JPH0334286B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a protective relay device, and particularly to a protective relay device that detects a maximum amount of electricity using the amount of electricity in a power system.

[Technical background of the invention]

An example of a relay that selects and detects the largest amount of electricity from among a plurality of electrical quantities in a power system is a maximum value overcurrent relay as shown in FIG. In FIG. 1, the maximum voltage is determined from voltages proportional to a plurality of input currents I ₁ , I ₂ . . . I _o via a maximum value detection circuit 1,
Level detection circuit 2 detects a voltage proportional to the maximum current I _MAX
This is a relay 3 that outputs an output when the value exceeds the level detection value _K0 . In addition, in the case _of a maximum value suppression _ratio differential relay as shown in _FIG . At the same time, the maximum current I _MAX is detected from among the input currents I ₁ , I _{2 ,} . This relay derives an output when the output I _d -I _MAX exceeds the level detection value K ₀ by the level detection circuit 2, and has the characteristics shown in FIG. 3.

Conventionally, a circuit as shown in FIG. 4 has been generally used as the maximum value detection circuit 1. Fourth
In the figure, X ₁ , X ₂ ...X _o are input voltages,
D ₁ , D ₂ ...D _o is rectifier 7, C is capacitor 8, R
has a resistance of 9.

[Problems with background technology]

In the configuration shown in Figure 4, if the values of capacitor 8 and resistor 9 are selected so that the discharge time constant CR becomes a large value, the input voltages X ₁ , X ₂ ...X _o can be charged to the maximum value. The voltage of the capacitor 8 is hardly discharged at a cycle of approximately the commercial frequency, and thus has the function of the maximum value detection circuit 1. However, the maximum value detection circuit 1 described above has input voltages X ₁ , X ₂ . . .
If the _maximum value of , output V _put
has the disadvantage that it contains ripples. In addition, since the rectifier circuits are connected in parallel, if there are many terminals in the input circuit, the rectifier D 2 ...D _o is connected from the input X ₁ in the maximum value state to the input X ₂ ...X _o circuit in the _other state. The influence of current flowing backward cannot be ignored, and there have been problems such as errors occurring due to changes in the number of input terminals or influences of currents in other circuits other than the input circuit that has the maximum value.

[Purpose of the invention]

The present invention has been made with the aim of solving the above problems, and provides a protective relay device that not only can immediately respond when the maximum value of input voltage becomes small, but also has a maximum value detection circuit that does not include ripple components. is intended to provide.

[Summary of the invention]

In the present invention, a plurality of input electric quantities are detected at intervals of, for example, 1/12 of one cycle of a commercial frequency, and the maximum value among them is sequentially replaced while the maximum value within the time up to each detection point is held. The circuit temporarily holds the value, and, for example, after one cycle has elapsed, the maximum value held during the one cycle is transferred to another holding circuit, and this value is derived as the maximum value output.

[Embodiments of the invention]

Examples will be described below with reference to the drawings. Fifth
The figure is a block diagram of one embodiment of the protective relay device according to the present invention, in which the control power source is not shown and only the signal circuit is shown.

In FIG. 5, reference numeral 10 denotes a changeover switch to which a plurality of input electric quantities X ₁ , X _{2 . .} .
Switching is performed by S ₁ to select and output one arbitrary input quantity of electricity. The output of this switch 10
v ₁ is introduced into comparator 12. This comparator 12 compares the two introduced signals v ₁ and v ₂ (described later), and when v ₁ > v ₂ , output signal S ₄ is set to "1", and v ₁
When v ₂ , output signal S ₄ is set to "0". Furthermore, the output v ₁ simultaneously receives the control signal from the comparator 12.
It is introduced into the first holding circuit 11 via the first opening/closing circuit 13 whose opening/closing is controlled by _S4 . The output v ₂ of the first holding circuit 11 is introduced into the comparator 12, and at the same time the control signal S ₂ from the signal controller 14 is input to the comparator 12.
It is introduced into a second holding circuit 16 via a second switching circuit 15 controlled by , and a maximum value output v ₃ is derived from this second holding circuit 16 . Further, the first holding circuit 11 is configured to receive a control signal _S3 from the signal controller 14 and reset it.

