Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific current responsive fault sensor
Reexamination Certificate
1999-09-28
2001-12-11
Leja, Ronald W. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific current responsive fault sensor
Reexamination Certificate
active
06330142
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a trip device comprising setting selector switches designed to define first protection parameters representative of an overload or a short-circuit and accessible to a user, display means, a processing unit connected to current sensors and to the setting selector switches, the processing unit comprising:
first digital processing means connected to the current sensors and to the setting selector switches in order to perform basic protection functions,
second digital processing means connected to the first processing means and to communication means enabling second protection parameters to be set by remote setting.
Known trip devices conventionally comprise potentiometers and/or selector switches on the front panel enabling the protection parameter settings to be adjusted. Others comprise a keypad combined with a display enabling the protection parameter settings to be adjusted and read. The latter trip devices also sometimes comprise means for remote setting of the parameters.
U.S. Pat. No. 5,311,392 describes a trip device comprising two microprocessor-based processing circuits. Such a trip device
1
is illustrated in FIG.
1
. It comprises a first microprocessor-based processing circuit
2
designed to perform protection against overloads and short-circuits, i.e. the long delay, short delay, instantaneous and, if applicable, earth protection functions. This first processing circuit is conventionally connected to current sensors
3
, to selector switches
4
located on a front panel of the trip device, to a cause of trip display device
5
and to a trip coil
6
. It comprises a second microprocessor-based processing circuit
7
designed to perform communication functions and additional monitoring and protection functions (as regards voltage, phase displacement, power, frequency, etc). The second processing circuit
7
is connected to the first processing circuit by a two-way link. It is also connected to the current sensors
3
and to voltage sensors
8
. It is also connected to a first interface
9
designed to be connected to a remote display device
10
, and to a second interface
11
designed to be connected to a computer
12
. The second processing circuit
7
also performs a backup protection function in case of malfunctioning of the first processing circuit. The unbroken line in
FIG. 2
represents a time/current tripping curve used by the first processing circuit
2
, taking into account the protection parameters defined by the selector switches
4
.
The second processing circuit performs the backup function taking into account a second tripping curve represented in a broken line in FIG.
2
. The protection parameters corresponding to the second tripping curve are systematically higher than the values set by the selector switches. They can be preset, unable to be modified by the user, or adjustable by means of the interfaces
9
and
11
, or be set by a shift of the first curve. The second processing circuit is continuously supplied by an auxiliary power supply
13
and comprises a trip output connected to the trip coil
6
. In normal operation, the first processing circuit
2
performs the current protection functions according to the current measured by the current sensors
3
and the parameters defined by the selector switches, the second processing circuit performing additional measuring and protection functions. In the event of a failure of the first processing circuit, the second processing circuit performs the current protection functions using the same current values measured by the current sensors
3
and the backup parameters corresponding to the second curve of FIG.
2
.
SUMMARY OF THE INVENTION
The object of the invention is to achieve a trip device having means for adjusting the protection parameters suitable for both a bottom-of-the-range trip device and a top-of-the-range trip device.
According to the invention, this object is achieved by the fact that the display means are connected to the second processing means, the processing unit comprising means for comparing the first and second parameters, means for determining third protection parameters representative of the lower of the first and second parameters, the display means displaying the third protection parameters and the processing unit producing a trip signal according to the current measured by the current sensors and to the third protection parameters.
According to a first alternative embodiment, the first processing means produce a first trip signal according to the current measured by the current sensors and to the first protection parameters, the second processing means producing a second trip signal according to the current measured by the current sensors and to the third protection parameters, a logic OR circuit supplying a trip signal when it receives a first or a second trip signal.
According to a second alternative embodiment, the first processing means preferably produce a trip signal according to the current measured by the current sensors and to the third protection parameters.
According to a development of the invention, the trip device comprises a keypad connected to the processing unit, designed to define fourth protection parameters and accessible to a user, the processing unit determining the third protection parameters from the lowest of the first, second and fourth parameters.
According to another development of the invention, the trip device comprises a cover covering the setting selector switches, the trip device comprising means for disabling the setting adjustment function of the keypad in a closed position of the cover.
The cover is preferably constituted by a door located on a front panel of the trip device and covering the setting selector switches in the closed position of the cover, the door comprising a spigot actuating a complementary element of the processing unit in the closed position of the cover so as to cause the setting adjustment function of the keypad to be disabled. The spigot is preferably breakable so that disabling of the setting adjustment function of the keypad in the closed position of the cover can be over-ridden.
REFERENCES:
patent: 4945443 (1990-07-01), DeBiasi et al.
patent: 5311392 (1994-05-01), Kinney et al.
patent: 0 693 812 A1 (1996-01-01), None
patent: 0 716 491 A1 (1996-06-01), None
Bellotto Henry
Suptitz Eric
Weynachter Luc
Leja Ronald W.
Parkhurst & Wendel L.L.P.
Schneider Electric Industries SA
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