An international tender may specify a 30kV distribution network, while Chinese manufacturers commonly organize comparable products under a 35kV system class and a 40.5kV highest equipment voltage. This difference in naming can create uncertainty for buyers: is the Chinese product compatible, oversized or simply described under another convention?
The answer depends on more than the number printed in a catalog.
During technical review for a Burundi overhead line package, Younxin had to reconcile project descriptions, drawings and Chinese product categories before preparing the supply proposal. The process offers a useful checklist for other EPC and utility projects.
The following values should not be confused.
This is the voltage used to identify the network, such as 30kV or 35kV. It is a system designation and may follow local utility practice.
This is the maximum system voltage for which the equipment is designed. Chinese 35kV-class switchgear and line apparatus are commonly associated with a 40.5kV equipment rating.
Equipment must withstand specified power-frequency and lightning impulse voltages. Two products described with similar nominal voltage labels may still have different insulation levels.
For this reason, a supplier should not convert every occurrence of “30kV” to “35kV” without checking the technical schedule.
Confirm the rated voltage, rated current, short-time withstand current, operating method, pole-mounting arrangement and whether the device is designed only for isolation or also for load switching.
A gang-operated isolator provides a visible open point. It is not automatically a circuit breaker and may not be suitable for interrupting fault current.
For a drop-out fuse, check the voltage class, continuous current, breaking capacity, creepage distance and fuse-link rating. The fuse link should be selected according to transformer size, inrush current, feeder duty and protection coordination—not simply because it fits the fuse tube.
The arrester selection requires more than a nominal voltage. Confirm rated voltage, maximum continuous operating voltage, nominal discharge current, grounding arrangement and system earthing method.
An arrester intended for a 10kV system cannot be assumed suitable for a 30kV line. A mixed-voltage BOM should be treated as a technical query, not quoted without clarification.
Review:
Pollution, altitude and humidity can change the required external insulation even when the voltage class remains the same.
A description such as “3 × 1 × 150mm² MV cable” gives the conductor arrangement and cross-section, but not the insulation class. The buyer should confirm whether the cable is 12/20kV, 18/30kV, 26/35kV or another rating.
The termination must then match the cable’s conductor material, insulation diameter, screen structure, armor and indoor or outdoor application.
The transformer high-voltage winding, low-voltage winding and downstream distribution board must form one coherent system. In the Burundi project review, a 400V, 650A low-voltage board made it essential to verify the transformer’s stated secondary voltage rather than copying an ambiguous line from the source document.
Voltage compatibility does not guarantee installation compatibility. Pole-top equipment must also match:
When a reference drawing was originally developed for a concrete or timber pole, the mounting system should be redesigned for the actual steel pole. Reusing the same drawing without reviewing clamps and brackets can create unsafe site modifications.
Before approving a substitute or equivalent product, compare the following:
| Item | Project requirement | Proposed product | Confirmation needed |
|---|---|---|---|
| System | Nominal voltage and earthing method | Applicable system class | Client/utility approval |
| Equipment voltage | Highest voltage | Rated voltage / Um | Must be equal or higher as required |
| Insulation | Impulse, power-frequency, creepage | Test values | Must meet project standard |
| Current | Continuous and fault duty | Rated current and withstand | Check operating duty |
| Mechanics | Load, dimensions, interfaces | Product drawings | Check pole and conductor fit |
| Standard | IEC, EN, local or utility rules | Test standard | Confirm equivalence |
| Accessories | Brackets, links, fuse links, bolts | Included scope | Avoid installation shortages |
Written technical approval is especially important when:
The approval record should identify both the original requirement and the proposed equivalent. This protects the buyer, supplier and installer from later misunderstanding.
The most reliable equipment selection comes from reviewing the BOQ together with drawings, the single-line diagram and utility requirements.
Younxin can help international project buyers translate mixed-language technical lists, compare Chinese equipment classes and prepare a clarification schedule before quotation. Send your 30kV project documents and we will identify the parameters that require confirmation.
Not necessarily. In many product systems, 40.5kV is the highest voltage for equipment associated with a nominal 35kV network.
Transformer capacity is important, but protection coordination, inrush current, system voltage and upstream/downstream devices must also be considered.
Termination components fit specific insulation diameters, screens, conductor sizes and cable constructions. Voltage and cross-section alone do not guarantee a correct fit.