FIG. 6 is a block diagram of one embodiment of the signal controller 14. In FIG. 6, 26 is an oscillator which generates a constant frequency _{of 0} , and a first frequency divider 27 with a period of T _{1
This output 1 is} used as the control signal _S1 . Further, the output ₁ is introduced into a second frequency divider 28 and divided into a frequency output ₂ with a period T ₂ of the commercial frequency, and is further divided by a delay circuit 29 for Δt ₁ time (for example, 0.2 times the period T ₂₎ . time) and its output ₃ is taken as the control signal _S2 . Also, the output ₃ is a delay circuit 3.
0 by a very small time Δt ₂ (Δt ₂ <<T ₁ ), and its output ₄ is taken as the control signal S ₃ .

FIG. 7 shows a time chart of the above explanation. Also, in FIG. 6, the OR circuits 31, 3
2, when a START command (one shot pulse in this case) is issued, the S ₂ and S ₃ signals are output simultaneously and are used to reset to a predetermined value.

Next, the operation of FIG. 5 will be explained with reference to the flow chart of FIG. 8 and the time chart of FIG. 9.
First, by applying a control voltage to each component shown in FIG. 5, the first and second holding circuits 11,
16 outputs v ₂ and v ₃ are arbitrarily determined predetermined values V _K
(for example, 0) (step 1). Here, it is assumed that the predetermined value V _K includes an arbitrary initial value among the input electric quantities X ₁ , X ₂ . . . X _o . Next, signal controller 1
One electric quantity _{( for example , X 1} ) are selected and output as output _v1 (step 2). Next, in the comparator 12, the output v ₂ (the initial value is _VK ) of the first holding circuit 11 is compared with the output v ₁ from the changeover switch 10 (step 3). If v ₁ > v ₂ , the first switching circuit 13 is closed by the signal S ₄ from the comparator 12,
The output v ₂ of the first holding circuit 11 is output from the value of V _K
It becomes the same value as v ₁ and is kept at that size (step 4). Moreover, in the case of v ₁ ≦ v ₂ , the first switching circuit 13 is not closed, and the output v ₂ of the first holding circuit 11
retains its original value (V _K ). Then, in _the subsequent period _{T 1} , _the next input electricity _amount T ₁ ) (step 5), and after a slight delay (for example, 0.2 times the period T ₂ ), the signal controller 14
The second switching circuit 15 is closed by the control signal S ₂ from the second holding circuit 16, and the output v ₃ of the second holding circuit 16 is rewritten to the same value as v ₂ and held (step 6). Subsequently, the control signal _S3 causes the first holding circuit 11 to
The output v ₂ of is reset to a predetermined value V _K (step 7). Thereafter, the maximum value _v3 is output by repeating the above operation with a period _T2 .

In order to simplify the explanation, the time chart in FIG. 9 assumes that the input electrical quantities are three electrical quantities X ₁ , X ₂ , and X ₃ , and that the period T ₁ of the changeover switch 10 is 1/12 of the period at the commercial frequency. It is double. Also, the second
The solid line time chart corresponds to the output _v3 of the holding circuit 16. Further, the maximum value during the previous T ₂ period is held by the second holding circuit 16, and at the same time, the first holding circuit 11 detects the maximum value during the T ₂ period, and the maximum value during the T ₂ period ends. 2 holding circuit 16
Move to.

Note that a control signal is used to control the switching circuit 13 described above.
S ₃ may also be used. That is, the first switching circuit 13 is closed when the first input electricity amount X ₁ of the T ₂ period is received without performing a reset using the control signals S ₂ and S ₃ from the signal controller 14 . In this case, the output v ₂ of the first holding circuit 11 becomes the maximum value of the input electric quantities X ₁ , X ₂ ...X _o during the T ₂ period,
After this value is transferred to the second holding circuit 16, the next
When the changeover switch 10 selects the electrical quantity X ₁ at the beginning of the T ₂ period, it is reset to the instantaneous value of the electrical quantity X ₁ . In this way, the output voltage v ₁ of the changeover switch 10
The predetermined value when controlling the holding circuit which inputs T to a predetermined value after the completion of the _T2 period is not necessarily a constant value, but can be a value of a specific input at a specific time. Even in this case, the maximum output v ₂ of this holding circuit in the next T ₂ period is equal to and has exactly the same effect as the case where it is controlled to a constant value.

