JP2003259544A - Digital protective relay - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital protective relay capable of attaining complete non- operation in exciting inrush current and positive operation in case of a system accident. <P>SOLUTION: This digital protective relay consists of a protective element and an inrush current countermeasure element. The inrush current countermeasure element comprises a second harmonic determination computing means which outputs a second harmonic determination signal, when the rate of the second harmonic component for a first harmonic component included in AC current satisfies a prescribed condition, an overcurrent determination computing means which outputs a current determination signal when the AC voltage satisfies the prescribed condition, and an undervoltage determination computing means which outputs a voltage determination signal when the AC voltage satisfies the prescribed condition. If an accident occurs in a protective section and the second harmonic determination signal, the current determination signal, and the voltage determination signal satisfy a prescribed condition, an output permit signal is outputted to an output control part. Under the condition where the inrush current is flowing, the current determination signal and the voltage determination signal permit the output of the second harmonic determination signal so as to output an output inhibiting signal to the output control part. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital protective relay used for protecting a power system.

[0002]

2. Description of the Related Art FIG. 9 shows a conventional digital protective relay 1.
FIG. 3 is a configuration diagram of the above, and is a functional block diagram for explaining arithmetic processing executed in the central arithmetic processing unit (CPU) 2 of the digital protective relay 1. Central processing unit (CP
U) 2, the AC input current I converted to a digital value
Of the fundamental wave (1f) component I1f and the second harmonic (2
f) Perform digital arithmetic processing using the component I2f.

The central processing unit (CPU) 2 comprises a protection element section 3 and an inrush current countermeasure element section 4. The protection element unit 3 represents a basic relay element that protects the power system.
The inrush current countermeasure element unit 4 extracts the fundamental wave (1f) component I1f and the second harmonic (2f) component I2f from the AC current input I, and the amplitude value calculation units 41 and 42 respectively calculate the amplitude value | I.
A calculation process for obtaining 1f | and | I2f | is performed.

The second harmonic (2f) determination calculator 43 includes a fundamental wave (1f) and a second harmonic (2f) contained in the AC current input.
When the relationship of 1 satisfies a predetermined condition, a second harmonic determination (2f determination) process of determining that the current is an inrush current and outputting the current is performed.
The NOT calculation unit 5 performs a process of inverting the output signal of the second harmonic (2f) determination calculation unit 43. In the output control unit 6, A
In the ND calculation unit 61, the output signal of the protection element unit 3 and NOT
A process of taking a logical product with the output signal of the arithmetic unit 5 is performed.

Here, the necessity of measures against the inrush current will be described. Since the inrush current generated when the breaker of the electric power transformer is turned on or the section of the electric car in the electric car feeding circuit is rushed into the digital protective relay 1 as if it were an accident, the protection relay element It may cause malfunction (works even though it is not an accident). Therefore, it is necessary to distinguish between the inrush current and the current due to the accident, and as a means for that, it is noted that the inrush current contains many second harmonics (2f).

When the ratio of the second harmonic (2f) to the fundamental wave (1f) contained in the alternating current input is equal to or more than a predetermined value,
Second harmonic detection element (hereinafter,
2f element) is widely applied as an inrush current countermeasure element. As described above, the conventional digital protective relay having the countermeasure against the inrush current detects the second harmonic current contained in the inrush current and outputs the relay by the 2f element which outputs when the content rate satisfies the predetermined condition. The operation is prevented.

[0007]

In the above-mentioned conventional device, when the second harmonic (2f) component is contained in the fault current more than the predetermined value, even if the protection element section 3 outputs, the inrush current countermeasure element section 4 ON signal is OFF in NOT operation unit 5
There is a problem that it becomes a signal and blocks the protection command from the AND operation unit 61.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a digital protective relay that surely becomes inoperative when excited by an inrush current and operates reliably when an accident occurs. The purpose is to do.

A digital protective relay according to claim 1 of the present invention performs a protective relay operation by introducing an alternating current and a voltage, and a protective signal for protecting an object to be protected when a predetermined condition is satisfied. And an inrush current countermeasure element that generates an output blocking signal that prevents the protection command from being erroneously output to the protected object when a transformer excitation inrush current occurs, and an output permission signal when a system fault occurs. Section, and an output control section that determines whether to output a protection command to a protected object or not to output it according to an output blocking signal of the protection element signal and an inrush current countermeasure element section or an output permission signal. In the protection relay, the inrush current countermeasure element section outputs a second harmonic determination signal when the ratio of the second harmonic component to the first harmonic component contained in the alternating current satisfies a predetermined condition. A second harmonic determination calculation unit that outputs a current, an overcurrent determination calculation unit that outputs a current determination signal when the AC current satisfies a predetermined condition, and a voltage determination signal when the AC voltage satisfies a predetermined condition. When an accident occurs in a protection zone and the second harmonic determination signal, the current determination signal and the voltage determination signal satisfy predetermined conditions, the output permission signal Is output to the output control unit, and while the inrush current is flowing, the output of the second harmonic determination signal is permitted by the current determination signal and the voltage determination signal, and the output blocking signal is output. It is configured to output to the control unit.

