JPH0898396A - Digital type protective relay device - Google Patents

Abstract

PURPOSE: To provide a protective relay device capable of impeding opposite phase wrong detection due to a fluctuation of system/frequency, by locking a virtual opposite phase in the case of detecting it by a frequency shift due to ratio of a opposite phase component, when the opposite phase component, obtained by different phase calculation from a sampling value of a system input, is at a decision level or more. CONSTITUTION: In the first opposite phase component detecting part 1, a prescribed formula is used to obtain an instantaneous value of opposite phase current, further to obtain an effective value by a 2-product method, and in the second opposite phase component detecting part 2, a formula different from this formula is used to obtain an instantaneous value of opposite phase current, further to obtain an effective value by a 2-product method. In a reverse phase abnormality decision part 3, a detection value I2 of the opposite phase component detecting part 1 is compared with a decision level ε and output when in a relation where I2 >ε. In a virtual opposite phase detecting part 4, from detecting value I2 , I2 ' of the opposite phase component detecting parts 1, 2, when a relation is I2 >K.I2 ', a virtual opposite phase due to a shift of frequency is judged, and a supervisory timer 6 outputs a opposite phase abnormal detection signal NG in the case that an output of the opposite phase abnormality decision part 3 from a logical circuit 5 is continued for a prescribed time.

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 device, and more particularly to a reverse phase monitoring function thereof.

[0002]

2. Description of the Related Art As shown in FIG. 4, a digital type protective relay device samples and holds a plurality of system inputs from PT, CT, etc. by a sample hold circuit 11, switches system input channels by a multiplexer 12, and
The digital signal is converted by the / D converter 13 and the CPU 1
Compute the protective relay at 4.

Reverse phase monitoring is performed as input monitoring of the PT and CT circuits of the protective relay device. The anti-phase current I ₂ is calculated as 3I ₂ = I _a + a ² I _b + aI _c (1) (where a is a vector operator and represents ε ^j120 °), but is 30 ° in the digital relay device. (N) is currently sampled by sampling every (n
When −1), (n−2), ... Are sampled 30 ° before, 60 ° before, etc., the anti-phase current I _{2 (n)} is obtained by the equation (2).

I _{2 (n)} = I _{a (n)} + I _{b (n-4)} + I _{c (n-8)} (2) I _{2 (n)} is taken as an instantaneous value by, for example, a 2-product method, I ₂ ²
The effective value of the negative phase current I _{2 is obtained} as _(n) + I ₂ ² _(n-3) .
However, I _{2 (n-3)} is an instantaneous value obtained during sampling three times before.

FIG. 5 shows the structure of the anti-phase monitoring section. The anti-phase component detecting section 21 obtains the instantaneous value of the anti-phase current by the above equation (2) and further detects the anti-phase current I ₂ by the two-product method. Then, the reverse-phase abnormality determination unit 22 compares the determination level ε and determines that there is a reverse-phase abnormality when I ₂ <ε, and outputs the reverse-phase abnormality detection signal NG from the monitoring timer 23 when the reverse-phase abnormality output continues for a predetermined time. It is configured to output. Since the anti-phase component detected by the two-product method in the detection unit 21 is used for determining the anti-phase current level,
Actually it is used as a reverse phase seeking to I ₂ ² values without asking to I ₂ values to simplify the arithmetic processing.

[0006]

The above-mentioned digital relay device obtains the anti-phase current I ₂ by digital operation for anti-phase monitoring, but since it is necessary to use a value prior to the current sampling, the frequency is reduced. Vulnerable to fluctuations.

[0007] The above _{(2) I b (n-} 4) of the formula (1) given a ² for determining the I _b (240 ° advances = delay 120 °) is used to 120 ° previous data, When the frequency fluctuates, an error occurs because the sampling and the sampling angle of the device differ.

I _a = Asin wt, I _b = Asin (wt
-120 °), and I _c = Asin (wt-240 °), there should be no positive phase component but negative phase component, but 30 ° sampling is intended when the frequency of the system drops by 1%. It becomes 7 ° sampling. This 30 °
_Let τ be the difference with _{Ib (n-4)} = Asin (wt-120 °-(30 ° -τ))
× 4) = Asin (nt−240 ° + 4τ), and an apparent antiphase component is generated. The error at this time is shown in FIG.

When the judgment level ε of the anti-phase monitoring is set to 20% of the rated value, an abnormality is erroneously detected when the system frequency is 47.26 Hz or lower or 52.71 Hz or higher. Many systems lock when an abnormality is detected, but if the frequency of the system drops, all the protective relay devices connected to the system will be locked.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a digital protective relay device capable of preventing erroneous reverse phase detection due to fluctuations in the system and frequency. To provide.

[0011]

In order to achieve the above object, a digital protection detection circuit according to the present invention first obtains a reverse phase component from two sampling methods using different phase operations from system input sampling values. And a second anti-phase component detection unit, and an anti-phase abnormality determination unit that outputs when the anti-phase component from the first or second anti-phase component detection unit exceeds the determination level.
The output of the apparent anti-phase detector that detects the apparent anti-phase component due to the frequency shift based on the ratio of the anti-phase components obtained by the two methods and the output of the anti-phase abnormality detector when the apparent anti-phase component is detected And a logic circuit that operates.