FIG. 10 shows an embodiment in which a one-chip microcomputer is used as the signal controller. 10th
In the figure, 33 is a one-chip microcomputer that includes at least a memory, an oscillator, an arithmetic controller (CPU), and an input/output device. 3
4, 35, and 36 are signal decoders for decoding each code signal. Therefore, when a START command is input to the one-chip microcomputer 33, processing is performed according to the flowchart shown in FIG. 12, and the code signal is sent to each signal decoder 34, 35, 36. and output signals S ₁ , S ₂ , and S ₃ respectively.

FIG. 11 is a block diagram of another embodiment of the signal controller, in which a logic signal is exchanged directly with an external circuit without using input/output as a code signal. The symbols in the figure correspond to those in FIG. 10 above.

FIG. 13 is a configuration diagram of another embodiment of the protective relay device according to the present invention. Reference numerals 16 to 16 in the figure correspond to those in FIG. 17 is a second comparator which compares the output v ₂ from the first holding circuit 11 and the output v ₃ from the second holding circuit 16 and sets the larger one as the final output.

Next, the operation shown in FIG. 13 will be explained with reference to the time chart shown in FIG. 9 and the flow chart shown in FIG. 14. Furthermore, the output from the selector switch 10
The operation until v ₁ and the output v ₂ from the first holding circuit 11 are compared and the larger output is transferred to the second holding circuit 16 at regular intervals is the same as the operation in FIG. . In this embodiment, the following operations are further added to the operations described above.

That is, in the second comparator 17, the output v ₂ from the first holding circuit 11 and the output v ₃ from the second holding circuit 16 are compared, and if v ₂ > v ₃ , the second comparison is performed. The second switching circuit 15 is activated by the signal from the device 17.
is closed, and the output v ₃ of the second holding circuit 16 is the first
is held at the same value as the output v ₂ from the holding circuit 11 of . On the other hand, in the case of v ₂ ≦v ₃ , the second switching circuit 15
is not closed, so the output v ₃ of the second holding circuit 16 retains its original value. That is, as soon as the relationship v ₂ > v ₃ is established between the output v ₂ of the first holding circuit 11 and the output v ₃ of the second holding circuit 16 within one detection period, the first holding circuit 11 output v ₂ to the second holding circuit 16, the detection accuracy becomes finer, indicating superior characteristics.

FIG. 15 shows still another embodiment of the protective relay device according to the present invention. Reference numerals 10 to 14 in the figure correspond to those in FIG. A plurality of input electrical quantities are introduced into the changeover switch 10, and the input electrical quantities are derived one by one according to the control signal from the signal controller 14, as in the above embodiment. 1st
The output v ₁ from the changeover switch 10 is introduced into the first comparator 12, and at the same time, the output v 1 is introduced into the first comparator 12 via the first switching circuit 13 controlled by the first comparator 12.
is introduced into the holding circuit 11 of. First holding circuit 1
1 output v ₂₁ is introduced into the first comparator 12 .
Furthermore, the output v ₁ of the first changeover switch 10 is introduced into the second comparator 19 and at the same time
9 is introduced into the second holding circuit 18 via a second opening/closing circuit 20 controlled by 9. Further, the output v ₂₁ of the first holding circuit 11 is introduced into the third comparator 21 and the second changeover switch 22, and the output v ₂₂ of the second holding circuit 18 is also introduced into the third comparator 21 and the second changeover switch 22. It is introduced into the changeover switch 22 of No. 2. In addition, the second
The changeover switch 22 is controlled by the third comparator 21. Furthermore, the first holding circuit 11 receives the control signal _S2 from the signal controller 14, and
The holding circuit 18 receives a control signal from the signal controller 14.
Make sure to receive _S3 .

