JP3104531B2 - Step-out detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a step-out detecting device,
In particular, the present invention relates to a step-out detection device suitable for protecting a power system in which generators are operating in parallel.

[0002]

2. Description of the Related Art A step-out phenomenon is a loss of synchronization between generators at electric stations at both ends of an electric center due to an accident in a power system or the like.

Assuming that the step-out phenomenon is captured from a phase change between the electric stations at both ends, the two electric stations are operated at a phase angle of 60 ° to 70 ° or less in a system normal time.
At most 1 when there is no loss of synchronism even in the case of system fluctuation
The fact that 35 ° is considered to be the maximum and that 180 ° is clearly exceeded at the time of step-out makes it possible to very clearly distinguish other system disturbances from step-out (Japanese Patent Laid-Open No. 55-125022).

FIG. 2 shows a conventional step-out detecting device. 1
Is the voltage waveform at the A-end substation, 2 is the voltage waveform at the B-end substation,
3 is a B-end rectangular wave, and 4 is a pulse. The B-side rectangular wave of No. 3 is generated by using the rectangular wave generating circuit, and the pulse No. 4 is obtained by counting the number of pulses at one sampling interval (30 °) by the pulse number quantizing circuit.

For this reason, a counter type A / D conversion circuit is required, and special circuits such as a rectangular wave generation circuit and a pulse number quantization circuit are also required.

Further, the phase measurement error accompanying the use of the dedicated circuit is that the number of pulses is quantized to 4-bit data, so that 1 L
From SB = 2 °, the quantization error becomes ± 1 °, and the phase difference between both ends becomes 2 ° at the maximum.

FIG. 3 shows the phase characteristics in which the voltage VA at the A-end electrical station is a reference vector (0 °) and the voltage VB at the B-end electrical station is a determination vector. In the figure, the y characteristic, that is, the characteristic that operates when VB exists to the left of line y with respect to VA (when 90 ° ≦ phase angle ≦ 270 °) can be determined to be out of step.

Similarly, the x characteristic in FIG .
To determine if VB is below line x.
Thus, the phase exceeds 180 °, so that it can be determined that the step- out occurs.

As a means for detecting a step-out based on a combination of the x-axis and the y-axis, it has been conventionally used. For this purpose, voltage phase information is required. The present invention is a means for transmitting voltage phase information. And means to find the y-axis.

[0010]

The conventional step-out detecting device requires a dedicated circuit such as a square wave generating circuit, a pulse number quantizing circuit and a counter type A / D converter circuit for detecting a step-out. Since the circuit requires regular maintenance and inspection, it is not reliable and economical. Further, when a failure occurs in the dedicated circuit, an error occurs in step-out detection, and it becomes impossible to accurately distinguish between other system disturbance and step-out. Therefore, in order to determine this distinction very clearly,
Provided is a step-out detection method capable of improving reliability and economy by simplifying the dedicated circuit for step-out detection.

[0011]

In order to achieve the above object, the present invention detects the amount of AC electricity at one end of a specific section of a power system, and calculates the phase data of the one end from the amount of AC electricity at one end.
And detecting the amount of AC electricity at the other end of the specific section.
To obtain the phase data of the other end from the AC electricity amount of the other end.
The phase data at one end of the specific section and the phase data at the other end
Using the data, the phase of one end of the specific section and the other end
If the phase difference between the phases is equal to or greater than a predetermined phase difference, the power
In a step-out detection device that determines that a step-out has occurred in a system, an AC electric amount detection unit that detects an AC amount at one end of a specific section of the power system at each sampling interval, and a continuous AC electric amount detected at each sampling interval. to If the sign is the same two AC electric quantity outputs a constant phase data to the other end of the specific section, and between the sampling
The signs of two consecutive AC electricity quantities detected at different intervals are different
In this case, the negative value of the AC electricity amount is from V0 to the positive value of V1.
, The phase data θ1 is calculated by the equation θ1 = tan ⁻¹ (V
1 / (√3 × V1-2 × V0))
Two consecutive AC powers detected at each sampling interval
When the sign of the air volume is different, the alternating current
, The phase data θ2 is changed to a negative value V7.
Using the equation θ2 = tan ⁻¹ (V7 / (√3 × V7−2 × V6))
And phase information output means for outputting phase data.
Wherein the phase information and the phase data of the other end of said specific section
The phase data at one end of the specific section output by the output means
The phase at one end of the specific section and the position at the other end of the specific section.
If the phase difference between the phases is equal to or greater than a predetermined phase difference, the power system
It is characterized in that it is determined that a step-out has occurred .