[0012]

Since the first and second anti-phase component detecting sections respectively detect the anti-phase components by the two methods using different phase operations, when the system frequency fluctuates, the inverse methods detected by the two methods are detected. The values of the phase components will be different. The apparent anti-phase component detection unit detects the apparent anti-phase due to the frequency shift based on the ratio of the different anti-phase components. The anti-phase abnormality determining unit compares the anti-phase component detected by the first or second anti-phase detecting unit with the determination level and outputs the anti-phase abnormality when the anti-phase component becomes large. If detected, the logic circuit locks its output. Therefore, it is possible to prevent the erroneous detection of the reverse phase abnormality due to the fluctuation of the system frequency.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described in the prior art, the reverse phase current I ₂
Is calculated by the equation (1).

3I ₂ = I _a + a ² I _b + aI _c (1) I _{2 (n)} = I _{a (n)} + I _{b (n-4)} + I _{c (n-8)} (2) I ₂ ' _(n) = _{Ia (n)} -Ib _(n) + _{Ib (n-2)} -Ic _(n-2) (3) Equations (2) and (3) are digital equations of Equation (1). This is a calculation method (see FIG. 2). When the anti-phase component is detected using the equations (2) and (3), the anti-phase component detected becomes equal when the system frequency does not change.

However, as shown in FIG. 3, the apparent negative phase currents show different values when the system frequencies are deviated.
Assuming that the anti-phase currents obtained from the equations (2) and (3) are I ₂ and I ₂ ′, respectively, the apparent anti-phase current I from FIG.
₂ is approximately I ₂ ≈2I ₂ ′.

FIG. 1 shows the configuration of the anti-phase monitoring section of the digital protective relay device, where 1 is the instantaneous value of the anti-phase current calculated using equation (2) and the effective value is calculated by the two-product method ( Detection method 1) First anti-phase component detection section, 2 obtains an instantaneous value of anti-phase current using equation (3), and further obtains an effective value by the two-product method (detection method 2) Second anti-phase component The detection unit 3 is a reversed-phase abnormality determination unit that compares the detection value I ₂ of the reversed-phase component detection unit 1 with the determination level ε and outputs when I ₂ > ε.

Reference numeral 4 denotes a detection value I ₂ ,
From I ₂ ′, I ₂ is compared with K · I ₂ ′ (coefficient K is selected to be 1.5), and when I ₂ > K · I ₂ ′, I ₂ is regarded as an apparent opposite phase due to frequency shift Apparent reverse-phase detector 5 to judge
A logic circuit for passing the output of the anti-phase abnormality judging section 3 on condition that there is no output in the apparent anti-phase detecting section, 6 outputs an anti-phase abnormality detection signal NG when the output from the logic circuit 5 continues for a predetermined time. It is a monitoring timer.

With the above configuration, when the apparent anti-phase detector 4 detects the apparent anti-phase, the anti-phase abnormality detection output from the anti-phase abnormality determiner 3 is locked by the logic circuit 5. Therefore, erroneous detection of the reverse phase abnormality based on the system frequency fluctuation is prevented. Therefore, the true reverse phase is the reverse phase detection unit 4
The reverse-phase abnormality detection signal NG is output only when it is detected by.

Even if the detection methods of the anti-phase component detecting units 1 and 2 are exchanged, the anti-phase abnormality can be similarly detected. Further, the detection of the negative phase current is not limited to the expressions (2) and (3). Further, in the embodiment, the anti-phase component detection circuit obtains the effective value I ₂ from the instantaneous value by the two-product method. However, in order to simplify the calculation, it is possible to obtain I ₂ ² and use this as the anti-phase component. Good.

[0020]

Since the present invention is configured as described above, it has the following effects.

(1) It is possible to prevent erroneous detection of abnormality due to frequency fluctuations in the system even though the apparatus is not abnormal.

(2) No special hardware is required,
It can be configured only by program processing.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a reverse phase monitoring unit according to an embodiment.

FIG. 2 is a current vector diagram illustrating a phase of a sampling value.

FIG. 3 is a diagram showing an anti-phase component based on system frequency fluctuations.

FIG. 4 is a block diagram of a digital protective relay device.

FIG. 5 is a configuration diagram of a reverse phase monitoring unit according to a conventional example.

[Explanation of symbols]

1, 2, 21 ... Anti-phase component detection section 3, 22 ... Anti-phase abnormality determination section 4 ... Apparent anti-phase detection section 5 ... Logic circuit 6, 23 ... Monitoring timer 11 ... Sample hold circuit 12 ... Multiplexer 13 ... A / D Converter 14 CPU I ₂ Reversed phase current ε Judgment level

Claims (1)

[Claims] 1. A first and second anti-phase component detection section for respectively obtaining anti-phase components by two methods using different phase operations from sampling values of system inputs, and first or second anti-phase component detection. And a reverse-phase abnormality determination unit that outputs when the reverse-phase component from the unit exceeds the determination level, and an apparent reverse-phase detection that detects the apparent reverse-phase component due to the frequency shift based on the ratio of the reverse-phase components obtained by the two methods. And a logic circuit that locks the output of the anti-phase abnormality detection unit when an apparent anti-phase component is detected, and a digital protective relay device.