231results about "Emergency protective arrangements responsive to undesired changes" patented technology

A microprocessor based overcurrent trip unit which generates trip signals as an adjustable function of current and time, has a visual representation of the trip function on a front panel with 2-color LEDs associated with the trip function serving as indicators of trip conditions when red, and of a selected programmable parameter when green. The green LEDs flash to indicate parameter selected for modification in a program mode and illuminate steady in a view mode.

A protection device protecting a load circuit by shutting off a power thereof depending on an estimated present temperature of a wire provided in the load circuit to connect a load. The protection device has a first temperature estimation device estimating a rising temperature of a conductor including the wire based on both a current in the conductor and thermal properties of the conductor, a second temperature estimation device estimating a falling temperature of the conductor based on the thermal properties, a third temperature estimation device estimating an arc-induced rising temperature of the conductor when arcing occurs in the conductor, and a fourth temperature estimation device estimating the present temperature of the conductor deduced from the above estimated temperatures. If the estimated temperature exceeds a predetermined allowable temperature, the protection device shut off the power of the load circuit.

A temperature of an electrolytic capacitor 24 incorporated in equipment is detected, a remaining lifetime in actual use is calculated based on a temperature-lifetime law, and the remaining lifetime is indicated. A thin film tape 23 is wound around a temperature sensor 22 for insulation, and the electrolytic capacitor 24 and the temperature sensor 22 are accommodated in a heat-shrinkable tube 25, the secondary temperature sensor 22 is brought into tight contact with the primary electrolytic capacitor 24.

A motor controller includes: a motor control part for driving and controlling a motor; an estimated temperature computing part for computing an estimated temperature of a winding of the motor; and a motor protecting part for protecting the motor from being burned when the estimated temperature becomes larger than a predetermined temperature. A temperature rise value of the estimated temperature is computed according to operating conditions of the motor at the time of passing electric current through the winding. This temperature rise value is added to an estimated temperature stored in the estimated temperature storing part to update the estimate temperature. To compute the temperature rise value, an optimum temperature rise value is computed by the use of a plurality of temperature-rise value computing expressions.

In a method for ascertaining temperatures (tqm, tqh, tom, tok) in an oil-cooled transformer, the transformer terminal voltages (2), the winding currents (3) and the ambient temperature (6) are measured. Furthermore, the status (5) of fans and pumps and the switch position (4) of a stepping switch are established. The measured and established variables (2, 3, 4, 5, 6) are fed to a thermohydraulic model (7), in which state variables (19) are calculated with auxiliary variables (9), which are losses (10) in the transformer, heat transfer parameters (11), flow resistances (13) and the oil flow (12), and a hydraulic network of the oil circuit, which has branches and nodes. The state variables (19) are the average temperatures (tqm) and the hotspot temperatures (tqh) in loss-producing parts of the transformer and the average oil temperatures in branches (tom) and in nodes (tok) of the hydraulic network of the oil circuit. When there is a change in the variables measured and established (2, 3, 4, 5, 6), the auxiliary variables (9) are adapted appropriately, and the rate of change of the state variables (19) is subsequently ascertained and new state variables (19) are consequently calculated. With this method, temperatures (tqm, tqh, tom, tok) and their changes in the transformer are ascertained without temperature sensors, whereby the optimum operation of the transformer is ensured, an early detection of errors and risks takes place and the optimum point in time for service work can be established.

A motor protection circuit for an electric motor driven by a pulse width modulated amplifier. It has a capacitor and a first conduction path connected to a first terminal of the capacitor and connectable to a first conductor. It also has a second conduction path connected to the second capacitor terminal and connectable to a second conductor. There is a DC voltage difference between the first conductor and the second conductor. There is a third conduction path between the first terminal and the second terminal. The third conduction path having a resistance which is lower than the resistance of the first conduction path plus the resistance of the second conduction path. The third conduction path passes through a switch which has an input connection to be opened and closed thereby. The input connection is for receiving a signal indicating a motor overload condition, whereby the capacitor discharge switch is closed when the signal indicates the motor overload condition and the capacitor discharge switch is opened when the signal does not indicate the motor overload condition. A charge on the capacitor increases when the signal does not indicate the motor overload condition and the charge on the capacitor decreases when the signal indicates the motor overload condition. The circuit also has a voltage comparator receiving the voltage of the capacitor. The voltage comparator produces a signal for shutting down the motor.

In a method, computer program and system for determining an operational limit of a power transmission line, time-stamped current phasor information and voltage phasor information for a first end and a second end of the line are determined, an ohmic resistance of the line is computed from the phasor information, and an average line temperature is computed from the ohmic resistance. This allows to determine the average line temperature without dedicated temperature sensors. The average line temperature represents the actual average temperature and is largely independent of assumptions regarding line parameters.

Methods, apparatus, and articles of manufacture control a device or system that has an operational limit related to the rate or frequency of operation. The frequency of operation is controlled at a variable rate calculated to maximize the system or apparatus performance over a calculated period of time short enough that a controlling factor, such as power consumption, does not vary significantly during the period. Known system parameters, such as thermal resistance and capacitance of an integrated circuit (IC) and its package, and measured values, such as current junction temperature in an IC, are used to calculate a time-dependent frequency of operation for the upcoming time period that results in the best overall performance without exceeding the operational limit, such as the junction temperature.

To precisely detect the temperature of a power assist motor without using a temperature sensor and enhance an overheating protection function. A calorific value calculating unit calculates a calorific value based upon the difference between a calorific value by current supplied to a motor and the quantity of heat radiation. The output of the calorific value calculating unit is accumulated and an accumulated value is input to an accumulated value buffer. A cumulative value TS acquired by adding initial temperature T0 to a cumulative value Td is input to a ratio map of a target current value, ratio is read, and a target base current value is limited according to the ratio. The cumulative value TS used in the map is not an actual motor current value and is calculated based upon unlimited current acquired in an unlimited current calculating unit.

