NBCP - Electrical

• Installations


  • Should not cause visual pollution
  • Should prioritize public safety, convenience, aesthetics, and good viewing
• Placement of installations


  Along alleys or back streets is permissible
• Location of poles and clearances of power lines along public roads

  1. All poles on public roads must be covered by an Approved Pole Location (APL) plan from the Municipal Engineer

  2. Poles and transformer supports should be situated no more than 500mm inside from the road right-of-way or property line

  3. They must not obstruct sidewalks, pedestrian paths, road drainage canals/structures, whether existing or proposed
• Primary lines


  • Should maintain a minimum vertical clearance of 10 m from the crown of the pavement when crossing highways, and 7.5 m from the top of the shoulder/sidewalk when installed along the side of highly urbanized areas
• Secondary, neutral, and service lines

  • Must maintain a minimum vertical clearance of 7.5 m from the crown of the road pavement when crossing highways, and from the top of the shoulder/sidewalk when installed along the side of highly urbanized areas
• Clearances of supporting structures

  • From fire hydrants: Not less than 5 m
  • From street corners: Poles and towers shall not be set so far from the corners as to necessitate the use of flying taps that are inaccessible from the poles
  • From curbs: Not less than 150 mm, measured from the curb away from the roadway
• Attachments on and clearances from buildings

  • Require an Approved Attachment Plan from the local Building Official
  • Where buildings exceed 15 m in height, overhead lines shall be arranged to leave a clear space or zone at least 2 m wide adjacent to the building or beginning not over 2.5 m from the building to facilitate the raising of ladders for firefighting purposes
• Open supply conductors attached to buildings

  • Conductors of more than 300 volts to ground shall not be carried along or near the surface of buildings unless guarded or made inaccessible
  • Conductors and other current-carrying parts of electric supply lines shall be arranged to provide adequate clearance from the ground or other accessible space, or shall be provided with guards to isolate them effectively from accidental contact
  • Undergrounded metal-sheathed service cables, service conduits, metal fixtures, and similar noncurrent-carrying parts, if located in urban districts and where liable to become charged to more than 300 volts to ground, shall be isolated or guarded to prevent accidental contact by unauthorized persons. Alternatively, noncurrent-carrying parts shall be solidly or effectively grounded
  • Clearance of wires from building surfaces shall be not less than those required in Table II
  • Service-drop conductors passing over a roof shall be securely supported by substantial structures, preferably independent of the building
• Conductors passing by or over buildings

  • Unguarded or accessible supply conductors carrying voltages over 300 volts may run beside or over buildings
  • Vertical or horizontal clearances to any building or its attachments shall adhere to specified requirements. The horizontal clearance governs above the roof level until the diagonal equals the vertical clearance
  • This rule doesn't restrict the installation of a trolley contact conductor over the approximate center line of the track it serves
• Guarding of supply conductors


  • Conductors of 300 volts or more shall be properly guarded by grounded conduit, barriers, or otherwise, under specific conditions: When required clearances cannot be obtained, or when conductors are placed near windows, verandas, fire escapes, or other accessible places within reach of persons
• Alternative solutions for required clearances

  • If required clearances cannot be obtained, supply conductors shall be of Grounded Metallic Shield, Jacketed Primary Cables grouped or bundled and supported by grounded messenger wires
• Service drop conductors


  • Shall not be readily accessible and, when not in excess of 600 volts, shall conform to specified requirements
  • Clearances over roofs: Conductors shall have a clearance of not less than 2.5m from the highest point of roofs over which they pass. Exceptions are granted based on certain conditions
  • Clearance from the ground: Conductors must maintain a clearance of at least 3m from the ground or from any platform or projection within reach
  • Clearance from building openings: Conductors must maintain a horizontal clearance of not less than 1m from windows, doors, porches, fire escapes, or similar locations. They should be run at least 500mm above the top level of a window or opening
• Service drop of communication lines

  • When crossing a street, service drop communication lines must have a clearance of not less than 5.5m from the crown of the street or sidewalk
  • At its point of attachment to the building or pedestal, service drop communication lines shall have a minimum clearance of 3m above ground
• Installation restrictions near swimming and wading pools

  • No parts of swimming and wading pools should be placed under existing service drop conductors or any other overhead wiring
  • Overhead wiring should not be installed above: Swimming and wading pools and the area extending 3m outward horizontally from the inside of the walls of the pool, Diving structures, Observation stands, towers, or platforms
• Wiring methods


  • Service entrance conductors must be installed in rigid steel conduit, asbestos cement conduit, or concrete encased plastic conduit from the point of service drop to the meter socket and from the meter socket to the disconnecting equipment
  • If the service entrance conductors are protected by approved fuses or breakers at their outer ends, they can be installed in any recognized wiring method
• Abandoned lines


  Lines or portions of lines that are no longer required shall be removed
• Attachment restrictions


  • Power or communication poles, lines, service drops, and other line equipment must be free from any attachment for antennas, signs, streamers, etc.
• Grounding of metallic sheaths


