uksi/1994/3021",
      "affecting_title": "The Electricity Supply (Amendment) (No. 2) Regulations 1994"
    },
    {
      "type": "added",
      "affecting": "uksi/1994/3021",
      "affecting_title": "The Electricity Supply (Amendment) (No. 2) Regulations 1994"
    },
    {
      "type": "revoked",
      "affecting": "uksi/1992/2961",
      "affecting_title": "The Electricity Supply (Amendment) Regulations 1992"
    }
  ],
  "provenance": {
    "source": "legislation.gov.uk",
    "source_url": "https://www.legislation.gov.uk/uksi/1988/1057/regulation/30",
    "retrieved_at": "2026-10-29T16:05:02.727864+00:00"
  },
  "licence": "Open Government Licence v3.0",
  "licence_url": "https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/",
  "attribution": "Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives."
}