Electronic trip device comprising an initialization device

Details Electronic trip device comprising an initialization device Electronic trip device comprising an initialization device

2000-07-13

2001-09-04

Hofsass, Jeffery (Department: 2632)

Communications: electrical

Condition responsive indicating system

Specific condition

C340S652000, C340S650000, C340S649000, C340S638000

Reexamination Certificate

active

06285292

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to an electronic trip device comprising:
a processing unit receiving current signals representative of currents flowing in a power system to be protected, comprising protection means and supplying a tripping signal when said currents exceed preset tripping values, and
an initialization device for initialization of said processing unit.
In known electronic trip devices, tripping functions give an opening order of the circuit breaker when at least one current flowing in a pole of the circuit breaker exceeds a preset current threshold for a time greater than that corresponding to the tripping curve. Among these functions, the long delay or thermal function, the short delay or magnetic function, and the ground fault protection function can be mentioned.
Certain trip devices comprise thermal memory functions after tripping applied to the long delay function. A trip device of this kind is described in the Patents FR 2,719,169 or U.S. Pat. No. 5,617,078.
In this type of trip device, a storage device simulates the thermal behavior by using the discharge characteristics of a capacitor into a resistor. This device is well suited for a long delay thermal function with tripping and opening of the circuit breaker.
Other trip devices comprise memories to store current values or circuit breaker tripping or status information. These memories are generally RAM supplied with power by a battery or a capacitor of very high value, or EEPROM with electrical write or delete. Management of these memories is associated with tripping and initialization after tripping. If initialization is performed after power supply interruptions due to intermittent faults, it is very difficult to check the integrity of the data contained in the memories.
Thus, for intermittent faults which do not give rise to tripping but which stop the current supply to trip devices, known devices are not efficient.
Moreover, if these intermittent faults are faults processed by short delay or earth protection functions, processing initialization each time the power supply returns would be too onerous and would take too long. For example in the case of a cell with a resistor and a capacitor, one device would be required per type of protection and the charge of the capacitor would have to be controlled permanently.
OBJECT OF THE INVENTION
The object of the invention is to achieve a trip device comprising an initialization device enabling quick initialization of the protection functions and having very reliable initialization values.
In a trip device according to the invention, the initialization device comprises means for initialization after an interruption comprising:
at least one storage register connected to the protection means to store a value of at least one quantity of a protection function and to supply a value of said at least one quantity when initialization of the processing unit is performed,
a back-up power supply circuit to supply power to said at least one storage register,
means for monitoring the back-up power supply circuit connected to an input of said at least one storage register to reset the value of the register to zero when a voltage of the back-up power supply circuit drops below a preset threshold.
The means for initialization after an interruption preferably comprise a first storage register connected to the protection means and to the monitoring means to store a value of a quantity representative of a short delay protection function.
The means for initialization after an interruption preferably comprise a second storage register connected to the protection means and to the monitoring means to store a value of a quantity representative of an earth protection function.
Advantageously, the means for initialization after an interruption comprise a third storage register connected to the protection means and to the monitoring means to store a value of a quantity representative of a long delay protection function.
In a preferred embodiment, the protection means, at least one storage register, and the monitoring means for monitoring a power supply circuit are arranged in a single integrated circuit.
In a particular embodiment, the back-up power supply circuit comprises a diode connected between a main power supply line and a back-up power supply line, and a capacitor connected between the back-up power supply line and a reference line.
Advantageously, the initialization device comprises means for initialization after an interruption and means for initialization after tripping.


REFERENCES:
patent: 5101316 (1992-03-01), Levain
patent: 5115371 (1992-05-01), Tripodi
patent: 5220479 (1993-06-01), Fraisse
patent: 5367427 (1994-11-01), Matsko et al.
patent: 5850330 (1998-12-01), Perron et al.
patent: 5974545 (1999-10-01), Obermeier et al.
patent: 6127742 (2000-10-01), Weynachter

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