TNB Electricity System

Learn more about TNB Electricity System


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
  • Overhead lines and underground cable are used extensively for high and extra high voltage distribution

Medium Voltage

  • 3 phase configuration
  • Impedance-earth (NER)
  • Overhead lines and underground cable are used extensively for medium 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:                                                                                                                                                                                                                                                                              

System 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 practices in Peninsular Malaysia are governed by the following:

  • Electricity Supply Act 1990 - Act 447
  • Licensee Supply Regulations 1990
  • Electricity Regulations, 1994
  • Occupational, Safety & Health Act 1994
  • 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

  • Single-phase, two-wire, 240 V, up to 12 kVA maximum demand
  • Three-phase, four-wire, 415 V, up to 72kVA (100A) maximum demand
  • Three-phase, four-wire, C.T. metered, 400/230 V, up to 1000 kVA maximum demand

Medium­ Voltage ­&­ High­ Voltage

  • Three-phase, three-wire, 11kV for load of maximum demand 1,000 kVA to 5,000kVA
  • Three-phase, three-wire, 22kV for load of  maximum demand 1,000kVA to 10,000kVA
  • Three-phase, three-wire, 33kV for load of maximum demand 5,000kVA to 25,000kVA
  • Three-phase, three-wire, 132kV and 275kV for exceptional high load maximum demand above 25,000kVA

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


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How to Register as a TNB Electrical Contractor

Learn more on How to Register as a TNB Electrical Contractor

Step 1:

You need to register as an electrical contractor approved and certified by the Energy Commission

Step 2:

Submit the registration form together with a valid Contractors License from the Energy Commission at our Customer Service Centre (Customer Service Centre is subject to the area where the company chooses to perform the work e.g. if you are operating in Klang, go to our Klang branch to register)

Step 3:

The Customer Service Centre will update your company information into the system

Note: To register as a TNB e-Contractor, go to our myTNB Self Service Portal.


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Electricity Supply Application Handbook (ESAH)

Click here to learn more about the Electricity Supply Application and download the handbook.