Fault levels

Fault levels on our network are affected by both internal and external factors, such as the Transmission Network Service Provider’s network, generators and customer connections.

Internal factors

Fault level increases due to augmentation works within our network are managed by putting policies in place to ensure that works will maintain short circuit fault levels within allowable limits.

External factors

Fault level increases due to external factors are monitored by annual fault level reporting, which estimate the prospective short circuit fault levels at each substation. The results are then compared to the maximum allowable short circuit fault level rating of the switchgear, plant and lines to identify if plant is operated within fault level ratings.

We obtain upstream fault level information from Transmission Network Service Provider’s annually and changes throughout the year are communicated through joint planning activities.

New connections of distributed generation and embedded generation which increase fault levels are assessed individually to ensure limits are not infringed. Known embedded generators are added to our simulation models so that the impacts of these generators on the system fault levels are determined.

High voltage fault level limits

The table below lists design fault level limits that apply at our installations. It is recommended this table is used when designing your network.

Network typeVoltage (kV)Existing installation current (kA)New installation current (kA)
Sub-transmission132/11025/31.525 (3s)
Sub-transmission662525 (3s)
Sub-transmission3313.125 (3s)
Distribution2213.125 (3s)
Distribution1113.125 (3s)

Low voltage fault levels

Calculation of low voltage (LV) fault levels can be found within the Standard for Distribution Line Design Overhead (PDF 15.2 mb) and Standard for Distribution Line Design Underground (PDF 608.8 kb).

Pole transformer size is written on the transformer tank and is visible from the ground. Pad mount and ground substation size is also written on the tank.

If the downstream LV fault level is required (overhead area) you should visit the site and determine conductor sizes and length.

Transformer fusing information can be found within the Queensland Electricity Connections Manual (PDF 5.1 mb).

Requesting detailed information

If you wish to obtain more detailed fault level information, there are two ways you can do this:

Option 1 - Locate the information in available data

Determine the zone substation you are supplied from (available from your electricity retailer) and then locate the relevant substation and associated fault level within the Annual Fault Study Summary Report (XLSX 479.8 kb)

Option 2 - Complete our online enquiry forms

Please note there is a fee for this service. Its a two step process as follows:

  • Step 1 - Complete the Fault Level Enquiry form and you'll receive an email with an attached text (.txt) file which is a summary of your competed form. Save this text file and attach it to your Asset Relocation Enquiry (see step 2).
  • Step 2 - Submit an Asset Relocation Enquiry via the Electrical Partners Portal attaching your saved Fault Level Enquiry form summary text file.