RU2391679C1 - Method for automatic monitoring of resistance of insulation of buses of direct current sources from housing - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: absence of short circuit between direct current source circuits and the housing is determined first. For this purpose two measurements of housing current are taken between the common negative bus and the housing: with a limiting resistor connected in the circuit of the current measurement device, and then with addition of a control direct voltage source to the circuit. Presence of circuits of the controlled direct current sources which are short-circuited with the housing is determined from the current difference value. If there is no short circuit, two measurements of housing current are taken between the common negative bus and the housing with and without a control direct voltage source connected in the circuit. The equivalent resistance of insulation is calculated form the difference between the measured current values and the voltage value of the control source.

EFFECT: more reliable monitoring of resistance of insulation of circuits of galvanically connected direct current sources, broader functional capabilities due to possibility of monitoring in case of deliberate connection of the common negative bus with the housing.

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Description

The invention relates to measuring equipment, in particular to the field of automatic control of insulation resistance of circuits of unregulated and regulated DC sources, galvanically coupled, having one common bus, for example negative, of buses that are energized or de-energized.

A known method for determining the resistance of current leakage paths to earth in electrical systems by as 2010247. This method is applicable, in particular, to determine the paths of current leakage to earth of poles of galvanically coupled DC voltage sources connected in series (batteries). Since each element of the battery has an internal resistance, by shunting it, you can change the voltage on the element and, knowing the voltage on others, make up a system of equations. Moreover, the number of elements in the system can be any. The resistance of the shunt should be commensurate with the value of the internal resistance of the element.

The disadvantage of this control method is the large energy consumption in the process of monitoring series-connected sources of electrical energy and the inoperability of the method of monitoring series-connected receivers when the leakage path resistance is less than or equal to the resistance of the coil. The equipment of the control object (OK) does not allow operation during cyclic changes in the supply voltage.

Closest to the technical nature of the proposed method is a method of controlling the insulation resistance of busbars of DC sources a. from. 309320, which consists in the fact that before each connection of the monitored bus to the sensitive element, it is shorted to the housing through a resistance equivalent to the resistance of the sensitive element, this eliminates the influence of capacitive current from capacitors.

The disadvantage of this control method is the inability to operate the device with intentional communication of the common source bus with the chassis.

The objective of the proposed method is to increase the reliability of monitoring the insulation resistance on the body of the circuits of unregulated and regulated sources of direct current, galvanically connected, having one common bus, for example minus; the tires can be energized and de-energized, and in the case of a deliberate connection of the common negative bus with the chassis (expansion of functionality).

This task is achieved by first determining the absence of a short circuit of the DC source circuits to the case, for which two measurements of the case current between the common negative bus and the case are performed, first with the inclusion of a limiting resistor in the current meter circuit, and then with the addition of a control source DC voltage, calculate the difference between the two measured currents and the magnitude of this difference is judged on the presence of short-circuited specific circuits of controlled DC sources with a housing, and in the absence of a short circuit, two measurements of the case current between the common, negative bus and the case are made with and without the inclusion of a control DC voltage source in the current meter circuit and the equivalent insulation resistance is calculated from the difference in the measured currents and the voltage value of the control source.

Monitoring the insulation resistance of the source bus according to the proposed method is as follows.

A simplified electrical circuit of galvanically coupled unregulated sources of the object of control is shown in figure 1. V1, V2, V3, V4 - voltage sources with a common negative bus; V3, V4 - primary power supplies of the control object OK (blocks B1 and B2, respectively), V1, V2 - power supply sources (C) OK, blocks A1 and A2 load blocks (equipment) of the corresponding sources, Rл - line resistance, Rш - resistance shunt. The common negative bus is connected to the housing by a jumper mc outside the OK blocks.

A simplified electrical diagram of a variant of the device that provides control by the proposed method is shown in figure 2. The device is part of the test equipment (KPA) (based on hardware and software) and is controlled by a software module (PM) according to a specific algorithm. The device contains (FIG. 2): K1-K3 - a relay controlled by the KPA command issuing module (the module issues commands using the PM algorithm); Ш - common negative busbar of direct current sources of the control object (OK); K - housing; IP1 - current meter in KPA; Vk is a control DC source, Rogr is a limiting resistor, R is an auxiliary resistor to prevent a circuit break in the common negative housing.

The control device of the housing is connected during the electrical tests OK in the gap between the grounding jumper and the housing according to Fig.3.

Measurement of all voltage sources OK is carried out by measuring modules KPA. The device is controlled by a software module (PM), while sequentially repeating control cycles are automatically executed.

Device operation

1. When a command is issued to start monitoring the OK source buses, the software module generates a request for the voltage of the OK sources and the first value of the package current (Iк1) between the negative bus and the case with connected RGR.