A real time thermal monitoring and prediction system (TMPS) is provided for use in monitoring and operating a transformer. The TMPS may be used to estimate a maximum loading level for the transformer over a future time period using a dynamic thermal model for the transformer and ambient temperature forecasts. The transformer may be loaded to its maximum loading level during power congestion or a service restoration process.

Electrical power grid monitoring apparatus, articles of manufacture, and methods of monitoring equipment of an electrical power grid are described. According to one aspect, an electrical power grid monitoring apparatus includes a communications interface configured to access electrical data indicative of electrical energy received at a plurality of consumer locations from an electrical power grid at a plurality of moments in time, the consumer locations being coupled with one or more unbalanced single phase feeders of a distribution system of an electrical power grid and which individually comprise a plurality of components configured to conduct the electrical energy from at least one electrical energy source to the consumer locations, and processing circuitry coupled with the communications interface and configured to use the electrical data to estimate a state of the electrical power grid and to identify one of the components as being in a potentially degraded state using the estimation of the state of the electrical power grid.

The system includes a distance protective relay for power lines which includes a logic capability which is responsive to settings entered into the relay by an end user to implement the value of those settings into stored thermal model equations which emulate the temperature of the power line conductor. The logic within the relay is organized and has the capability of receiving the setting values entered by the user and to use those in the logic equations to determine the temperature of the conductor.

A protection system for an electrical device may include at least one temperature sensitive element located in a region adjacent to a component of the electrical device and configured to provide an output related to an actual temperature in the region. The system may also include a controller configured to determine the actual temperature in the region based on the output of the at least one temperature sensitive element and to determine a predicted temperature of the component based on the actual temperature in the region and on a predetermined heat dissipation characteristic of the electrical device.

An overcurrent detection circuit includes a current detection resistor that generates a voltage in proportion to current flowing through a switching element and a comparator that compares the voltage detected via the current detection resistor and a reference voltage generated by a reference voltage generation circuit to thereby detect overcurrent flowing through the switching element. In particular, the reference voltage generation circuit includes: a first resistance voltage dividing circuit that resistance-divides a standard voltage by connecting, in series, two types of resistors having different temperature characteristics; a second resistance voltage dividing circuit that resistance-divides the standard voltage by connecting, in series, resistors having the same temperature characteristics; and an instrumentation amplifier that generates the reference voltage according to the difference between the divided output voltages of the first and second resistance voltage dividing circuits.

The power supply controller performs the power-supply-path protection operation to restrict power supply through the switch element if a value of temperature increase of the power supply path W with respect to the reference temperature To exceeds the temperature threshold value and remove the restriction if the temperature decreases to the temperature threshold value or lower. And the controller performs the switch protection operation to restrict the power supply through the switch element if the value of the flowing current exceeds the current threshold value and remove the restriction after the reference time H elapses. And also the controller adds the additional value F to the value of temperature increase on condition that the value of the flowing current exceeds the current threshold value in the power supply protection operation and compares a post-addition temperature to the temperature threshold value.

A circuit breaker system for providing thermal protection to a conductor conducting current from a power source to a load. While the power source is connected to the load, a microcontroller is powered by the current passing through the conductor to thermally model the temperature of the conductor. If the microcontroller determines that the temperature of the conductor has risen to an undesirable or unsafe level, the circuit breaker disconnects the power source from the load and the current no longer passes through the conductor. With no current passing through the conductor, the microcontroller no longer receives power from the conductor. Instead, the microcontroller continues to model the temperature of the conductor as the conductor cools to an ambient temperature by receiving power from an energy storage device. Accordingly, the microcontroller continuously models the temperature of the conductor until the temperature of the conductor cools to the ambient temperature.

The protective relay for an induction motor includes a first program function which establishes a first thermal threshold value for a start condition of the motor, using a start condition thermal model. The thermal condition of the motor is determined by measuring the motor's thermal response to stimulus. A comparator compares the start condition thermal representation with the first thermal threshold value and monitors whether the first thermal threshold value is exceeded by the start condition thermal representation. A second thermal threshold value is established for a run condition of the motor, including a selected time constant which results in the time-current curves of the start and run conditions being substantially continuous. A representation of the thermal condition of the motor is then developed in response to stimulus current. A comparator then compares the run condition thermal representation with the second thermal threshold value.

A thermal protection apparatus for an AC traction motor including a stator, a rotor, a blower fan and an inverter includes a method and apparatus for predicting the motor temperature assuming that the blower is operational. The method and apparatus also determines an estimated motor temperature by measuring the motor resistance or the rotor slip. The estimated motor temperatures compared to the predicted motor temperature to determine the condition of the motor cooling system.

A controller is operable in one of a plurality of operational modes, which include an estimated temperature computation performing mode for performing computing of an estimated temperature of the motor and an estimated temperature computation non-performing mode for stopping the computing of the estimated temperature of the motor. An operational mode of the controller is changed from the estimated temperature computation performing mode to the estimated temperature computation non-performing mode according to a predetermined condition in a stopped state of the motor.

A controller for an electric compressor sets a temperature rise region A, a temperature drop region B, and a steady region C from change in temperature of switching elements, and sets a carrier frequency for each of the set regions. In the region A, the carrier frequency is changed according to the element temperature so that the carrier frequency decreases with increase of the element temperature at startup of a motor. In the region B and the region C, the carrier frequency is changed according to the number of revolutions of a compression mechanism, so that the carrier frequency decreases with increase of the number of revolutions of the compression mechanism, regardless of the element temperature.