RU85270U1 - DEVICE OF RESISTANCE RESISTANCE OF MULTIPLE CONSUMERS - Google Patents

Abstract

A device for monitoring the insulation resistance of several consumers, containing a supply transformer, a differential switch, a reacting organ, two resistors, a switching device, to the output of which consumers are connected, characterized in that, in order to expand the functionality of the existing device, the first resistor shunted by the reacting organ is turned on parallel to one of the poles of the switching apparatus, the common point of the differential switch, the first resistor reacting ana and the switching device is grounded via a chain of series-connected normally open contact reactant and a second resistor body.

Description

The utility model relates to the field of relay protection and can be used to control the insulation resistance of three-phase consumers.

A device for remote control of a three-phase electric motor of a pumping unit (1). The channel of zero sequence currents is used as a signal transmission channel in this device. All three phases are covered by a TA zero sequence current transformer. A relay is connected to the TA output through the amplifier. This relay controls the magnetic starter coil.

It is known that circuits with zero-sequence current transformers do not sense three-phase load currents, but respond to leakage currents through the insulation of any of the phases even if a person touches live parts that are under voltage.

The disadvantages of this scheme include low sensitivity to leakage currents through insulation, the actual value of which, in the absence of reliable galvanic connection between the insulation of electrical equipment and the elements of the grounding circuit in operating conditions, does not exceed several milliamps (2).

In addition, this circuit can be used to control the insulation resistance of only one three-phase consumer.

Closest to the proposed utility model is a method for monitoring and protecting the insulation of electrical consumers in networks with a grounded neutral (3).

This method consists in the use of a non-linear sensor, one of the terminals of which is connected to the housing of the electrical equipment, and the other terminal is connected to a grounding conductor.

At high leakage currents, a low internal resistance of the sensor is obtained, which guarantees a safe shutdown by protective grounding. Moreover, to measure the insulation resistance, the dependence of the voltage drop across the sensor on the insulation resistance is used.

The main disadvantages of this scheme:

- the need to install a separate sensor and responsive body for each consumer;

- the dependence of the resistance of the nonlinear sensor on temperature;

- a decrease in the sensitivity of the sensor when an additional leakage current loop occurs in the event of damage to the insulation of the electrical enclosure;

- the need to calibrate the reacting organ when working with a non-linear sensor;

- the impossibility of the circuit in a network with isolated neutral.

The utility model is aimed at improving the reliability of the device for monitoring the insulation resistance of several consumers by expanding the functionality of the proposed device.

An insulation resistance monitoring device for several consumers, comprising a supply transformer, a differential switch, a reacting organ, two resistors, a switching device, to the output of which consumers are connected, according to the proposed utility model, in order to expand the functionality of an existing device, the first resistor shunted by the reacting organ is turned on parallel to one of the poles of the switching apparatus, and the common point of the differential switch, the first resistor , the reacting organ and the switching apparatus is grounded through a chain of series-connected make contact of the reacting organ and the second resistor.

Figure 1 presents a diagram of a device for monitoring the insulation resistance of several consumers.

Three-phase consumers - 4, - 5, - 6 are fed from a supply transformer - 1 through a differential switch - 2 and a switching device - 3. In parallel to one of the poles of the switching device - 3, a resistor - 7 is connected together with a reacting organ - 9. At the same time, the common point differential switch - 2, resistor - 7 and reacting organ - 9 is grounded through a chain of series-connected make contact - 10 reacting organ - 9 and resistor - 8.

A device for controlling the insulation resistance of several consumers is as follows.

When the switching device is turned on, 3 consumers - 4, - 5, - 6 receive power from the power transformer - 1. At the same time, the working phase currents of consumers - 4, - 5, - 6, flow through the power contacts of the switching device.

After switching off the switching device - 3 (for example, during a technological break) through the resistor - 7 leakage currents flow through the insulation of consumers - 4, - 5, - 6. Typically, differential switches have a minimum setting of the operating current, not sensitive to leakage currents flowing through insulation of electrical consumers, and for the diagnosis of its resistance are not suitable, operating only with earth faults through a low resistance (with a short circuit).

The magnitude of the voltage drop across the resistor - 7 depends on its resistance and on the magnitude of the leakage current through the insulation of consumers - 4, - 5, - 6. This voltage is applied to the reacting organ - 9.

If the insulation resistance of one or several consumers is lower than the permissible values, the leakage current flowing through the resistor will increase - 7. This current is not enough for the differential switch - 2 to operate. But at the same time, the voltage drop across the resistor - 7 will exceed the required value for the reacting organ to operate - 9 threshold value. After the reacting organ - 9 is activated, its make contacts - 10 form a circuit for the leakage current to flow, the value of which is limited only by the resistance of the resistor - 8 and can exceed the value required for the differential switch to operate - 2.

This device allows you to control the insulation resistance of several consumers both in the hot state during a technological break, and immediately before switching on.

Information sources

1. A.c. 1064375, H02I 13/00. A device for remote control of a three-phase electric motor of a pump installation / N.M. Popov. - Bull. No. 48, 1983.

2. Matytsin D.V. Diagnostics of the insulation condition of a submersible electric motor / D.V. Matytsin. - Actual problems of science in the agricultural sector: materials of the 59th international scientific-practical conference: in 5 volumes. - Kostroma: KSAA, 2008. Volume 5: Agribusiness. Social Sciences. Electrification and automation of agriculture / ed. S.A. Borodia, Yu.P. Pyatina, A.V. Rozhnova. - Kostroma: KSAA, 2008 .-- 198 p., Pp. 165-167.

3. A method of monitoring and protecting the insulation of electrical consumers in networks with a grounded neutral: Patent No. 2265949, RU, H02M 7/08 / A.I. Pakhomov. - Declared. 02/06/2003.

Claims (1)

A device for monitoring the insulation resistance of several consumers, containing a supply transformer, a differential switch, a reacting organ, two resistors, a switching device, to the output of which consumers are connected, characterized in that, in order to expand the functionality of the existing device, the first resistor shunted by the reacting organ is turned on parallel to one of the poles of the switching apparatus, the common point of the differential switch, the first resistor reacting ana and the switching device is grounded via a chain of series-connected normally open contact reactant and a second resistor body.