Abstract: The voltage at the test tap of a high voltage bushing is applied to a bushing coupler which includes circuitry to sense and process voltages generated at the test tap and convert the voltages into corresponding data signals. Data signals corresponding to the test tap voltages are then transmitted wirelessly to a bushing monitoring system. The wireless transmission may be, for example, via an optical coupling (e.g., fiber optics) arrangement or an electromagnetic radiation (e.g., RF transmission) arrangement. Thus, the signals from the bushing coupler are wirelessly transmitted to a monitoring system which is not conductively connected to the bushing coupler and the test tap. The bushing coupler includes a power supply which is chargeable from the test tap or wirelessly from the bushing monitoring system which is adapted to receive values of the high voltage applied to the bushing and to calculate changes in the values of selected bushing parameters.

Abstract: A protective system far a power transformer having a neutral line connected to ground where large currents can flow in the neutral line due to electro-magnetic disturbances. The system includes circuitry for: (a) sensing the current level in the neutral line and whether it exceeds a predetermined threshold for a predetermined period; and (b) sensing and processing the harmonic content of the load current and determining the existence of certain relationships of the “even” and “odd” harmonics. Signals, including alarms, indicative of excessive conditions are produced. The system may also include circuitry for sensing the load current level and generating a signal alarm if the load level is above a given value when the harmonics and the DC current have values in excess of certain predetermined values.

Abstract: The voltage at the test tap of a high voltage bushing is applied to a bushing coupler which includes circuitry to sense and process voltages generated at the test tap and convert the voltages into corresponding data signals. Data signals corresponding to the test tap voltages are then transmitted wirelessly to a bushing monitoring system. The wireless transmission may be, for example, via an optical coupling (e.g., fiber optics) arrangement or an electromagnetic radiation (e.g., RF transmission) arrangement. Thus, the signals from the bushing coupler are wirelessly transmitted to a monitoring system which is not conductively connected to the bushing coupler and the test tap. The bushing coupler includes a power supply which is chargeable from the test tap or wirelessly from the bushing monitoring system which is adapted to receive values of the high voltage applied to the bushing and to calculate changes in the values of selected bushing parameters.

Abstract: A protective system far a power transformer having a neutral line connected to ground where large currents can flow in the neutral line due to electro-magnetic disturbances. The system includes circuitry for: (a) sensing the current level in the neutral line and whether it exceeds a predetermined threshold for a predetermined period; and (b) sensing and processing the harmonic content of the load current and determining the existence of certain relationships of the “even” and “odd” harmonics. Signals, including alarms, indicative of excessive conditions are produced. The system may also include circuitry for sensing the load current level and generating a signal alarm if the load level is above a giver) value when the harmonics and the DC current have values in excess of certain predetermined values.