RU225846U1 - STAND FOR RESEARCH OF ELECTRIC DISCHARGES - Google Patents

Abstract

The utility model relates to experimental equipment for laboratories involved in the development of means for ensuring the safety of electrical installations. The stand for studying electrical discharges has current sensors, spark gaps simulating a discharge, with the ability to change discharge conditions, a current and voltage oscillogram recorder, a circuit breaker, contacts for connecting a power source and load. The functionality of the stand is increased. 5 ill.

Description

The utility model relates to experimental equipment for laboratories involved in the development of means for ensuring the safety of electrical installations.

Currently, a device is known for determining the discharge parameters of overvoltage protection devices (RU 2280879, IPC G01R 31/24 (2006.01), G01R 19/25 (2006.01), published July 27, 2006), consisting of a voltage source, a voltage divider and an oscilloscope with the ability to save recorded oscillograms.

The disadvantage of the device is the inability to use it to determine the parameters of means of protection against sequential electric discharge. In addition, there is no possibility to evaluate such parameters of the electrical discharge as resistance value and heat generation power.

A device is known for testing devices for protection against arc breakdown and spark gaps (RU 200084U1, IPC G01R 31/08 (2006.01), published 10/05/2020), containing a circuit breaker, a stopwatch, an arc generator, a starter, a limit switch, an adjustable load, an ammeter .

The disadvantage of the device is that it does not have the ability to test protection devices against parallel arc breakdown and spark gaps. In addition, there is no possibility to evaluate such parameters of an electric discharge as resistance value, heat generation power, as well as assessment of harmonic components of current and voltage.

The closest to the claimed device is a device for testing protection devices against serial and parallel arc breakdowns and spark gaps (RU 211441, G01R 31/08 (2006.01), published 06/06/2022), containing a circuit breaker, a stopwatch, an arc generator, a starter , limit switch, adjustable load, ammeter, switch for selecting the type of discharge and sample cable for creating a parallel discharge.

The disadvantage of the device is that it does not have the ability to evaluate such parameters of an electric discharge as the value of its resistance, the power of heat release at the site of the discharge, the duration of unstable discharges, as well as the assessment of the harmonic components of current and voltage. In addition, there is no possibility of varying the conditions of the electrical discharge, since it is assumed that the parallel discharge will be reproduced only in the cable.

The utility model solves the problem of creating a stand with expanded functionality that makes it possible to simulate various conditions for the flow of electrical discharges and record their parameters due to the possibility of changing the design of the spark gaps and using an oscilloscope to record the current and voltage of electrical discharges.

The technical result is achieved by the fact that in a stand for studying electrical discharges, containing electrical circuits for simulating sequential and parallel types of discharge, a switch for selecting the type of discharge, a circuit breaker, spark gaps simulating a discharge, contacts for connecting a power source and load, an electrical circuit for each is proposed the type of discharge should be equipped with a separate current sensor, and the spark gaps should be designed with the ability to change the conditions of the electric discharge. It is additionally proposed to equip the stand with a recorder of current and voltage oscillograms.

The graphic materials attached to the description show:

fig. 1 - electrical diagram of the proposed stand;

fig. 2 - design of the spark gap used for sequential discharge;

fig. 3 - design of the spark gap used for parallel discharge;

fig. 4 - oscillogram of voltage and current of sequential discharge;

fig. 5 - oscillogram of parallel discharge voltage and current.

The following symbols are used on graphic materials:

1, 2 - contacts of a dismountable connection for connection to a power source;

3 - automatic switch;

4 - spark gap, simulating a sequential discharge;

5 - sensor for recording load current;

6 - spark gap, simulating a parallel discharge;

7 - parallel discharge current recording sensor;

8 - switch;

9 - current and voltage recorder;

10, 11 - detachable connection contacts for connecting to the load;

12 - electrodes for simulating sequential discharge;

13 - designs of dielectric fastening of electrodes;

14 - electrodes for simulating parallel discharge;

15 - insulation.

“a”, “b” - positions of the discharge type switch.

Description of the operation of the proposed stand for the study of electrical discharges.

The stand for studying electrical discharges works as follows. The power source is connected to pins 1 and 2 of the detachable connection, and the circuit load is connected to pins 10 and 11. Contacts 10 and 11 are made collapsible, allowing you to connect power supplies and load devices with different characteristics.

Switch 8 selects the type of discharge: serial or parallel discharge. When the switch selects position “a”, the sequential discharge is examined. In this case, the current will flow from the source through the circuit: spark gap 4, current sensor 5, load, and the measuring channels of the recorder 9 will be connected to measure the voltage at the spark gap 4 and the current with sensor 5.

