SU1368823A1 - Device for checking earthing of mobile electric plants - Google Patents

Abstract

The invention relates to electrical engineering and contributes to the improvement of electrical safety and speed of the device by its automation. The device contains grounding conductors 1 and 2, switching device 4, power supply unit 6, unit 11 sig gy of distribution. The introduction of blocks 5 and 7 of triggering pulse and test potential with normally open contact 8, rectifier 9, two-threshold amplitude discriminator 10, output relay element 12 and signaling unit 13 allows, at 7 U, through discriminator 10, output relay element 12 and switching device 4 disconnect the mobile electrical installation 3 from the network. If and from L pr Uon,, then the unit 1 1 signaling is activated, indicating that it is normal. In the presence of faults, when the signal at the input of the discriminator 10 is small or equal to zero, the alarm unit 13 is triggered, indicating that the device is faulty. 1 il. (L with O) with 00 oo with

Description

The invention relates to electrical engineering and can be used in alternating current networks to control the touch voltage.

The purpose of the invention is to increase the electrical safety and speed of the device by automating it.

The drawing shows a diagram of the proposed device.

The device contains a main earthing device 1, an auxiliary earthing device 2, a housing 3 of a mobile electrical installation, a switching device 4, a trigger pulse shaping unit 5, a power supply unit 6, a test potential generating unit 7 with a normally open contact 8, a rectifier 9, two-threshold amplitude discriminator 10, alarm unit 11 (U is normal), output relay element 12, alarm unit 13 The device is faulty. Moreover, the earthing switch 1 is connected to the housing 3, the first input of block 5 and the input of block 6 are connected to the network, the second input of block 5 is connected to the first output of block 6, the first and second inputs of block 7 are respectively to the second output of block 6 and the output of block 5, output unit 7 - to the phase of the network and the housing 3, the input of the rectifier 9 through the contact 8 is connected to the earthing switch 2, as well as the housing 3, and the output to the input of the discriminator 10, block 11, element 12, block 13 are connected respectively to the first, second and the third outputs of the discriminator 10. The output of the element 12 is connected to the input of the switching apparatus 4, the contacts of which connect the mobile electrical installation to the network.

Block 5 consists (option) of a pulse maker when the network voltage passes through zero, the output of which includes a delay circuit with time tj. As a pulse shaper, a device containing a limiter, two triggers, three NOT elements and an NAND element can be used when the input signal passes through zero. In this case, pulses with a frequency of 2 f occur where fj. - network frequency. The pulse duration is determined by the response time of the AND elements and the time for setting the trigger to the initial state. From the output of the pulse former, the signal goes to the first input of the first element I, and to the second input

0

five

0

five

0

&

5 0 5

five

0

logical unit from power supply unit 6. This is necessary for stable operation of block 7. At the output of block 5, one pulse is formed with a time delay t. , the value of which determines the moment of the start of block 7 relative to the phase zero, i.e. ground current amplitude.

The test potential formation unit 7 is a one-shot with a pulse input: when a pulse is applied to the second input from block 5, a current pulse with an amplitude and duration different from the input pulse arises at its output.

Unit 7 includes a thyristor, a reed switch, a capacitor, and two resistors. When a pulse is applied from block 5 and powered from block 6, the thyristor opens, the reed switch operates and closes its normally open contacts. At the output of the unit between the terminals, a single-phase circuit current flows.

As the capacitor charges, the voltage on the reed relay drops off and, having reached the release voltage, releases its contacts. The single-phase circuit is interrupted.

The duration of a single-phase pulse / current can be calculated by the formula

C / RI, - with In 0.1,

where RI is the resistance of the coil reed switch; С - capacitor capacitance.

The two-threshold amplitude discriminator 10 is implemented on the basis of operational amplifiers operating in the mode of comparators and logic elements, moreover, Uon,: U,,, where U ,, are the reference voltages of these amplifiers.

The device works as follows.

When the switching device 4 is turned on, the mobile electrical installation is connected to the network, a constant stabilized voltage appears at the output of block 6, and a pulse of several tens of microseconds appears at the output of block 5. At the output of block 7, respectively, a current pulse of a single-phase closure of duration c / occurs. At the same time, contact 8 is closed and a pulse arrives at the input of the discriminator 10, the amplitude of which determines the level of touch voltage and "p. If those. Normally, at the outputs of op-amps of the discriminator 10 logical units, the alarm unit 11 is triggered. If Unp Ucn, then the output of the Disabled discriminator 10 unit is a logical unit, the output relay element 12 is triggered and the mobile electrical installation by the device 4 is disconnected .

In the presence of faults, when at the input of the discriminator 10 the signal is small or equal to zero, i.e. ,, block 13 is triggered, which indicates a malfunction of the control device. The unit also works with faults resulting in the appearance of logical zeros at the output of both amplifiers of the discriminator 10.

Claims (1)

Invention Formula A device for monitoring the grounding of mobile electrical installations, comprising a main earthing switch connected to the housing of a mobile electrical installation, auxiliary earthing switch, power supply unit, first unit Signaling and switching apparatus, characterized in that, in order to increase electrical safety and speed, a test potential formation unit, rectifier, two-pitch amplitude discriminator, second signaling unit, relay element, pulse starter shaping unit, first input are introduced into it which is connected to the network, the second input is to the first output of the power supply unit, the first input of the test potential formation unit is connected to the second output of the power supply unit the trigger pulse forming unit, and the output is connected to the mains phase and the mobile electrical installation case, the rectifier input is connected to the mobile electrical installation case and through the normally open contact of the test potential generation unit to the auxiliary earthing switch, the two-threshold amplitude discriminator input is connected to the output of the microphone, the first output is with the first signaling unit, the second output is with the output relay element, the output of which is connected to the input of the switching device, the third output is with the second m alarm unit.