RU2602753C1 - Method of power supply buses relative to housing electrical insulation resistance monitoring - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention relates to electric engineering, particularly to automated control systems, and is used during monitoring of electric radio products electric circuits insulation resistance, disconnected from power supply. At first stage with closed buses between housing and buses test signal is established, significantly exceeding noise level, which enables both buses high accuracy insulation resistance measurement connected in parallel. At second stage first low level source is connected between power supply buses, enabling fast load capacity charge and neutralizing active load resistance effect on measurement results. At that, low signal level excludes damage of power consumers by power supply circuits. And second signal source is connected between housing and one of buses, which provides high accuracy of leakage resistance measurements.

EFFECT: technical result consists in possibility of monitoring with minimum energy consumption, with high response rate and with minimum effect of interferences.

1 cl, 4 dwg

Description

The present invention relates to electrical measuring equipment, in particular to automated control systems, and is used in the manufacturing and operation of systems having an extended power supply system, for example, in aircraft and rocket science, shipbuilding, etc. to improve the control and measuring and protective functions of the system automatics.

Insulation resistance is a very high value, however, insulation depends on many effects that can lead to a sharp decrease: mechanical damage, vibration, excessive heat or cold, dirt, oil, and corrosive vapors from the air or the process. It can be violated, for example, during installation work on the product or due to shaking during transportation of this product.

A known method of measuring insulation resistance and protection against short circuits on the case of power circuits of diesel locomotives (RF patent No. 2415445). Its essence is that they change the configuration of the measured circuit by shunting and make a series of measurements of the measured circuit, at which, at the beginning of the measurement, the potentials of different sections of the circuits are measured with respect to the case, then the section of the circuit is bypassed with a resistor of known nominal value and the potential values of the same sections of the circuits are measured in steady state, and according to these parameters, the insulation resistance of the separately positive and negative circuits is calculated, at the same time, the voltage distribution between the circuit and the case, and when one of these voltages is reduced to a value close to zero, provided that the other voltage is in the range above the previously selected threshold, it is believed that a breakdown of the insulation of the corresponding circuit has occurred and it is decided to protect by removing the excitation from a generator supplying a power circuit.

The disadvantages of this method are the inability to control the insulation parameters in the absence of a supply voltage, due to the significant influence of the parameters of the switched off power source (capacitive and active components) and the complexity of the implementation of the device.

A known method of measuring insulation resistance, described in RF patent No. 2180124, the essence of which is that short impulses are applied to the network, synchronized with the moment the voltage passes through zero with the frequency of the control current source at the electric poles of the network, short pulses and control alternating current are isolated in the current of the controlled element. The active component of the current of the controlled element is determined on the basis of measuring the length of time between the moment of transition through zero of the test signal of the alternating current of the controlled element and the moment of the appearance of a short pulse. The presence of damage in the controlled element is determined by the fact of an increase in the active component of the current.

The disadvantage of this analogue is the significant influence of the parameters of the switched off power source (capacitive and active components) and low noise immunity, since a filter with a wide passband is required to isolate a short pulse at the measurement site.

Signs of an analogue that coincide with the essential features of the claimed invention is the presence of a connection operation between the controlled circuits of the test signal.

Reasons that prevent obtaining a technical result are the presence of an influence on the measured circuit by connecting measuring resistors and a large measurement cycle.

The closest in technical essence to the claimed object is a method of measuring insulation resistance in DC circuits (RF patent No. 2384855). Its essence is that two resistors are connected to the poles of the DC circuit. The other two resistors are connected in parallel to the load. A measuring circuit consisting of a series-connected measuring voltage source and a current meter is connected to the connection point of the resistors. The voltage source is connected to alternately changing the polarity of the poles. The equivalent measuring current is determined as half the sum of two absolute values of the currents measured sequentially in time at different polarity of the voltage source and the insulation resistance is determined by the corresponding formula.

The disadvantages of the prototype are the large error in the control of the insulation parameters, which appears due to the significant influence of the parameters of the switched off power supply (capacitive and active components), high energy consumption, since a low-impedance load can remain between the power buses when the power supply is off, and a long measurement time, how between power buses there can be an equivalent capacity of up to 0.1-1.0 F.

The objective of the invention is the creation of a method of controlling the electrical insulation resistance of the power busbars of an object relative to the housing, providing control with minimal energy consumption, with high speed and high resolution.

The technical result is achieved due to the fact that the main control operation - the measurement of the equivalent resistance of the busbar insulation resistances connected in parallel, is performed with minimal energy consumption with a test signal, which ensures the minimum error from the influence of interference and without the participation of large capacitances between the power buses. And the measurement of insulation resistance between the case and the bus is controlled in the presence of a compensating signal of a low level.

This is achieved by the fact that the process of monitoring the insulation resistance is supplemented by the operations of measuring various configurations of the circuit, and the connection of a compensating signal of a low level between the supply buses increases the accuracy of the measurement and reduces the time it takes to complete the monitoring procedure as a whole.