The operation shown in FIG. 15 will be explained using the flow chart shown in FIG. 16 and the time chart shown in FIG. 17.
First, _the outputs v _{21 ,
v22} is set to an arbitrarily determined predetermined value _VK .
Next, according to the control signal S ₁ from the signal controller 14, the first changeover switch 10 changes the input electrical quantities X ₁ , X ₂ . . _.
From among them, only one quantity of electricity (for example, X ₁ ) is selected according to a determined period T ₁ and a determined order and outputted as an output v ₁ . Next, the control signals S ₂ and S ₃ from the signal controller 14 cause the first comparator 12 to operate, and the first comparator 12 switches between the output v ₂₁ of the first holding circuit 11 and the first switching. Output from switch
v ₁ is compared, and if v ₁ > v ₂₁ , the first switching circuit 13 is closed by the signal from the first comparator 12, and the output v ₂₁ of the first holding circuit 11 becomes the output v Retains the same value as ₁ . On the other hand, when v ₁ ≦v ₂₁ , the first switching circuit 13 is not closed, and the output v ₂₁ of the first holding circuit 11 maintains its original value. Then, by the successive period T ₁ , the changeover switch 1
The input electricity _amount
1.2 times) after the period T ₂ (T ₂ ≫ _{T 1} ), the output v ₂₂ is reset to a predetermined value by the control signal from the signal controller 14, and then the control signal S ₂ from the signal controller 14, By _S3 , the operation shifts to the second comparator 19 side, and the second holding circuit 18 is activated by the second comparator 19.
output v ₂₂ and output from the first changeover switch 10
v ₁ is compared, and if v ₁ > v ₂₂ , the second switching circuit 20 is closed by the signal from the second comparator 19, and the output v ₂₂ of the second holding circuit 18 becomes the output v ₁ . kept at the same value. When v ₁ ≦v ₂₂ , the second switching circuit 20 is not closed, and the output v ₂₂ of the second holding circuit 18 maintains its original value. Then, the changeover switch ₁₀ changes the input electricity _amount
is selected and the subsequent steps are repeated, but after a period _T2 longer than the commercial frequency (for example, 1.2 times) has elapsed, the output v21 is reset to a predetermined value by the control signal _S2 from the signal controller 14, and then the output _v21 is reset to a predetermined value. Then, the operation of the first and second comparators is repeated at a cycle of _2T2 . Moreover, the first holding circuit 1
The output v ₂₁ of the first holding circuit 18 and the output v ₂₂ of the second holding circuit 18 are constantly compared by the third comparator 21, and the second changeover switch 22 changes the output v ₂₁ according to the signal from the third comparator 21. and output v ₂₂ , whichever is greater is the maximum value
Output as v ₃ .

In addition, in FIG. 17, in order to simplify the explanation, the input electrical quantities are three electrical quantities X ₁ , X ₂ , and X ₃ , and the period T ₁ of the first changeover switch 10 is 1 of the period T ₂ at the commercial frequency. /12 times.

In the above embodiment, the output v ₂₁ from the first holding circuit 11 and the output v ₂₂ from the second holding circuit 18 are respectively introduced into the third comparator 21, and the comparison result by the third comparator 21 is the second changeover switch 22
I was trying to output it via . However, as shown in the time chart of FIG. 17, between times _t1 to _t2 and _t3 to _t4 , the output _v21 from the first holding circuit 11 is different from the previous times _t0 to t1 and _t , respectively. The maximum value between _{t 2} and t ₃ is held, and the output v ₂₂ of the second holding circuit ₁₈ is held at the previous time between t ₂ and t 3.
The maximum value between t ₁ and t ₂ is maintained. That is, one of the two holding circuits holds the maximum value. Therefore, the times t ₁ - t ₂ and t ₃ - _{t 4}
If the signal controller 14 is controlled to take out the output v ₂₁ from the first holding circuit 11 during the period t 2 and take out the output v ₂₂ from the second holding circuit 18 from time t ₂ to t ₃ , the configuration is as follows. Of course, it becomes easier.

FIG. 18 is a configuration diagram of still another embodiment of the protective relay device according to the present invention. Reference numerals 10 to 17 in the figure correspond to FIG. 13. 23 is a second changeover switch, and 24 is a sign inverter. That is, the second changeover switch 23 receives the output from the first changeover switch as is and inverted, respectively, and is controlled to open and close by the control signal _S4 from the signal controller 14. . Therefore, the only difference in configuration from the embodiment shown in FIG. 13 described above is that a second changeover switch 23 and a sign inverter 24 are added, and the subsequent operations are also the same as in the case of FIG. 13. The same is true.

If the second changeover switch 23 is switched at twice the frequency of the first changeover switch 10 by the control signal _S4 from the signal controller 14,
This is a maximum value detection circuit when the input electric quantities X ₁ , X ₂ . . . X _o are full-wave rectified, and can extract the maximum absolute value. At this time, the first holding circuit 1
The value of 1 is the value obtained by extracting the maximum value of each electric quantity every half cycle of the input electric quantities X ₁ , X ₂ ...X _o , so the period
T ₂ is a period slightly longer than 1/2 of the electrical quantity period (e.g.
0.6 times).

