SU1597773A1 - Method of determining resistance of insulation of d.c.mains - Google Patents

Abstract

The invention relates to a measurement technique and can be used to measure the insulation resistance of a DC network relative to a common bus under operating voltage. The purpose of the invention is to increase speed. The method consists in that the measurement of the insulation resistance is carried out in two stages. At the first measurement stage, the potential between the common bus and one of the tires of the monitored network is changed by connecting an additional EMF source between them and the current I _{1 is} measured through this source. At the second stage, the potential between the common bus and the other bus of the monitored network is changed by connecting between them the same additional EMF source and the current I _{2 is} measured through this source. According to the measurement results of the currents I ₁ and I _2, the sought-after insulation resistances are calculated using the formulas. 1 il.

Description

The invention relates to electrical measuring technology, in particular, to measuring the resistance of the insulation of a DC network relative to a common bus under operating voltage.

The purpose of the invention is to increase speed.

The drawing is an electrical diagram explaining the essence of the method.

A device for implementing the method consists of an EMF source 1, which determines the operating voltage E in the monitored electrical network, the control object 2, which includes buses of the electrical network, connected to the common bus (case) through resistances 2.1 and 2.2 of the electrical output (R, and R ) and I have 1191e relative to common tire capacity 2.3 and 2.4. (C, and Cj), switch 3, additional source 4 VDS of constant voltage E) and current meter 5 (ammeter).

The first and second terminals of the switch 3 are connected to the poles of the network through the terminals, and the third output is connected via a series-connected additional source 4 of a constant-voltage voltage and a current meter 5 with the first terminal for connecting the control object 2, the second and third terminals for connecting the control object 2 connected to the corresponding pins of switch 3.

SP

with

h |

with

The method is carried out as follows.

The source of the EMF 1 is switched on, alternately applied with the help of the switch 3 is the direct voltage from the additional source of the EMF 4 between the common bus and the electrical network, the current is measured with the help of the ammeter 5.

The method for determining the resistance of the extrusion (RJ and Rj) is carried out in two stages. At the first stage, the potential of an additional source of EMF is applied between the common bus and one of the tires of the controlled line, for example, the upper one in the drawing. Due to the redistribution of potentials, the process of recharging of capacities 2.3 and 2.4 takes place. Perezar capacitance occurs quickly (instantaneously), as the charge-discharge circuits of tanks do not contain active resistances. The restocking of capacitances occurs in chains containing sources of emf with zero internal resistances. At the end of the fast recharge process, an ammeter 5 measures the current flowing through the additional EMF source A. The value of this current I is determined by

EI E + EI R; R7

(one)

At the second measurement stage, the source 35 of the additional emf is connected to each other by a common bus and a second bus of the controlled circuit. And in this case, for the reason indicated, a fast (instantaneous) recharge of 40 capacitors 2.3 and 2.4 occurs, after which the current I is measured through the source of additional emf. From consideration of the equivalent circuit it follows that the value of the current. 1. is defined as follows:

The method of determining the insulation resistance of the network of direct current, which consists in alternately shunting the poles of the network relative to the zero bus and using the formulas for the value of the resistance of the insulation of the network poles, which in order to improve speed, bypassing source of EMF with zero internal resistance, measure the current through it, and the value of resistance R, and R, the isolation of the poles of the network is calculated by the formulas.

E

R,

7

one,. 1, (E and -

1.E „-I, (Е-Е„)

t EI-E 1 - + -1y R.

to -

By solving the system of equations (1) and (2), we obtain the desired expressions for the values of the insulation resistances R, and R-j:

45 where E is the voltage of the controlled network;

voltage of additional (2) source of emf;

I, and I - currents flowing through the dog 50 is an additional source of EMF, with alternate shunting of the poles of a controlled electrical network.

Rf

I, E-I-CE + EJ

0

five

0

five

0

50

R,

(3)

1, Е „+ Т, (Е-Е„)

The proposed method allows to reduce the duration of the measurement process, which is essential for the operational control of insulation resistance in dynamic systems with rapidly changing parameters in the presence of large capacities between the buses of the monitored network and the common bus (case), by minimizing the duration of transients recharge and capacitances 2.3 and 2.4 due to the use of an additional source of emf with zero internal resistance.

Claims (1)

1.E „-I, (Е-Е„) to - R l e g / .3 12.2 4.