RU1829080C - Fear for protection of synchronous machines against asynchronous mode - Google Patents

Abstract

Use: to quickly detect the asynchronous running of synchronous machines, which allows you to take measures to eliminate it or disconnect the synchronous machine from the network. The essence of the invention is that the stator current and voltage are measured, the generalized vectors of these values are calculated, the phase angle between the generalized stator vectors and the axis of the control phase of the stator winding between the generalized voltage vector of the stator and the axis of the control phase are calculated stator windings. The angle between the instantaneous values of the current and voltage of the stator is calculated, not more than once per period of the voltage of the industrial frequency, which increases the speed. 1 ill.

Description

The invention relates to electrical engineering, in particular to the field of relay protection of synchronous machines.

Relay protection devices based on various operating principles are used to detect accidentally occurring asynchronous modes (AP) of synchronous machines. Protection that responds to the stator current value is one of the simplest and is provided by the PUE mainly for protection of out-of-pole synchronous motors (DM). However, this protection does not always satisfy the requirements of sensitivity, especially when used for powerful turbo-engines and turbo-generators.

The aim of the invention is to increase the speed of protection.

The introduction of new blocks and the organization of connections between them and known blocks allows to achieve increased performance in detecting asynchronous mode

synchronous machine by determining the instantaneous value of the phase angle between the current and the stator voltage.

The drawing shows a block diagram of the claimed device.

The device contains a current transformer (ПТ) 1 and a voltage transducer (ПН) 2, with their inputs connected to the outputs of the primary current transformers (ТТ) and voltage (ТН), respectively, a module for calculating the module of the generalized stator current vector (BESHT) 3, three of its own inputs connected to the three outputs of PT1, a unit for calculating the module of the generalized stator voltage vector (BVMN) 4, with its inputs connected to the outputs of PN2, a unit for calculating the phase angle between the generalized vector of the stator current and the axis of the control phase of the stator winding (BVUT) 5, vy input of which is connected to the output BVMTZ and the second input - to the output of PT1 control phase. shear angle calculator

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phases between the generalized stator voltage vector and the axis of the control phase of the stator winding (BVUN) 6, the first input of which is connected to the output of the BVMN4, and the second input to the output of the control phase PN2, the unit for calculating the angle between the current and the stator voltage (BVUT) 7, the first input of which is connected to the output of BVUT5, and the second input to the output of BVUN6, the first comparison circuit (CC) 8, with its input connected to the output of BVUTN7, the second comparison circuit (CC) 9, with its input connected to the output of BVUTN7, the first time delay organ (OVV) 10, with its input connected to the output an ode to CC8, the second time-keeping unit (OVV) 11, with its input connected to the output of CC9, matching circuit (I) 12, its first input connected to the output of CC8, and the second input to the output of OVV11, and also the output organ (B0) 13 connected by its inputs to the output OVV10 and I12.

The invention is carried out as follows.

Transmitters PT1 and PN2 can be made in the form of transformer sensors. BVMTZ, BVMN4, BVUT5, BVUN6 can be performed in the form of hybrid functional converters Trukh and two variables.

BVUTN7 performs the function of a conventional adder - subtracting another input quantity from one input quantity, this can be done on a summing operational amplifier. Comparison schemes CC8 and CC9 can be performed on comparators, time-keeping bodies OVV10 and OVV11 - on digital counters (provided that there is a pulse generator of a reference frequency), the outputs of which are decoders. To build SS8, SS9.0VB10 and OVV11, K155, K531 series ICs can be used. As a match circuit, I12-IS K155LAZ. The output organ B013 can be performed in the same way as the executive body in the prototype device.

The device operates as follows. The inputs PT1 and PN2 receive quantities proportional to the phase currents and voltages of the three-phase stator system from the primary current transducers and voltages CT and VT, respectively, from the outputs of PT1, quantities proportional to the input currents are fed to the input of the BVMTZ, at the output of which we obtain the value proportional to the square root of the sum of the squares of the input quantities according to the formula (1)

III V2

(iA2-HB2 + ic2)

0)

where II is the module of the generalized stator current vector of the three-phase system;

iA, iB, ic are the instantaneous values of the stator phase currents of a three-phase system.

From the PN2 outputs, values proportional to the input voltages are fed to the input of БВМН4, at the output of which we obtain a value proportional to the square root of the sum of the squares of the input quantities according to formula (2)

Iui

(2)

V (UA:

+ UB2 + Uc2)

where I U I is the module of the generalized voltage vector of the stator of a three-phase system;

UA.UB.UC are instantaneous phase voltage values of a three-phase stator system.

From the output of BVMTZ the signal goes to the first input of BVUT5, to the second input of this

unit receives a signal from one of the outputs PT1, proportional to the current of the control phase of the stator. At the output of BVUT5 we obtain a value proportional to the phase angle between the generalized stator current vector of the three-phase system and the axis of the control phase of the stator winding. VBUT5 implements the function given in formula (3):

35 | d

p arccos - t-tp

(3)

where p is the phase angle between the generalized stator current vector of the three-phase system

and the axis of the control phase of the stator winding (in this case, phase A).

