JPS5825233B2 - level detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a level detection device that operates at high speed and returns quickly.

Conventionally, there is a level detection device shown in FIG. 1 which operates at high speed and returns at high speed.

In Fig. 1, 1 is a diode rectifier, 2 is an input V, and when the absolute value of the rectifier is greater than the absolute value of the reference level VL for rectangular wave conversion, it outputs a signal of "1", and when it is smaller, it outputs a signal of "0". A square wave conversion device that outputs a signal, 3 is a NOT circuit, 4 is an input “
1 is a timer that detects the time T, which is a signal, 5 is a photo delay timer that extends the input signal for 12 hours, and 6 is a NOT circuit.

FIG. 2 is a waveform diagram showing the operation of the conventional device.

In FIG. 2, A is the input waveform vi, V is the output V1 of the rectifier 1 that rectifies the input waveform Vi, and C is the first level when V is greater than VL, i.e. The output waveform v2 of the rectangular wave converter 2 which outputs the signal J and outputs the second level, that is, the "0" signal when . Waveform V3, E, the period when V3 is positive is T
On-delay timer 4 that outputs an output waveform when larger than 1
The output waveform V4 is the output V6 of the off-delay timer, which stretches the signal v4 by 12 hours, and the output waveform V6 of the repeater 6, which inverts the signal v5.

The off-delay timer circuit 5 is for making the pulsed input continuous, and the expansion time T2 is half cycle + α (10 m5 + α in the 50 Hz system).

Time T of on-delay timer circuit 4. determines the return time of the detection level device, and is set to an arbitrary value of T<half cycle.

The reference level VL for rectangular conversion of the rectangular wave conversion device 2 is the input V
When an input of detection level V is input as i, the pulse width of v3 in FIG. 2 is set to T.

FIG. 2a shows that the input Vi is lower than the detection level VD, that is, the operating state, and FIG. 2b shows that the input Vi is lower than the detection level VD, that is, the inactive state.

In FIG. 2a, since the input waveform Vi is lower than the detection level VD, the period during which the rectified waveform V of Vi is smaller than the set level VL is shortened, and the pulse width of the output waveform V3 of the NOT circuit 3 is the second T, shorter as shown in Figure a.

Therefore, the output waveform v4 of the on-delay timer 4 becomes a "10" signal as shown in FIG. 2a, and the output waveform V5 of the off-delay timer 5 also becomes a "0" signal.

Final output V.

inverts the V5 signal to become a "1" signal.

On the other hand, Fig. 2 shows that the input waveform Vi is smaller than the detection level VD, and the period during which the rectified waveform 1 of Vi is smaller than the reference level VL is long (so that the pulse width of the output waveform V3 of the NOT circuit 3 is T, longer.

Therefore, the output waveform of on-delay timer 4 is V,
The output is a pulse as shown in the diagram.

The output waveform v5 of the off-delay timer 5 is the pulse output V
4 becomes continuous, resulting in a continuous "1" signal as shown in Figure 2, and the final output V.

inverts the signal of V and becomes a "0" signal.

Rectangular wave conversion reference level VL of the rectangular wave converting device 2 in FIG.
As mentioned above, when an input of the detection level VD limit is input as the input waveform Vi, the period during which the rectified waveform V of Vi is smaller than the set level VL is T4, that is, V3 in FIG.
Set the pulse width to be T1.

Specifically, expressed as a mathematical formula, T.

VL = Vo Sln X 180° T1≦half cycle Set VL so that

However, according to the conventional method, when a high frequency input as shown in FIG. 3A is input as the input waveform Vi, the rectified waveform v1 is smaller than the reference level VL even if the input level is below the detection level VD. The period during which the ON-delay timer circuit 4 changes becomes shorter, the pulse width of the output v3 of the NOT circuit 3 becomes narrower as shown in FIG.
It becomes "0" as shown in the figure.

Therefore, the final output V. outputs a "1" signal and enters the operating state.

For high-frequency inputs, even if the input level is small, the time it takes for the input waveform to become lower than the reference level is short. It is easier to operate against.

An example of a level detection device is an overcurrent relay.

Overcurrent relays are sometimes used as stoppers for distance relays when used to protect power systems.

Therefore, if the distance relay malfunctions when high frequency input is received from the grid, it is required that the overcurrent relay, which is a stopper, does not malfunction due to the high frequency.

In such cases, conventional devices are completely powerless.

That is, in the conventional example of FIG. 1, as shown in the waveform diagram of FIG. 2, the pulse width of the pulse waveform V3 that appears when the level of the rectified waveform V1 of the input waveform Vi is smaller than the reference level VL is:
When T is smaller, an operation signal is output, and when T is larger, it is inactive.

