Other

Advanced Power Technologies, LLC

Gary R Hoffman

Jeffrey S Anderson

Edward S Kwon

Hong Cai

Mikhail Benis

Thomas C Tennille

Jeffrey Anderson

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.

Method and apparatus for monitoring high voltage bushings safely

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.

Method and apparatus for protecting power transformers from large electro-magnetic disturbances

The cooling system for a power transformer is activated by sensing and processing the frequency characteristic including the harmonic contents, of the inrush current into the transformer, when the transformer is first energized. The cooling system may include motors operating devices such as oil circulating pumps and fans causing a coolant to flow about the power transformer. The cooling system is deactivated by sensing when the transformer is de-energized and when its temperature is below a predetermined level.

Apparatus and method for cooling power transformers

A system for cooling a power transformer which generates heat, when driving a load, includes cooling devices, such as fans and pumps, located about the transformer, which are powered for circulating a coolant about the transformer. Each cooling device has a motor which is energized in response to given temperature (heat) conditions. In systems embodying the invention, the currents flowing through the motors of cooling devices are sensed and monitored to determine whether the cooling devices are functioning correctly and to substitute functional cooling devices for those which are malfunctioning. Sensing the currents in the motors enables the early detection of fault conditions in the cooling system. It also enables the monitoring of operating conditions and running time of the cooling devices to aid in the maintenance and operation of the cooling system.

Cooling system for power transformer

A load tap changer (LTC) having a plurality of windings is coupled to one of the primary and secondary windings of a power transformer in order to regulate the output voltage of the power transformer. The LTC includes a plurality of taps physically and electrically connected to the LTC windings and the transformer's output voltage is increased/decreased by moving along the taps a contacting element whose movement is controlled by a rotating shaft driven by a motor. The tap being contacted is determined by sensing the direction and number of shaft rotations and by checking the number of shaft rotations specified to go from a tap to the next tap being contacted. The time for a full rotation of the shaft is also measured. Also, the temperature of the tanks containing the LTC taps and the power transformer is measured for each tap position.

Apparatus and method for monitoring tap positions of load tap changer

A load tap changer (LTC) having a plurality of windings is coupled to one of the primary and secondary of a power transformer in order to regulate the output voltage of the transformer. The LTC includes a plurality of taps physically and electrically connected to and along the windings and a contacting element is selectively moved along the taps to increase or decrease the output voltage of the transformer. The power transformer and the LTC windings are placed in a main tank and the taps are placed in an LTC tank. The temperature in the main tank and the temperature in the LTC tank are monitored by means of first and second temperature probes whose outputs are used to sense the temperature differential (T) between the main tank and the LTC tank and to determine if the LTC tank temperature exceeds the main tank temperature for a period of time exceeding a specified time period. Also included is circuitry for sensing the rate of change of Tand determining if it exceeds a predetermined value.

Sensing load tap changer (LTC) conditions

In circuits and systems embodying the invention the condition of a battery may be tested and monitored while the battery is supplying a load current to a load and without interrupting that operation. A selectively enabled switch causes a test current to selectively flow through the battery and a test resistor of known value. The voltage across the test resistor is sensed to determine the value of the test current. The voltage across the battery is measured under two conditions, with the test current and without the test current flowing through it. These measurements and knowing the value of the test current enable the internal resistance of the battery under test to be calculated and monitored.

Apparatus and method for testing battery condition

The load current drawn from a power transformer is sensed to determine if and when the load current exceeds a predetermined threshold. The length of time the load current exceeds the threshold is also sensed. By monitoring the excess current flow and the length of time for which it flows, it is possible to anticipate a rise in the winding temperature of the power transformer and to initiate cooling before the windings have reached a critical temperature, as a function of the ambient temperature and/or the temperature of the transformer. Thus, systems embodying the invention include circuitry for sensing the current drawn from and/or by a transformer, determining when the current exceeds a predetermined value and timing circuits for sensing the length of time for which the excess current flows. The timing circuits are needed, in part, to differentiate between a transitory overload condition and a static, continuous, overload condition.

In systems embodying the invention, a &ldquo;downed&rdquo; power line is detected by sensing whether there is an open circuit along the power line and producing an indication that an open circuit condition exists. In response to an indication that an open circuit condition exists, the system compares the nature of the voltage and/or current signals present on the power line at the time an open circuit condition is indicated to exist, with a preprogrammed stored condition which includes typical signals to be expected when a &ldquo;break&rdquo; occurs along a power line. When a downed power line is detected, power is then removed from the affected line.

Sensing downed power lines

A substation for distributing electric power includes protective relays whose trip points are made to be a function of temperature, the protective relays being used to control the opening and closing of circuit breakers for protecting against fault conditions in at least one of the power input and power output portions of the power distribution system. In one embodiment, a temperature probe which is used to sense the temperature at a selected point of the substation supplies the temperature information to a microcontroller which is programmed to set the trip point of selected protective relays as a function of the sensed temperature.

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Randolph, NJ, United States of America

Gary R Hoffman