RU2403580C2 - Method for measurement and control of equivalent insulation resistance of unearthed power electric direct-current mains, including electromotor networks with voltage static converters and related device for implementation thereof - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: one pole of controlled mains is bridged with a resistor, and a bypass is modified so that to reduce voltage to earth of this bypass pole precisely by half as compared with voltage to earth of this pole before bridging, and a device comprises a comparator, a power amplifier, a relay with a switching contact block, a second analogue signal reading and storage device, an ohmmetre, a keyed decoding resistor array (DRA) and new element communications have ensured a new uncomplicated high-accuracy and high-reliability measurement and control device.

EFFECT: higher reliability of measurement and control of insulation resistance of a controlled electric direct-current mains.

2 cl, 1 dwg

Description

The invention relates to instrumentation for measuring, monitoring and signaling about a decrease in the insulation resistance of DC power networks below the norm and is used to measure and constantly monitoring the insulation resistance of DC electric networks on ships, ships, mines, subways and where There are branched separate DC networks.

The proposed method and device for measuring and controlling the insulation resistance of power DC electric networks relates to techniques for improving the fire and electrical safety of operating power generating circuits, converting electrical energy to various DC electric networks isolated from earth.

There is a method of increasing fire safety of systems for generating and converting electricity by evaluating leakage currents in AC or DC power circuits with a grounded neutral or a grounded pole. The method is based on highlighting the difference between the input and output currents of the load at the power board. The difference in these currents is used to judge the level of fire safety, evaluating the possibility of an electric arc between the current-carrying conductors of the cable and the ground (housing). The leakage currents also judge the electrical safety of the operating personnel and provide protection at low leakage currents. An example is a residual current device of the UZO-20 type according to TU 16-92 IZHTSh.656111085TU of the city of Stavropol, the Signal plant. The disadvantages of this method are the relatively low reliability of fire safety and a limited scope.

A known method of measuring the insulation resistance of DC networks relative to the ground (housing), which consists in the use of an additional source of constant measuring voltage, and to eliminate the influence of the operating voltage of the monitored network before measuring compensate for the network voltage relative to the ground (housing) by introducing an adjustable constant voltage source, after which they turn on the source of the measuring voltage and readout the readings of the measuring device (Auth. Certificate. USSR No. 369515, publ. 11/08/1979, BI No. 10).

The disadvantage of this method is the need for two sources of constant voltage - compensating and measuring. In electric vehicle power networks, it is often difficult to constructively and technologically provide good compensation for the supply voltage of the control object.

A known method and device for measuring the insulation resistance in DC networks according to the USSR author's certificate No. 370551 according to MKI G01R 27/18, characterized in that in order to measure the insulation resistance under operating voltage an additional circuit is introduced from a DC power source and a diode connected in parallel network wires, and their common point is connected to another terminal of the current device. The disadvantage of this method and device is the large measurement error, since the insulation resistance of the network pole is a function of the magnitude of the supply voltage. With large voltage fluctuations of the controlled DC network, the error in measuring the insulation resistance also changes (increases).

The prototype is a relatively new method and device for measuring the insulation resistance of the power network of electrical installations of vehicles under operating voltage (RF patent No. 2175138 C1 G01R 27/18, B60L 3/00. Published October 20, 2001 Bull. No. 29), in which the measurement method insulation resistance of the power network of electrical installations of vehicles under operating voltage, at which a measuring DC voltage is applied to the power network, the transient process of recharging the capacities in the controlled network is stopped, without waiting for its end, the voltage is measured insulation resistance, the current of the measuring voltage source and calculate the insulation resistance of the power network relative to the ground by dividing the measured voltage by the measured current.

The insulation resistance measuring device comprises a measuring voltage source, a limiting resistor, an indicator, a measuring circuit driver, a microprocessor unit, two voltage sensors, two current sensors.

