RU1799476C - Device for testing insulation resistance of distributed electric supply - Google Patents

Abstract

The invention relates to electrical engineering, in particular to devices for monitoring and measuring the insulation resistance of marine electrical networks with insulated neutral, powered by several generators. An isolation resistance control device for a branched electric network contains a measuring voltage source, a decoupling filter, a resistive shunt, a comparison element, a setpoint control unit, a bias control unit, a switch, a setpoint resistance, a clock generator, a synchronization mode switch, a probing voltage generator, a receiver clock, control signal distributor. 2 ill.

Description

The invention relates to electrical engineering, in particular to devices for monitoring and measuring the insulation resistance of marine electrical networks with insulated neutral, powered by several generators. Generators can operate both in parallel and on individual loads, while the insulation resistance of the network varies widely. In this regard, it becomes necessary to adjust the alarm settings and to exclude the mode of parallel measurement of the network resistance by more than one device.

The aim of the invention is to increase the reliability of the operation of the device by reducing the number of communication lines and Eliminating the need to use block contacts of sectional switches.

FIG. 1 and 2 illustrate the invention.

The device contains a measuring voltage source 1, a decoupling filter 2, a resistive shunt 3, a comparison element 4, a network bias control unit 5, a clock generator 6, a probing voltage generator 7, a setpoint control unit 8, a commutator 9, a setpoint resistance of 10 , a clock receiver 11, a master-slave synchronization mode switch1 12, a control signal distributor 13.

The source of the measuring voltage 1 is connected to the monitored network through the isolation filter 2, and the second output to the housing through the shunt 3 and to the signal input of the comparison element 4. General

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the connection point of the filter 2 and the source 1 is connected to the input of the network bias control unit 5, the output of which is connected to the input of the switch 9. The clock generator b is connected via the switch 12 to the line output of the device connected to the communication line. A probe voltage generator 7 is connected to the same output through the setpoint adjuster 8, and the output of the setpoint adjuster 8

connected to the reference input of comparison element 4; Switch 9 is connected to the line output by a first output; and the second - through the resistance of the setpoint 10 to the housing. Also, a synchronization receiver 11 is connected between the housing and the linear output, the output of which is connected to the input Setting 0 of the control signal distributor 13. The synchronization output of the distributor 13 is connected to the input of the clock generator b, and one of the outputs Measurement (in accordance with the device number) is connected to the inputs of the measuring voltage source 1 and the probe voltage generator 7.

The measuring voltage source 1 can be carried out according to known stabilized source circuits and contains a semiconductor switch for connecting the source to the controlled network. Various types of optocouplers can be used as a key, for example, AOT 127,

The decoupling filter 2 serves to smooth out the variable voltage component that affects the output of the source and is also performed according to known schemes. :. -.

Comparison element 4 is a comparator, one input of which

stepped controlled signal, and on the other

- reference voltage. When the level of the monitored signal exceeds the reference voltage, the comparator is triggered, and a potential log appears at its output. 1, which is 6; can be used for signaling. As a comparator, microchips of types 521, CAZ, 140 UD20IT.D can be used. ;: - -; -.

The bias control unit 5 is designed to detect the mode of parallel operation by the value of the constant at the direct displacement of the network relative to the housing, which occurs when the measuring voltage source is operating. The magnitude of the displacements depends on the voltage of the source, the internal resistances of the source with the filter and the value of the network resistance. With normal operating values of the insulation resistance of the network, the bias voltage changes insignificantly

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limits, which allows you to use it as an informative sign of parallel operation.

Fig. 1 shows a design of block 5, which contains 2 comparators (upper and lower tolerance voltage levels) and element I. Comparators are made on a chip type 140 UD20. The voltage of the upper tolerance level is applied to the non-inverting input of the first op-amp, and the voltage of the lower tolerance level is applied to the inverting input of the second op-amp. The inverting input of the first op-amp and the non-inverting input of the second op-amp are connected together and act as the input of block 5 connected to the common point of source 1 and filter 2. If the voltage of the network bias is between the upper and lower tolerance levels, then the outputs of both op-amps and the element And potential is equal to the log. 1. Deviation of the bias voltage of the upper or lower lower leads to a violation of the combination log. 1 at the inputs of the element And and the appearance of the potential log. Oh at its exit. The value of the upper tolerance level is selected based on possible deviations of the source voltage, and the lower one from the minimum voltage, taking into account the voltage drop at the internal resistance of the decoupling filter at the minimum acceptable operational level of insulation resistance. In almost any electrical network, switching transients occur, accompanied by the appearance of a constant component of the voltage of the network relative to the housing. However, the likelihood of false information about parallel operation tends to zero during control over tolerance levels, and its duration is limited by the time of transients in the network. If necessary, the reliability of the control can be improved by reducing the time interval during which the bias voltage is monitored.

The clock 6 and probe voltage generators 7 are series-connected voltage sources and semiconductor switches, with the voltage of the clock source selected over the voltage of the probe voltage source to select the pulses according to the voltage value. The probe voltage source comprises a diode in the output circuit to protect the semiconductor switch from reverse voltage.