Generally, when an inrush current occurs, the voltage value is close to the rated value. On the other hand, when a system fault occurs, a large current is generated and the voltage value drops significantly. Therefore, according to this means, in the case of a system fault, the current value increases and the voltage value decreases, so the output permission signal is output instead of the output blocking signal. Further, in the case of an inrush current, the current value increases but the voltage value is close to the rated value, so that the output blocking signal is output. As a result, even if an accident occurs in which the second harmonic component exceeds a predetermined value, the accident current and the inrush current can be discriminated.
The protection command can be reliably output to the protected object, and the reliability of the digital protective relay can be improved.

In the digital protective relay according to [Claim 2] of the present invention, in [Claim 1], the inrush current countermeasure element unit outputs an ON signal when the logical product of the current determination signal and the voltage determination signal is established. A first AND operation unit for outputting, an on-delay timer for delaying the output signal of the first AND operation unit for a first predetermined time including 0 (zero), and a NOT for inverting the output signal of the on-delay timer An arithmetic unit, a first off-delay timer that delays the second harmonic signal for a second predetermined time including 0 (zero), an output signal of the first off-delay timer, and an output of the NOT arithmetic unit. A second AND operation unit that outputs an ON signal to the output control unit when a logical product with the signal is established is provided.

According to this means, when the system fault occurs while the second harmonic signal is in the ON state, the logical product of the voltage determination signal and the current determination signal is established, and the output signal of the AND operation unit is turned ON. The signal becomes a signal, the output is turned on after a first predetermined time from the start of the on-delay timer, and this is inverted by the NOT calculation unit to be an off signal. As a result, the logical product with the second harmonic determination signal is turned off, and the output blocking signal is not output. Therefore, the state in which the protection command is not output can be avoided. When the fault current containing a large amount of the second harmonic component is removed, the second harmonic signal changes from the ON signal to the OFF signal. After that, the output of the off-delay timer is turned off after the second predetermined time. As a result, since the output blocking signal can be made non-output after the signal of the protection element section becomes non-output, it is possible to prevent the unnecessary protection command from being output to the protected object at the time of eliminating the accident, and the digital type protection is provided. The reliability of the relay can be improved.

A digital protective relay according to [Claim 3] of the present invention is for protecting an object to be protected when a predetermined condition is satisfied by introducing an alternating current and a voltage of a power system to perform a protective relay operation. Protective element part that outputs the protection signal of the power supply and the inrush that generates the output enable signal that prevents the protection command from being erroneously output to the power system when the transformer excitation inrush current occurs, and the output enable signal in the event of a system fault. A current countermeasure element section, and an output control section that determines whether to output a protection command to the protected object or not to output it by the protection element signal and the output blocking signal of the inrush current countermeasure element section, or the output permission signal. In the digital protective relay provided, the inrush current countermeasure element portion is a first protection element included in the alternating current.
A second harmonic determination calculation unit that outputs a second harmonic determination signal when the ratio of the second harmonic component to the harmonic component satisfies a predetermined condition; and a current determination when the alternating current satisfies a predetermined condition An undercurrent determination calculation unit that outputs a signal and an overvoltage determination calculation unit that outputs a voltage determination signal when the AC voltage satisfies a predetermined condition. An accident occurs in a protection zone, and the second harmonic determination is performed. When the signal, the current determination signal, and the voltage determination signal satisfy predetermined conditions, the output permission signal is output to the output control unit, and the current determination signal and the The output of the second harmonic determination signal is permitted by the voltage determination signal, and the output blocking signal is output to the output control unit.

According to this means, for the same reason as in [claim 1], even if an accident occurs in which the second harmonic component exceeds a predetermined value, the accident current and the inrush current can be discriminated. Can be reliably output to the protected object, and the reliability of the digital protective relay can be improved.

The digital protective relay according to [Claim 4] of the present invention is the first OR which outputs an ON signal when the logical sum of the current determination signal and the voltage determination signal is established in [Claim 3]. An operation unit, a second off-delay timer that delays the output signal of the first OR operation unit by a third predetermined time including 0 (zero), and the second harmonic signal.
A logical product is established between a first off-delay timer that delays a second predetermined time including 0 (zero), an output signal of the first off-delay timer, and an output signal of the off-delay timer of the OR operation unit. Is configured to include a third AND operation unit that outputs an ON signal to the output control unit.

