Digital implementation of the overcurrent determination and time delay before tripping in a static circuit breaker trip unit allows the trip unit circuit to be manufactured in a single chip configuration. The signal after A/D conversion is compared within a magnitude comparator to determine pickup. A pulse stream proportional to the square of the overcurrent signal is developed by multiplying the outputs of two magnitude comparators which compare the A/D level with a continuous binary count. The time delay determination is obtained by means of 3 cascade connected divide by two counters with their outputs connected to a data selector, or by a rate-limiter circuit which uses a fixed frequency to gate a pulse stream proportional to the overcurrent level squared.

Digital I2 T pickup, time bands and timing control circuits for static trip circuit breakers

A circuit breaker having an electronic fault sensing and trip initiating unit which provides increased versatility and ability to coordinate the circuit breaker with other interrupting and protective devices in a wide variety of electrical distribution systems. Electronic circuits and components are provided to vary the ampere rating of the breaker, to adjust current carrying capacity, to provide a long time delay trip, a short time delay trip and an instantaneous trip depending on the amplitude of high fault currents, to provide a ground fault trip, to shorten or lengthen the trip time for short time delay faults and for ground faults, and to provide shunt trip capability. The tripping mechanism is magnetic and mechanical, and includes a plunger movable between a trip and non-trip position controlled by an electronic switch in the electronic circuitry, and a toggle mechanism which is unlatched by the plunger when it moves to the trip position. A bimetal trip mechanism is provided as back-up protection if the ambient temperature not sensed by the electronic circuitry exceeds a pre-determined level.

Circuit breaker having an electronic fault sensing and trip initiating unit

A voltage converter including a transformer having a primary winding connected in series with a switch for cutting-up a supply voltage and having a secondary winding associated with a capacitor providing a D.C. low voltage, and a self-oscillating control circuit of the switch for detecting the end of the demagnetization of an auxiliary winding of the transformer, to turn the switch on, and for detecting the current in the on-state switch to turn it off when this current reaches a reference point. The reference point is made variable according to the voltage across the auxiliary winding.

Self-oscillating control circuit voltage converter

A method for transmitting information over a communication network between a population of remote terminals and a central location having a capacity of simultaneously communicating with a predetermined number of remote terminals in the population. A first time period is fixed during which every remote terminal may initiate one attempt to communicate with the central location over the communication network. Respective times within the first time period are established at which each of the remote terminals will initiate its attempt to communicate with the central location. A number of the remote terminals which successfully communicate with the central location to transmit information therebetween is monitored. The first time period is then decreased to a second time period if the number of remote terminals which successfully communicate with the central location is less than the capacity of the central location. Respective times within the second time period are then established at which remote terminals which have not initiated their respective attempts to communicate with the central location will initiate their attempts to communicate with the central location. The above steps are repeated to establish a time period at which the number of remote terminals which communicate with the central location is approximately equal to the capacity of the central location. The time period thus set is maintained until each of the remote terminals has initiated its attempt to communicate with the central location.

Data return for a television transmission system

A PC computer monitors the energy consumed at a plurality of local stations placed behind the electrical meter of the utility company for individual billing of the local users, a bidirectional communication line being used between the PC computer and the plurality of local stations. A command from the PC computer causes the totalized energy to be stored at each station, and thereafter the PC computer derives individually the results for separate energy estimations and central billing.

Circuit breaker - associated backpack unit for lower-link communication with a PC computer monitoring system and energy monitoring system using a plurality of such backpack units

Digital overcurrent relay apparatus utilizing sampling, digital conversion and digital comparison techniques is described. The apparatus provides a trip signal after an alternating current in a line being monitored by the apparatus exceeds a preset pick up value for a period of time which is an inverse function of the magnitude of the current expressed in multiples of pick up value.

Overcurrent relay apparatus

A multi-function solid state trip unit for automatic electric circuit breakers incorporates indicators functioning to signal which of the functions, e.g., short circuit, overload or ground fault, was operative in tripping the circuit breaker. A bypass circuit is included to insure that tripping of the circuit breaker is not jeopardized by failure of the indicators.

Multi-function solid state trip unit with trip indicating means

A static trip unit for automatic electric circuit breakers includes an analog to digital converter for converting an analog signal proportional to the magnitude of current flowing in a distribution circuit to a digital signal having a pulse frequency proportional to the second power of the analog signal. When the analog signal exceeds a preselected threshold level, a binary counter is conditioned to accumulate the digital signal pulse. A decoder monitors the pulse count accumulating in the counter and issues a trip signal when the pulse count reaches a preselected total.

Static trip unit for circuit protective devices

A series flyback switching regulator, having a transformer with a primary coil for receiving an unregulated input voltage and a secondary coil for providing a regulated output voltage, includes a circuit for limiting the magnitude of a substantial overload or short circuit current. The current limiting circuit senses the magnitude of current flowing through the primary coil and sets a current limit level which is based upon a predetermined maximum current allowed in the primary coil. The current limiting circuit also senses the magnitude of the voltage present at the secondary coil of the transformer and reduces the current limit level, based upon a sensed reduction in the secondary coil voltage. The input voltage is removed from the primary coil when the magnitude of the current through the primary coil exceeds the current limit level as reduced by the sensed reduction of the voltage appearing across the secondary coil.

Switching regulator current limit circuit

A drive circuit responsive to an applied electrical signal for generating a voltage to control the actuation of an electromagnetic relay is disclosed. The voltage has a first and a second level for picking-up and holding-in, respectively, the relay. The first voltage level has a peak value which is developed by an internal charging circuit and is additive to the second voltage level supplied by an external source. The first voltage level is higher than required to actuate the relay which enhances the pick-up speed of the relay.

Robert P. DePuy

Papers

Overcurrent relay apparatus

Multi-function solid state trip unit with trip indicating means

Static trip unit for circuit protective devices

Switching regulator current limit circuit

Fast relay turn on circuit with low holding current