FIG. 19 shows still another embodiment of the protective relay device according to the present invention. Reference numerals 10 to 17 in the figure correspond to FIG. 18. 25 is a full wave rectifier circuit. That is, in this embodiment, a full-wave rectifier circuit 25 is added in place of the second changeover switch 23 and sign inverter 24 added in FIG. Therefore, the operation itself is the same as in the case of FIG. 18. In this case, further explanation will be omitted.

〔Effect of the invention〕

As explained above, according to the present invention, by sequentially inputting a plurality of input quantities of electricity, the maximum value from among these input quantities of electricity is held, and the held maximum quantity of electricity is transferred to other quantities at regular intervals. Since the structure is configured so that the output is transferred to the holding circuit of The maximum value can be detected without the possibility of occurrence of.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a maximum value overcurrent relay, Figure 2 is a configuration diagram of a maximum value suppression ratio differential relay, Figure 3 is a characteristic diagram of a maximum value suppression ratio differential relay, and Figure 4 is a diagram of a conventional maximum value overcurrent relay. A value detection circuit diagram, FIG. 5 is a configuration diagram of an embodiment of a protective relay device according to the present invention, FIG. 6 is a configuration diagram of an embodiment of a control signal device, FIG. 7 is a time chart for explaining operation, and FIG. Figure 8 is a flowchart, No. 9
The figure is a time chart for explaining the operation, Figure 10 is a configuration diagram of an embodiment using a 1-chip microcomputer as a control signal, and Figure 11 is a 1-chip microcomputer.
A block diagram of another embodiment using a microcomputer, FIG. 12 is a flowchart, and FIG. 13 is a block diagram of another embodiment of the protective relay device according to the present invention.
4 is a flowchart, FIG. 15 is a configuration diagram of still another embodiment of the protective relay device according to the present invention, FIG. 16 is a flowchart, FIG. 17 is a time chart for explaining the operation, and FIG. FIG. 19 is a block diagram of still another embodiment of the protective relay device according to the invention. 1... Maximum value detection circuit, 2... Level detection circuit, 3
...Maximum value overcurrent relay, 4...Differential circuit, 5...Addition circuit, 6...Maximum value suppression ratio differential relay, 7...Diode, 8...Capacitor, 9...Resistor, 10, 2
2, 23... Selector switch, 11, 16, 18... Holding circuit, 12, 17, 19, 21... Comparator, 1
3, 15, 20...Switching circuit, 14...Signal controller,
18, 31, 32...OR circuit, 24...sign inverter, 25...full wave rectifier circuit.

Claims (1)

