Electricity: measuring and testing – Electromechanical switching device – Circuit breaker
Utility Patent
1998-04-13
2001-01-02
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Electromechanical switching device
Circuit breaker
C361S153000, C324S423000
Utility Patent
active
06169405
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a functional test process for a mechanical switching element, particularly a mechanical switching element structured as a trigger in a high-voltage power switch, in which process a coil core is set in motion by the magnetic action of a current flowing through a coil, the coil having an electrical pulse applied to it, and the characteristic of the current through the coil being measured and differentiated by means of a monitoring device.
BACKGROUND INFORMATION
In a conventional functional test process for a mechanical switching element of an electrical switching system (
Elektrizit{umlaut over (a)}tswirtschaft,
Vol. 94 (1995), Issue 7), a functional test is performed in the rest state, i.e. a measurement pulse which is applied to a load circuit at predetermined time intervals is so short that no movement of the switching element is triggered. Only the conductivity of the load circuit is tested in this way. Therefore it is not possible to check the mechanical mobility of the switching element.
U.S. Pat. No. 5,270,900 describes an electromagnetic switching element which is formed from a coil with a core and which is used for opening and closing a valve. The movement of the core which leads to opening of the valve is triggered with an electrical pulse which is applied to the coil. The time during which the valve remains open is predetermined by a counter. In order to determine the time point for the counter to start, the current characteristic in the coil is measured and differentiated. After the derivative of the measured current has reached a previously determined value, the counter is started. After the counter runs down, the valve is closed again using the switching element.
SUMMARY OF THE INVENTION
The present invention provides a process and a system for the functional testing of a mechanical switching element, in which the mechanical functionality of the switching element is checked without completely performing a switching process of the switching element.
This task is accomplished, according to the present invention, in that the electrical pulse is cut off as soon as the derivative of the measured current characteristic reaches a particular value.
A significant advantage which is achieved with the invention is the possibility of flexibly checking the switching element using a limited movement of the core of the coil. Because of the movement of the core in the coil, the coil inductivity and the magnetic flow are changed. Therefore the time characteristic of the current in the coil is influenced by the movement.
By monitoring the time derivative of the current characteristic in the coil, cutting off the electrical pulse which is applied to the coil is directly dependent on the movement of the core.
The point in time used for cutting off the electrical pulse, which is determined by differentiation of the current characteristic through the coil, is only dependent on the movement of the core which has actually taken place. Thus a lesser movement of the core results in the electrical current being cut off sooner under certain operating conditions (e.g. elevated temperature). Therefore the actual path distance which the core has traveled until the electrical pulse is cut off is essentially independent of the external operating conditions. This is important in order to guarantee that the process according to the present invention can be used under different conditions, without any risk of mistakenly triggering a switching process in the high-voltage power switch in the course of the testing process.
Advantageously, it can be provided that the pulse level is less during the functional test than during an actual triggering process.
This can be achieved, for example, in that a pre-resistor precedes the coil in the circuit during the functional test.
In another advantageous development of the present invention, it can be provided that the electrical pulse is cut off as soon as the derivative of the measured current characteristic first changes its sign after the start of the electrical pulse.
The time at which the derivative of the measured current characteristic changes its sign is a point that can be particularly well determined by means of measurements. It is therefore especially suitable as a trigger time for cutting off the electrical pulse.
Advantageously, it can also be provided that a constant voltage source is used as the source for the electrical pulse.
A constant voltage source is an easily available apparatus for generating electrical voltage pulses.
It can also be advantageous that after the electrical pulse is cut off, a pulse-width-modulated sequence of additional pulses is generated in the coil, their current average over time causing a controlled movement of the coil core.
In this way, the plunger can be moved to the locking device, in controlled manner, without resulting in unlocking. The idle stroke of the trigger can then be measured.
As an advantageous development of the device for implementing the functional test process, it can be provided that the device has a pulse emitter for supplying an electrical pulse, a monitoring device for measuring and differentiating the current characteristic in the coil, a subsequent comparator, a device for adjusting the threshold value of the comparator, and a control device for cutting off the electrical pulse as soon as the derivative of the measured current characteristic has reached a particular value.
In this way, the structure of the control device is simple to establish, and does not need to be individually adapted to the conditions which prevail in functional testing of different variants of electromagnetic triggering devices in each instance.
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“Condition Monitoring in High- and Medium Voltage Switchgear Assemblies”, Jochen Kreusel et al., Elektrizitatswirtschaft [Electricity Management], vol. 94, issue 7 (No Month Available), 1995, pp. 350-358.
Baltzer Martin
Gonzalez Rocco
Schuckar Detlev
Kenyon & Kenyon
Metjahic Safet
Nguyen Vincent Q.
Siemens AG
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