An electrical circuit interrupter device with 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 a parameter selected for modification in a program mode and illuminate steady in a view mode.

Overcurrent protection device with visual indicators for trip and programming functions

A microprocessor based overcurrent trip unit includes an analog circuit for monitoring phase currents in the electrical interrupting device. The analog circuit is adapted to interface with the microprocessor over a range of selectable setpoints for instantaneous tripping and at the same time accurately monitor the phase currents even during a condition when the current sensing transformers are saturated. The overcurrent trip unit also allows the function of the long time delay characteristics of protection curve to be varied in order to provide better coordination with the characteristics of other overcurrent tripping devices in an electrical distribution system, such as a current limiting fuse, thereby enhancing the overall reliability of the system. For example, the function may be varied to provide either a fixed or FLAT, It, I 2 t and I 4 t functions. The overcurrent tripping device also allows for relatively wide adjustment ranges for the long time delay and short time delay protection portions of an overcurrent protection curve. In order to prevent any overlapping of the protection ranges, the long time delay portion is prevented from tripping the interrupting device prior to the short time delay portion.

Overcurrent protection device

A hybrid monolithic IC that is standardized for controlling various types of electrical equipment, such as circuit breakers, motor controllers and the like. The IC is a hybrid monolithic IC, fabricated in CMOS technology, The shortcomings of utilizing CMOS technology for linear or analog circuitry is overcome by the implementation of the IC to provide a monolithic IC that is relatively less expensive than using multiple ICs or a single IC fabricated from biCMOS technology.

Sure chip plus

Process and apparatus for calibrating an electrical device such as a circuit breaker, motor controller or monitor is taught. A precision power supply device is interconnected by way of appropriate input channels to the device to be calibrated for supplying a precise accurate calibration variable as an input. A personal computer PC is interlinked by way of a communications network with the apparatus to be calibrated and is also interlinked with the precision supply device so that the personal computer PC has available the exact value of input variable utilized. Gain adjustment calibration is made by supplying the predetermined value of circuit variables, for instance 10 amperes or 120V to the input terminals of the device being calibrated. Upon command, the personal computer PC instructs the device being calibrated to deliver to the personal computer PC those values of input variable which the device being calibrated interprets as the input variable value. The personal computer PC compares this value with the actual value and generates a correction factor which the personal computer PC sends back to the device being calibrated for storage in an EEPROM. Consequently, during subsequent use after the calibration procedure has been completed and the calibration features have been safely "locked" away in the EEPROM, all readings will be adjusted by the aforementioned calibration factor to compensate for errors which may exist in other portions of the device being calibrated.

Process for auto calibration of a microprocessor based overcurrent protective device and apparatus

The computer-aided application of reclosers in distribution systems is detailed. An expert system (with coordination macros) built into a coordination program can help distribution engineers establish a functional protection system. The coordination program featured is the V-PRO package. Recloser characteristics and modeling of these characteristics during overcurrent protection studies using the package are discussed. The coordination of reclosers and fuse-links is described. Examples illustrating how the package is used for recloser and fuse-link coordination are given. >

Computer-aided recloser applications for distribution systems

Transformer protection considerations are discussed, and V-PRO, a computer-based coordination program that can significantly reduce the time that it takes the protection engineer to evaluate alternative schemes, is discussed. An overview of the package is given, and some application examples are presented. >

D.A. Gonzalez

Papers

Rule-based coordination program evaluates distribution transformer overcurrent protection alternatives