Abstract: A dehumidifier for an electrical-equipment air intake has an outer housing wall and a floor of a material with a high specific thermal conductivity downwardly closing the outer housing wall, having a downwardly tapering funnel-shaped inner surface formed with a central downwardly open port, and having a rounded edge where the surface meets the port. An inner air-permeable housing inside the outer housing wall holds a moisture-absorbing mass in the inner housing so that air drawn in through the port can pass through the mass and then into a space between the inner and outer housings. A moisture sensor between the housings and a heater in the mass are connected to a controller that energizes the sensor and cooks moisture out of the mass such that the moisture condenses on the floor and runs over the edge out through the port.

Abstract: An electric power apparatus has a oil-filled vessel in which a float is connected to a float shaft that rotates as the float rises and falls with the level of oil. A level indicator has a display shaft extending along and pivotal about an axis, and coupled to the float shaft. An indicia display adjacent the shaft is swept by a pointer fixed on the shaft and juxtaposed with the indicia display go that the level of the oil in the vessel is indicated by the pointer. A disk fixed to the shaft has an outer periphery with a region of a shape having a radius varying angularly from one end of the region to an opposite and of the region. A noncontact proximity sensor is radially spacedly juxtaposed with the region of the disk for producing an output corresponding to the radial distance between the region and the sensor.

Abstract: A tap changing assembly for power transformers having vacuum interrupters each of which is associated with a radio interrogated surface wave sensor capable of detecting whether the respective vacuum interrupter opens circuit in a timely manner. The sensors are interrogated by an interrogating unit transmitting high-frequency signals to the sensors and associated with a monitoring circuit responsive to signals received by the interrogating unit for signalling the status of the vacuum interrupter.

Abstract: The invention relates to an oil filter installation for cleaning or cleaning and dessication of the oil in a tap changer at a power transformer or a plunger core coil, wherein a measuring device for detecting the volume flow of the throughflowing oil is provided and the electric pump motor is influenced by way of an interposed frequency converter in accordance with the result of a comparison of this measured value with a target value.

Abstract: A tap changing assembly for power transformers having vacuum interrupters each of which is associated with a radio interrogated surface wave sensor capable of detecting whether the respective vacuum interrupter opens circuit in a timely manner. The sensors are interrogated by an interrogating unit transmitting high-frequency signals to the sensors and associated with a monitoring circuit responsive to signals received by the interrogating unit for signalling the status of the vacuum interrupter.

Abstract: An air demoisturizer for an oil expansion vessel of an electrical power unit like an oil-filled transformer, tap changer or choke, has a heating element in the body of absorbent and utilizes a heat-regeneratable absorbent which is cut off by a moisture detector from the oil expansion vessel when the absorbent is saturated and is thermally regenerated. The demoisturizing column is provided in line with an oil receiver through which the dry air is passed before reaching the oil expansion vessel.

Abstract: A liquid level indicator for an oil-filled transformer, power choke or tap changer in which a sensor part has a float which rises and falls with the oil level and rotates a sensor shaft and the sensor shaft is coupled to an indicator shaft on which a pointer is provided to cooperate with a dial. The gauge also includes a contactless angle encoder operating with a magnetic hub and coupled to the indicator shaft for outputting a signal representing the oil level.

Abstract: A liquid level indicator for an oil-filled transformer, power choke or tap changer in which a sensor part has a float which rises and falls with the oil level and rotates a sensor shaft and the sensor shaft is coupled to an indicator shaft on which a pointer is provided to cooperate with a dial. The gauge also includes a contactless angle encoder operating with a magnetic hub and coupled to the indicator shaft for outputting a signal representing the oil level.

Abstract: An air demoisturizer for an oil expansion vessel of an electrical power unit like an oil-filled transformer, tap changer or choke, has a heating element in the body of absorbent and utilizes a heat-regeneratable absorbent which is cut off by a moisture detector from the oil expansion vessel when the absorbent is saturated and is thermally regenerated. The demoisturizing column is provided in line with an oil receiver through which the dry air is passed before reaching the oil expansion vessel.

Abstract: A method of controlling a step switch. From the measured values of current, voltage and phase angle at an electric drive motor during actuation of the step switch the individual picked-up active output is calculated. From the active output the corresponding torque at the drive motor is calculated. The torque in the step switch which is crucial for controlling is determined on the basis of the torque by using a specifically calculated transfer function. The transfer function is newly determined every time the switch is actuated, with the values of the preceding switch operation or the preceding switch operations being taken as a basis of the new calculation.

Abstract: A temperature pickup for an oil-filled transformer or tap changer has within a resistance thermometer standard housing, the circuitry for duty-factor-modulated output of a measurement signal, interference circuitry which can slur the resulting wave form and an interface circuit which subjects the output signal to polarity reversal to produce an output symmetrical with respect to ground potential. This enables zero crossings to be detected and the time lapse between zero crossings or passages to be ascertained and the temperature calculated from the duty-factor ratio.

Abstract: A tap selector for a power transformer switchable under load is monitored by detecting the effective values of current and voltage of the drive motor of the tap changer. The power is calculated and from that the instantaneous torque and the latter is compared with setpoint values either of the torque and position of the tap selector or in terms of characteristic segments of the torque versus time graph with normalized segments of a setpoint graph so that, with serious deviation an immediate shutdown of tap selector operations is ensured or information can be generated as to trends or the need for maintenance.

Abstract: A method of monitoring a tap changer in which measured values representing the status of the tap change operation are associated with positions of the tap changer and the position range or time range for the tap change is subdivided into partial intervals for which characteristic values of the measurement are calculated by a calculating rule, e.g. averaging. These characteristic values are compared with stored parameter data and operation categories are established which are then used exclusively for the further information processing.