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Share the equipment and project requirements. If you need help selecting a model, describe the application.
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Illustrative utility distribution site.Utility & Secondary Distribution
Plan a feeder extension, transformer change or substation upgrade around the circuits that must stay in service. Mark retained equipment, temporary supplies and permitted outage windows on the single-line diagram.
Projects on this page
Upgrading an existing substation
Distribution substation upgrades
A utility adding a transformer bay or splitting a loaded feeder needs an operating plan for both construction and the final arrangement. Mark the cables, busbars and protection that will remain.
- Equipment selection
- Check outage windows, alternate supply capacity, fault duty and protection before and after the change. Reserve space and cable routes for the next feeder.
- Send with the enquiry
- Existing and proposed single-lines, peak demand by feeder, fault levels, switching sequence and drawings of the retained switchgear.
Replacing a transformer while an adjacent feeder stays live
A replacement unit can fit the foundation and still fall outside the planned outage if its cable terminals move or the existing protection panel needs modification. Give bidders the existing and proposed single-lines, the limiting outage window and a dimensioned sketch of the connections that will stay in place.
Compare the three stages of the changeover
| Operating condition | Question to settle | What to request |
|---|---|---|
| Before transfer | Which existing feeder or tie can carry the transferred load? | Mark the temporary source, tie and cables carrying the transferred load. Request the permissible loading, protection settings and any customer interruptions from the utility. |
| During the outage | Where do the retained cables, panels and civil works meet the new supply? | Show the isolation boundary and equipment that remains energised. Compare terminal positions, retained cable lengths, shipping dimensions and site connections before fixing the outage date. |
| After energisation | How will the new transformer bay and future feeders connect to the existing bus? | Show the final tie position, feeder names and spare positions. Assign responsibility for protection tests, cable checks, commissioning and handover to the network operator. |
What is changing on the network?
Start with the change shown on the network drawing. Use the same terminal and circuit labels in the equipment schedule and in each supplier’s quotation.
Will the replacement fit the existing connections?
In this example the feeder and LV board stay in place. Compare the proposed unit with the existing installation before agreeing the replacement scope.
Existing transformer duty
Send the old nameplate and the latest load record. Compare the proposed voltage ratio, tap range, impedance and winding connection with the project requirements.
Cable entries and terminals
Photograph both cable approaches and mark terminal heights, orientation and phase identification. Compare them with the supplier’s outline drawing to see whether the retained cables can reach the proposed terminals.
Foundation and access
Mark the existing base, fixing points, access opening and route for removing the old unit. Ask for the proposed footprint, handling mass and lifting arrangement.
Outage and handover
State the available outage window and which adjacent circuits must remain available. Ask who will disconnect and reconnect the cables, complete site tests and return the circuit to service.
Equipment for the project scope
MV switchgear
For an extension, match each new panel to its feeder function and identify the connection to retained equipment.
View MV switchgear
Oil-immersed transformers
For a replacement unit, compare the required electrical duty and terminal positions with the proposed transformer outline.
View oil-immersed transformers
Prefabricated substations
For a new supply point, review the transformer, switching equipment and enclosure as one package, with the external terminals identified.
View prefabricated substations
Single-phase transformers
For a single-phase overhead replacement, check the support arrangement and line connections as well as the nameplate.
View single-phase transformersSend with the enquiry
Give each bidder the same marked-up single-line diagram so the equipment and site work can be compared on the same basis.
Network drawing
Single-line diagram with circuit names, connection point and retained equipment.
Electrical duty
Rated voltages, frequency, load or required capacity, and available fault-level data.
Existing installation
Nameplates, site photographs, cable entries, footprint and outage restrictions.
Compare quotation scopes
Check each bid against the same drawing. Identify the equipment included, the existing connections and any work priced separately.
| Project | What to mark on the drawing | What to ask the bidder to price |
|---|---|---|
| Extend a feeder | Mark the connection to the existing feeder, incoming and outgoing circuits, and the normally open point if the network is a ring. | List the new panels by circuit. State the switching, protection and metering functions, and identify work at the connection to the existing equipment. |
| Replace a transformer | Identify the MV feeder, LV board, cable ends and foundation you intend to retain. Record the old unit’s nameplate and terminal positions. | Request the proposed transformer data sheet and dimensioned outline. List any cable, termination or foundation changes separately. |
| Add a supply point | Show the incoming feeder, transformer and outgoing circuits. Mark the external terminals and the proposed enclosure footprint. | Request either separate equipment prices or a complete prefabricated station. Ask the bidder to list internal connections, external cable work and site work separately. |
Request with the quotation
- An itemised equipment schedule with included and separately priced work.
- Data sheets and dimensioned drawings showing terminal positions and installation interfaces.
- A list of exclusions and responsibilities for cable terminations, site installation and site testing.