Testing unusual relay characteristics

Adrian Parker - Application engineer

Testing older-style electromechanical over-current relays with the versatile MPRT protection relay test set is a fast, convenient process thanks to an easy-to-use curve tracing tool. Part of the AVTS software suite that accompanies MPRT test sets, the new tool, which is intuitive in operation and involves no fiddly onscreen boxes to complete, works with a simple scan of the relay characteristics.

To digitise one or more curves, the user simply calls up a suitable blank log-log graph screen with the AVTS software, and then superimposes the scanned image of the relay characteristics on it. The next stage is to align the top left and bottom right points of the scanned characteristic with the underlying blank graph screen and without further effort, the individual curves can then be digitised.

The whole process takes only around five minutes and as the results can be stored, it only needs to be done once for each type of relay. When the digitisation process is complete, the MPRT test set can be used to test the relay to its actual characteristic. Should the multiplier or time dial setting fall between the published curves, the AVTS software will automatically interpolate between the curves, allowing it to display and use exactly the right characteristic.

All aspects of the new AVTS curve-tracing tool are implemented in a single window that, together with the absence of multiple boxes to complete, make it the easiest and most convenient solution currently available for digitising protection relay characteristic curves. www.megger.com.