Leakage Reactance testing is highly sensitive to transformer winding deformation. When these type changes occur, electrical losses increase and make the transformer less efficient. Additionally, these type indications, as reflected in the impedance of a transformer, can be used as a diagnostic tool to help maintain the health of the transformer and ensure its continued service.
A 10 ampere Digital Low Resistance Ohmmeter is sufficient for many low resistance measurement applications. However, industry standards and guidelines will recommend, if not require a minimum of a 100 amps DC source when evaluating connections relating to medium and high voltage power system apparatus. Very small changes in contact resistance can have significant impacts on these apparatus in terms of how they perform in service. The use of higher current helps in the precision of the measurement and is therefore preferred when evaluating connections in higher voltage applications.
A secondary injection test is a method of verifying the electrical operational characteristics of a circuit breaker. While not specifically addressing components in the primary current path of a circuit breaker, secondary injection testing is used to verify operational settings and characteristics in the decision making portion of the circuit breaker (solid state trip device). This type of electrical operational testing can be conducted without the need for large, high powered primary injection test equipment. Since this method of testing only uses low level signals that the trip device would normally see from current sensor secondaries, it can also be less time consuming and generally safer than performing primary injection testing.