2. After a request for current Ik1, a command TKU2 is issued, by which relays K2 and K3 are activated and a control source Vk is connected to the current meter circuit. After t1 (0.25 s), a second measurement of the case current (Iк2) is performed. After requesting the current Ik2, the software module calculates the difference of the two currents Δ1 = Ik1-Ik2.

Time t1, the limits of the measured values of currents and the calculated value of the insulation resistance for making appropriate decisions according to the algorithm are finally set according to the results of work with the control object.

3. The software module performs an analysis of Δ1 (for the case of Rogr = 1 kΩ, Vк = 1 B):

- at Δ1 = 0 mА (Iк1 = Iк2 = 0) there are no OK source circuits associated with the case, PM generates the parameter "case control system" (CCM) SCC = 1 (Norm),

- when Δ1 = 1mA (Ik2 = Vk / Rogr mA) - a short circuit to the common negative bus housing, the PM generates the parameter SKK = 2;

- at Δ1 = 1mA (Ik1 = V1 / RGR mA) - a short circuit to the case of the positive bus of the source V1, the PM forms the parameter SKK = 3;

- when Δ1 = 1mA (Ik1 = V2 / Rogr mA) - a short circuit to the case of the positive bus of the source V2, the PM forms the parameter SKK = 4;

- when Δ1 = 1mA (Ik1 = V3 / Rogr mA) - a short circuit to the case of the positive bus of the source V3, the PM forms the parameter SKK = 5;

- at Δ1 = 1mA (Ik1 = V4 / Rogr mA) - a short circuit to the case of the positive bus of the source V4, the PM forms the parameter SKK = 6;

- when Δ1 = 1mA (Ik1 = V / Rogr mA) - a short circuit to the case body of the plus circuit of any source, the PM generates the parameter SKK = 9;

- when Δ1 <1 mA there are no short-circuited circuits of OK sources on the case, the software module implements the algorithm for calculating Re according to claim 4.

.4. In the absence of a short circuit according to claim 3, the TKU1 command is issued, it is excluded from the Rogr meter circuit and the first measurement of the housing current Ik3 is performed, after the PM current request Ik3, the TKS2 command is issued, it is excluded from the Vk meter circuit and the second measurement of the housing current Ik4 is performed, after request current Ik4, PM calculates the current difference Δ2 = Ik4-Ik3, the equivalent resistance R3 by the difference of currents and voltage Vk

.

5. The software module performs a Re analysis.

- If the resistance Re> Rdop (permissible value of the insulation resistance specified for the electrical tests OK), the PM forms the parameter SKK = 1.

- If the resistance Re <Rdop, the software module analyzes Ik4.

- If Ik4 = 0 (the expression Ik4-Ik3 is taken in absolute value), the value of Re is equal to the insulation resistance of the common negative bus. PM forms the parameter CCM = 7.

- If Ik4 ≠ 0, the PM forms the parameter SKK = 8, on the body of the source circuit.

6. After the formation of each parameter of the CCM, the software module generates frame 1, issues a command TCS1 and starts a new control cycle from step 1

The CCM parameter is constantly monitored in the CPA.

The termination of control is performed by a command that causes the program module to stop working.

The search for the circuits of the positive bus of the OK source associated with the housing according to claim 5 should begin with the source whose voltage is equal to the product of the equivalent insulation resistance according to claim 5 and the case current Ik4 ≠ 0 according to claim 4 (assuming that the most the only possible connection with the chassis is the connection of one source bus).

The proposed technical solution gives a positive effect when used, which consists in increasing the reliability of control, expanding functionality.

The proposed method can be used in test equipment (hardware and software systems) for working with complex objects of control and in "intelligent" means of measuring the insulation resistance of sources of other devices.

At the enterprise, the above method has been worked out and laid down in the technical documentation of the CPA for testing the objects of control.

Claims (1)

A method for automatically controlling the insulation resistance of circuits of galvanically coupled DC sources by measuring the case current and tolerance control of the calculated equivalent insulation resistance using a software module with information output, characterized in that first they determine the absence of a short circuit of the DC source circuits to the case, for which two measurements of the case current between the common negative bus and the case at first with the inclusion in the circuit of the current meter limiting of the resistor, and then with the addition of a control DC voltage source into the circuit, the difference between the two measured currents is calculated and the value of this difference is judged on the presence of short-circuited specific circuits of controlled DC sources with a case, and in the absence of a short circuit, two measurements of the case current between the common negative bus and housing with the inclusion in the circuit of the current meter control source of constant voltage and without it, and calculate the equivalent insulation resistance by the difference and Merenii current value and the reference voltage source.

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