SU1617523A1 - Device for relay protection of electric machine - Google Patents

Abstract

The invention relates to electrical engineering, in particular to the relay protection of electrical machines. The purpose of the invention is to increase the sensitivity and enhance the functionality by determining the damaged phase of the stator winding. If any short circuit occurs in the stator winding (for example, coil in phase A), an additional magnetic field of the closed coils is formed, which changes the phase induced in the EMF converter. As a result, the timing of the clock signal and the signal from the inverter 11 at the inputs C of the JK-flip-flop 17 coincide, the latter switches, the display unit 7 indicates the faulty phase of the electric motor. The machine is disconnected from the network. 3 il.

Description

This invention relates to a relay protection technique for an electrical machine and can be used to protect the stator winding of a three-phase motor.

The purpose of the invention is to increase the sensitivity and enhance the functionality by determining the damaged phase of the staggered winding.

Figures 1 and 2 show the block and schematic diagram of the device proposed; in fig. 3 and 4 are the time diagram of the device and the vector diagram of currents and emf.

The device (Fig. 1) contains a unit 1 for measuring and comparing the phase voltage of an EMF of a ring converter 2 embedded in a machine 3, in which the first input is connected to the ring converter 2 through the setting unit 4, the second input to the current transformer 5, and the output through pea1- The first element 6, the display unit 7 and the element OR 8 are connected to the tripping circuit of the switch control 9.

The unit 1 for measuring and comparing the phase of the EMF (Fig. 2) of the ring measuring transducer 2 is made in the form of a pulse distributor on the inverters 10-13, AND-NE elements 14-16, as well as 1K-triggers 17-19. The start of the pulse distributor is negligible through the diode 20 pulses from a peak transformer 21 connected to the current transformer 5. And myils on

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in code 10, they appear only when going through zero in the positive half period. The pulse time is 2b ms. When a triggering pulse appears at the input of the inverter 10, three consecutive pulses of duration A / 6 ms appear at the output of inverters 11–13, which are fed to the inputs of 1K-flip-flops 17-19 (FIG. 3). The setpoint block is made in the form of a phase shifter (capacitor 22 and resistor 23), peak transformer 24, and diode 25. A phase shifter is required for the timing of the trigger pulse at the synchronization inputs C of the flip-flops 17-19. Triggers 17-19 are switched only when there are 1K pulses from inverters 11-13 and on inputs C of a synchronizing pulse from peak transformer 24. Triggers 17-19 are also used as reacting organs, the outputs of which through the display unit 7 (for example, three photodiodes and three relays with self-pickup) and the OR element 8 are connected to the control circuit of the switch 9,

According to FIG. 4, where Cf, Zd are the angles between the current vectors of the phase Au and the EMF of the converter in the failsafe mode (E) during a loop circuit (a vector zone, it is induced by a current 1, in the closed turns of phase A) and single-phase earth fault (zone EMF vector Ep, induced by current 3 IKQ), the maximum displacement zone of the vector of the EMF converter does not exceed 115, which corresponds to v6.0 ms in the time diagram (Fig. 3). The setting of block 4 is set by resistor 23 and consists in shifting the clock pulse over the time diagram until it coincides in time with the trigger pulse from transformer 21, i.e. in setting Cf equal to ЗА- There is no signal at outputs 17-19.

In the event of any short circuit in the stator winding (for example, a coil in phase A), an additional magnetic field occurs

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the number of turns that will change the phase of the EMF induced in the converter (the phase of the EMF will be in the area (see Fig. 4, E). As a result, the time of appearance of the synchronizing signal and the signal from the inverter at inputs C and 1K-trigger 17 is the same switches over, the display unit 7 will indicate the faulty motor phase. The machine will be disconnected from the network.

Thus, the device has an increased sensitivity (there is no need to recuperate from inrush current) and allows you to determine the damaged phase.

The feasibility of the proposed device consists in reducing the size of the damage and reducing the time. And, consequently, the cost of post-accident repair.

Claims (1)

Invention Formula Relay protection device of an electrical machine with an annular transducer built into the machine with output winding pins, containing a reacting organ, a current transformer and an actuator designed to be connected to a breaker control circuit, in order to increase sensitivity and expand functional capabilities by determining the phase of the damaged stator winding, it is additionally equipped with a measuring unit and comparing the phase emf of the ring He set the setting block, the display unit, and the actuator was made as an OR element, the inputs of which are connected through the series-connected display unit and the reacting body to the output of the measuring unit and comparing the phase EMF of the ring converter, the first input of which is connected to the terminals to the outputs of the ring converter, and the second input - with the findings of the secondary winding of the current transformer. -9f- V / i is k 0 ABC 1 P Trigger pulse TO Phase Converter (diode 25) Etc( P Phase / ({element and Phase in (item 12) Phase C 1 element 13) P t, MC 20 t, Mc ten ZOt.MC ten go t, mc Yu Fig.Z 20 t, MC PACK