Title of Invention

CIRCUIT ARRANGEMENT FOR RAPIDLY TRIPPING LOW-VOLTAGE POWER BREAKERS .

Abstract

A circuit arrangement for rapidly tripping low-voltage power breakers having an electronic tripping unit, in the case of which a switching element (S), which is operated in the short circuit during normal operation and which is connected in parallel with a rapid-response tripping magnet (M) of the low- voltage breaker, has a current applied to it which is proportional to the current monitored by the low-voltage power breaker, and a monitoring circuit for the current monitored by the low-voltage power breaker, which monitoring circuit cancels the short circuit across this switching element 9s0 when fixed threshold value is reached, characterized in that in each case one transformer (T4, T5, T6) is connected in series with the current inputs of the electronic tripping unit, the secondary sides of said transformers being connected in series with one another on the DC voltage side via bridge rectifiers (GL4, GL5, GL6) and with the switching element (S), so that the circuit arrangement requires no intervention in the current path of the tripping unit, making it suitable for retrofitting.

Full Text

Description Circuit arrangement for rapidly tripping low-voltage power breakers The invention relates to a circuit arrangement for rapidly tripping low-voltage power breakers having an electronic tripping unit by a switching element, which is operated in the short circuit during normal operation and which is connected in parallel with a rapid-response tripping magnet of the low- voltage power breaker, having a current applied to it which is proportional to the current monitored by the low-voltage power breaker, and the short circuit across this switching element being cancelled if the current monitored by the low-voltage power breaker reaches a fixed threshold value. In the case of high currents, for example owing to a short circuit in the power supply system, even undelayed tripping of a low-voltage power breaker may still be too slow since the signal processing in the microprocessor of the electronic release requires a certain amount of time. In the case of low- voltage power breakers in which the power for the tripping unit is drawn from the power supply system itself via further current transformers and rectifiers, when the power breaker is first used there is also not yet any power available for as long as an associated charging capacitor has not yet been charged. It has therefore already been proposed, in the event that a high current is detected in the power supply system, to allow this high current to commutate directly onto the tripping magnet of the power breaker. For this purpose, the secondary sides of the current transformers provided for the supply of power to the tripping unit are connected to the tripping unit via bridge rectifiers and via a short-circuit path of a switching element. The rapid-response tripping magnet is connected in parallel with the switching element, for example a reed relay, a transistor, driven from a uniform-field coil, a field sensor or the like, and is short-circuited during normal operation. Only at high short-circuit currents in the power supply system, for example 35 kA, does the parallel short-circuit path open such that the rapid- response tripping magnet is activated. The circuit requires intervention in the current path of the tripping unit and is therefore not suitable for retrofitting existing systems. The invention is based on the object of specifying a circuit arrangement for rapidly tripping low-voltage power breakers which is also suitable for retrofitting. The power supply should also come from the previously used power transformers. No changes should be made to the electronic tripping unit. The object is achieved according to the invention as disclosed hereunder. Accordingly, in each case one transformer is connected in series with the current inputs of the electronic tripping unit. The secondary sides of these transformers are connected in series with one another on the DC voltage side via bridge rectifiers and with the switching element. The rapid-response tripping magnet, which is connected in parallel with the switching element, is (as is known) short- circuited during normal operation with the parallel short-circuited path of the switching element. Only at high short-circuit currents in the power supply system does the parallel short-circuit path open such that the rapid-response tripping magnet is activated. The transformers provide the required electrical isolation and may have a transformation ratio of 1:1, for example. The circuit can be retrofitted at any time in switches of existing switchgear assemblies. As the previously known circuit for rapidly tripping a low-voltage power breaker, it has the advantage that, in the event of a short circuit in the monitored power supply system, tripping takes place very rapidly and even when the power breaker switches to a short circuit when it is closed. The invention