Setpoint adjustment block 8 is a constant converter

the current flowing through the communication line when the probing voltage generator is turned on at a proportional voltage value. The block can be implemented on the basis of self-generating DC sensors.

Switch 9 is a semiconductor switch and can be implemented on a transistor optocoupler of the LOT 127 type.

The resistance of setpoint 10 is a resistor whose value is selected based on the minimum acceptable level of insulation resistance for one section of the network.

The clock receiver 11 is an optocoupler connected to the communication line through a limiting resistor and a zener diode, which ensure the passage of synchronization pulses and blocking the input circuit of the optocoupler when exposed to the probing voltage.

The master-slave synchronization mode switch 12 is designed to manually transfer one of the devices installed on the network into the master (synchronizing) mode with respect to other devices whose synchronization generators are not connected to the communication line. The indicated measures for selecting the synchronization mode are carried out when installing devices on the object.

The control signal distributor 13 contains a precision oscillator with a frequency divider and provides synchronization signals (for controlling the clock generator), Measurement (a sequence of signals, the number of which is equal to the number of devices installed in the network), as well as receiving a clock pulse at the input Setting 0 (to bring the device into single time mode).

A possible embodiment of the distributor is shown in FIG. 2 and contains a generator of stable intervals with quartz stabilization made on a chip 512 ПС10 (DD1), as well as a divider of control signals made on a chip 561 IE9 (DD3, DD3, DD4). The divider provides the formation of 14 and control signals Measurement. The clock is generated by a type 561 TM2 (DD6) chip. Elements AND DD4.1, DD4.2 are designed to transmit pulses to the input of the DD3 chip after filling DD2, Elements OR DD5.1, DD5.2 are designed to organize a new cycle after the end of the 14th signal. The sequence of operation of the device in the system is determined by the position of the jumper S1 connecting one of the outputs of the chips DD2, DD3 with the output of the unit. In manufacturing, each device (in accordance with the jumper connection) is assigned its own serial number, and devices are used at the site in order of increasing numbers, which excludes the simultaneous inclusion of two devices in the monitoring mode.

A single-wire communication line was used to transmit signals between the devices; the hull of the vessel serves as a return wire.

The described device operates as follows. When the first device is switched on in the measurement mode, the electric network receives an offset from the measuring voltage source, which is registered by the offset control units of those devices connected to network sections operating in parallel with the first. The offset control units provide an enable signal to the switches, thereby enabling the connection of the setpoint resistances to the communication line. At the command of the signal distributor, the probe voltage generator of the first device is simultaneously turned on and the current determined by the resistance of the settings of the parallel-running devices starts to flow through the setting control unit. The output voltage of the setpoint adjusting unit takes a value proportional to the value of the setpoint given to the particular network configuration. If at the same time in the network there has been a decrease in the insulation resistance below the obtained setting value, then the comparison element is activated, providing an alarm about insulation damage.

After the time allotted for the operation of the first device ends, the second device is turned on and all the processes proceed similarly to the previous one and so on.

Thus, with each measurement in the resistance monitoring device, a setpoint voltage is automatically generated that adaptively changes according to the specific network configuration. An informative parameter is the constant component of the network bias that occurs during operation of the measuring source. The setting value corresponding to a particular network configuration is determined by probing the communication line with a constant voltage and transforming the DC value into a proportional voltage. At the same time, there is no need to use the block contacts of the sectional switches, which is not always possible in connection with their limited number and their use in automation circuits. In addition, due to the need to generate a logical signal corresponding to the network structure, the number of communication lines decreases by N-1 (where N is the number of installed monitoring devices), which increases noise immunity and reduces damage, which ultimately increases the reliability of the entire insulation resistance monitoring systems. An additional effect is to simplify automation schemes and reduce installation costs.

The novelty of the claimed device lies in the choice of an informative sign of parallel operation (constant bias voltage of the network) and the original method of generating the setpoint signal (connecting the set resistance of the setpoint to one line and probing the line with a constant voltage). The device also originally solved the problem of transmitting synchronization signals and settings on one line, which greatly simplifies the operation of devices.

Formula of a device A device for controlling the insulation resistance of a branched electric network containing a measuring voltage source connected to a resistive shunt by a first output, and a decoupling filter connected to a controlled

Networks, a comparison element, a unit for adjusting settings, the output of which is connected to the reference input of the comparison element, which means that, in order to increase

reliability of operation, a switch, a clock generator, a synchronization mode switch, a probe voltage generator, a clock receiver, a control switchboard are additionally introduced into the device

signals, the bias control unit, the input of which is connected to the connection point of the measuring voltage source and the decoupling filter, and the output to the input

a switch connected in series with the resistance of the setpoint to the linear output, a clock generator connected to the linear output through a switch of the synchronization mode,

a probe voltage generator connected to the linear output via the setting adjustment unit, a clock receiver connected to the linear output, a control signal distributor,

the Synchronization output of which is connected to the input of the clock generator, the output, the Measurement output, is to the control input of the measuring voltage source and the probe voltage generator, and

input 0 is connected to the output of the clock receiver, the second output of the resistive shunt is connected to the housing, the connection point of the measuring voltage source and the resistive shunt is connected to the signal input of the Comparison element.

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