In other words, when the level of the input waveform Vi is high, the pulse width of V3 becomes smaller than T, so an operation signal is output, and when the level of Vi is low, the pulse width of V3 becomes larger than T1, so it becomes inactive. .

Therefore, as shown in the waveform diagram in Figure 3, for a high-frequency input as the input waveform Vi with a frequency above T1 (with a period of 2T or less), the pulse width of v3 will always be shorter than T. However, even if the level of the input waveform Vi is lower than VD, it always outputs an operating signal as long as it is higher than the level VL, which has the disadvantage that it is inherently easy to operate with high frequency input.

Since conventional devices use a diode rectifier in the input section, accurate level detection cannot be performed for minute inputs that are lower than the diode's pumping voltage.

The present invention has been made to eliminate the drawbacks of the conventional method, and when the level of the positive half wave of the input waveform Vi is higher than the reference level for rectangular wave conversion, a signal of the first level is output, A first square wave converter that outputs a second level signal when the level of the positive half wave is smaller than the reference level for square wave conversion and when the input waveform Vi is negative; When the level of the input waveform Vi is below the reference level for rectangular wave conversion, a level signal is output. a second rectangular wave converter that outputs a signal at a second level; determines the time when the output of the first rectangular wave converter is at the first level; and when this time continues for a first settling time or more, the second level of the signal is output. a first timer that outputs a signal at the first level; determines the time when the output of the second square wave converter is at the first level; and when this time continues for a first settling time or more, outputs the signal at the second level; a second timer that outputs a signal; a third timer that determines the time during which the outputs of the first timer and the second timer are both at a second level; and outputs a signal when this time continues for a second settling time or more; By setting the first settling time to a predetermined value, there is no response to high frequency input above a certain frequency, and the input signal is directly converted into a rectangular wave without rectifying it. Therefore, it is an object of the present invention to provide a device that can accurately detect the level even for minute inputs that are lower than the diode energy voltage.

FIG. 4 is a block diagram showing one embodiment of the present invention.

In FIG. 4, I is the reference level V at which the input waveform Vi is positive.
When LI is a dog, it sends a signal of ``1'',
A rectangular wave conversion device 8 outputs a second level signal when the input waveform Vi is smaller than the negative reference level vL2, and outputs a second level signal when the input waveform Vi is smaller than the negative reference level vL2. The output rectangular wave converter, 9 and 10 are on-delay timers with a settling time of T3, 4 is an on-delay timer with a settling time of T1, 11 is a 08 line, and the rest are the same as in FIG.

FIG. 5 is a waveform diagram showing the operating principle of the present invention.

Figure 5 A shows the input waveform Vi, and the mouth shows the reference level V when Vi is positive.
When it is larger than LI, it outputs a signal of "1", and when it is smaller, it outputs a signal of "0".

The output Vi3 of the rectangular wave converter I outputs a signal of "1" when vi is smaller than the negative reference level VL□, and outputs a signal of "0" when vi is smaller than the negative reference level VL□.
The outputs vi2, 2, and E of the rectangular conversion device 8 that output signals of
Output waveform Vi3. It is Vi4.

is the output waveform V2 of the OR circuit 11 representing the OR of Vi3°.4, and T to N are the same as in FIG.

In FIG. 5, the reference level VLI for rectangular wave conversion of the rectangular wave converter T and the reference level ■L2 for rectangular wave conversion of the rectangular wave converter 8 are IVL, I = IVI, 21, and the detection level VD is used as the input Vi. When the limit human power is applied, the pulse width of V3 in FIG.

Ten-on delay timer 9,100 settling time T3)-T
Set it so that it becomes 1.

Father, T3 is set to T3=□ when you want it to be inactive no matter how high the level of high frequency input of fcHz or higher comes in.

fc FIG. 5a shows that the input Vi is lower than the detection level VD, that is, an operating state, and FIG.

In Fig. 5a, the input waveform Vi is large, so the mouth of Fig. 5a,
The width of the rectangular waves of V, 1 and Vi□ shown in C is thick (becomes
Time T when input Vi becomes smaller than vil and larger than VL2.

becomes smaller, and the pulse width To+T3 of V3 becomes smaller than T.

Therefore, V4 becomes "0" as shown in FIG.

Figure 5 is the mouth of Figure 5 a because the input vi is small.

The width of the rectangular waves of Vil and Vi2 shown in C becomes smaller,
The time T when the input vi is smaller than VL and larger than VL2.

is large (and the pulse width of V3, To + T3, becomes T, which is shorter than T3).