will be explained in more detail below by way of example with reference to the drawing. The drawing shows a block diagram of the circuit arrangement according to the invention. The drawing schematically illustrates part of an electronic tripping unit for a low-voltage power breaker on a three-phase power supply system. The secondary sides of current transformers T1, T2, T3 form, together with bridge rectifiers GL1, GL2, GL3, the power supply for an electronic release (not shown in any more detail here) . The DC voltage outputs of the bridge rectifiers GLl, GL2, GL3 are connected in parallel and lead to a charging capacitor C. The voltage across the charging capacitor C is regulated by a switching transistor V. A diode D prevents the charging capacitor C from discharging when the switching transistor V is driven. The charging capacitor C ensures that the operation of the downstream release is maintained even in the case of interruptions to the current or short-term low currents in the power supply system. In each case one transformer T4, T5, T6 is connected in series with the current inputs of the electronic tripping unit. The secondary sides of these transformers T4, T5, T6 are connected in series with one another on the DC voltage side via bridge rectifiers GL4, GL5, GL6 and with a switching element S. As is known, a rapid-response tripping magnet M of the associated low-voltage power breaker is arranged in parallel with the switching element S. The switching element S (shown merely schematically here) may be a reed relay, a transistor, a field sensor or the like. It is short-circuited during normal operation or is operated in the short circuit. The switching element S is driven by the tripping circuit, for example a drive circuit (not shown here) for a switching transistor, which represents the switching element S. In the event of a predetermined response value being exceeded, the short circuit of the switching element S is cancelled and the current commutates to the tripping magnet M, which causes the low-voltage power breaker to be tripped rapidly. WE CLAIM: 1. A circuit arrangement for rapidly tripping low-voltage power breakers having an electronic tripping unit, in the case of which a switching element (S), which is operated in the short circuit during normal operation and which is connected in parallel with a rapid-response tripping magnet (M) of the low-voltage breaker, has a current applied to it which is proportional to the current monitored by the low-voltage power breaker, and a monitoring circuit for the current monitored by the low-voltage power breaker, which monitoring circuit cancels the short circuit across this switching elements when fixed threshold value is reached, characterized in that in each case one transformer (T4, T5, T6) is connected in series with the current inputs of the electronic tripping unit, the secondary sides of said transformers being connected in series with one another on the DC voltage side via bridge rectifiers (GL4, GL5, GL6) and with the switching element (S), so that the circuit arrangement requires no intervention in the current path of the tripping unit, making it suitable for retrofitting. 2. The circuit arrangement as claimed in claim 1, wherein the transformers (T4, T5, T6) have a transformation ratio of 1:1. A circuit arrangement for rapidly tripping low-voltage power breakers having an electronic tripping unit, in the case of which a switching element (S), which is operated in the short circuit during normal operation and which is connected in parallel with a rapid-response tripping magnet (M) of the low- voltage breaker, has a current applied to it which is proportional to the current monitored by the low-voltage power breaker, and a monitoring circuit for the current monitored by the low-voltage power breaker, which monitoring circuit cancels the short circuit across this switching element 9s0 when fixed threshold value is reached, characterized in that in each case one transformer (T4, T5, T6) is connected in series with the current inputs of the electronic tripping unit, the secondary sides of said transformers being connected in series with one another on the DC voltage side via bridge rectifiers (GL4, GL5, GL6) and with the switching element (S), so that the circuit arrangement requires no intervention in the current path of the tripping unit, making it suitable for retrofitting.

Documents:

370-kolnp-2006-granted-abstract.pdf

370-kolnp-2006-granted-claims.pdf

370-kolnp-2006-granted-correspondence.pdf

370-kolnp-2006-granted-description (complete).pdf

370-kolnp-2006-granted-drawings.pdf

370-kolnp-2006-granted-examination report.pdf

370-kolnp-2006-granted-form 1.pdf

370-kolnp-2006-granted-form 18.pdf

370-kolnp-2006-granted-form 2.pdf

370-kolnp-2006-granted-form 3.pdf

370-kolnp-2006-granted-form 5.pdf

370-kolnp-2006-granted-gpa.pdf

370-kolnp-2006-granted-reply to examination report.pdf

370-kolnp-2006-granted-specification.pdf

370-kolnp-2006-granted-translated copy of priority document.pdf