SU1298691A1 - Insulation resistance converter for a.c.isolated neutral systems - Google Patents

Abstract

This invention relates to electrical measuring technology. The purpose of the invention is to reduce the dynamic error. The converter contains test current generator 2, low-pass filters 3 and 5, transformer 7 and demodulator 18. To achieve this goal, key 4 is entered, high-pass filter 6, multiplier 7, adder B, reference generators 9 and 10, voltages, comparators 1 and 12, transducer 13 time interval — voltage S element OR 14, switch 15, modulator 16, and new functional connections are formed. The description presents one of the embodiments of the converter 13 time interval - voltage, 3 slug. 00 toK

Description

The invention relates to electrical measuring technology and is intended for continuous measurement of the insulation resistance of ac networks with insulated neutral, energized or de-energized, and issuing a normalized signal, for example, for ship automation systems and information gathering.

The purpose of the invention is to reduce the dynamic measurement error.

Fig. 1 shows a functional diagram of an insulation resistance converter; 2 shows the voltage across the equivalent impedance of the insulation during the transient process (a), the required amplitude-frequency characteristic of the second low-pass filter (b), the voltage at the output of the high-pass filter (c), the required transfer characteristic of the first comparator ( d); Fig. 3 shows a time-voltage converter.

The device contains a controlled network I5 of a series-connected direct current generator 2, a low-pass filter 3, a key 4, a low-pass filter 5, a high-pass filter 6, a multiplier 7 and an adder 8. The generators 9 and 10 of the reference voltages are connected to the first inputs of the comparators and 12, the converter 13, the time interval of the voltage, the element OR 14 and the serially connected switch 15, the modulator 16, the transformer 17 and the demodulator 18, the First input and the output of the multiplier 7 are connected to the second inputs of the Comparators 11 and 2, respectively. The output of the element GSHI 14 is connected to the control input of the switch 15. The output of the controlled network 1 sub-. It is connected to the input of the low pass filter 5, and the output of the demodulator 18 is the output of the insulation resistance converter.

Converter 13 time interval - voltage contains the element NOT 19, RS-flip-flop 20 with dynamic control, generator 21 of the reference voltage () s key 22, integrator 23 with reset, exponential

Suppose that a consumer with a large phase capacitance relative to the housing has been connected to the controlled network. The voltage (excluding the network component) is equivalent to the impedance of the insulation in this case

24, divider 25, device 26, the selection form shown in FIG. 2a. ki and storage, delay element 27. In order to provide a maxi-converter of resistance to the isolation of alternating-current networks, it operates as follows.

maximum suppression of the variable components of the input signal with frequencies that are multiples of the network, and at the same time

five

0

P

0

five

When the supply voltage is turned on, the output of the low-pass filter 5 is set to zero, the voltage is set to the output of the upper-pass filter 6, and therefore, to the output of multiplicated tech 7. Since the voltage is at the second inputs of the comparators 11 and 12 is smaller than the reference voltages on their first inputs, the outputs of these -camparators are set to logical O signals. This leads to the closure of key 4, to the establishment of zero voltage at the output of the converter 13, the time interval is voltage and to establishing switch 15 to position 2.

Current 1 from generator 2 filter

key 4 flows into the controlled network 1, causing a charge of the equivalent capacitance (GUJ) of the insulation. The change in voltage across the full impedance of the isolation is transmitted to the output of low-pass filter 5. Since the content of the high-frequency components in the spectrum of such a signal is small, the voltage at the output of high-pass filter 6 is also small and less. The voltage U of generator 9 is low. As a result, the signal level at the output of comparator 1 does not change, key 4 remains closed and the process of charging the insulation capacitors ends by setting the voltage isolation to the equivalent resistance (S, j):

.. from generator z through 3 low frequencies and closed

.and.

 R,

t)

The change in the voltage across the impedance of the insulation e of the low-pass filter 5 through the switch 15 (in position 2), the modulator 16, the transformer 17, the demodulator 18 goes to the output of the converter. The end of this process means that the converter is on the working mode.

Suppose that a consumer with a large phase capacitance relative to the housing has been connected to the controlled network. The voltage (excluding the network component) on the equivalent impedance of the insulation in this case has the form shown in Figure 2a. Dp to ensure maximum

e form shown in figa. Dp to ensure maximum

maximum suppression of the variable components of the input signal with frequencies that are multiples of the network, and at the same time maxi

It is possible to keep the form on the signal (FIG. 2a) at the lowest frequency during transmission. The filter 5 should have the frequency response of the form shown in FIG. 26, its coefficient zero. transmissions must be located at frequencies equal to

5 where

D

01

1-Q,

where Q,

P is the circular frequency of the first harmonic of the network voltage.

