SU779929A1 - Device for continuous testing of insulation of three-phase electric network with insulated neutral wire - Google Patents

Description

metric devices 22, 23 with a total nomographic scale of 24 and a limit leakage latch 25 consisting of

threshold element 26 and signal torus 2T.

The device works as follows.

The measuring circuits of the ring phases, branch units 1, 2, 3, 4, 5, b are connected between the zero 28 of a three-phase network (not shown) and ground 29 and are controlled by the corresponding phase voltages of one of the phases 30, 31, 32 and linear voltages. 33, 34, 35 of the other two phases 3Q, 317 32.

With an increase in the conductivity of the insulation in any of the phases 30, 31, 32, for example, in phase 30, a bias appears between the zero and the 28-: ..-. a three-phase network and the Earth 29, which is simultaneously separated by projecting phase 30 and linear voltage 33 between two other phases 31, 32 by means of ring phase-sensitive blocks 1, 2, respectively. If the projection value is simultaneously positive, element AND 16 of the phase detection unit with an increased insulation conductance 7 is activated, which causes switching on switches 10, 11. At this, the profile gauge devices 22, 23 are connected with the general nomographic scale, 24, and the alarm unit is triggered. nineteen.

If the system of conductivities for isolating phases 30, 31, 32 of a three-phase network is symmetric, the bias voltage between zero three-phase network and Earth 29 is zero, the device does not provide information about the insulation parameters, in this case between any of the phases 30, 31, 32 three-phase, for example, phase 31, and Earth 29 is connected to sample conductivity 36. In this case, profile ratiometric devices 22, 23 will show the tangent of dielectric loss angle

To and asymetry active conduits. of isolation f on the lines of these parameters constituting the nomographic scale 24..,

./General

where is the total reactive conductivity of the insulation of a three-phase network

ffdSuT is a three-phase network insulating conductivity. u / go5m.

where ugf. г is an additional active conductivity, which causes unsymmetry of a three-phase network. In this case, ACf go where gf is the value of exemplary conductivity 36.

Consequently, the overall active conductance of the insulation is geSmgr, /

the active conductivity of the insulation of any of the phases 30, 31, 32

Reactive is the total conductivity of the insulation. .. / a is reactive 5 conductivity of any phase of phases 30, 31, 32

.1 If the insulation conductivity system is asymmetrical, the displacement voltage between zero 28 and the three-phase network and the Earth 29 is not zero, then one of the elements 16 and 17, 18 of the phase detection unit with the increased insulation conductivity 7, 8 ,

5 9, include the corresponding of the switches 10, 11, 12, 13, 14, 15 and through them - profile ratiometric devices 22, 23, with a common nomographic scale of 24. In this case

Q triggers the corresponding of the signaling units 19, 20, 21. On a nomographic scale of 24, the coefficients K and f are determined. If now in the corresponding of phases 30, 31, 32, in which the conductivity has increased

isolation, include the exemplary conductivity 36, then on a nomographic scale of 24 we get a new value

.llStt-,

c 6i4 where Agf is the initial asymmetry of the active conductivities of isolation of phases 30, 31, 32. of a three-phase network.

When the limiting value of the conductivity of the insulation is reached, the limit leakage latch 25 is triggered, and the warning device 27 sends a sound or light signal. The use of a device for the continuous monitoring of the isolation of three-phase electrical networks with isolated nets will increase the accuracy and efficiency of control by using one

f pairs of profile ratiometric instruments with a common nomographic scale ..

Claims (2)

1. Device for continuous monitoring of three-phase isolation from electrical networks with insulated neutral, containing three pairs of phase-sensitive phase-sensitive units, included in their measuring circuits between the three-phase zero and Earth, profile ratiometric devices with a common nomographic scale to determine the parameters of the insulation, characterized in that, in order to increase the accuracy and speed of control, a limit leakage latch is inserted into it and in each phase the phase detection unit With increased insulation conductance, the corresponding outputs of the phase detection units with increased insulation conductance are connected in parallel. 2. The device according to claim 1, wherein the unit is such that the phase detection unit with increased insulation conductance is made in the form of a switch, an analysis unit and an element, the inputs of which are connected to the inputs of the switches and the outputs of annular phase-sensitive blocks and the output element I is connected to the control inputs of the switches and the signaling unit, and the outputs of the switches are connected to two profile ratiometric instruments with a common nomographic scale and to the input of the leakage limiter consisting of a series-connected threshold element and a signaling device. Sources of information taken into account in the examination 1. USSR author's certificate 401937, cl. G 01 R 31/02, 1970.