JPH0759248A - Digital protective relay - Google Patents

Abstract

PURPOSE:To monitor the input signal system of a protective relay having high sensitivity relay function, where the input waveform is saturated under normal state, positively. CONSTITUTION:System voltage or current is fed through a same input signal circuit to sampling circuits 11-16 and A/D converters 21-26 to produce a low sensitivity digital value and a high sensitivity digital value which are employed in the protective operation at an operating section 3. Deciding sections 61-63 make decisions whether the low sensitivity digital value is in its nonsaturated region whereas deciding sections 64-66 make decisions whether the high sensitivity digital value is in its nonsaturated region. Logical product deciding sections 67-69 make decisions that the input signal system is abnormal when both digital values are in their nonsaturated regions for same phase.

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 for performing a protection operation by using an electric quantity from a system as digital data, and more particularly to a protective relay device having a monitoring function of an input signal system.

[0002]

2. Description of the Related Art In a digital type protective relay device, in addition to performing various protective calculations from the voltage and current inputs of a sampled system, normality / abnormality of each input signal system is monitored. For example, in order to monitor the normality / abnormality of the input signal system from the three-phase zero-phase current or voltage, it is determined by the following equation whether or not the set value is exceeded.

[0003]

[Equation 1] (ch1 + ch2 + ch3) ² > K K = 2 × (3 ^1/2 LSB × SET) ² However, ch1; input R phase of monitored system ch2; input S phase of monitored system ch3; monitored system Input T-phase K; Coefficient LSB; Minimum value that can identify the input SET; Settling value This calculation is performed in R and S as shown in (a) of FIG. 2 in a no-accident state in which no zero-phase voltage occurs in the system. , T phase, the sum becomes zero, but when the zero phase occurs in the system, the sum does not become zero as shown in FIG.
When the value at this time becomes larger than the value K set by the set value SET or the like, the monitoring output of the input signal system abnormality is obtained.

[0004]

In the conventional digital protective relay device, the input is always required to be in a non-saturated state in order to monitor the input signal system by the zero-phase monitoring.

However, some relay characteristics require high-sensitivity detection.
Although the input waveform is saturated under normal load as shown in (b) of Fig. 7, if the input signal system is set so as to have an unsaturated input waveform (a in the figure) during an accident, zero-phase monitoring for this same input is performed. Since the input waveform is normally saturated,
The addition result of the three phases in the above equation does not become zero, and although the input signal system is normal, the zero-phase monitoring results in an abnormality.

The above problem is not limited to the zero-phase monitoring, but cannot be monitored even in a monitoring system called duplex mismatch monitoring when the load is saturated under normal load conditions. When these cannot be monitored, the monitoring is not performed, which may make it difficult to secure reliability against occurrence of a failure in the input signal system.

An object of the present invention is to provide a digital type protective relay device which ensures monitoring of an input signal system of a protective relay device having a highly sensitive relay function in which an input waveform is saturated in a normal state.

[0008]

In order to solve the above-mentioned problems, the present invention takes in the voltage or current of each phase of the system through an input signal system including sampling and A / D conversion, and this input signal system In a digital type protective relay device that performs a protective operation with high sensitivity and low sensitivity relay characteristics respectively from the input digital value of, the digital value obtained from the input signal system is in the non-saturation range of the low sensitivity relay. A judgment calculation unit that judges each phase, a judgment calculation unit that judges each phase that the digital value obtained from the input signal system is in the non-saturation region of the high-sensitivity relay, and a judgment calculation unit of both judgment calculation units And a logical product determination unit that determines that the input signal system is abnormal when the determination outputs are satisfied at the same time.

[0009]

The normality / abnormality of the input signal system is monitored based on whether or not the digital values obtained from the same input signal system are in the non-saturation region of the low-sensitivity relay and in the non-saturation region of the high-sensitivity relay at the same time.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a block diagram showing the essential parts of a digital protective relay device according to an embodiment of the present invention. Sampling circuit 1 ₁ to 1 ₃ for the low-sensitivity relay, phase detection signal i _R of the voltage or current from the grid of various transformer, i _S, a i _T uptake at a high rate, sequentially each at a constant sampling period To sample. A / D converter 2 ₁ to 2 ₃ converts each sampling signal of the sampling circuit ₁ 1 to 1 ₃ digital value I _R corresponding, I _S, to I _T.

[0011] Similarly, a sampling circuit 1 ₄ to 1 ₆ for high-sensitivity relay takes a low ratio through different input signal circuit from the same lineage, phase detection signal i _R ', i _S', sampling the i _T ' Then, the corresponding digital values I _R ′, I _S ′ and I _T ′ are obtained by the A / D converters 2 ₄ to 2 ₆ .