[0012]

According to the out-of-step detection device of the present invention, the AC electric quantity at one end of the specific section of the power system is detected at each sampling interval, and the signs of two consecutive AC electric quantities detected at each sampling interval are the same. In the case of, the constant phase data is output to the other end, and when the signs of two consecutive AC electric quantities detected at each sampling interval are different, the negative value is changed to the positive value.
Changes from a positive value to a negative value.
By using a predetermined arithmetic expression for each
Since the complete phase data is calculated and the phase data calculated by a predetermined phase calculation formula is output to the other end instead of the fixed phase data, the counter type A / A is used as in the conventional step-out detection device. It is possible to detect whether a step-out state has occurred in the power system without providing a dedicated circuit such as a D conversion circuit.

[0013]

FIG. 1 shows an embodiment of a step-out detecting device according to the present invention. Graph 1 shows the voltage waveform at the A-end electrical station, and Graph 2 shows the voltage waveform at the B-end electrical station. A / D conversion is performed on the voltage sampling data from the voltage waveform 2 at the B-end electrical station at one sampling interval (30 °) for each sampling. When the previous data V ₁ and the current data V ₂ are both positive and negative, the phase information 30 ° is transmitted as the phase information θ data .

When the previous data V ₀ is negative and the current data V ₁ is positive, the phase information θ ₁ calculated by the equation (1) of the predetermined phase calculation formula is transmitted to the A-end substation .

[0015]

(Equation 1)

Since Equation 1 is 0 ° ≦ θ ₁ ≦ 30 °, it always satisfies the Taylor expansion condition. Therefore, it is approximately calculated by Taylor expansion.

If the previous data V ₆ is positive and the current data V ₇ is negative, the phase information θ ₂ calculated by the equation (2) of the predetermined phase calculation formula is transmitted to the A-end substation .

[0018]

(Equation 2)

Since Equation 2 is 0 ° ≦ θ ₂ ≦ 30 °, it always satisfies the Taylor expansion condition. Therefore, it is approximated by Taylor expansion.

In the phase measurement error of the present invention, when the angle information θ is quantized into 4-bit data, the phase difference between both ends is at most 2 °, which is the same accuracy as that of the conventional device.

[0021]

According to the present invention, there is no need for a dedicated circuit such as a square wave generating circuit for detecting a step-out or a pulse number quantizing circuit.
You.

A conventional counter type A / D conversion circuit
In a step-out detection device using a road, the timing of the counter
Therefore, it is necessary to accurately detect the point where positive → negative and negative → positive change.
However, according to the present invention, a predetermined phase
By operating along the formula, it changes from positive to negative, negative to positive.
A / D counter type
It is the same as having those circuits without using a conversion circuit.
It is possible to detect phase states equal to or more than the same.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an embodiment of a step-out detection device according to the present invention.

FIG. 2 is an explanatory view showing a conventional method of a step-out detection device.

FIG. 3 is an explanatory diagram showing phase characteristics of the out-of-step detection device of the present invention.

[Explanation of symbols]

1. Voltage waveform at A-end electrical station, 2 ... Voltage waveform at B-end electrical station, 3 ... B-end rectangular wave, 4 ... pulse.

Claims (1)

(57) [Claims] 1. An AC electric quantity at one end of a specific section of a power system is detected, and phase data of said one end is detected from the AC electric quantity at said one end.
And detecting the amount of AC electricity at the other end of the specific section.
To obtain the phase data of the other end from the AC electricity amount of the other end.
The phase data at one end of the specific section and the phase data at the other end
Using the data, the phase of one end of the specific section and the other end
If the phase difference between the phases is equal to or greater than a predetermined phase difference, the power
In a step-out detection device that determines that a step-out has occurred in a system, an AC electric amount detection unit that detects an AC amount at one end of a specific section of the power system at each sampling interval, and a continuous state that is detected at each sampling interval. When the signs of the two AC electric quantities are the same, the constant phase data is output to the other end of the specific section, and two consecutive two detected at each sampling interval.
When the sign of the AC electricity quantity is different and the AC electricity quantity is a negative value
Changes from V0 to a positive value V1, the phase data
θ1 is calculated by the equation θ1 = tan ⁻¹ (V1 / (√3 × V1-2 × V0))
, And is detected at each sampling interval.
When two consecutive AC quantities have different signs.
When the amount of flowing electricity changes from positive value V6 to negative value V7
In this case, the phase data θ2 is calculated by the equation θ2 = tan ⁻¹ (V7 / (√3 ×
V7−2 × V6)) and output the phase data.
Means for outputting phase data at the other end of the specific section and the phase information output means.
Phase data of one end of the specific section output by the stage;
Using the phase of one end of the specific section and the phase of the other end.
If the phase difference is equal to or greater than the predetermined phase difference, disconnect from the power system.
A step-out detection device for determining that a key has occurred .