How to Buy Electrical Complete Equipment: A Project Checklist

2026-08-14 20:25:34

Buying electrical complete equipment is not simply about comparing prices. The right choice depends on voltage level, load profile, environment, standards and future expansion plans. This checklist will help engineers and procurement teams evaluate switchgear, transformers, substations and power-quality equipment with confidence.

Step 1: Define the Electrical Parameters

Before contacting suppliers, collect the following data:

• System voltage: high-voltage side (e.g., 10 kV, 35 kV) and low-voltage side (e.g., 400 V, 690 V)

• Short-circuit level: maximum prospective fault current at the connection point

• Load current: normal, peak and future load currents

• Frequency: 50 Hz or 60 Hz

• Ambient conditions: temperature, humidity, altitude, pollution level, indoor/outdoor

Step 2: Choose the Transformer

The transformer is the heart of any substation. The two most common technologies are:

Oil-Immersed Transformers

• Best for: outdoor substations and budget-sensitive projects

• Capacity range: 30 kVA to 2,500 kVA common

• Advantages: high overload capacity, long life, low initial cost

• Cooling: natural oil circulation with radiators

Resin-Cast Dry-Type Transformers

• Best for: indoor installations, high-rise buildings, hospitals, data centers

• Insulation: vacuum-cast epoxy resin

• Insulation class: F or H

• Advantages: fire-resistant, low noise, no oil leakage risk, suitable for sensitive environments

• Cooling: natural air (AN) or forced air (AF) with temperature control

Step 3: Select High-Voltage Switchgear

Match the HV switchgear to the network topology:

• Ring networks: gas-insulated, solid-insulated or air-insulated RMUs

• Large substations: metal-clad withdrawable switchgear such as KYN28-12 or KYN61-40.5

• Outdoor feeders: cable branch boxes with DIN-standard connectors

Step 4: Select Low-Voltage Switchgear

Choose between fixed-type and withdrawable-type assemblies based on maintenance needs and feeder density:

• Fixed type (GGD, XL-21): main distribution boards and motor control centers with limited feeder changes

• Withdrawable type (MNS, GCK, GCS): critical facilities requiring minimal downtime

Step 5: Plan Power Quality and Protection

• Power-factor correction: install LV capacitor banks to keep power factor above 0.9 and avoid utility penalties.

• Surge protection: add surge arresters at HV cable entries and LV distribution boards.

• Earth fault protection: specify residual-current devices and earth-fault relays for personnel safety.

• Automation: consider FTU/RTU interfaces for remote monitoring and fault location.

Step 6: Verify Standards and Documentation

Ensure the supplier provides:

• Type-test reports from an accredited high-voltage test laboratory

• Compliance with IEC, GB, DL or local standards

• Single-line diagrams, layouts and foundation drawings

• Operation and maintenance manuals

• Spare-parts list and commissioning support

Common Mistakes to Avoid

• Undersizing the transformer for future load growth

• Choosing indoor switchgear for outdoor installation without proper IP rating

• Ignoring altitude de-rating for sites above 1,000 m

• Specifying fixed panels where withdrawable units are needed

• Overlooking power-factor correction requirements

Frequently Asked Questions

How much spare capacity should I plan?

A good rule of thumb is to size the transformer at 70–80% of its rated capacity under normal operation, leaving room for load growth.

What information does a supplier need for a quotation?

Provide single-line diagrams, voltage levels, load list, short-circuit level, environmental conditions, required standards and delivery schedule.

Can complete equipment be supplied with SCADA integration?

Yes. Many HV switchgear and compact substation designs can be equipped with FTU, RTU or smart terminal units for SCADA and distribution automation.

Get a Tailored Proposal

Every power distribution project has unique requirements. Our engineering team can help you select transformers, HV/LV switchgear, compact substations and distribution boxes that match your technical and budget targets. For a detailed quotation, feel free to consult us via email.