JPH0224095B2 - - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention is used for frequency relay devices, especially power systems, and is used for either under-frequency detection or over-frequency detection depending on the set value. The present invention also relates to a frequency relay device that can be used.

(Prior Art) Generally, in a power system, the system frequency is always maintained at a constant frequency. If the balance between the power generation amount and the load power amount in the power system is disrupted due to a system failure, etc., the system frequency will rise or fall; Frequency relay devices are used to perform system separation, power generation limitation, and load limitation. FIG. 1 shows an example of the configuration of a conventionally used frequency relay device. In the figure, PT is an auxiliary transformer that converts the secondary voltage of a potential transformer (not shown) to a level suitable for input to the relay. R-S phase voltage from the auxiliary transformer PT
V _RS is introduced into the frequency relay. BP is a square wave conversion circuit that converts the grid voltage waveform from the auxiliary transformer PT into a square wave. DIV is a frequency dividing circuit that divides the output of the square wave conversion circuit BP into 1/2m (m=1, 2, 3...). OSC is an oscillation circuit that oscillates a reference frequency fosc for period measurement. AND is an AND circuit which receives the output of the frequency divider circuit DIV and the output of the oscillation circuit OSC as inputs, respectively. C is a counting circuit and the above-mentioned AND circuit
Count the number of AND output pulses. SET sets the setting value using the setting circuit. COM is a comparison circuit that compares the contents of the counting circuit C and the set value of the setting circuit SET. TI is a judgment circuit, which inputs the output of the comparison circuit COM and generates a judgment pulse to be described later.
The relay operation is determined by JP. C.C is a control circuit which receives the output of the frequency divider circuit DIV and generates a clear pulse CP for the counting circuit C and a judgment pulse JP for the judgment circuit TI.

FIG. 2 shows waveforms at various parts of the frequency relay device shown in FIG. 1 above. The operation of this frequency relay device will be explained using FIG. 2.
The output of the frequency dividing circuit DIV is a waveform with a mark/space ratio of 1 and a pulse width corresponding to the number of m cycles of the input to the auxiliary transformer PT (in the figure, m=1). During the time when this signal has a logical value of "1", the reference clock generated from the oscillation circuit OSC is counted by the counting circuit C. Next, this count value is compared to the setting value set in the setting circuit SET and the comparison circuit.
When the count value is smaller than the set value, "0" is output, and when it is larger, "1" is output to the determination circuit TI. Then, after the logic value of the frequency divider circuit DIV changes from "1" to "0", a judgment pulse is generated from the control circuit C/C after a scheduled time.
According to JP, in the case of underfrequency detection relay devices,
If the count value is larger than the set value, the judgment circuit TI
The output of is set to the active state and the trip output is derived.

On the other hand, in the case of an overfrequency relay device, the output of the determination circuit TI is set to the operating state when the count value is smaller than the set value. In addition, in order to repeat continuous frequency measurements, the counting circuit C uses the judgment pulse JP.
Subsequently, it is cleared by the clear pulse CP generated from the control circuit C. In the response waveform diagram in Fig. 2, the system frequency starts to fluctuate at time t ₁ , the relay device operates at time t ₂ due to underfrequency detection or overfrequency detection, and the judgment circuit TI derives the judgment output. The case is shown.

(Problems to be Solved by the Invention) As is clear from the above description, in the conventional configuration, whether the frequency relay device is used for underfrequency detection or overfrequency detection is determined by its circuit configuration; It was possible to detect only one of them. Therefore, when the system conditions of the power system to be protected change and it becomes necessary to change from under-frequency detection protection to over-frequency detection protection, the relay device must be replaced each time, or the judgment made in the configuration shown in Figure 1. Required modification of circuit TI. Furthermore, frequency relay devices used to protect generator motors in pumped storage power plants are designed to detect insufficient frequencies for overload protection when used as motors, and to detect overspeed when used as generators. It is necessary to perform overfrequency detection for protection, but in the case of conventional equipment, two frequency relay devices, an underfrequency detection relay and an overfrequency detection relay, are required to perform both types of detection. Ta.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a frequency relay device that can perform both overfrequency detection and underfrequency detection with one device, depending on the set value.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention provides a frequency relay device with a setting circuit for setting a setting value that is a reference for determining operation, When the setting value is set to perform underfrequency detection for a predetermined frequency, underfrequency detection is performed, and the setting value is set to perform overfrequency detection for a predetermined frequency. The configuration was configured to perform overfrequency detection when the

(Function) First, if the setting value of the setting circuit is set to detect underfrequency, a trip output is derived through a series of logic circuits when the system frequency falls below the setting value, and conversely, it detects overfrequency. In the case of detection, if the set value is set in the opposite way to the above, a trip output can be derived when the system frequency exceeds the set value. In either case, this can be done only by changing the setting value of the setting circuit.