  • Metallic sheaths or jackets of overhead power or communication cables must be grounded at a point as close as possible to ground level whenever they change from overhead to underground installations
• Oil-insulated transformers installed outdoors


  • Combustible material, buildings, and parts of buildings must be safeguarded from fires originating in oil-insulated transformers. Safeguards may include space separations, fire-resistant barriers, or enclosures that confine the oil of a ruptured transformer tank
  • Oil enclosures must have trapped drains in cases where oil removal is important
• Dry-type transformers installed indoors

  • Transformers rated 112-1/2 KVA or less must have a separation of at least 300mm from combustible material unless separated by a fire-resistant heat-insulating barrier or unless completely enclosed except for ventilating openings
  • Transformers of more than 112-1/2 KVA rating must be installed in a transformer room of fire-resistant construction or separated from combustible material by specified distances or a fire-resistant heat-insulating barrier
• Askarel-insulated transformers installed indoors

  • Askarel-insulated transformers rated in excess of 25 KVA must be furnished with a pressure relief vent and installed in a vault if rated more than 35,000 volts
  • Transformers installed in poorly ventilated places must have means for absorbing gasses generated by arcing inside the case, or the pressure relief vent must be connected to a chimney or flue carrying such gasses outside the building
• Oil-insulated transformers installed indoors


  • Oil-insulated transformers installed indoors must be placed in a vault constructed according to specified guidelines, except for certain exceptions
• Guarding of transformers


  • Transformers must be guarded with mechanical protection, a case or enclosure, and guarding of exposed live parts. Voltage warning signs or markings must be provided
• Provisions for transformer vaults


  • New buildings with an expected load demand of 200KVA or above must be equipped with a transformer vault. Transformers may be mounted on poles or structures within the property if sufficient space is available, provided all required clearances can be maintained and there are no contaminations on insulators or bushings that could pose hazards
  • Transformer vaults must be easily accessible to qualified personnel for inspection and maintenance. They should be situated where ventilation is adequate and where the probability of flooding is minimized
• Mechanical Protection


  • Measures must be taken to minimize the possibility of damage to transformers from external causes if they are located exposed to physical damage
• Case or Enclosure


  • Dry-type transformers must be provided with a non-combustible, moisture-resistant case or enclosure to protect against accidental insertion of foreign objects
• Exposed Live Parts


  • Transformer installations must comply with provisions for guarding live parts as outlined in PEC Rule 1056
• Voltage Warning


  • Signs or visible markings indicating the operating voltage of exposed live parts must be provided on the equipment or structures
• New Building


  New buildings with an expected load demand of 200KVA or above must be equipped with a transformer vault
• Location


  Transformer vaults must be easily accessible to qualified personnel for inspection and maintenance. They should be situated where ventilation to the outside air is possible without using flues or ducts, whenever feasible
• Walls, Roof, and Floor

  • Vault walls and roofs should be constructed of reinforced concrete (minimum 150mm thick), masonry or brick (minimum 200mm thick), or 300mm load-bearing hollow concrete blocks. If hollow concrete blocks are used, the inside surface must be coated with cement or gypsum PLASTER (minimum 20mm thick). The vault FLOOR must be concrete (minimum 100mm thick)
• Doorways


  • Each doorway must have a tight-fitting door approved for such locations. Doorways must have a sill or curb tall enough to contain the oil from the largest transformer, with a minimum HEIGHT of 100mm. Entrance doors must be equipped with locks accessible only to qualified personnel, arranged to allow quick opening from the inside
• Ventilation Location

  • Ventilation openings should be positioned away from doors, windows, fire escapes, and combustible materials
• Ventilation Arrangement

  • Vaults ventilated by natural air circulation may distribute openings roughly, with HALF THE TOTAL AREA near the floor and the remainder near the roof or sidewalls. Alternatively, all required ventilation areas may be concentrated near the roof
• Ventilation Size


  • Vaults ventilated to an outdoor area without ducts or flues should provide a combined net area of all openings not less than 0.006 sq mm per KVA of transformer capacity in service, with a minimum net area of 0.1 sqm FOR CAPACITIES UNDER 50 KVA
• Ventilation Covering


  • Ventilation openings must be covered with durable gratings, screens, or louvers to ensure safety
• Ventilation Dampers


  • Automatic dampers used in ventilation openings of oil-insulated transformer vaults should be designed to function at fire temperatures, minimizing accidental closing
• Ventilation Ducts


  • Ventilating ducts must be constructed of fire-resistant materials
• Drainage


  • Vaults containing over 100 KVA transformer capacity should ideally have drains to carry off oil or water accumulation, unless local conditions make this impractical
• Water Pipes and Accessories

  • Foreign pipe or duct systems should not enter or pass through a transformer vault. If unavoidable, maintenance-requiring appurtenances should be located outside the vault. Fire protection or water-cooled transformer facilities are exceptions and not considered foreign to the electrical installation