The arithmetic unit 3 uses each digital value to carry out a protective arithmetic operation having a low-sensitivity relay characteristic and a protective arithmetic operation having a high-sensitivity relay characteristic, and the arithmetic operation result is output via the output control unit 4. The CPU 5 controls the timing control of each unit and the input / output of data necessary for calculation.

Monitoring circuit 6 as input signal system monitoring means
Is, A / D inputs the phase digital value from the transducer 2 ₁ to 2 _6, determination computing unit ₆₁ - the magnitude of the non-saturated set values to different values in the low-sensitivity and high-sensitivity Equipped with 6 ₆ .

In this embodiment, the maximum input of the low-sensitivity relay is 49.5 A, and the maximum input of the high-sensitivity relay is 0.24 A. The non-saturation set value at this time is 0.4 on the low sensitivity side.
A, and if there are digital values I _R , I _S , and I _T equal to or more than this value, the determination calculation units 6 _{1 to} 6 ₃ determine that the low-sensitivity side inputs are unsaturated.

Similarly, on the high sensitivity side, the digital value I _R ',
If I _S 'and I _T ' are less than 0.2 A, the judgment calculation units 6 _{4 to} 6
₆ is judged to be unsaturated.

In each of the judgment calculation units 6 _{1 to} 6 ₆ , the judgment result of the signal of the same phase on the low sensitivity side and the high sensitivity side, for example, the R phase signals I _R and I _R ′ is the logical product judgment unit 6 ₇ It determines the presence or absence of simultaneous establishment of both the determination result by 6 _9.

The timer units 6 _{10 to} 6 ₁₂ obtain the abnormality determination output NG of the input signal system when the determination results of the logical product determination units 6 _{7 to} 6 ₉ continue for a certain time or longer.

In the present embodiment, the logical product judging sections 6 _{7 to} 6 ₉
The simultaneous establishment determination by means that both the low-sensitivity side and the high-sensitivity side have obtained unsaturated inputs, and such a state is impossible if the input signal system is normal.

Therefore, when at least one of the logical product determination sections 6 _{7 to} 6 ₉ outputs simultaneously established, it can be determined that an abnormality has occurred in the input signal system. Timer section 6 _{10-6 12,} abnormality determination by to the conditions of the monitoring output to continue a certain time, to prevent the determination of the simultaneous establishment erroneous like when an accident occurs in the system.

[0020]

As described above, according to the present invention, the voltage or current of each phase of the system is taken in via the input signal system including sampling and A / D conversion, and the input digital value of this input signal system is used for each. In a digital protection relay device that performs protection calculation with high-sensitivity and low-sensitivity relay characteristics, the digital value obtained from the same input signal system is in the non-saturation range of the low-sensitivity relay and in the non-saturation range of the high-sensitivity relay. Since the input signal system is monitored for normality / abnormality depending on whether or not there are simultaneous occurrences, even in a device equipped with a high-sensitivity relay, the non-monitoring state of the input signal system by conventional zero-phase monitoring, etc. is eliminated and protection is performed. This has the effect of improving the reliability of the relay device.

[Brief description of drawings]

FIG. 1 is a block diagram of essential parts showing an embodiment of the present invention.

FIG. 2 is a vector diagram of conventional zero-phase monitoring.

FIG. 3 is a waveform diagram of non-saturation and saturation of the input signal system.

[Explanation of symbols]

1 ₁ 1 ₆ ... Sampling circuit 2 ₁ 2 ₆ A / D converter 3 Calculation unit 4 Output control circuit 5 CPU 6 ₁ 6 ₆ Judgment calculation unit 6 ₁₀ 6 ₁₂ Timer

Claims (1)

[Claims] 1. A voltage or current of each phase of the system is taken in through an input signal system including sampling and A / D conversion, and high-sensitivity and low-sensitivity relay characteristics are respectively obtained from input digital values of this input signal system. In the digital protective relay device that performs the protection calculation by performing the protection calculation, the determination calculation unit that determines, for each phase, that the digital value obtained from the input signal system is in the non-saturation range of the low-sensitivity relay, and the digital signal obtained from the input signal system. It is determined that the input signal system is abnormal when both the judgment calculation unit that judges that the digital value is in the non-saturation range of the high-sensitivity relay and the judgment outputs of the same phase of both judgment calculation units are satisfied at the same time. And a logical product determining section for performing the digital protection relay.