Primary Injection Test is a comprehensive electrical testing method used to verify protection chain of a power system by injecting a high current directly into the primary side(the main power-carrying conductors)

Primary injection testing checks the entire protection chain, including:

•Main contacts

•Current transformers (CTs)

•Internal wiring

•Trip unit / protection relay

•Mechanical trip mechanism

Because current flows through the same path as in real operation, it is the most realistic functional test.

Pros:

•Most realistic test because it tests everything in the loop.

•Detects wiring issues, CT polarity errors, and breaker problems.

Cons:

•Requires high current source.

•Harder and more dangerous than secondary injection.