SU1709454A1 - Measurement unit for current protection of d c network - Google Patents

Abstract

This invention relates to direct current protection against short-circuit currents. The aim of the invention is to increase the sensitivity. This is achieved by triggering the actuator 2 only at a large value of the derivative of the current, and if at this time it lasted longer than a predetermined time, then small increments of the load current will not be analyzed by the current measurement element 4, the likelihood of current increments will decrease loads and the number of false positives. 3 il.

Description

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This invention relates to electrical engineering, in particular, to protection of direct-current networks from short-circuit currents (short-circuit). analyzing the change in current.

The aim of the invention is to increase the sensitivity, s

Figure 1 shows the block diagram of the measuring unit; 2 shows timing diagrams explaining his work: FIG. 3 is a block diagram of a triggering organ.

The measuring unit for current protection of the DC network contains a sensor

1 is a current derivative, a triggering body 2. made in the form of a comparator, a time element 3 and a current change measurement element 4. The output of the current derivative sensor 1 is connected to the input of the starting device 2, the output of which is connected to the inputs of the element 4 for measuring the change in current and time element 3. Input, time element 3 is connected to the second input of a change in the trigger threshold of trigger 2. Element 3 times delay the leading edge of the signal.

The measuring unit operates as follows.

Curves 5 (FIG. 2) show the time derivative of the current derivative. The first two curves 5 (left) refer to the load condition. In the first case, the initial value of the current derivative does not reach the initial value of the threshold 6 of the trigger of the trigger 2, although it exceeds its final threshold 7 of the trigger. The signal 8 at the output of the starting body 2 in this case is absent. In the second case, the derivative of the current exceeds the initial value of the threshold in response, at the output of the triggering organ

2po signal 8, however, its duration is less than the time delay of time element 3, and the threshold is not reduced, since the output "tman 9 time element 3 is missing.

In the case of K.E. the triggering time of trigger 2 is greater than the delay of time element 3, signal 9 appears at its output, triggering threshold of trigger 2 decreases to threshold level 7, current measurement element 4 begins to analyze the magnitude of the operating pair. 3

The quality of the working parameter can be used as the duration of the rise of the eye, and the current rise. In the first case, the element (8nt 4 is a time relay, in the second, the integrator, the control input of which is connected to the output of the starting organ, and the information input to the output of the current sensor (the last link in figure 1 is not shown).

Starting organ 2 (FIG. 3) is a null organ 10 comparing the input voltage to its upper input with the reference voltage obtained at the voltage divider from

resistors 11 and 12. The lower input of the zero-body 16 is connected to the slider of the first resistor 11, the first output of which is connected to a reference voltage source, and the second output to the first output of the second resistor 12. whose second INPUT is connected to a common point. The second resistor is shunted by key 13, the control input of which is connected to the output of time element 3. As can be seen from FIG. 3, the trigger threshold of the triggering organ 2 is reduced by reducing the magnitude of the nud-organ reference voltage 10. Another solution is possible when the scale of the input voltage does not change, but the scale of the input voltage (it increases ), then the key 13 must shunt one of the shoulders of the input voltage divider.

The invention makes it possible to increase the sensitivity of protection of a direct current network.

Claims (1)

Claims Measuring unit for current protection of direct current setc, containing a derivative CATIC, the output of which is connected to the input of the starting element, made 8 as a comparator, the output of the starting body is connected to the inputs of the time element and the measuring element Current, about tl tft h and y with and so, that, for the purpose of sensitivity increase, the time element is squeezed as an element of front edge and pulse, the output of which is supplied to the second input of the starting organ. Haspt / KO t noftj P eight KJ, FIG. 2 one Phage. 3