What is the primary benefit of using a manufacturer's test kit for primary-injection testing?

The primary benefit of using a manufacturer's test kit for primary-injection testing is higher accuracy in measurements. These test kits are specifically designed and calibrated by the manufacturers to ensure precise readings and reliable performance. By using equipment that meets certain specifications and tolerances, the technician can achieve measurements that greatly reduce uncertainty and error margins associated with the testing process. This accuracy is crucial, especially when establishing the performance characteristics of protection relays and circuit breakers, as it directly impacts the reliability and safety of electrical systems.

Other options, while beneficial in their own contexts, do not address the main advantage of accuracy directly tied to the test kit's design and calibration.