According to this means, when the system fault occurs while the second harmonic signal is in the ON state, the output signal of the OR operation unit to be output becomes the OFF signal due to the logical sum of the voltage determination signal and the current determination signal. The output is turned off after the third predetermined time from the start of the off-delay timer. As a result, the logical product with the second harmonic determination signal is turned off, and the output blocking signal is not output. Therefore, the state in which the protection command is not output can be avoided. When the fault current containing a large amount of the second harmonic component is removed, the second harmonic signal changes from the ON signal to the OFF signal. After that, the output of the off-delay timer is turned off after the second predetermined time. As a result, the output blocking signal can be set to non-output after the signal of the protection element section is set to non-output, so that it is possible to prevent unnecessary protection commands from being output to the protected object at the time of accident interruption, and to protect the digital type. The reliability of the relay can be improved.

A digital protective relay according to [Claim 5] of the present invention is for protecting an object to be protected when a predetermined condition is satisfied by introducing an alternating current and voltage of a power system to perform a protective relay operation. Protective element section that outputs the protection signal of PT and the output blocking signal that prevents the protection command from being erroneously output to the protected object when the transformer inrush current occurs, and the output inrush signal that generates the output enable signal in the event of a system fault And a current control element section, and an output control section that determines whether to output a protection command to the power system or not to output the protection command based on the protection element signal and the output blocking signal of the inrush current protection element section or the output permission signal. In the digital protective relay according to the present invention, the inrush current countermeasure element portion is configured so that when the ratio of the second harmonic component to the first harmonic component contained in the alternating current satisfies a predetermined condition A second harmonic determination calculation unit that outputs a signal, a change width overcurrent determination calculation unit that outputs a current determination signal when the AC current increases by a predetermined value or more from the past amount, and the AC voltage is a predetermined value or less. And an undervoltage determination calculation unit that outputs a voltage determination signal when an accident occurs in a protection zone, and the second harmonic determination signal, the change width current determination signal, and the voltage determination signal have a predetermined value. When the condition is satisfied, the output permission signal is output to the output control unit, and in the state where the rush current is flowing, the change width current determination signal and the voltage determination signal are used to detect the second harmonic determination signal. The output is permitted and the output blocking signal is output to the output control unit.

According to this means, for the same reason as in [claim 1], even if an accident occurs in which the second harmonic component exceeds a predetermined value, the accident current and the inrush current can be discriminated. Can be reliably output to the protected object, and the reliability of the digital protective relay can be improved.

The digital protective relay according to [Claim 6] of the present invention is the digital protective relay according to [Claim 5], in which the inrush current element portion is provided with a signal from the change width overcurrent determination calculation portion and from the shortage calculation portion. O when the logical product of the voltage judgment signals of
A first AND operation unit for outputting an N signal and the first A
A third off-delay timer for delaying the output signal of the ND operation unit for a fourth predetermined time including 0 (zero), and the third off-delay timer.
The signal from the NOT operation unit that inverts the signal of the off-delay timer and the signal from the second harmonic determination operation unit are set to 0 (zero).
A first off-delay timer for delaying a second predetermined time, including an output signal of the first off-delay timer,
When the logical product with the output signal of the NOT operation unit is established, O
A second AND operation unit that outputs the N signal to the output control unit is provided.

According to this means, when the second harmonic signal is in the ON state, when an accident occurs, the logical product of the voltage determination signal and the current determination signal is established, so that the output signal of the AND operation unit for outputting is the ON signal. And is inverted in the NOT operation unit and becomes O
It becomes an FF signal. As a result, the logical product with the second harmonic determination signal is turned off, and the output blocking signal is not output. Therefore, the state in which the protection command is not output can be avoided. Further, when the current signal becomes the OFF signal due to the continuation of the accident, the off-delay timer is started and turned off after the fourth predetermined time, so that the output blocking signal can be continuously made non-output. Further, when the fault current containing a large amount of the second harmonic component is removed, the second harmonic determination signal changes from the ON signal to the OFF signal. After that, the output of the off-delay timer is turned off after the second predetermined time. As a result, the output blocking signal can be made non-output after the protection element signal has become non-output, so that it is possible to prevent unnecessary protection commands from being output to the protected object at the time of accident interruption, and it is possible to prevent digital output. The reliability of the protective relay can be improved.