When researching patent and other scientific and technical information, the applicant did not find sources in which information about technical solutions containing the totality of the distinguishing features of the proposed method would be provided. At the same time, technical solutions are known that contain individual features of the claimed object, however, the properties and effect that these features inform these objects are different than in the proposed solution, therefore, the indicated differences are significant.

The essence of the invention lies in the fact that when checking the insulation of the power supply busbars to the chassis in a de-energized state, procedures are used to significantly reduce the influence on the process of controlling the presence of large filter capacities and low active resistance between the buses, which vary over a wide range, which significantly distorts the results, increases energy costs and lengthens the measurement time.

An equivalent circuit of a controlled object (KO) is shown in FIG. 1a)

where + F and -F are the positive and negative power buses, respectively, to which the energy consumers and the energy source are connected,

R0 is the equivalent resistance of the total resistance of all consumers connected between the positive and negative power buses and the internal resistance of the power source (in the off state),

С0 is the equivalent total capacity of all consumers connected between the positive and negative power buses and filter capacities of the power source (in the off state),

R1 and R2 are the equivalent insulation resistance relative to the housing of the + F bus and the -F bus, respectively, of all energy consumers connected to the power source,

C1 and C2 are the equivalent capacitance between the chassis and the + F and -F buses, respectively, from all energy consumers connected to the power source,

K is the body of the product.

Between the power supply buses all consumers are connected (the resistance of which can fluctuate in the range from 1 to 100,000 or more Ohms), which are shunted by filter capacities (up to 0.5-1.0 F) R0 and C0.

On figb) shows an equivalent diagram of the first cycle of measuring KO,

where E0 is the source of the test signal,

DT is a current sensor that measures the current generated by the source E0 and the equivalent load of R1 and R2, C1 and C2 connected in parallel,

L - jumper connected between the + F and -F buses and shunting R0 and С0.

In FIG. 1c) shows an equivalent circuit of the second cycle of measuring KO,

where E is the first source, the connection of which eliminates the influence ("neutralizes") on the measurement process of R0 and C0,

Uk is the second source of the test signal for measuring R1 or R2.

In FIG. 2 is an exemplary diagram of a device explaining the principle of operation of the proposed method, FIG. 3 is a flowchart of an implementation of a method for measuring insulation resistance of power buses from a housing, and FIG. Figure 4 shows the dependence of the values of equivalent resistance Re on R1 and R2.

In figure 2, the following notation.

1 - controlled object,

1.1 is the equivalent insulation resistance of the first tire,

1.2 is the equivalent insulation resistance of the second bus,

2 - the first power bus,

3 - housing bus,

4 - second power bus,

5, 12, 13, 14 and 15 - keys that provide the connection of the corresponding signals to the buses,

6 - analog-to-digital Converter ADC,

7 - control unit and calculation,

8 - the registrar,

9 - digital-to-analog converter DAC,

10 - key management register,

11 - current sensor,

16 - source of compensating voltage,

17 - bus "Start".

The figure 3 adopted the following notation.

1 - start the control process;

2 - determine the initial conditions for monitoring: the permissible value of the insulation resistance for each bus Rd1 and Rd2 (for example, Rd1> Rd2), and the monitoring time Tk;

3 - combine tires with jumper L;

4 - apply a test signal (voltage) Ео> Е between the case and tires F1 and F2;

5 - measure the response of Io to the test effect;

6 - calculate Re according to the formula: Re = Ro / Io;

7 - compare Re with acceptable Rd1 and

if Re> Rd1, then go to step 15, and

if Re≤Rд1, then go to paragraph 8;

8 - compare Re with Rd2 and,

if Re≤Rd2, then go to paragraph 15, and

if Re> Rd2, then go to step 9;

9 - install voltage E between the buses F1 and F2 instead of the jumper L;

10 - install a test signal (voltage) Uк between the housing and the first feeder bus;

11 - measure the response of Ik to the test signal Uk;

12 - calculate R1 by the formula: R1 = E / ((Ik + (E-Uk / Re)) (Provided that E = Uk, the formula is simplified to R1 = Uk / Ik);

13 - compare R1 with Rд1 and,

if R1 <Rд1, then go to step 15, and

if R1≥Rd1, then go to paragraph 14;

14 - compare R1 with the value calculated by the formula

Rd2 * Re / (Rd2-Re) and,

if R1≤Rd2 * Re / (Rd2-Re), then go to paragraph 16, and

if R1> Rd2 * Re / (Rd2-Re), then go to step 15;

15 - set the sign of going beyond the tolerance field;

16 - compare the current control time T with a given control completion time Tk and,

if T <Tk, go to step 5a,

if T≥Tk, go to paragraph 17;

17 - complete the process of monitoring the insulation of power buses.

