Transformer Substations and High-Voltage (HV) Systems
The detail most often missed in a substation isn't voltage drop, it's short-circuit coordination.
Where coordination errors start
In a substation operating at 36 kV and above, protective selectivity ensures a fault trips only the affected line. If this calculation isn't done at the design stage, a fault at one point opens the main breaker feeding the entire substation.
The process starts with a site survey; grounding resistance is measured and the single-line diagram is drawn up from it. The power transformer, HV cells and protection relays are then sized together.
ONAN-type cooling
ONAN-type transformers, cooled by natural air circulation, cost less and have no moving parts such as fans. Rated power depends on ambient temperature and natural airflow.
ONAF-type cooling
ONAF-type transformers add forced-air cooling and can carry higher power within the same enclosure. They're preferred in hot climates or enclosed transformer buildings, though fan maintenance becomes an extra item in the process.
What's Included
- Substation site survey and single-line diagram
- Power transformer selection and sizing
- HV switchgear installation and cable termination work
- Protection relay coordination and setting calculation
- Grounding system design and measurement
- Commissioning tests and reporting
- Lightning protection and insulation coordination
In a transformer with a Dyn11 connection, the secondary voltage carries a 330-degree phase shift relative to the primary.
Standards We Apply
| Feature | SF6-Insulated | Vacuum Circuit Breaker | Air-Insulated |
|---|---|---|---|
| Space Requirement | Low | Medium | High |
| Maintenance Frequency | Low | Medium | High |
| Typical Use | Dense urban site | Medium-scale site | Large open site |
Frequently Asked Questions
How long does substation installation typically take?
Do you also handle revisions to an existing substation?
Would you recommend a vacuum breaker over an SF6-insulated cell?
Who oversees the commissioning tests?
Is grounding measurement included in the package?
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