Electrical System

The Electrical system for the above development together with all the associated substation equipment, feeder cable etc. is to be provided by the local Supply Authority. The developer has to provide a substation building and hand it over to the Authority for installation of their electrical equipment.

The voltage of TNB distribution network at that area is rated at 3-phase 33KV or 11KV 50Hz with resistance earthed neutral grounded system. The 33KV/11KV high voltage supply will be stepped down to 415V by means of transformer and then fed to consumer’s LV Main switchboard for subsequent distribution to the various location in the building for general lighting, small power, production machines and other M&E equipment power requirement. Unless otherwise stated, all the equipment to be supplied would be operating at 415V 50Hz three phase 4-wires with neutral solidly grounded voltage system.

The LV electrical system works and equipment to be provided shall cover of the following :-

  • LV Main Switchboards-auto power factor regulation capacitor bank.
  • Sub-switchboard & Distribution Boards for lighting & small power distribution.
  • LV Main Incoming & Submain Cabling Works- Cable Supporting System.
  • LV Equipment Earthing System.

The LV Main Switchboard would be of metal clad floor standing type design to BS 5486 Part 1 (1977) specification. The switchboard shall be suitable for indoor operation on solidly earthed neutral system and all equipment shall be capable of withstanding the prospective symmetrical fault level of at the rated voltage.

An emergency power system is an independent source of electrical power that supports important electrical systems on loss of normal power supply. A standby power system may include a standby generator, batteries and other apparatus. Emergency power systems are installed to protect life and property from the consequences of loss of primary electric power supply.

With regular generators, an automatic transfer switch is used to connect emergency power. One side is connected to both the normal power feed and the emergency power feed; and the other side is connected to the load designated as emergency. If no electricity comes in on the normal side, the transfer switch uses a solenoid to throw a triple pole, single throw switch. This switches the feed from normal to emergency power. The loss of normal power also triggers a battery operated starter system to start the generator, similar to using a car battery to start an engine. Once the transfer switch is switched and the generator starts, the building & emergency power comes back on (after going off when normal power was lost).

Unlike emergency lights, emergency lighting is not a type of light fixture; it is a pattern of the building & normal lights that provides a path of lights to allow for safe exit, or lights up service areas such as mechanical rooms and electric rooms. Exit signs, Fire alarm systems (that are not on back up batteries) and the electric motor pumps for the fire sprinklers are almost always on emergency power. Other equipment on emergency power may include smoke isolation dampers, smoke evacuation fans, elevators, handicap doors and outlets in service areas.