The method of measuring the insulation of the power supply bus is implemented using the example of the device shown in Fig. 2, in which insulation resistance 1.1 and 1.2 are connected between the housing 3 and the power supply bus 2 and 4 of the monitored object, the values of which are equal to the equivalent resistance of the actual insulation resistance of the loads connected to the power bus KO 1. Bus 2 is connected to the inputs of the first 5, second 12 and third 13 keys, and the first input of the ADC 6, the second input of which is connected to the information output of the current sensor 11. The output of the current sensor 11 is connected to the output ohm of the first key 5, and the input is with the first output of the DAC 9, the second output of which is connected to the bus of the housing 3. The input of block 7 is connected to the output of the ADC 6, the second input is connected to the bus of Start 17, and the first output of the block 7 is connected to the input of the DAC 9 The second output of block 7 is connected to the input of the registrar 8 and to the input of the key management register 10, the first output of which is connected to the control input of the first key 5, the second is connected to the control inputs of the second 12 and fifth 15 keys, and the third to the control inputs of the third 13 and Fourth 14 keys. The outputs of the third 13 and fourth 14 keys are interconnected, the outputs of the second 12 and fifth 15 keys are connected to the outputs of block 16, and the inputs of the keys 14 and 15 are connected to the second bus 4 KO 1.

The device operates according to the algorithm shown in figure 3, which implements the proposed method. In the initial state, the device inputs are connected to the power buses and the housing of the controlled object, the equivalent circuit of which is shown in FIG. 1a). (The values of R0 and C0 can vary over wide ranges and significantly affect the monitoring results when measuring by known methods.) On the “Start” command, keys 5, 13 and 14 are closed, thereby connecting the feeder buses to each other, and between case 3 and tires 2, 4, the shaper of the test signal of the DAC 9, which sets the level of the test signal, is connected through the current sensor 11. An equivalent circuit is shown in Fig. 1b). Block 7 records the value of the test signal in the DAC 9, and the ADC 6 digitizes the values of the physical quantities of the test signal E0 and the sensor signal Ik0, which transmits to block 7. Block 7 calculates the value of the equivalent resistance Re by the formula Re = Eо / Iко and compares Re with acceptable insulation values for each of the tires (see Fig. 3) Rd1 and Rd2. Based on the comparison results, block 7 either completes the measurement cycle by writing a control result to the recorder 8 or changes the configuration of the circuit by issuing through the register 10 commands for opening the keys 13 and 14 and closing the keys 12 and 15 (see Fig. 1c). Between power buses 2 and 4, a test signal E is applied (for example, the voltage is significantly less than the supply voltage, up to 1V, and therefore the consumption from it will be minimal). In DAC 9, block 7 records the value of the test signal Uk, which is fed through the current sensor 11 between the case 3 and the first bus 2 (in our case, between the case 3 and the bus 2, but you can send a test signal between the case 3 and the bus 4).

The ADC 6 digitizes the values of the physical quantities of the test signal Uk and the sensor signal Ik, which transmits to block 7. Block 7 calculates the value of the equivalent resistance R1 according to the formula:

R1 = E / ((Ik + (E-Uk / Re)). Moreover, if Uk is chosen so that it is equal to E, the formula is simplified to R1 = Uk / Ik);

Block 7 checks the conditions

Rd1 <R1 <Rd2 * Re / (Rd2-Re)

(or Rd2 <R2 <Rd1 * Re / (Rd1-Re), if a test signal is sent between the housing 3 and bus 4, and the insulation resistance R2 is measured).

Based on the comparison results, block 7 completes the next cycle of the control procedure, recording the control result in the recorder 8, and proceeds to the next cycle if the current control time T is less than the specified control execution time Tk.

FIG. 4 illustrates where the zone of values of Re is located at which the insulation resistance values of both tires will be higher than the permissible values of Rd1 and Rd2

The possibility of carrying out the invention is confirmed by the fact that the authors conducted simulation of control processes and have already developed and tested a mock device that implements this method.

Thus, the proposed method for monitoring the electrical insulation resistance of the power bus relative to the housing provides control with minimal energy consumption, with high speed and high accuracy.

Claims (1)

A method for monitoring the electrical insulation resistance of power buses relative to the housing by connecting a test signal between the housing and the monitored bus, measuring the response signal to this effect and comparing the result with the acceptable one, characterized in that the feeder buses are closed with a jumper at the first stage, and a test signal is supplied between the housing and the tires high level, sufficient to eliminate the influence of interference, measure the response to the test effect and calculate the value of the parallel connection of the insulation resistances and tires relative to the housing, which is compared with the acceptable one, and at the second stage, between the feeder tires, the first source of low signal level is connected, which provides an accelerated charge of capacitors with a low load resistance and the establishment of a small potential difference between the tires, safe for blocks representing the feeder load, and between one of the buses and the chassis connect another source, the output signal of which may be equal to the first or different from it; by the magnitude of the response to the action of the second source, the insulation resistance value of one tire relative to the housing is calculated and the conditions are checked
Rd1 <R1 <Rd2 * Re / (Rd2-Re) or
Rd2 <R2 <Rd1 * Re / (Rd1-Re),
where R1 and R2 are the insulation resistance of the power bus relative to the housing, respectively;
Rd1 and Rd2 - the minimum allowable insulation resistance of power buses relative to the housing, respectively;
Re - equivalent resistance in parallel connected R1 and R2,
and based on the results of the verification of which they conclude about the quality of tire insulation.

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