The disadvantages of this method and the device that implements it are the great complexity of implementation, especially in terms of compensation to zero voltage on the insulation resistance of an uncontrolled pole, the measurement voltage must be chosen significantly higher than the voltage of the controlled network, which significantly complicates and increases the cost of the device, reduces its reliability, and the presence of two current sensors and two voltage sensors leads to an increase in the measurement error of the insulation resistance. The disadvantage of this method and device is also the fact that in the process of measuring the insulation resistance there is a recharge of the capacities of the electric network from zero to the full voltage of the network. If an operator touches one pole of a network in such a network without applying a method and device for monitoring insulation resistance, then it falls under a voltage that is significantly lower than the voltage of the network, and when applying this method and device in a similar situation, a person falls under the full voltage of the network, due to which electrical safety conditions are significantly worsened when monitoring a DC power network.

The proposed method for measuring and monitoring the equivalent insulation resistance of DC electrical power networks isolated from earth and the device for its implementation, the block diagram of which is shown in Fig. 1, is free from the disadvantages inherent in the prototype, this is achieved by the fact that the proposed method for measuring and monitoring the equivalent insulation resistance of DC electric power networks isolated from the ground, including electrical networks with static converters under operating voltage, consisting in the fact that at first the voltage relative to the ground of one pole of the monitored DC network is measured, then the same pole is shunted with respect to the earth (case) with a resistor, characterized in that the shunt resistor is changed in such a way that the voltage of this pole relative to the ground decreases exactly in twice compared with the voltage of this pole relative to the ground before shunting, after which the shunt resistor is turned off and its value is measured, which will be numerically equal to the equivalent tape resistance of a controlled DC network.

A device is also proposed for measuring and monitoring the equivalent insulation resistance of DC power electrical networks isolated from earth, including electric motion networks with static converters under operating voltage, which contains a pulse generator with a switching key K1 at the output, the first device for sampling and storing an analog signal (UVHAS), resistive constant voltage divider, characterized in that the resistive constant voltage divider divides the stored in UVHAS the voltage is two, and a comparator with first and second inputs, a power amplifier (UM) and a relay (P) with a switching group of contacts at the output, a second UVHAS device, an ohmmeter with upper and lower output and a key-driven decoding resistive matrix are additionally introduced into the device (DRM) with upper and lower terminals, and the introduced comparator with the first input connected to the midpoint of the resistive voltage divider, and the second input, the comparator connected to the upper output of the decoding resistive matrix, in addition, the upper through the relay contacts of the ohmmeter is connected to the upper output of the ohmmeter through the second UVHAS, and through the relay contacts and the contacts of the K1 key connected in series, the upper output of the DRM is connected to the positive pole of the controlled DC network, and the lower terminals of the DRM and ohmmeter are connected to the body (ground )

The proposed method and device in comparison with the prototype provides a significant increase in reliability and allows you to measure and control the insulation resistance in any range of insulation resistance values in various DC power networks isolated from the ground (housing).

The device for measuring and monitoring the equivalent insulation resistance of DC power networks isolated from earth, including electric motion networks with static converters under operating voltage, contains a pulse generator 1 with a switching key K1 2 at the output, the first device for sampling and storing an analog signal (UVHAS) 3, a resistive DC voltage divider 4, a comparator 5 with first and second inputs, a power amplifier (PA) 6 and a relay 7 (P) with a switching group of contacts at the output P 1-1 8, a second device for sampling and storing an analog signal 9, an ohmmeter 10 with upper and lower terminals, key-driven decoding resistive matrix (DRM) 11 with upper and lower terminals, and the introduced comparator 5 is connected to the midpoint of the resistive voltage divider by the first input 4, and the second input, the comparator 5 is connected to the upper output of the decoding resistive matrix 11, and the upper output of the DRM (11) is connected to the upper output of the ohmmeter 10 through series-connected make contacts 8 of the relay 7 and the second input device firing and storing the analog signal 9, in addition, the top terminal of the DRM (11) is connected to the positive pole of the controlled DC network 12 through series-connected disconnecting contacts of the relay P1-1 8 and the closing contacts of the key K12, and the lower terminals of the DRM11 and ohmmeter 10 are connected to the housing (ground) 13, and all the elements of the circuit are powered from the power supply 14.

