SU744353A1 - Apparatus for monitoring leakage in direct-current power supply - Google Patents

Description

one

The invention relates to the field of electrical engineering and is intended both to control leakage currents in the valuable with a series-connected distributed load, and to determine the location of a ground fault. The device can be used, for example, to monitor leakage currents and determine the location of the earth fault at the power supply level of the electrolysis baths.

A device is known for automatically controlling the isolation of a mine traction network of direct current at an alternating operational current, containing its AC bridge, one arm of which is connected to a controlled network through a coupling capacitor and a bridge diagonal includes a reference element and an actuator. This device uses the application of non-recurring onorate current to the monitored network. The device signals a closure to earth or an unacceptable reduction from the stationary mine network, while the accident site remains unknown and is searched for using the usual methods.

It is also known that electrical equipment 2 is protected against leakage of current to the ground, which contains a switching device that alternately connects a positive II negative wire of the direct current network to the grounding system, a reference signal generator, a distributor and a local authority. This device uses the principles of comparing rectangular impulses in a grounding network with a reference oscillator signal. When shorted to ground or unacceptable isolation is relatively

On the 10th of the earth at the output of the comparator, an imbalance signal appears and the device turns off the newly created line. However, this device relieves the leakage current of the entire linn as a whole and does not allow isolation

15 total leakage current lnnn share of each object. In order to control the leakage current of a large number of nose “consistently connected objects of non-breaking load, it is advisable to know which one is

20 gives the largest leakage current to carry out measures to improve the overall network.

The aim of the invention is to extend the functionality by using ns25 of use per valuable distributed load carrier.

This goal is achieved by the fact that, in a known device for monitoring current, a leakage current of a net current containing a power supply interface, connected to the conductor and to the output organ, made in the form of a voltage difference amplifier, is made in the form of two parallel resistive valve branches, the valves of which are connected in the forward direction between the grounding conductor and the conductor, with one branch of the connecting filter connected to the conductor before, the other - after controlled loading and the midpoints of the specified filter are connected to the inputs of the difference amplifier of the two voltages.

The basic electrical circuit is shown in FIG. one; external connection diagram in FIG. 2

The offered device includes a connecting filter consisting of diodes 1, 2 and resistors 3-6; two voltage difference amplifier, connected by its inputs to the middle points of the connecting filter parallel to resistors 5 and 6 and consisting of an operational amplifier 7, resistors 8-12 and a capacitor 13, branches 14-15 of the connecting filter, device output 16 connected to recording equipment and alarm.

In addition, in the diagram of external connections (Fig. 2) are indicated - resistances, serially connected, distributed load; ut . n - resistance of leakage current to earth; Lt. 1-fyr.n - leakage currents; / and and / 15 - currents in the x 14 and 15 branches of the connecting filter, respectively.

The device works as follows.

Leakage currents, the magnitude of which depends on the ohmic resistance of the insulation, pass successively through the insulation of the circuit and the connecting filter. Diodes 1 and 2 of the connecting filter cause leakage currents to its branches only from objects that have a positive potential relative to the point of attachment of the corresponding branch. Consequently, the current in branch 14 of the attachment filter is determined by the leakage current / ut. i and / ut.2 (Fig. 2), and the current in the branch 15, moreover, the current / ut. 3. For leakage currents / ut. 1 and / 2, with the pairwise equality of the resistances of the resistors 3 and 4 and 5 and 6 (Fig. 1) branches

14 and 15 are equal and parallel resistances. Then the current flowing in the branch 14, formed by leakage currents / ut. i and / ut r is determined by the expression

U.1 + ut.2

L4 -2

According to the above, the current in the branch

15will be more for leakage current from the controlled object / ut. h- The voltage drop formed on the resistors 5 and 6 of the connecting filter during the flow of currents / and / is in its branches x goes to the inputs of the difference amplifier of two voltages 7. In the amplifier of the difference of two voltages, the voltage is subtracted .5 from Voltage Ui5 Ii5Re A voltage appears at the output of the amplifier, which is proportional to the difference of the voltages t / 14 and L / i5W K (U ,, - and ,,).

The coefficient of proportionality K depends only on the ratio of the resistances of the resistors 8-11 and provided that they are equal in pairs, and Rio-Rn will be equal to

D) CZK

From the expression

D - / corner.

9

It is seen that the output voltage of the difference between two voltages is directly proportional to the leakage current of the object being monitored. Thus, sequentially connecting the device to the control objects, by the magnitude of the leakage current

it is possible to determine on which of them the earth fault occurred. The device must be used with the device for automatic control of control objects and signaling and recording equipment.

The use of the device in non-ferrous metallurgy to control and eliminate leakage currents in batches of electrolysis baths will allow energy savings of up to 15 million kVAh per year per batch of electrolysis baths powered by 600 V.

Claims (2)

Invention Formula Device to control leakage current in DC network containing a connecting filter connected to the conductor and to the output body, made in the form of the amplifier of the difference of two voltages, characterized in that in order to expand the functionality by using a network with a series-connected distributed load, the connecting filter is made in the form of two parallel resistive-valve branches, the valves of which are connected in the forward direction between the grounding conductor and the conductor, one branch of the connecting filter - after a controlled load, and the midpoints of the specified filter are connected to the amplifier inputs of the difference of two voltages. Information sources, taken into account in the examination of the USSR 1. Copyright certificate № 399956, cl. H 02 H 3/16, 1973. 2. Patent of France No. 2188171, cl. H 02 H 3/16, 1974. 14