Short-Circuit Withstand: Refer to Type Test Data
The assessment of power equipment’s short-circuit withstand capability (its ability to endure short-circuit currents without sustaining damage) is based on short-circuit test data found in type test reports. Key metrics include the rated short-time withstand current (Icw) and its duration, as well as the rated peak withstand current (Ipk). Industry experts note that assessing this capability involves looking at three specific figures: short-circuit withstand current (kA), duration (1s/3s), and peak current.
True capability is confirmed only when the data meets standards for the specific model listed in the test report.
Three Key Data Points
- Rated short-time withstand current (Icw): e.g., 50kA/1s or 80kA/3s;
indicates the equipment can withstand the short-circuit current for the specified duration without damage. - Rated peak withstand current (Ipk): The peak value of the short-circuit current (typically 2.0–2.5 times the Icw); verifies dynamic stability (mechanical withstand capability).
- Short-circuit breaking capacity (Icu/Ics): The circuit breaker’s capacity to safely interrupt short-circuit currents.
Assessment Methods
First, check the type test report. The short-circuit test report (conducted according to GB/T 3906/IEC 62271) lists the test current, duration, and results for the specific model.
Second, consider the system’s short-circuit current.
The equipment’s short-circuit withstand current must exceed the prospective short-circuit current of the system where it is installed (calculated based on grid short-circuit capacity), ensuring an adequate safety margin.
Third, evaluate component coordination. Ensure the circuit breaker’s short-circuit breaking capacity matches the withstand capability of the switchgear enclosure.
Fourth, verify report alignment.
Ensure the report corresponds to the specific model and parameters being procured to prevent the misuse of certification documents.
Pitfalls to Avoid
First, “inflated data”: the rated short-circuit current lacks supporting test data, leading to cabinet rupture during a fault.
Second, “mismatched reports”: test reports correspond to different models.
Third, “component incompatibility”: the circuit breaker’s breaking capacity is lower than the system’s short-circuit current, creating a high risk of failure to operate.
Trends and Recommendations
Short-circuit capacity selection is moving toward “digital selection”: matching system short-circuit calculation software with equipment parameter databases, with test data made publicly accessible.
For purchasers, the recommendation is to “verify short-circuit reports, cross-check against system short-circuit current, and allow for a safety margin.”
Short-circuit withstand capability is a safeguard for safety—test data represents true performance.