[Scope of Claims] 1. A protective relay device that sequentially selects input electrical quantities from among a plurality of input electrical quantities from a power system and detects the maximum value among them, wherein the plurality of input electrical quantities are a changeover switch that sequentially selects and outputs one quantity of electricity according to a predetermined order by sampling at a higher frequency than the changeover switch; a first holding circuit that respectively introduces the output _v1 from the changeover switch; and a comparison switch. The output v ₂ from the first holding circuit is also introduced into the comparator, and when the output v ₁ from the changeover switch is larger than the output v ₂ from the first holding circuit, the first A signal controller that controls the value of the output v ₂ of the holding circuit to be equal to the output v ₁ from the changeover switch, and a signal controller that shifts and outputs the value of the first holding circuit output v ₂ after one cycle of the commercial frequency has elapsed. A protective relay device comprising: a second holding circuit for controlling the output of the first holding circuit; and the above-mentioned signal controller for resetting the output of the first holding circuit after the transfer of the output of the first holding circuit is completed. . 2. In a protective relay device that sequentially selects input quantities of electricity from among a plurality of input quantities of electricity from a power system and detects the maximum value among them, the plurality of input quantities of electricity are detected at a frequency higher than the commercial frequency. a changeover switch that sequentially selects and outputs one quantity of electricity according to a predetermined order of sampling; a first holding circuit and a first comparator that respectively introduce the output _v1 from the changeover switch; The output v ₂ from the first holding circuit is also introduced into the first comparator and also into the second comparator, so that the output v ₁ from the changeover switch is the output v from the first holding circuit. a signal controller that controls the value of the output v ₂ of the first holding circuit to be equal to the output v ₁ from the changeover switch when the value of the output v ₂ of the first holding circuit is larger than ₂ ; The outputs v ₂ and v ₃ of the first and second holding circuits are compared in a second comparator with a second holding circuit that transfers the output value after one cycle of the frequency has elapsed. When the output v ₂ of the first holding circuit is greater than the output v ₃ of the second holding circuit, the output v ₃ of the second holding circuit
A protection joint characterized in that it is provided with the above-mentioned signal controller that transfers the same value as the output v ₂ of the first holding circuit to obtain an output value, and resets the output of the first holding circuit after the transfer. Electrical equipment. 3. A second changeover switch is provided next to the first changeover switch, and the output from the first changeover switch is introduced directly and through a sign inverter, respectively, and controlled by a signal controller. A protective relay device according to claim 2, characterized in that: 4 Claim 2, characterized in that a full-wave rectifier circuit is interposed at the next stage of the first changeover switch.
Protective relay device as described in section. 5. In a protective relay device that sequentially selects input quantities of electricity from among a plurality of input quantities of electricity in a power system and detects the maximum value from among them, the plurality of input quantities of electricity are sampled at a frequency higher than the commercial frequency. a changeover switch that sequentially selects and outputs one quantity of electricity according to a predetermined order; a first holding circuit and a first comparator that respectively introduce the output _v1 from the changeover switch; The output v ₂ from the first holding circuit is also introduced into the first comparator, and when the output v ₁ from the changeover switch is larger than the output v ₂ from the first holding circuit, the first holding circuit circuit output
A signal controller that controls the value of v ₂ to be equal to the output v ₁ from the changeover switch, compares the output v ₁ from the changeover switch and the output v ₂ from the first holding circuit, and selects the larger output. a second holding circuit in which is transferred at a constant cycle, and a second holding circuit output and a first holding circuit output v ₂ within a subsequent predetermined period.
A protective relay device comprising: a second comparator for comparing the . 6. In a protective relay device that sequentially selects the input electrical quantities from among the input electrical quantities from the power system and detects the maximum value among them, the plurality of input electrical quantities are sampled at a frequency higher than the commercial frequency. a first changeover switch that sequentially selects and outputs one quantity of electricity according to a predetermined order; and a first changeover switch that introduces the output _v1 from the first changeover switch only during an arbitrary first detection period. The output v ₂₁ from the first holding circuit is also introduced into the first comparator, and the output v ₁ from the first changeover switch is connected to the first holding circuit. Output from v ₂₁
When the output of the first holding circuit is greater than v ₂₁
a signal controller for controlling the value of to be equal to the output v ₁ from the first changeover switch, and introducing an output v ₁ from the first changeover switch in a second detection period following the first detection period. a second holding circuit and a second comparator;
An output v ₂₂ from the holding circuit is also introduced, and when the output v ₁ from the first changeover switch is larger than the output v ₂₂ from the second holding circuit, the output v ₂₂ of the second holding circuit is The signal controller described above controls the value to be equal to the output v ₁ from the first changeover switch, and the output v ₂₁ during the first detection period by alternately repeating the operation of the first and second detection periods. A protective relay device comprising a second changeover switch that derives the larger of the outputs v22 and _v22 during the second detection period. 7. In a protective relay device that sequentially selects the input electrical quantities from among the input electrical quantities from the power system and detects the maximum value among them, the plurality of input electrical quantities are sampled at a frequency higher than the commercial frequency. a first changeover switch that sequentially selects and outputs one quantity of electricity according to a predetermined order; and a first changeover switch that introduces the output _v1 from the first changeover switch only during an arbitrary first detection period. The output v ₂₁ from the first holding circuit is also introduced into the first comparator, and the output v ₁ from the first changeover switch is connected to the first holding circuit. Output from v ₂₁
When the output of the first holding circuit is greater than v ₂₁
a signal controller for controlling the value of to be equal to the output v ₁ from the first changeover switch, and introducing an output v ₁ from the first changeover switch in a second detection period following the first detection period. a second holding circuit and a second comparator;
An output v ₂₂ from the holding circuit is also introduced, and when the output v ₁ from the first changeover switch is larger than the output v ₂₂ from the second holding circuit, the output v ₂₂ of the second holding circuit is the aforementioned signal controller that controls the value to be equal to the output v ₁ from the first changeover switch; the third comparator that introduces the output from each of the first and second holding circuits; A protective relay device comprising a second changeover switch that derives the larger comparison result from the third comparator.