Understand the interface decision

Selectivity cannot be assessed only by ranking breaker amperes. Device characteristics, fault levels and source behavior matter, particularly where converters or multiple supplies are present. Some events may legitimately require a complete shutdown; the protection philosophy must distinguish them from faults that should remain local.

Protection decisions depend on the actual earthing arrangement, available fault energy and equipment instructions. Treat the following as review inputs for the responsible electrical designer. Device names alone cannot establish a coordinated or compliant installation.

Put these inputs in the review record

Use a project-specific worksheet to capture the following information. For each entry, name the document, revision and person responsible for resolving any uncertainty.

• Fault locations and the intended isolation boundary for each. Identify the exact configuration and the supporting document.
• Protective-device characteristics and coordination evidence. Keep the design assumptions visible in the project record.
• Available fault contribution from every connected source. Name the responsible reviewer and resolve any missing information.
• Auxiliary and protective functions that must remain available after a trip. State how this entry will be verified during acceptance.

Define the acceptance boundary

Require a protection study or manufacturer-supported coordination method appropriate to the design. Do not promise full selectivity beyond the documented fault-current range. Record any limitations and their effect on turbine shutdown and site service continuity.

A practical acceptance matrix connects each assessed fault with the devices expected to operate. This makes an unexpected upstream trip visible as a deviation rather than treating every loss of power as equivalent.