Therefore, v4 outputs a pulse once every half cycle and becomes inactive, as shown in Figure 5a.

As mentioned above, the reference level I of the square wave converter shown in FIG.
VL, I and +vL,, the value of 1 is when the limit input of detection level VD comes in as input waveform Vi (input V,
The time T when is smaller than VL and more dog than VL2.

Plus T3)-T. Set it so that

To express this concretely using a mathematical formula, −T IV I=lVj21=VDstn(, period Xl80
°) becomes 1.

FIG. 6 is a waveform diagram showing the operation when a high frequency input with a frequency power of 2T3 or more is input as the input waveform Vi.

6A is an input waveform v1T3 with one or more frequencies, and no matter how thick the level of
The pulse width T of the output waveform Vi□ of the rectangular wave converter 8 is always smaller than T3.

Therefore, as shown in FIG.
3°v, both become "0" signals.

Therefore, the output waveform V3 of the NOT circuit 3 is “
1" signal, and the final output is "0" and is inactive.

That is, in this invention, as shown in FIGS. 4 and 5, the positive rectangular wave output vi1 and the negative rectangular wave output vi of the input waveform Vi are
By delaying each of Vi3.2 by time T3 by on-delay timers 9 and 10, a rectangular wave Vi3. V
i4 obtained vi3. When vi4 becomes 10'', pulse waveform v3 is obtained, and when the pulse width of pulse waveform V3 is smaller than T, an operation signal is output.

When the dog is inactive.

Therefore, Fig. 6 wave 111ZKyyj@K・xisiv
For a high frequency input of iomia"゛i or more (period is 2T3 or less), both the positive rectangular wave Vi1 and the negative rectangular wave Vi2 of Vl, and the width of the rectangular wave is less than T3, so the on-delay timer 9 and 10, the waveforms Vj3 and Vj4 delayed by the time T3 become "0".

Therefore, V3 becomes a continuous "1" signal and eventually becomes inactive.

In this way, in this invention, after converting the input waveform i into a rectangular wave, it is delayed by the time T3 by the on-delay timer, so when the frequency of the input waveform Vi is one or more, the Mendeley delay T3 is determined by the timer delay time T3. , it is assumed that there is no input, and the final output is inactive.

Therefore, the frequency of the high-frequency waveform input as ■ is fc
When it is above Hz, if T3 is set so that fe=□ and T3, the device will not operate even if a high frequency waveform above fcHz is input.

Here, the difference in operating characteristics between the conventional device and the device of the present invention will be described with reference to FIG. 1, which shows the relationship between the frequency f of the input electrical quantity and the detected value.

In the case of the conventional device, if the frequency of the input electrical quantity is f, the above equation becomes the operating equation of V.

” T1 π 1 (1) When 2πf・−ku−, that is, f×□ 2 2 2T.

Heart〉 V, 5in2πf・-VL 2 T π 1 (2) 2π1-1≧−, that is, when f≧−1 2 2
2T1 When V1≧vL -, -, ::o, when vi''゛VL'J'' becomes smaller), the level detection device is always smaller than T1, and the detected value is vD at the commercial frequency (assumed to be 50Hz). Since it is designed so that the above formula (1), (
From 2), the relationship between the input frequency and the detected value is expressed graphically as follows:
The result is shown in Figure 7a.

As can be seen from Fig. 1 a, f is thicker (the more it moves) The output value becomes small, and at f-, VL is the detected value of 2T.

It becomes.

In the case of the device of the present invention, when the frequency of the input electrical quantity is f, the following equation becomes the operating value of Vi.

T, π 1 (1) When 2πf・−〈−2, that is, f×− 2 2 2T.

−T V−siH2rcf −−L−”≧VL 2 f = 1/2 When T, f = 1/2 in the above formula.
T.

By substituting , the operating formula becomes the following.

VL ■〉 πT3 1: 2 T.

(2) 2πf-ko≧- and 2πf- is <2, i.e. 2
2 2 2 1 When □≦fku□, T12T3 V; when cos2πf-ノ≧VL 2 1 f--, substitute f-1 in the above equation 2 T, 2 T.

The operating formula is roughly as shown above.

T3 π 1 (3) When 2πf・−≧−2, that is, f≧− 2 2 2T3 Inactive for all V inputs.

(・,・For all inputs vi, the time span in which vi becomes longer than vL is shorter than T3, so it appears as if the input electricity amount is 0) The input frequency is detected from the above equations (1) to (3) Figure 1 shows the relationship with the values.