From the output of the low-pass filter 5, an exponential signal is fed to the output of the high-pass filter b, causing at its output a CUg (t)) reaction of the form shown in Fig. 2c.

The comparator I1 should have a transfer characteristic with a hysteresis of the type shown in Fig. 2d. The impact of a signal U (t) on its input causes an output pulse t with a duration t ,, disconnecting, with the help of key 4, at this time the generator 2 from controlled network, starting converter 13, time interval — voltage, and switching switch 15 to position 1. After the pulse at the output of converter 13, time interval — voltage is arising and holding

and

1E

 l

 ФВ4

where C

- constant filter time 6 high frequencies. In the multiplier 7 of the form feed voltage Uy (t), opposite to the sign of the voltage and y (t) of the filter 5 and the value such that the voltage at the output of the adder 8

Ug (t) U5 (t) + V (t) and,

where .UK is the value of U to which Ug (t) tends (Fig. 2a).

While the voltage value is greater than Ujjf, the output of comparator 12 is a logical 1 signal, and the switch 15 (controlled via OR element 14) is in position 1. Resetting the comparator 12 will reset the voltage to zero and connect to the modulator input 16 filter output 5 low pass.

Thus, in spite of the fact that in a controlled network I there is a switching of a consumer with large capacitances of phases relative to the housing and a transient occurs.

with constant time s. i

from a.

converter output in time

-eo

3 /. . About B-v DM

 OF

on m

where Sd ;, is the time constant of demodulator 18, the voltage Uig appears.

This voltage carries information about R | and approximately (with an error of no more than 10–15%) equal to the asymptotic value of the voltage (U K to which the voltage tends.

The transform-transform function. the pad 13 (fig.Z) has the form

and „k.e

one

where k is a coefficient depending on the time constant Of5. Converter 13 works as follows.

In the initial state, the inputs of the converter 13 are the logic signal O from the comparators 11 and 12 signals. At the output of the trigger 20, the signal is the logical 1, the integrator 23 is held and the device 26 is sampled and stored in zero state.

On the front of the pulse arriving at the first input of the converter 13, the time interval is a voltage; at the output of the trigger 20, a logical signal O is set up, allowing the operation of the integer 23 and the device 26 of sampling and storage.

Under the influence of the same pulse, the key 22 closes and the integrator 23 during the period of time t integrates the constant voltage supplied from the oscillator 21 of the reference voltage. At the end of this process, the output voltage of the integrator 23 is as follows:

„

g.

 whale "

ri-t- --i .тт °

Where

Ing

- constant rator 23.

integration time

five

The voltage at the output of the exponential 24

„And., R .., 0113

), With-and

 BUT

So

 u7

how t

.tn

is smiling

5, 129 Output voltage divider 25

 p 1, iu.A Jfl

15 A

 (pb (P84It is the voltage at an interval of time t; j, determined by the parameters of the delay element 27, after the end of the pulse from the output of the comparator 11 is stored in the device 26 for sampling and storage.

The return of the converter 13 is the time interval - the voltage to the initial state occurs through a cut of the pulse arriving at the second input of the converter 1 3 the time interval; not - the voltage. It also resets the integrator 23 and the device 26 for sampling and storage,

Claims (1)

Formula invented shadows An alternating current network insulated impedance converter that contains a test DC generator, the first and second low-pass filters and a series-connected modulator, transformer, and demodulator, the first run of the test DC generator connected to the chassis, the second output is connected to the input of the first low-pass filter, and the output of the demodulator is the output of the isolation resistance converter, which is - 0 3.5 five thirty so that, with the purpose of reducing the dynamic measurement error, the first and second reference voltage generators, the first and second comparators, the time interval converter — voltage, key, OR element and series-connected high-pass filter — are introduced into it, multiplier, adder and switch 5 with this, the second input of the switch is combined with the input of the high-pass filter and the second input of the adder and connected to the output of the second low-pass filter, the input of which through the key is connected to the output of the first low-pass filter from, the outputs of the first and second generators of the reference voltages are connected to the first inputs of the first and second mapping, respectively, the second inputs of which are connected respectively to the first input and output of the multiplier, the output of the first comparator is connected to the control input of the key, input the converter start-up time interval - voltage and with the first input of the OR element, the output of the second comparator is connected to the second input of the SHSh element and with the converter zeroing input, the time interval - voltage, the output of which is connected to th multiplier input and output of OR elementa- connected to the control input KOM1 "5utato- pa vpsod which is connected to the input of the modulator. well a "If u" 1298691 hell  four "Vtw. FC & G Editor H: Bobkova Zkj Compiled by I. Mihalev Tehred I.Popovich Proofreader A. Zimokosov (Order 885/48 Circulation 731 Subscription VNISHI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, Projecto st., 4 "L.