Abstract

Fast circuit breaker and protective relays play an important role of protecting locomotive’s electrical circuits from damage caused by short circuit or overload. Undisturbed operation and proper circuit protection depends on the technical condition and fine calibration of the over-current trips. Therefore the relays should be subject to periodic inspection and adjustment due to locomotive maintenance schedule. A test stand for automatic determination of relays tripping current has been designed and assembled. The tests can be carried out without removing a relay from a locomotive. The tripping current value is determined by supplying the trip circuit with the slowly increasing current. The value of current is measured and held on instant of trip activation. The test procedure can be set to automatic or semi-automatic. In automatic mode, the signals available in the joints placed on the forehead of locomotives are used, that were originally designed for multiple unit control. Connecting the diagnostic plugs to the joints allow to automatically executing a sequence of unlocking the relays before the main current test is conducted. In semi-automatic mode the joints are not used. Unlocking the relays must be made manually and additional wires have to be connected to the relay feedback contacts in order to determine the instant of relay tripping. Both in automatic and semi-automatic mode the diagnostic current leads must be connected to the trip of a relay. Dedicated diagnostic software was developed, which can be accessed from the locomotive by the means of wireless communication. The tests can be performed repeatedly, for example to adjust the tripping current setting. The software holds the last tripping current value for each of the relays. After the test, a report is generated that contains the results for each of the tested relays, taking into account its symbol and name, the current response and the assessment criteria. Database of all reports is stored on a main computer. The developed test stand allows to verify and fine adjust of the relays tripping current in electric locomotives circuits. Remote control of the procedure from the inside of a locomotive enables the tests to be carried out by a single person. Automation of the test procedure reduces the time required to perform the test and improves the reproducibility of the results.

Authors (3)