SU1418843A1 - Method of overload protection of a.c. generator - Google Patents

Abstract

This invention relates to electrical engineering, in particular, to relay protection. The purpose of the invention is to improve speed. The device contains a current sensor 2 connected to a null organ 3 and a comparison node 4, an element of OR-NOT 5, an element of AND 6, a generator of pulses 7, a binary counter 8 and a comparison block 9. When the generator current sine wave passes through zero at the output zero - organ 3 appears as a logical unit signal. At the output of node 4, a logical unit signal appears when the generator current reaches a predetermined value. This signal is sent to the element OR-NOT 5, l then to the input of the element AND 6. The other inputs of the element 6 receive signals from the pulse generator 7 and null Morgan 3. The signal from the output of the element H is fed to the input of the binary counter 8, counting the number corresponding to the meter stroke yrnyif the signal goes to the inputs of the compare block 9, the other inputs of which receive a binary number corresponding to the angle Cf. If the number corresponding to Cfrp is less than the number corresponding to tf, then the output of block 9 is a signal to turn off the generator. 2 Il. c-C you are the first (L (X 00 ro

Description

Fig1

The invention relates to electrical engineering and is intended to protect alternators, in particular, generators of ship power stations from overloads.

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

FIG. 1 shows a functional diagram of a device implementing an overload protection method; in fig. 2 - generator current charts for emergency and trouble-free situations.

At the output of the alternating current generator 1, a current sensor 2 is connected, connected to the null current organ 3 and the node 4 comparing the current of the generator with a given value, the output of which the inputs of which are connected to the generator of 7 pulses, and the output via a binary counter 8 to the block 9 of the comparison; position 10 marked bus power.

FIG. 2 marked: i - generator load current; 1 - given current limit value; Cf is the measured angle from the moment of the sinusoid transition of the generator current through zero until the current is equal to the specified value; given boundary value of the angle C | ; oi, is the angle from the moment of transition of the sinusoid current of the generator to the moment of equality of the current setpoint equal to 1 MowJ i sinusoid of the emergency current of the generator.

The method is carried out as follows.

From the generator 1 output, the current enters the current sensor 2, which is connected to the stator winding circuit of the generator. From sensor 2, the current is fed to the input of the null organ 3 and to the input of node 4 of the comparison

for the time corresponding to the angle qi. From the output of the logic element And 6 pulses arrive at the input of the binary counter 8, counting the number corresponding to the angle cf. From the output of counter 8, the number in binary code goes to the first inputs of block 9 of the comparison. A binary number corresponding to the corner of C p is fed to the second inputs of the comparison block 9. If the number corresponding to the if angle is less than the number corresponding to the angle, the output of block 9 is a signal to turn off the generator, i.e. if the measured angle tf is less than the specified limiting angle, which is 20, then the current exceeds the allowable limits and a signal is given to turn off the generator.

We estimate the increase in the speed of protection. Let the generator current increase above the value of the 1.5 I current (curve i, fig. 2). At the point

one

nom

A for which I 7 is triggered by this protection. At point B, the protection trips, the setpoint current of which

equal to 1.5 expression

 IOM

For point A we write

max Sintf - - 1

(one)

For point at

Ma c sino

1.5 1,

(2)

Dividing equality (1). On (2)

1dts, ks sing) 0,5 I

nom

1 ", ks Sl

1.53

we get

sin c sin oL

 3

By analyzing the sin function values for angles less than 20 °, you can make

generator current with a given value, 45 conclusion that the angle is approximately

At the output of the null organ 3, a signal of a logical unit appears at the transition of the sinusoid current of the generator through zero. At the output of node 4, a logical unit signal appears when the generator current reaches a predetermined value. The signal from the output of node 4 is fed to the input of the logical element OR NOT 5, which inverts this signal. From the outputs of the zero-organ 3, the element OR NOT 5 and the generator 7 pulses, the signals arrive at the input of the logic element And 5, which allows the passage of pulses from the generator 7 pulses

50

55

three times smaller than angle Ы,. Consequently, the protection performance has increased threefold.

Claims (1)

Invention Formula The method of protecting the alternating current generator from overload is measured by measuring the stator current, comparing it with this given value and forming a signal to shut off when the current of the stator exceeds a predetermined value that differs in that three times smaller than angle Ы,. Consequently, the protection performance has increased three times. Invention Formula The method of protecting an alternating current generator against overload is by measuring the stator current, comparing it with the current value and generating a shutdown signal when the stator current exceeds a predetermined value, characterized in that the moment of equality of the current generator with a given value, comparing-, PC. Zmn / PL By this, and if the measured angle is less than a given value, a signal is generated to turn off the generator. Figg