(Example) An example will be described below with reference to the drawings. Third
The figure is a configuration diagram of an embodiment according to the present invention.

In FIG. 3, the same reference numerals as in FIG. 1 indicate the same components. COM ₂ is a second comparison circuit, which compares the set value by the setting circuit SET with a predetermined fundamental frequency of the system, and when the set value is smaller than the fundamental frequency of the system, that is, underfrequency detection is detected. When the set value is greater than the fundamental frequency of the grid, in other words, when overfrequency is detected, an output "1" is derived and the inhibit gate (INHIBIT) is used. Introduced into the gate (AND ₂ ). TI ₁ is the first judgment circuit, into which the output from the first comparison circuit COM and the judgment pulse JP are introduced, and when the set value is greater than the grid frequency (overfrequency detection), its output becomes "1". On the other hand, when the set value is smaller than the grid frequency (when underfrequency is detected), the output is "0". TI ₂ is the second
This is a judgment circuit in which the output from the first comparator circuit COM and the judgment pulse JP are introduced, and when the set value is smaller than the grid frequency (when underfrequency is detected), its output is set to "1"; When the set value is larger than the system frequency (at the time of overfrequency detection), the output becomes "0". The inhibit gate (INHIBIT) is connected to the output of the first judgment circuit TI ₁ and the output of the second comparison circuit COM ₂ , and the output of the first judgment circuit TI ₁ is "1", and ,
When the output of the second comparison circuit COM ₂ is "0",
Introduce "1" output to the OR gate (OR).
The AND gate (AND ₂ ) is the second judgment circuit.
The output of TI ₂ and the output of the second comparison circuit COM ₂ are introduced, and when both outputs are "1", a "1" output is introduced to the OR gate (OR). The OR gate (OR) is the output of the inhibit gate (INHIBIT) and the AND gate (AND ₂ ).
The outputs of both are introduced, and when either input is "1", a trip output is derived.

Next, the operation of the frequency relay having the above configuration will be explained. Consider the case where the setting value is set so that the frequency relay device shown in FIG. 3 performs underfrequency detection. The set value in this case is set below the fundamental frequency of the system. In this case the second comparator circuit COM ₂
The output of is "0". In the above setting state, when the grid is healthy (the grid frequency is maintained at a predetermined fundamental frequency) and when the grid frequency increases, the set value is smaller than the frequency in either case, so the The output of the first judgment circuit TI ₁ is “0”, and the output of the second judgment circuit TI ₂ is “1”
becomes. At this time, the output of the inhibit gate (INHIBIT) and the output of the AND gate (AND ₂ ) are both "0", so the output of the OR gate (OR) is also "0" and no trip output is derived. .

On the other hand, when the system frequency decreases to below the set value, the output of the first judgment circuit TI ₁ becomes "1",
The output of the second determination circuit _TI2 becomes "0". Therefore, the output of the AND gate (AND ₂ ) is "0"
However, the inhibit gate (INHIBIT)
The output "1" of the first determination circuit TI ₁ and the output "0" of the second comparison circuit COM ₂ are introduced to derive the output "1". So or gate (OR)
The trip output is derived from .

Next, consider the case where the setting value is set so that the frequency relay device shown in FIG. 3 performs overfrequency detection.
The set value in this case is set to be higher than the fundamental frequency of the system. At this time, the output of the second comparison circuit COM ₂ is "1". When the grid is healthy in the above-mentioned settling state (the grid frequency is maintained at a predetermined fundamental frequency) and when the grid frequency has decreased, the set value is greater than the frequency in either case, so the The output of the first judgment circuit TI ₁ is "1", and the output of the second judgment circuit TI ₂ is "0"
becomes. At this time, the output of the inhibit gate (INHIBIT) and the output of the AND gate (AND ₂ ) are both "0" and no trip output is derived.

On the other hand, when the system frequency increases and exceeds the set value, the output of the first judgment circuit TI ₁ becomes "0",
The output of the second determination circuit TI ₂ becomes "1". The output of the inhibit gate (INHIBIT) is "0", but the AND gate (AND ₂ ) outputs "1" from the second judgment circuit TI ₂ and the output from the second comparison circuit.
The output "1" of COM ₂ is introduced to derive the output "1", and the trip output is derived from the OR gate (OR).

As explained above, according to the present invention, by adding only a small number of circuits to the conventional device, both underfrequency detection and overfrequency detection can be performed depending on the setting value of the setting circuit, thereby expanding the adaptability of the device. In addition, it is possible to standardize frequency relay devices.

FIG. 4 shows another embodiment according to the present invention, in which the second determination circuit TI ₂ in the circuit configuration shown in FIG.
The circuit configuration is shown with . In FIG. 4, the output of the first comparator circuit COM is introduced into the first judgment circuit TI ₁ , and further into the first judgment circuit TI _1.
The output of is introduced into the first inhibit gate (INHIBIT) and as the inhibit input of the second inhibit gate (INHIBIT ₂ ). The output of the second comparator circuit COM ₂ is also introduced into the second inhibit gate (INHIBIT ₂ ) and as an inhibit input of the first inhibit gate (INHIBIT).