When switch 8 selects position “b”, spark gap 4 and sensor 5 are disconnected from the circuit. Instead, a spark gap 6 and a current sensor 7 are connected to the circuit, parallel to the load. The measuring channels of the recorder 9 are connected to measure the voltage at the spark gap 6 and the current by sensor 7 flowing through the parallel discharge.

In case of serial breakdown, the discharge current represents the load current, which can significantly exceed the parallel discharge current. Using a single current sensor to record these currents can introduce significant measurement errors. Therefore, in the circuit shown in FIG. 1, it is proposed to use two separate sensors to record currents of each type of discharge.

Any conductors separated by a dielectric medium can be used as spark gaps. The distance between them can be either fixed or variable.

The spark gap for studying a sequential discharge is shown in Fig. 2. It consists of two 12 metal electrodes with rounded edges. The distance between the electrodes is adjusted using threaded connections in the dielectric structures 13 on which they are attached. In fig. Figure 3 shows the spark gap for studying parallel discharges. It consists of two electrodes 14, one of which is made in the form of a wire core, and the second in the form of a metal structure in contact with the wire. There is a hole in the wire insulation. The distance between the electrodes is changed by moving the hole in the insulation relative to the metal structure.

The time instants of the beginning and end of the discharges are estimated from the recorded current and voltage oscillograms, this makes it possible to accurately estimate the duration of the discharge. In addition, by recording current and voltage oscillograms, the device allows you to assess the power released at the site of damage, the discharge resistance, as well as analyze the harmonic components in the current and voltage, both before the occurrence of an electric discharge and during the discharge.

A specific example of using a stand for researching electrical discharges.

An example of the use of the proposed stand is a stand consisting of the following components: circuit breaker BA47-29 for a current of 32A; current sensor for recording sequential discharge 75SHIP1-30-0.5; current sensor for recording parallel discharge 75SHIP 1-5-0.5; PKUZ switch; oscilloscope GDS-71042 V. The RPSh-5 rheostat was used as a load, connected in series with a total resistance of 7 Ohms, and a voltage of 220 V was supplied to the stand through a laboratory autotransformer TDG2-1.

Examples of spark gaps are shown in Fig. 2 and 3.

To register the parameters of the sequential discharge, switch 8 is moved to position “a”. The design shown in Fig. 1 was used as electrodes for reproducing the discharge. 2, in which the distance between the electrodes was set to 1 mm. Examples of sections of oscillograms of voltage and current of a sequential discharge recorded using an oscilloscope and a current sensor are shown in Fig. 4. The oscillograms show that at 0.14 s a short-term closure of the contacts occurred, followed by the occurrence of an arc discharge lasting several periods. Calculations carried out using known methods made it possible to establish that the maximum instantaneous value of the arc current did not exceed 40 A. The arc resistance, changing during combustion, reached a value of 887 Ohms. The maximum instantaneous arc power was 1587 W. The current non-sinusodial coefficient varied from 0.59 to 0.98.

To register a parallel discharge, switch 8 was moved to position “b”. The stand is powered by a physical model of a 220 V electrical network. The design shown in Fig. 1 is used as electrodes for reproducing discharges. 3. The results of recording the discharge current and voltage are presented in Fig. 5. From the obtained oscillograms it is clear that the discharge occurred at a time of 0.15 s. In shape it corresponds to an unstable arc discharge. The arc is extinguished every time its current first passes through zero. The instantaneous value of the arc current during the closure process reached 23 A, its resistance was 1529 Ohms, and the instantaneous power was 389 W. The non-sinusoidal voltage coefficient varied from 0.25 to 0.56.

From the obtained oscillograms of the discharge current and voltage, using known methods, it is possible to determine the resistance of electrical discharges, the power of heat release at the place of their occurrence, the duration of each of them, and also to assess the spectral composition of the current and voltage.

Thus, in comparison with the closest analogue, the proposed device makes it possible to simulate various conditions for the flow of electrical discharges and record their parameters using detachable contacts that allow connecting power sources and load devices with different characteristics, and using a current and voltage oscillogram recorder to evaluate power , released at the site of damage, discharge resistance, and also analyze harmonic components in current and voltage. Safe recording of the parameters of electrical discharges when they occur, both sequential and parallel with the load, under various conditions of their occurrence is ensured.

In addition, the device allows you to check the declared characteristics of protective devices for the above types of discharge when using different voltage sources and loads.

Claims (1)

A stand for studying electrical discharges, containing electrical circuits for simulating sequential and parallel types of discharge, a switch for selecting the type of discharge, a circuit breaker, spark gaps simulating a discharge, contacts for connecting a power source and load, characterized in that the electrical circuit of each type of discharge is equipped with a separate current sensor, the spark gaps are made with the ability to change the conditions of the electric discharge, while the stand is equipped with a recorder of current and voltage oscillograms with the ability to connect it through a switch to measure the voltage at the spark gaps of simulators of serial and parallel types of discharge and current sensors.