The digital protective relay according to [Claim 7] of the present invention introduces an alternating current for each phase of each terminal of the power transformer and calculates a differential current and a suppression current for each phase. A differential element section that outputs a differential element signal by judging an internal accident of a protected object when the combined electric quantity obtained from the relationship between the differential current and the suppression current is under a predetermined condition; An inrush current countermeasure element unit that generates an output blocking signal that prevents a protection command from being erroneously output to a protected object when an exciting inrush current occurs, and an output permission signal when a system fault occurs, and the protection element signal Output blocking signal of inrush current countermeasure element,
Alternatively, in a digital protective relay including an output control unit that determines whether to output a protection command to a protected object or not to output it by an output permission signal, in the inrush current countermeasure element unit, A second harmonic determination calculation unit that outputs a second harmonic determination signal when the ratio of the second harmonic component to the first harmonic component contained in the electric power transformer satisfies a predetermined condition; When the AC voltage of the power supply terminal is introduced, the amplitude values of all the phases of the phase voltage of the AC voltage satisfy a predetermined condition, and the amplitude values of all the phases of the line voltage satisfy a predetermined condition. When an internal accident occurs and the second harmonic determination signal and the voltage determination signal satisfy predetermined conditions, the voltage determination calculation unit that outputs a voltage determination signal outputs the output permission signal to the output control unit. Inrush current is flowing as well as outputting The state was configured to output the output inhibit signal instead of the output permission signal and the second harmonic determination signal and by said voltage determining signal to the output control unit.

According to this means, the voltage of each phase is reduced at the time of an internal ground fault in the power system including the power transformer and the line voltage is reduced at the time of an internal short circuit. An output permission signal is output instead of the blocking signal. Further, at the time of rush current, all the phases of the phase voltage and the line voltage are close to the rated value, so that the output blocking signal is output. As a result, even if an internal accident occurs in which the second harmonic component exceeds the specified value, the accident current and the inrush current can be discriminated, so that the protection command can be reliably output to the protection target, and the reliability of the digital protective relay is improved. Can be improved.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a block diagram showing a first embodiment of the present invention. In FIG. 1, the same functional portions as those in FIG. In the present embodiment, when a system fault occurs, even if there is a predetermined amount of the second harmonic component in the fault current, it can be determined as a fault.

The second one added for the above purpose is the second one.
An AND operation unit 44 is provided for the output of the harmonic determination operation unit 43, and the condition at the time of a system fault is set as a blocking input via the NOT operation unit 45. That is, an amplitude value calculation unit 46 of the AC voltage V, an undervoltage (UV) determination calculation unit 47 that inputs this amplitude value, an overcurrent (OC) determination calculation unit 48 that inputs the fundamental wave component of the AC current, An AND operation unit 49 is added.

Next, the operation will be described. In FIG.
The AC input current converted into the digital amount is introduced into the inrush current countermeasure element unit 4A, and the amplitude value calculation units 41 and 42 perform the amplitude value | I1f | of the fundamental wave (1f) and the second harmonic (2
Calculate the amplitude value | I2f | of f). The second harmonic determination calculation unit 43 outputs when the ratio of the second harmonic (2f) to the fundamental wave (1f) included in the alternating current input I is equal to or more than a predetermined value.

The output of the second harmonic determination calculator 43 is introduced to the AND calculator 44. The undervoltage determination calculation unit 47 outputs when the result of the amplitude value calculation unit 46 of the AC voltage input V becomes equal to or less than a predetermined value due to a system fault. The output of the undervoltage determination calculator 47 is introduced into the AND calculator 49. The overcurrent determination calculator 48 outputs when the amplitude value | I1f | of the fundamental wave (1f) included in the alternating current input I is equal to or larger than a predetermined value.

The output of the overcurrent determination calculator 48 is introduced into the AND calculator 49. The AND operation unit 49 takes the logical product of the output of the undervoltage determination operation unit 47 and the output of the overcurrent determination operation unit 48, and outputs the result. AND operation unit 49
Is introduced into the NOT operation unit 45, the output of the AND operation unit 49 is inverted, and the result is output.

The AND operation unit 44 takes the logical product of the output of the NOT operation unit 45 and the output of the second harmonic operation unit 43 and outputs the result. The NOT operation unit 5 is an AND operation unit 44.
Inverts the output of and outputs the result. The AND operation unit 61 calculates the logical product of the protection element unit 3 and the output of the NOT operation unit 5 and outputs the result.

As described above, according to the present embodiment, when a system fault occurs, the second harmonic component contained in the fault current becomes equal to or larger than the predetermined value in the second harmonic determination calculation section 43. However, because of the output from the undervoltage determination calculation unit 47 due to the decrease in the system voltage, it can be determined that an accident,
Further, the inrush current countermeasure unit 4A does not unnecessarily block the protection signal of the protection element unit 3.