As can be seen by comparing Fig. 1 a and b, in the present invention, compared to the conventional example, in the region f≦-, the detected value is closer to the true value VD, and when -<f<-, it suddenly becomes immobile 2T, 2T3 The creation has expanded, and in the region f≧−, it is inactive for all inputs T3.

As explained earlier, this is the effect of adding timer T3.

An example of a level detection device is an overcurrent relay.

Overcurrent relays are sometimes used as stoppers for distance relays when used to protect power systems.

If a distance relay malfunctions when high frequency input is applied from the power system, it is required that the overcurrent relay, which is a stopper, does not operate in response to high frequency input.

However, in the conventional system, the sensitivity to high-frequency input becomes better, and the system becomes very easy to operate.

However, according to the present invention, the sensitivity suddenly starts to deteriorate at a frequency of 1/2T, and at frequencies above 1/2T3,
It has physical properties that make it inoperable no matter what kind of input it receives, and it is extremely difficult to operate in response to frequency inputs above a certain level.

Generally, the frequency of the high frequency input from the power system is determined by the system constant, so if the settling time T3 in the present invention is set to a value equivalent to the frequency of the high frequency determined by the system constant, the problem of malfunction due to high frequencies will be eliminated.

In the above embodiment, as the rectangular wave conversion devices 1 and 8, we considered a device that outputs a signal of "1" when the absolute value of the input waveform is lower than the absolute value of the reference level for rectangular wave conversion. If you use a square wave conversion device that outputs a signal of ``0'' when it is a dog and a signal of ``1'' when it is small, and use a signal inversion device immediately after that, you can achieve exactly the same operation as the above example. Needless to say.

As described above, according to the present invention, when the level of the positive half-wave of the alternating human power quantity is lower than the reference level for rectangular wave conversion, a signal is output which is one level higher than the reference level of the rectangular wave conversion. is smaller than the reference level for rectangular wave conversion, and when the alternating human power quantity is a negative half wave, the first square wave converter outputs a second level signal, the level of the negative half wave of the alternating human power quantity; outputs a signal of the second level when it is below the standard level of square wave conversion, and when the level of the negative half of the alternating human power quantity is smaller than the standard level of square wave conversion, and when the alternating human power quantity of the positive half wave 2nd hour
a second rectangular wave converter that outputs a level signal, determining the time when the output of the first rectangular wave converter is at a level;
A first timer that outputs a signal of the first level when this time continues for a first settling time or more, determines the time when the output of the second square wave converter is the first level, and determines the time when the output of the second square wave converter is the first level. a second timer that outputs a signal of the second level when the signal continues for more than a settling time; By setting the first settling time of the first and second timers to appropriate values, fc=-(T3: first settling time).
For high frequency input of T3 or higher, it can be rendered inactive regardless of the magnitude of the input level.

Since it does not require a rectifier circuit using diodes, accurate level detection can be performed even for minute inputs.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of the conventional device, Fig. 2 is a waveform diagram showing the operation of the conventional device, Fig. 3 is a waveform diagram showing the operation of the conventional device when high frequency input is applied, and Fig. 4 is a block diagram showing an embodiment of the present invention, FIG. 5 is a waveform diagram showing the operation of the present invention, FIG. 6 is a waveform diagram showing the operation of the present invention when high frequency input is applied, and FIG. 7 is a waveform diagram showing the operation of the present invention when high frequency input is applied. FIG. 3 is a diagram showing operating characteristics of a conventional device and a device of the present invention. 1 is a diode rectifier, 2, 7.8 are rectangular wave converters, 3, 6 are NOT circuits, 4, 9, 10 are on-delay timer circuits, 5 is an off-delay timer circuit, and 11 is an OR circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1 When the level of the positive half-wave of the alternating human power quantity is higher than the standard level of square wave conversion, the first level signal is output, and the level of the positive half wave of the alternating human power quantity of electricity is higher than the reference level of square wave conversion. The first rectangular wave converter outputs a second level signal when the alternating human power quantity is a negative half-wave, and the level of the negative half wave of the alternating human power quantity is lower than the reference level for square wave conversion. It outputs the first level signal when Second issue
a rectangular wave converting device, a first timer that determines the time when the output of the first rectangular wave converting device is at a first rubel, and outputs a signal of the first rubel when this time continues for a first settling time or more; , a second timer that determines the time when the output of the second rectangular wave converter is at the first level, and outputs the signal at the first level when this time continues for a first settling time or more; A level detection device characterized by comprising a third timer that determines the time during which the outputs of the timer and the second timer are both at the second level, and outputs a signal when this time continues for a second settling time or more. .