Pole-Mounted Substation Equipment List: What a Complete 11kV / 33kV Package Includes

A pole-mounted substation is the simplest kind of substation to draw and one of the easiest to procure badly.

The transformer gets specified carefully. Then the cutouts come from one supplier, the arresters from another, the LV board from a third, and the connectors, earth rod and mounting channel from whoever the site agent could find. The package arrives in four shipments across five weeks, and commissioning stops because nobody bought the bimetallic lugs that connect an aluminium conductor to a copper bushing stud.

Nothing in that story is a design failure. It is a bill-of-materials failure, and it is entirely avoidable.

This article sets out what a complete 11 kV or 33 kV pole-mounted substation package actually contains, how the ratings cascade from the transformer size, and what to send a supplier to get a quotation you can build from.

What a pole-mounted substation is

A pole-mounted (or pole-top) substation takes an MV overhead line — typically 11 kV, 22 kV or 33 kV — down to LV, usually 400/230 V, on a single pole or an H-pole structure. Capacities generally run from 25 kVA up to 315 kVA, and up to 500 kVA on a double-pole structure.

The power path is short and the equipment count is small:

MV overhead line
      ↓
Surge arrester (protects against overvoltage)
      ↓
Drop-out fuse cutout (overcurrent protection + visible isolation)
      ↓
HV connection to transformer bushings
      ↓
Distribution transformer (MV → 400/230 V)
      ↓
LV cable to distribution box
      ↓
LV distribution box (main switch, ways, protection, metering)
      ↓
LV distributor / service cables

Every one of those stages has hardware that must be bought, and three of them have earthing requirements that must be coordinated.

The complete equipment list

1. MV protection and connection

Selection detail for these two devices is covered in depth in our companion guides: drop-out fuse cutout selection and surge arrester selection.

Products: 11-33kV Drop-out Fuse · 11-33kV Lightning Arrester · 11-33kV Composite Insulator · Power Fittings

2. The transformer

The single largest line item, and the one that sets every other rating.

Products: Distribution Transformers — including the S11-11kV hermetically sealed oil-immersed series, S11-24kV and 33 kV S11 variants, the S(B)H15 amorphous alloy series, and the SC(B)10 F-class epoxy resin dry type for 11 kV / 24 kV.

3. Structure and mounting

4. Earthing

Earthing is where pole substations most often fall short of the drawing, and it is cheap to get right at the ordering stage.

Two principles worth stating in the specification:

1. Bond the arrester earth lead directly to the transformer tank. The transformer insulation is stressed by the difference between its terminal and its tank, so connecting them at one point removes the lead voltage drop from that difference.
2. Confirm whether the HV and LV earths are combined or separated on this network. Practice varies by country and it changes both the hardware count and the layout.

Target earth resistance is commonly 10 Ω or lower for a distribution transformer earth, but the governing figure is whatever the local wiring or utility rules specify — check before committing.

5. LV side

Products: LV Distribution Box · LV Switchgear · Terminal Power Distribution (MCBs, RCBOs, surge protectors) · Power Cables · Cable Accessories

How the protection layers inside that board should be arranged — overcurrent, earth leakage, arc fault and surge — is covered in AFDD vs MCB vs RCCB vs RCBO.

6. Documentation

Frequently the reason a completed substation cannot be energised.

• Routine test certificates for the transformer
• Type test reports for protection devices
• Rating plate photographs and serial number schedule
• Dimensional and mounting drawings
• Installation and operating manuals in the project language
• Certificates of origin and conformity for customs and the client

Sizing the package: everything cascades from the kVA

Choose the transformer first — connected load, applied diversity, plus headroom for growth (20–30 % is a common allowance on distribution networks). Every other rating follows from it.

HV current = kVA ÷ (√3 × kV). LV current at 400 V ≈ kVA × 1.44.

Note how different the fuse links are between the two voltages for the same transformer — a 315 kVA unit needs roughly a 30 A link at 11 kV but only around 10 A at 33 kV. Reusing an 11 kV fuse schedule on a 33 kV project leaves the transformer with essentially no protection against secondary faults. Verify the final link selection against the specific transformer's inrush and through-fault curves; the table above is a starting point, not a substitute for coordination.

Six decisions that change the bill of materials

1. Oil-immersed or dry type. Changes the transformer, the mounting, and often the whole siting concept.
2. Silicon steel or amorphous alloy core. Higher capital cost, materially lower no-load loss over 25 years — run the numbers on the actual load factor.
3. Pollution class of the site. Drives creepage on cutouts, arresters and insulators, and the enclosure material on the LV box. Specify the whole pole to one pollution class.
4. Load-break or plain cutouts. An operating-practice decision, not an accessory decision.
5. Arrester discharge class, 5 kA or 10 kA. Set by lightning exposure and the value of the protected asset.
6. Metering scope. Adding CTs and a meter changes the LV box size, the way count and the enclosure.

