Identification of EM disturbances interfering the time-phase controller by short circuit tests

Short circuit tests are always preceded with powering MV side of the test transformer by unloaded LV side. Thereafter the controller must wait for release of the operator to start the test. Sometimes electromagnetically disturbed controller starts the test without release. Such situation is undesired and can be destructive for the device under test. Identification of the transient fields during powering the test transformer is indispensable by assessing hazard of EM interference of the controller. The previous investigation of the Authors gave the hint that repetitive damped oscillatory waves are component of electromagnetic environment. Origin of them is repetitive ignition and extinction of the short arc by closing the circuit breaker in the MV circuit. Adequate instrumentation to cope with the problem are D-dot and B-dot field probes. The paper reports such measurements along with recording the voltage signals. Investigations expands the scope of electromagnetic phenomena present in high current laboratory.