SU1663638A1 - Device for checking state of contacts in switching apparatus - Google Patents

Abstract

The invention relates to electrical engineering, in particular, to devices for monitoring the operating modes of switching equipment of both direct and alternating currents. The purpose of the invention is to increase the reliability and objectivity of the information. The device compares the temperature of the controlled contact during the flow of current through it with its electrothermal counterpart. The device blocks the process of comparing contact temperatures when an electric arc appears in the contacts being investigated, leading to additional heating of the contacts, and allows monitoring to be carried out only after the time required for the contacts to self-test to elapse. 2 Il.

Description

The invention relates to electrical engineering, in particular, to devices for monitoring the operating modes of switching equipment of both direct and alternating currents.

The purpose of the invention is to increase the reliability and objectivity of the information.

During emergency and operational shutdowns under load, the electric arc arising on the arcing contacts of the switching device has a thermal effect on the contacts, melts them. evaporates the metal from which they are made. The contact area and the contact force of the contacts decrease, their ohmic resistance grows, and the conditions for the passage of current through the contacts deteriorate. When currents flow through the switching device, its contacts heat up even

in the event that they were not exposed to an electric arc, and all parameters of the switching apparatus, including compressive force, are within acceptable standards.

Figure 1 shows the structural diagram of the device; in fig. 2 is a graph of the relationship between the current and the temperature of the contacts of the switching apparatus in a static mode.

The relationship between the current flowing through the contacts of a regulated switching device and their temperature in a static mode is represented by a line. When electrostatic wear of the contacts, or reducing the force of their compression, the contact temperature for the same values of currents will be higher. Corresponding relationship between the current flowing

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through worn or unregulated contacts and temperature, represented by line 5.

A device for monitoring the quality of the switching contacts of the switching device contains an electrothermal analogue of 1 controlled contacts connected in series with the contacts of a controlled switching device, a first sensor 2 of the temperature of an electrothermal analogue of contacts and a second sensor 3 of the contacts of a controlled switching device, a photosensor 4, the first large-scale amplifier 5, the second large-scale amplifier b and the third scale amplifier 7, the threshold element 8, the element 9 of the time delay, block 10 en lease information, block 11, logic unit 12 memory unit 13 display. As an electrothermal analogue of contacts, either separately taken analogous contacts connected in series with contacts of a controlled switching device 14 and having a standard compressive force, or one of the power circuit elements having increased ohmic resistance, for example, a measuring shunt, can be used.

The flow of load current through the power contacts of the switching apparatus causes them to heat up. This happens even if the contact parameters comply with the standard values. The relationship between the current flowing and the heating temperature is non-linear (Fig 2). The electrothermal analogue of the contacts of the controlled switching device is connected to the power circuit in series with the latter. The heating of the electrothermal analogue of contacts will be completely identical in nature to the heating of the main power contacts both in magnitude and in time. The signals from the outputs of the first sensor 2 of the temperature of the electrothermal analogue of the contacts and the second sensor 3 of the temperature of the contacts of the switching device go to the corresponding inputs of the first large-scale amplifier 5 and the second large-scale amplifier 6. At the same time, the gains of the large-scale amplifiers 5 and 6 are chosen so that the magnitude of the signals at their inputs, the signal at the output of the second large-scale amplifier b was by a certain number of percent corresponding to the tolerance of the control temperature uemogo contact from the standard temperature is smaller than the signal at the output of scaling amplifier thumbs 5. Next, scaled output amplifiers 5 and 6 signals are applied to first and second inputs information analyzing unit 10. The functional purpose of information analysis block 10 is to control the ratio of input signal levels. In this case, when the signal from the output of the first scale amplifier 5 is larger than the signal from the output of the second scale amplifier b, the output of the information analysis block 10 is O. Then the signal from the output of the information analysis block 10 goes to the first input of the logic block 11, is a two-input logic circuit I. When the position of the controlled switching device is turned off and on, as well as when it is turned on and off without a load, the photosensor 4 located in the area of the power contacts Ktov, not lit up, with its output to the entrance

0 scale amplifier 7 receives a signal corresponding only to the background illumination in the contact area, the signal from the output of the third scale amplifier 7 is fed to the input of the threshold element 8.

5 The setting of the threshold element 8 is selected so that it, if there is a signal at the input corresponding to the background equipment, does not work. At the output of the threshold element 8 there is a signal

0 1 that does not trigger the time delay element 9. As a consequence, the output of the element 9 time delay is also present signal 1, supplied to the second input of the block 11 logic.