The work of the method and device for measuring and controlling the equivalent insulation resistance of DC electrical power networks isolated from earth, including electric motion networks with static converters under operating voltage, is as follows. The device with one output through a switching group of contacts 2 of the K1 key is connected to the selected pole of the monitored network 12, and with the other output the control device is connected to the ground (housing) 13, the voltage relative to the ground of the positive pole of the monitored network through the opening contacts 2 of the key K1 is fed to the first input of the first the device for sampling and storing the analog signal 3 and is stored in UVHAS 3, a resistive divider for two 4 constant voltage is connected to the output of UVHAS 3, which removes from the midpoint The voltage twice reduced in the UVHAS 3 is reduced relative to the case (ground) of the positive pole of the controlled DC network 12, and is fed to the first input of the comparator 5, the pulse generator 1 is activated according to the specified program and switches the positive pole of the controlled network 12 from the first input of UVHAS 3 to the second input of the comparator 5 through the disconnecting contacts 8 of the relay 7, and a key-driven decoding resistive matrix 11 is connected to the second input, the matrix is formed by parallel-connected conductivities, which e divided into three tetrads weights conductivities of each tetrad are selected in accordance with the BCD code 1-2-4-2. Using the controlled keys DRM11, the resistance value of the DRM 11 is changed until the voltages at the inputs of the comparator are equalized, as a result of which the comparator 5 trips and the relay 7 trips, which contacts 8 connect the top output of the DRM to the upper output of the ohmmeter through the second device 9 UVHAS, and ohmmeter 10 indicates the value of the active resistance of DRM11, which will be numerically equal to the equivalent insulation resistance of the monitored DC network 12.

Claims (2)

1. The method of measuring and monitoring the equivalent insulation resistance of isolated from the earth power DC electric networks, including electric networks with static converters under operating voltage, which consists in first measuring the voltage relative to the earth of one pole of the controlled DC network, then shunting the same pole relative to the ground (housing) by a resistor, characterized in that the shunt resistor is changed in such a way that the voltage of this pole is It decreased in relative land exactly twice as compared with the value of this pole voltage with respect to ground to bypass, after which a shunt resistor is switched off and its magnitude is measured, which is numerically equal to the equivalent resistance of the network controlled insulation DC. 2. A device for measuring and monitoring the equivalent insulation resistance of DC electrical power networks isolated from earth, including electric motion networks with static converters under operating voltage, containing a pulse generator with a switch key K1 at the output, the first device for sampling and storing an analog signal (UVHAS ), a resistive DC voltage divider, characterized in that the resistive DC voltage divider divides the voltage value stored in UVHAS into two, and a comparator with first and second inputs, a power amplifier (UM) and a relay (P) with a switching group of contacts at the output P1-1 are additionally introduced into the device, and the comparator, power amplifier and relay are installed with the possibility of relay operation, provided that the voltages are the comparator inputs will become equal, a second analog signal sampling and storage device, an ohmmeter with upper and lower pins, a key-driven decoding resistive matrix (DRM) with upper and lower pins, the introduced comparator the input is connected to the midpoint of the resistive voltage divider, and the comparator is connected to the upper output of the decoding resistive matrix by the second input, and the upper output of the DRM is connected to the upper output of the ohmmeter via series-connected relay contacts and the second input device for selecting and storing the analog signal, in addition, the top output of the DRM is connected to the positive pole of the monitored DC network through series-connected disconnecting contacts of the relay P1-1 and closing contacts of the key 1, and lower terminals and HLR ohmmeter connected to the hull (ground).