On the other hand, since the system voltage is close to the rated value at the time of the inrush current, the output from the undervoltage determination calculation unit 47 is not made, so that it can be determined as the inrush current, and the inrush current countermeasure unit 4A protects the protection element unit 3 Block the signal. Therefore, even when the fault current includes a large amount of the second harmonic current, the inrush current countermeasure unit 4A does not output the output blocking signal of the protection command, and the reliability of the digital protective relay is improved. be able to.

(Second Embodiment) FIG. 2 shows a second embodiment of the present invention.
It is a block diagram which shows the embodiment of FIG. In FIG. 2, FIG.
The same functional parts as in FIG. In FIG. 2, the inrush current countermeasure element portion 4A-1 is
The output of the second harmonic determination calculation unit 43 is introduced into the off-delay timer 491, and the output of the AND calculation unit 49 is introduced into the on-delay timer 492 corresponding to the inrush current countermeasure element unit in the first embodiment described above. And the output of the off-delay timer 491 to the AND operation unit 44,
The output of the on-delay timer 492 is introduced into the NOT operation unit 45. In the present embodiment, the output from the inrush current countermeasure element portion is output via the time adjustment circuit, so that the operation of the output becomes reliable.

FIG. 3 shows the response of each judgment unit when an inrush current flows. When an inrush current flows, such as when a circuit breaker is turned on in the power system, when the content rate of the second harmonic (2f) current contained in the inrush current satisfies a predetermined condition, the second harmonic determination calculation unit 43 is output, and the off-delay timer 491 is also turned on. At this time, although the overcurrent determination calculation unit 48 outputs, the undervoltage determination calculation unit 4 outputs.
Since 7 returns, the AND operation unit 49 becomes an OFF signal, and the on-delay timer 492 also outputs an OFF signal,
It is inverted by the NOT operation unit 45 and introduced into the AND operation unit 44.

The AND operation unit 44 is the second harmonic determination operation unit 4.
Since the output of 3 and the output of the NOT calculation unit 45 are in the ON state, an ON signal is output, inverted by the NOT calculation unit 5, and introduced into the AND calculation unit 61. Therefore, when an inrush current flows, the output from the NOT calculation unit 5 is in the OFF state regardless of the output of the protection element unit 3, so the protection command is OF
It becomes the F state.

When an accident occurs while a rush current is flowing, in the prior art, an output blocking signal is output and the protection command is suppressed, but in the first embodiment of the present invention,
The overcurrent determination calculation unit 48 and the undervoltage determination calculation unit 47 are
Becomes an N signal, and the AND operation unit 49 outputs an ON signal,
The on-delay timer 492 outputs after the first predetermined time T1. The output of the on-delay timer 492 is inverted by the NOT operation unit 45 and introduced into the AND operation unit 44.

The AND operation unit 44 is the second harmonic determination operation unit 4.
Even though the output of 3 is in the ON state, the output of the NOT calculation unit 45 is in the OFF state, so an OFF signal is output and NOT
It is inverted by the operation unit 5 and introduced into the AND operation unit 61. The AND operation unit 61 receives the ON signal of the protection element unit 3 and NO.
The ON signal of the T operation unit 5 outputs the ON signal as a protection command.

Therefore, when an accident occurs while the inrush current is flowing, the digital protection relay 1A operates normally by setting the output blocking signal as non-output. As described above, according to this configuration, it is possible to obtain the same effect as that of the first embodiment.

(Third Embodiment) FIG. 4 is a block diagram showing a third embodiment. In FIG. 4, parts having the same functions as those in FIG. The difference between FIG. 4 and FIG. 1 is that instead of the undervoltage determination calculation unit 47 in FIG. 1 described above, an overvoltage determination calculation unit 493.
In place of the overcurrent determination calculation unit 48, an undercurrent determination calculation unit 494, and in place of the AND calculation unit 49, an OR calculation unit 4
910 is applied to each of them. Also in this embodiment, the same effect as in the first embodiment can be obtained.

(Fourth Embodiment) FIG. 5 is a block diagram showing a fourth embodiment. In FIG. 5, the same functional portions as those in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted. The difference between FIG. 5 and FIG. 4 is that the output of the second harmonic determination calculation unit 43 and the output of the OR calculation unit 4910 are input to the AND calculation unit 44 via the off-delay timers 491 and 451. Is. Others are the same as in FIG. In the present embodiment, the output from the inrush current countermeasure element portion is output via the time adjusting means, so that the operation by the output becomes reliable.

(Fifth Embodiment) FIG. 6 is a block diagram showing the fifth embodiment. In FIG. 6, the same reference numerals are given to the same functional portions as those in FIG. 1, and the description thereof will be omitted. The difference between FIG. 6 and FIG. 1 is that the overcurrent determination calculator 48 of FIG.
Instead of this, a change width overcurrent determination calculation unit 462 is provided. Also in the present embodiment, the same effect as in FIG. 1 can be obtained.