What gets forgotten

The items that stop commissioning are rarely expensive:

• Spare fuse links — order a percentage of the total with the first shipment
• Bimetallic connectors for aluminium-to-copper joints
• Earth rods, earth conductor and clamps
• LV cable lugs in the correct size for the transformer terminal studs
• Danger plates, phase identification and asset labels in the local language
• Anti-climbing device and enclosure lock
• Spare gaskets and, on non-sealed transformers, breather silica gel and topping-up oil

Why a single-source package is worth the comparison

Buying the substation as one package rather than eight line items removes the failure modes that cost programme time:

• Interfaces match. Bracket to pole, lug to bushing, cutout spacing to arrester spacing.
• One document pack. Certificates arrive together and in a format the client's engineer will accept.
• One shipment, one set of customs paperwork. Fewer partial deliveries sitting in a compound waiting for the missing item.
• Spares commonality. One fuse link type and one arrester type across a hundred substations, not five of each.
• One technical contact when the design changes at revision C.

Delixi Electric supplies the complete pole-mounted substation scope — transformers, cutouts, arresters, insulators, conductor, fittings, cable accessories and the LV board — as a coordinated package. For containerised and kiosk alternatives, see our Prefabricated Substation range.

What to send with your enquiry

1. System voltage (HV and LV) and frequency
2. Neutral earthing arrangement — required for arrester selection
3. Transformer capacity, or connected load and diversity if you want it sized
4. Vector group, impedance and tapping requirements
5. Prospective fault current at the point of connection
6. Pole type and structure: single or H-pole, existing or supplied
7. Site conditions: pollution class, altitude, ambient temperature range, seismic requirement
8. LV feeder schedule: number of ways, ratings, metering requirement
9. Earthing practice: combined or separated, target resistance
10. Standards to be met and any client-specific specification
11. Quantities, delivery schedule and destination port
12. Documentation and language requirements

Catalogues, drawings and certificates are available from our Download centre and Certificates pages.

FAQ

What is the maximum transformer size for a single-pole substation? Practice varies, but single-pole mounting is commonly used up to around 200 kVA, with H-pole or double-pole structures above that. The governing limits are the pole's mechanical rating and the local utility standard.

Do I need both a drop-out fuse and a surge arrester? Yes. They address different faults — the arrester limits overvoltage from lightning and switching, the cutout interrupts overcurrent and provides visible isolation. Neither substitutes for the other.

Oil-immersed or dry type for a pole-mounted substation? Oil-immersed hermetically sealed units are the norm for pole mounting: lower cost, well-proven outdoors, and no enclosure needed. Dry type is chosen where fire risk, indoor siting or environmental rules govern.

Is an amorphous alloy transformer worth the extra cost? Often yes on distribution networks. No-load loss runs continuously for the transformer's whole life, so on lightly loaded rural feeders the reduced no-load loss can repay the premium well inside the asset life. Compare on total loss cost at the actual load factor, not on purchase price.

How do I size the HV fuse link for the transformer? Calculate HV full-load current as kVA ÷ (√3 × kV), then select a link at roughly 1.5–3 times that value and verify against the transformer's inrush and through-fault damage curves. See the cutout selection guide for the full method.

Can you supply the whole substation as one package? Yes — transformer, HV protection, structure hardware, LV board and accessories can be quoted, manufactured and shipped as a coordinated scope with a single document pack.

Get your pole substation package priced

Send us the line data, transformer capacity and LV feeder schedule, and we will return a complete bill of materials with ratings, part numbers, drawings and datasheets — every interface checked before it ships.

Request a quotation → | Become a distributor →

Related reading

MV overhead line series

• How to Select Drop-Out Fuse Cutouts for 11kV, 24kV and 33kV Overhead Lines — voltage class, creepage, breaking capacity and K/T fuse link sizing for the HV protection in this package.
• How to Select Surge Arresters for 11kV, 24kV and 33kV Overhead Lines — Uc, Ur, discharge class, protective margin and the lead-length rule referenced in the earthing section above.
• What Is a Dropout Fuse? — a shorter introduction to the cutout and its construction.

LV side of the substation

• AFDD vs MCB vs RCCB vs RCBO: Where Arc Fault Protection Fits in LV Panels — how to arrange the protection layers inside the LV distribution box.
• Picking the Right Miniature Circuit Breaker (MCB): Curve Types (B/C/D), Icn, and Application Examples — setting curve and breaking capacity for the outgoing ways.