From the output of БВМН4, the signal goes to the first input of БВУН6, the second input of БВУН6 receives a signal from one of the outputs ПН2,

at the BVUN6 output, a signal proportional to the phase angle between the generalized stator voltage vector of the three-phase system with the axis of the control phase of the stator winding. BVUT6 implements the function given in formula (4)

UA

U ZGSSOZ E I I I

(4)

where ri is the phase angle between the generalized stator voltage vector of the three-phase system and the axis of the control phase of the stator winding (in this case, phase A).

The signals from the outputs of BVUT5 and BVUN6 are fed to the inputs of BVUTN7, which performs the summation according to formula (5): p - p, (5)

where p is the phase angle between the current and stator voltage of the three phase system.

The signal from the BVUTN7 output, proportional to the phase angle between the current and the stator voltage of the three-phase system, is fed to input CC8. In CC8, this signal is compared with a value proportional to the first angle setting. The first angle setting corresponds to the lower limit of the asynchronous mode zone (for example, 30 ° inductive). When the signal at the CC8 output exceeds this setting, the time for finding the angle (p of the phase shift between the current and the stator voltage of the three-phase system in the asynchronous mode zone begins) in the OVB10. If the time counted by the OVV10 exceeds the first time setting, the OVV10 and output organ of device B013. Otherwise, the countdown

08810 ceases at the moment p exits in the process of decreasing beyond the lower boundary of the asynchronous mode zone.

A new count starts from zero at the first subsequent entry of f into the asynchronous mode zone. The signal proportional to the angle (p, from the output of BVUTN7 also goes to the input of CC9, in this comparison scheme it is compared with the second angle setting. The value of this setting depends on the design of the engine, the level of residual excitation, the engine load and other factors and calculated on a case-by-case basis. It does not exceed a value proportional to the upper limit of the zone of asynchronous mode (90 ° inductive) .When the value proportional to angle p exceeds the value corresponding to the second angle setting, achinaets in OVV11 timing for detecting the asynchronous mode excited machine. The countdown to the time

08811 stops at the moment this time is equal to the second time setting, which corresponds to a certain slip. A signal appears at the OVV11 output, if the countdown has not yet been stopped, and the angle (p has again become larger than the second angle setting. The coincidence of these two conditions corresponds to the asynchronous mode of the excited synchronous motor. The signal from the OVV11 output, provided that there is a signal at the CC8 output, causes actuation of the output organ B013.

The introduction of new blocks and the organization of connections between them and the known blocks allows us to obtain a signal proportional to the instantaneous value of the phase angle angle p between the current and the stator voltage of the three-phase system, which makes it possible to remove such a restriction inherent in the prototype as the inability to measure the angle value more than once during a power frequency voltage period. Therefore, asynchronous mode is much faster.

Claims (1)

SUMMARY OF THE INVENTION A device for protecting synchronous machines from asynchronous operation, comprising current and voltage converters with clamps for connecting current and voltage transformers to the outputs, respectively, a phase angle calculation unit between the current and the stator voltage, the first and second comparison circuits, the inputs of which combined and connected to the output of the block for calculating the angle of phase shift between the current and voltage of the stator, the output of the first comparison circuit through the first body time delay connected to the first input of the output organ , the second input of which is connected to the output of the coincidence unit, the output of the second comparison circuit through the second delay element is connected to the second input of the coincidence unit, the first input of which is connected to the output of the first comparison circuit, characterized in that, in order to improve performance, an additional calculation unit is introduced module of the generalized stator current vector module, calculation unit of the generalized stator voltage vector module, unit for calculating the phase angle between the generalized stator current vector and the axis of the control phase of the stator winding a torus, a phase angle calculation unit between the generalized stator voltage vector and the axis of the control phase of the stator winding, with three inputs of the calculation unit of the generalized stator current vector module connected to three outputs of the current converter, three inputs of the calculation unit of the generalized stator voltage vector module with three outputs of the voltage converter, the output of the calculation unit of the module of the generalized stator current vector is connected to the first input of the block of calculation of the phase angle between the generalized stator current vector and the axis of the control phase of the stator winding, the second input of which is connected to the output of the control phase of the current converter, the output of the calculation unit of the generalized voltage vector module of the stator is connected to the first input of the calculation unit of the phase angle between the generalized voltage vector of the stator and the axis of the control phase of the stator winding, the second input of which connected to the output of the control phase of the voltage converter, and the outputs of the block for calculating the phase angle between the generalized stator current vector and the axis the control phase of the winding and the block for calculating the phase angle between the generalized stator voltage vector and the axis of the control phase of the stator windings are connected to the first and second inputs, respectively, of the block for calculating the phase angle between the current and voltage of the stator, and the current and voltage converters are made in three-phase design .