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.
Common methods of finding faults in direct buried cables is arc reflection or simply thumping. Thumping is a method that is performed by discharging a large amount of energy into a cable. This electrical energy will seek to arc across the path of least resistance to ground, which in this case would be the electrical insulating material that separates the center conductor from the outer shield, or concentric neutral. When that arc occurs it often makes an audible thumping sound in the vicinity of the arc. If thumping is being performed where there is high ambient noise, or for some reason cannot be heard, directional acoustic detectors can be used in pinpointing the fault location. However, this method may require the cable to be thumped for a lengthy period of time while walking the path of the cable and listening. If a TDR (Time Domain Reflectometer) is incorporated into the test, along with a thumper, then when the arc occurs, the TDR will reflected the change to the impedance of the insulation at the location of the fault. This would be the Arc Reflection method and can significantly reduce the thumping time necessary to locate the fault. It can be used to localize the fault and if necessary pinpointed using an acoustic fault detector.
Users can set up and shoot traces in no time by using the Auto OTDR function which analyzes the fiber under test and then chooses appropriate settings. The EventMap feature analyzes traces like an expert, calculating overall loss and reflectance, indicating events such as splices, splitters bends and connectors.
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