Consider the case where the setting value in the setting circuit SET of the frequency relay device shown in FIG. 4 is set to perform underfrequency detection. In this case, the output of the second comparison circuit COM ₂ is "0". In the settling state, when the grid is in good condition and when the grid frequency increases, the setting value is smaller than in either case, so the output of the first judgment circuit _TI1 is "0", and therefore the first judgment circuit TI1 output is "0". The output from the inhibit gate (INHIBIT) becomes "0". Since both inputs of the second inhibit gate (INHIBIT ₂ ) are "0", the output is "0" and no trip output is derived.

On the other hand, when the system frequency decreases to below the set value, the output of the first judgment circuit TI ₁ becomes "1",
At the same time, the output of the second comparator circuit COM ₂ becomes "0" and the first inhibit gate (INHIBIT) is output.
The output becomes "1" and the trip output is derived.

Next, consider a case where the setting value of the setting circuit is set to perform overfrequency detection. At this time, the output of the second comparison circuit COM ₂ is "1", and the output of the first inhibit gate (INHIBIT) is "0".
It is. On the other hand, the response of the second inhibit gate (INHIBIT ₂ ) is as follows.

First, when the system is healthy or when the system frequency drops, the system frequency is lower than the set value, so the first
The output of the determination circuit _TI1 becomes "1". Therefore, the output of the second inhibit gate (INHIBIT ₂ ) becomes "0". Next, when the system frequency increases, the output of the first judgment circuit TI ₁ is "0", while the output of the second comparator circuit COM ₂ is "1", so the second inhibit gate (INHIBIT ₂ ) The output of is "1" and the trip output is derived. Therefore, the configuration shown in FIG. 4 has the same response as the embodiment shown in FIG.

FIG. 5 shows another embodiment, in which it is determined whether the trip signal from the frequency relay device is derived by underfrequency detection or by overfrequency detection. The circuit configuration diagram is exactly the same as that shown in FIG. As is clear from the explanation of the circuit diagram shown in FIG. 3 above, the trip output from the first inhibit gate (INHIBIT) is due to underfrequency detection (UFTRIP output), and the trip output from the AND gate (AND ₂ ) is due to underfrequency detection. This is because the trip output of is due to overfrequency detection (OFTRIP).

According to the embodiment shown in FIG. 5, the underfrequency detection trip output and the overfrequency detection trip output can be output separately, so even if the protection sequences at the time of overfrequency and underfrequency detection are different, Each sequence circuit can remain connected, making maintenance and operation easier. It also has the advantage that over- and under-frequency can be identified even when the operation is displayed outside the device.

Although the above embodiment has been described as a circuit configuration using logic elements, it is not limited to this, and it is clear that the circuit configuration can also be realized by digital processing using a microcomputer.

[Effects of the Invention] As explained above, according to the present invention, one frequency relay device can be applied to both underfrequency detection and overfrequency detection, depending on the setting value, and the device can be used for both underfrequency detection and overfrequency detection. It is possible to provide a frequency relay device that can expand adaptability, reduce the size of the device, and standardize the device.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional frequency relay device, Figure 2
The figure is a response waveform diagram of the conventional device, FIG. 3 is a configuration diagram of one embodiment of the frequency relay device according to the present invention, FIG. 4 is a configuration diagram of another embodiment, and FIG. 5 is a configuration diagram of still another embodiment. It is. COM...Comparison circuit, _COM2 ...Second comparison circuit, SET...Setting circuit, _TI1 ...First judgment circuit, _TI2 ...Second judgment circuit, CPU...Arithmetic processing unit.

Claims (1)

[Claims] 1. In a frequency relay device that protects the power system by detecting whether the frequency of the power system is large or small by comparing the frequency of the power system with a detected frequency, a setting value is set for the detected frequency that serves as a reference for operation determination. a circuit, a determination circuit that compares a system frequency obtained by waveform-shaping the voltage input of the power system with a setting value of the setting circuit, and determines whether the system frequency is larger or smaller than the setting value; and a determination circuit that determines whether the system frequency is larger or smaller than the setting value. a comparison circuit that compares the set value and a predetermined fundamental frequency of the system, and determines whether to detect an underfrequency or an overfrequency depending on whether the set value is smaller or larger than the fundamental frequency of the system; When this comparison circuit performs underfrequency detection, the judgment circuit generates an operating output when it judges that the system frequency is smaller than the set value, while when this comparison circuit performs overfrequency detection, the judgment circuit generates an operation output when the system frequency is determined to be smaller than the set value. 1. A frequency relay device comprising: an output circuit that generates an operating output when it is determined that the frequency is greater than a set value.