(Sixth Embodiment) FIG. 7 is a block diagram showing a sixth embodiment. In FIG. 7, the same functional portions as those in FIG. 6 are designated by the same reference numerals and the description thereof will be omitted. The difference between FIG. 7 and FIG. 6 is that the second harmonic determination calculation unit 4 in FIG.
The output of 3 and the output of the AND operation unit 49 are input to the AND operation unit 44 via the off-delay timers 491 and 471. Others are the same as in FIG. Further, in the present embodiment, since the output from the inrush current countermeasure element portion is output via the time adjusting means,
The operation by the output becomes reliable.

(Seventh Embodiment) FIG. 8 is a block diagram showing a seventh embodiment. In the present embodiment, when a ground fault or a short circuit occurs, even if there is an output from the second harmonic determination calculation section 43, the protection signal is not unnecessarily blocked. .

In FIG. 8, the differential element section 7 is constructed by a known technique. The second harmonic determination calculation unit 43 calculates the first harmonic amplitude value | Id1f | included in the differential current Id,
It is output when the ratio of the second harmonic amplitude value | Id2f | included in the differential current Id satisfies a predetermined condition.

On the other hand, the non-power supply terminal voltage V of the power transformer which has been converted into a digital quantity is introduced into the inrush current countermeasure element section 4D, and the voltage amplitude value calculation section 81 causes the amplitudes of all the phases of the line voltage to be changed. The voltage amplitude value calculation unit 82 calculates the amplitude values of all the phases of the phase voltage, and outputs the calculated values to the overvoltage determination calculation unit 84.

The overvoltage determination calculation unit 84 outputs when there is no fault in the system including the transformer and the amplitude values of the line voltage and the phase voltage are respectively above a predetermined value. Among the outputs of the overvoltage determination calculation unit 84, the determination result of the line voltage is introduced to the AND calculation unit 85, and the determination result of the phase voltage is calculated by the AND calculation unit 86.
Will be introduced to. The AND operation section 49 outputs the result of the logical product of the AND operation section 85 and the AND operation section 86.

The AND operation unit 44 calculates the logical product of the output of the AND operation unit 49 and the output of the second harmonic determination operation unit 43,
This result is output to the NOT operation unit 5, and the NOT operation unit 5 inverts the result of the AND operation unit 44 and outputs it to the AND operation unit 61. The AND operation unit 61 calculates the logical product of the output of the NOT operation unit 5 and the output of the differential element unit 7 and outputs the result as a protection command.

According to the above configuration, an internal fault occurs in the power system including the power transformer, and the second harmonic component contained in the fault current is equal to or more than the predetermined value in the second harmonic determination calculation section 43. Even if a ground fault occurs, each phase voltage decreases, and a short-circuit accident causes the line voltage to decrease, and one or more outputs from the overvoltage determination unit 84 are not output, so it can be determined that an accident has occurred. The section 4D does not unnecessarily block the protection signal of the differential element section 7.

On the other hand, at the time of inrush current, the amplitude value of the line voltage and the phase voltage is close to the rated value.
4 is output, it can be determined that it is an inrush current, and the inrush current countermeasure unit 4D blocks the protection signal of the differential element unit 7. Therefore, even when the second harmonic current is included in the fault current in a large amount, the inrush current countermeasure element 4D does not output the output blocking signal of the protection command, thus improving the reliability of the digital protective relay. can do.

Although the seventh embodiment has been described with respect to the overvoltage detecting element, the overvoltage determining section 84 is replaced by an undervoltage determination, and the AND operation sections 85, 86, 49 are replaced by OR.
The same effect can be obtained as the arithmetic unit.

[0049]

As described above, according to the present invention, an output blocking signal is output to the output control section when an inrush current occurs,
It is possible to prevent unnecessary protection commands from being output,
At the time of accident, even if the second harmonic (2f) component is included in the accident current more than a predetermined value, the output permission signal is output to the output controller instead of the output blocking signal, and the protection command is surely sent to the protected object. Since it can output, a highly reliable digital protective relay can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a digital protective relay according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a digital protective relay showing a second embodiment of the present invention.

FIG. 3 is an operation diagram of FIG. 1 when an inrush current occurs and an accident occurs.

FIG. 4 is a configuration diagram of a digital protective relay showing a third embodiment of the present invention.

FIG. 5 is a configuration diagram of a digital protective relay according to a fourth embodiment of the present invention.

FIG. 6 is a configuration diagram of a digital protective relay according to a fifth embodiment of the present invention.

