Home > Business > For Housing Developers & Electrical Contractors > TNB Electricity System

TNB Electricity SystemPrint this page 


The transmission voltage networks are 500kV, 275kV and 132kV, whilst the distribution voltages are 33kV,
11kV and 400/230 volts. However, in the case of certain parts of Johor & Perak the distribution voltages may
also include 22kV and 6.6kV.

Supply­ Frequency

The supply frequency is 50Hz ± 1%.

Earthing­ System

High­ Voltage­ and­ Extra ­High­ Voltage

  • 3 phase configuration
  • Solidly earthed or impedance earthed
  • Overhead lines and underground cable are used extensively for high and extra high voltage distribution

Low­ Voltage­ 400/230V

  • 3 phase 4 wire system
  • Neutral point solidly earthed mixture of overhead lines, underground cables and aerial insulated cables
  • Mixture of overhead lines, underground cables and aerial insulated cables

Short­ Circuit­ Ratings

As a guide, the maximum fault levels for the various voltage systems are as follows. All equipment proposed to
be installed and connected to TNB supply must comply with the stated short circuit ratings:


Short circuit rating for 3s

500 kV

50 kA

275 kV

40 kA

132 kV

31.5 kA

66 kV

20 kA

33 kV

25 kA

22 kV

20 kA

11 kV

20 kA

6.6 kV

20 kA

400/230 V

31.5 kA


Act,­ Regulation ­and­ Code

The electricity supply and installation practice in Peninsular Malaysia are governed by the following:

  1. Electricity Supply Act 1990 - Act 447
  2. Licensee Supply Regulations 1990
  3. Electricity  Regulations, 1994
  4. Occupational, Safety & Health Act 1994
  5. Malaysian Standard MS IEC 60364 Electrical Installation of Buildings

Supply­ Voltage ­Options

Supply may be provided at any of the declared voltages:

275 kV, 132 kV, 33 kV, 22 kV*, 11 kV, 6.6 kV* and 400/ 230 V.

* certain parts of Johor and Perak only

Generally, supplies to domestic premises are given at single phase 2-wire or three phase 4-wire. However, the actual supply voltage provided depends on the magnitude of the individual applicant’s load requirements:

Low­ Voltage

  1. Single-phase, two-wire, 240 V, up to 12 kVA maximum demand
  2. Three-phase, four-wire, 415 V, up to 45 kVA maximum demand
  3. Three-phase, four-wire, C.T. metered, 400/230 V, up to 1000 kVA maximum demand

Medium­ Voltage ­&­ High­ Voltage

  1. Three-phase, three-wire and 11 kV for load of 1,000 kVA maximum demand and above
  2. Three-phase, three-wire, 22 kV or 33 kV for load of 5,000 kVA maximum demand and above
  3. Three-phase, three-wire, 66 kV, 132 kV and 275 kV for exceptionally large load of above 25 MVA maximum demand

It should be noted that voltages other than the above classifcations couldn’t be provided by TNB. However,
consumers can make their own transformation arrangements where necessary.

Back to top