5 Thus, at the first input of the logic block 11, which is a two-input logic circuit AND, there is a signal O, and at the second input of the logic block 11 there is a signal 1. This leads to the output

0 of logic block 11, signal O is present. Next, this signal is fed to memory block 12, it does not trigger it, and therefore, at output of memory block 12, there is a signal O, which hits

The 5th input of the display unit 13 will not cause its activation.

In the production of operational switching under load, as well as the disconnection of short circuits,

0 an electric arc, which even without causing noticeable wear of the power contacts of the controlled switching device, heats them for a while. This leads to the fact that after any disconnection5 of the switching apparatus accompanied by an electric arc, the signal at the output of the second temperature sensor 3 will become higher than the signal at the output of the first temperature sensor 2, and the signal at the output of the second large-scale amplifier 6 will be higher than the signal at the output of the first large-scale amplifier 5. At the output of the information analysis block 10, a signal 1 appears, which is fed to the first input of the logic block 11. In the process of disconnections under load at the contacts of the monitored switching device, the electric arc simultaneously acts on the photosensor 4. The signal from the output of the photosensor 4, falling on the input of the third scale amplifier 7, amplifies and from its output goes to the input of the threshold element 8. At the output of the threshold element 8, a signal O appears, which, on entering the input of the time delay element 9, leads to the appearance of the signal O at its output. The algorithm of the operation of element 9 is constructed in such a way that when it appears On the input signal, its output is also a signal O 0y When disappearance of the signal at the input member 9, which shows the disappearance of the electric arc, its output signal is changed to 1 signal only after a certain time. The value of this time interval is determined by the time theoretically and practically necessary for cooling the power contacts of the controlled switching device to ambient temperature (10 ... 15 min). Therefore, from the moment of occurrence of the electric arc and until the contacts cool down, a signal O is present at the second input of the logic block 11. For this reason, despite that. that as a result of the electric arc to the power contacts of the switching device, they have some time temperature higher than the temperature of the electrothermal analogue of the contacts, the contact temperatures do not occur, the output of the logic block 11 contains the signal O, which does not trigger the memory block 12 and the block 13 indications.

During the operation of the commutation apparatus, its contacts are subjected to electric arc erosion, the compressive force of the contacts weakens, and the ohmic resistance of the contacts increases. The temperature of the contacts of the switching apparatus for the same values of currents increases (curve B of figure 2).

The electrothermal analogue of 1 contacts, which does not twitch to the effects of arc erosion and does not have moving parts in its design, practically does not change its electrical, mechanical, and thermal characteristics. Therefore, the temperature of the electrothermal analogue of 1 contacts for the same values

currents remain unchanged. This leads to the fact that at the same currents in the power circuit, the signal at the output of the second temperature sensor 3 will be higher than the signal at the output of the first temperature sensor 2, and the signal at the output of the second scale amplifier 6 will be higher than the signal at the output of the first scale amplifier 5 At the output of the information analysis block 10, a signal 1 appears, which is fed to the first input of the logic block 11. Since the second input of the logic block 11 at that time has a signal 1, which indicates the absence of an electric arc and that it does not cause the contacts to heat up, the signal H also appears at its output. The signal G from the output of the logic block 11 is supplied to the input of block 12 of memory. The memory unit 12 is triggered, and a signal 1 appears at its output, which, upon entering the input of the display unit 13, causes its operation - the lighting of the light board. Ignition of the light panel indicates that the parameters of the power contacts of the controlled switching device have gone beyond the limits of permissible standard values.

Claims (1)

Claims An apparatus for monitoring the state of contacts of a switching apparatus, comprising an information analysis unit and an indication unit, characterized in that, in order to increase the reliability and objectivity of information, an electrothermal analogue of monitored contacts, a photo sensor, two temperature sensors, three large-scale amplifiers are introduced into it, the time delay element, the threshold element, the memory unit and the logic unit, while the electrothermal analogue of the monitored contacts is connected in series with the terminals for which they are connected and the studied contacts, the output of the first temperature sensor is connected to the input of the first scale amplifier, the output of the second temperature sensor is connected to the input of the second scale amplifier, the output of the photo sensor is connected to the input of the third scale amplifier, the output of which is connected to the input of the threshold element, the output of which is connected to the input of the time element delay, the output of the first scale amplifier is connected to the first input of the analysis unit, the output of the second scale amplifier is connected to the second input of the analysis unit, the output to torogo connected to the first input of the logic unit, the second input of which is connected to the output of the time delay element and the output logic block is connected to the input of the memory unit, whose output is connected to the input the display unit, while the first temperature sensor is located on the electrothermal analogue of the contacts, the second temperature sensor is located on the contacts controlled switching device, and the photo sensor is located in the contact area of the controlled switching device. / t HOOQ 3000 gooo yooo 1