FIG. 7 is a configuration diagram of a digital protective relay according to a sixth embodiment of the present invention.

FIG. 8 is a configuration diagram of a digital protective relay showing a seventh embodiment of the present invention.

FIG. 9 is a configuration diagram showing a conventional digital protective relay.

[Explanation of symbols]

1, 1A to 1D Digital protective relay 2 Central processing unit (CPU) 3 Protection element sections 4A to 4C, 4A-1 to 4D-1 Inrush current countermeasure element section 41 AC current fundamental wave (1f) amplitude value calculation section 42 AC current 2nd harmonic (2f) amplitude value calculation section 43 2nd harmonic (2f) determination calculation section 45, 5 NOT calculation section 46 AC voltage amplitude value calculation section 47 Undervoltage (UV) determination calculation section 48 Overcurrent ( OC) determination calculation unit 49, 44, 61, 85, 86 AND calculation unit 492 on-delay timer 491, 451, 471 off-delay timer 493, 84 overvoltage (OV) determination calculation unit 494 undercurrent (UC) determination calculation unit 4910 OR Calculation unit 462 Change width overcurrent (ΔI +) determination calculation unit 6 Output control unit 7 Differential element unit 71 Differential current calculation unit 72 Suppressed current calculation unit 73 Differential determination calculation unit 74 Difference current basic (1f) extraction unit 81 line voltage amplitude value calculating unit 82-phase voltage amplitude value calculating unit 83 the difference between the current second harmonic (2f) extractor

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tetsuya Sobue             1-24 East of 2-24 Harumi-cho, Fuchu-shi, Tokyo             Shiba System Technology Co., Ltd. F-term (reference) 5G043 AA01 AA05 AC02 BA07 BA12                       BB01 BC01 CB01 CC01 CC04

Claims (7)

[Claims] 1. A protection element section for introducing a protection system operation by introducing an alternating current and a voltage of a power system, and outputting a protection signal for protecting an object to be protected when a predetermined condition is satisfied, and a transformer excitation. An inrush current countermeasure element unit that generates an output blocking signal that prevents the protection command from being erroneously output to the protected object when an inrush current occurs, and an output permission signal when a system fault occurs, and the protection element signal and the inrush current countermeasure In a digital protective relay having an output control section for judging whether to output a protection command to a protected object or not to output it by an output blocking signal or an output permission signal of the element section, the inrush current countermeasure element section is provided. Is the first contained in the alternating current
A second harmonic determination calculation unit that outputs a second harmonic determination signal when the ratio of the second harmonic component to the harmonic component satisfies a predetermined condition; and a current determination when the alternating current satisfies a predetermined condition An overcurrent determination calculation unit that outputs a signal and an undervoltage determination calculation unit that outputs a voltage determination signal when the AC voltage satisfies a predetermined condition. An accident occurs in a protection section, and the second harmonic When the determination signal, the current determination signal, and the voltage determination signal satisfy a predetermined condition, the output determination signal is output to the output control unit, and when the inrush current is flowing, the current determination signal is A digital protective relay, wherein output of the second harmonic determination signal is permitted by the voltage determination signal, and the output blocking signal is output to the output control unit. 2. The digital protective relay according to claim 1, wherein the inrush current countermeasure element section outputs a ON signal when a logical product of the current determination signal and the voltage determination signal is established, and An on-delay timer that delays the output signal of the first AND operation unit by a first predetermined time including 0 (zero), a NOT operation unit that inverts the output signal of the on-delay timer, and the second harmonic signal. 0
A first off-delay timer that delays the return by a second predetermined time including (zero), an output signal of the first off-delay timer, and an output signal of the NOT calculation unit are logically ANDed to turn on the ON signal. Second AN output to output control unit
A digital protective relay having a D operation section. 3. A protection element section for introducing a protection system operation by introducing an alternating current and a voltage of a power system, and outputting a protection signal for protecting an object to be protected when a predetermined condition is satisfied, and a transformer excitation. An inrush current countermeasure element unit that generates an output blocking signal that prevents a protection command from being erroneously output to the power system when an inrush current occurs, and an output permission signal when a system fault occurs, and the protection element signal and the inrush current countermeasure element In a digital protective relay having an output control unit that determines whether to output a protection command to a protected object or not to output it by an output blocking signal or an output permission signal of the unit, the inrush current countermeasure element unit is , The first contained in the alternating current
A second harmonic determination calculation unit that outputs a second harmonic determination signal when the ratio of the second harmonic component to the harmonic component satisfies a predetermined condition; and a current determination when the alternating current satisfies a predetermined condition An undercurrent determination calculation unit that outputs a signal and an overvoltage determination calculation unit that outputs a voltage determination signal when the AC voltage satisfies a predetermined condition. An accident occurs in a protection zone, and the second harmonic determination is performed. When the signal, the current determination signal, and the voltage determination signal satisfy predetermined conditions, the output permission signal is output to the output control unit, and the current determination signal and the A digital protective relay, wherein output of the second harmonic determination signal is permitted by a voltage determination signal, and the output blocking signal is output to the output control unit. 4. The digital protective relay according to claim 3, wherein the inrush current countermeasure element unit outputs a ON signal when a logical sum of the current determination signal and the voltage determination signal is established, A second delay for delaying the output signal of the first OR operation unit by a third predetermined time including 0 (zero)
Off-delay timer, a first off-delay timer that delays the second harmonic signal by a second predetermined time including 0 (zero), an output signal of the first off-delay timer, and the OR operation. And a third AND operation unit for outputting an ON signal to the output control unit when a logical product with the output signal of the off-delay timer of the unit is established. 5. A protection element section for introducing a protection system operation by introducing an alternating current and a voltage of a power system, and outputting a protection signal for protecting an object to be protected when a predetermined condition is satisfied, and a transformer excitation. An inrush current countermeasure element unit that generates an output blocking signal that prevents the protection command from being erroneously output to the protected object when an inrush current occurs, and an output permission signal when a system fault occurs, and the protection element signal and the inrush current countermeasure In a digital protective relay having an output control section for judging whether to output a protection command to a protected object or not to output it by an output blocking signal or an output permission signal of the element section, the inrush current countermeasure element section is provided. Is the first contained in the alternating current
A second harmonic determination calculation unit that outputs a second harmonic determination signal when the ratio of the second harmonic component to the harmonic component satisfies a predetermined condition, and the difference between the present amount and the past amount of the alternating current. A change width overcurrent determination calculation unit that outputs a current determination signal when the quantity satisfies a predetermined condition, and an undervoltage determination calculation unit that outputs a voltage determination signal when the AC voltage satisfies a predetermined condition, When an accident occurs in the protection section and the second harmonic determination signal, the change width current determination signal, and the voltage determination signal satisfy predetermined conditions, the output permission signal is output to the output control unit. When the inrush current is flowing, the output of the second harmonic determination signal is permitted by the change width current determination signal and the voltage determination signal, and the output blocking signal is output to the output control unit. Characteristic digital type Mamoru relay. 6. The digital protective relay according to claim 5, wherein the inrush current countermeasure element portion is turned on when a logical product of a signal from the change width overcurrent determination calculation portion and a signal from the undervoltage determination calculation portion is established. First AND that outputs a signal
An arithmetic unit, a third off-delay timer that delays the output signal of the first AND arithmetic unit by a fourth predetermined time including 0, and a NOT arithmetic unit that inverts the signal of the third off-delay timer. A first off-delay timer that delays the signal from the second harmonic determination calculation section by a second predetermined time including 0, an output signal of the first off-delay timer, and an output of the NOT calculation section A second AND which outputs an ON signal to the output control unit when a logical product with the signal is established.
A digital protective relay characterized by comprising a computing section. 7. An alternating current for each phase of each terminal of the power transformer is introduced, a differential current and a suppression current for each phase are calculated, and obtained from a relationship between the differential current and the suppression current. When the combined electricity quantity is a predetermined condition, it is judged as an internal accident of the object to be protected, the differential element part that outputs the differential element signal and the protection command to the object to be protected when the transformer inrush current occurs. An inrush current countermeasure element portion that generates an output inhibition signal that prevents erroneous output and an output permission signal when a system fault occurs, and the protection element signal and the output inhibition signal of the inrush current countermeasure element portion,
Alternatively, in a digital protective relay including an output control unit that determines whether to output a protection command to a protected object or not to output it by an output permission signal, in the inrush current countermeasure element unit, A second harmonic determination calculation unit that outputs a second harmonic determination signal when the ratio of the second harmonic component to the first harmonic component contained in the electric power transformer satisfies a predetermined condition; When the AC voltage of the power supply terminal is introduced, the amplitude values of all the phases of the phase voltage of the AC voltage satisfy a predetermined condition, and the amplitude values of all the phases of the line voltage satisfy a predetermined condition. When an internal accident occurs and the second harmonic determination signal and the voltage determination signal satisfy predetermined conditions, the voltage determination calculation unit that outputs a voltage determination signal outputs the output permission signal to the output control unit. Inrush current is flowing as well as outputting The state, the digital protective relay and outputting the output inhibition signal instead of the output permission signal and the second harmonic determination signal and by said voltage determining signal to the output control unit.