JPH0373211B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shunt reactor protection device that detects an accident in a shunt reactor installed in a power transmission system and protects the shunt reactor by separating it from the system. The aim is to simplify and speed up accident detection.

The protection method for this type of shunt reactor is as follows:
A possible method for detecting accidents is to apply current differential relays, distance relays, etc. that have been conventionally used for line protection. However, the method using current differential relays has the disadvantage that a current transformer is also required on the ground side of the shunt reactor, and the method using distance relays requires separate relays for short circuits and ground faults. This has the disadvantage that it becomes economically expensive. Furthermore, as shown in Figure 6, in a shunt reactor, its characteristics are at point X ₀ on the R (resistance) - ₁ , every point exists such as Z ₂ , and therefore to apply conventional relays to detect faults, blind relays operate when the resistance value is greater than or equal to R ₁ , and operating when the resistance value is less than or equal to R ₂ . Blinder relay, reactance is
It is necessary to install a reactance relay that operates when the reactance is X ₁ or more, and a reactance relay that operates when the reactance is X ₂ or less, and to detect the shaded area as normal when all of these relays are inoperative, and the device configuration is complicated. There is the inconvenience of becoming

SUMMARY OF THE INVENTION An object of the present invention is to provide a shunt reactor protection device that can simplify the device configuration, speed up failure detection, and improve performance, while eliminating the above-mentioned disadvantages of the prior art.

In order to achieve the above object, the features of the present invention are as follows:
A current transformer and a voltage transformer that measure the current flowing into the shunt reactor and the terminal voltage, a converter that samples both measured values at the same time and at regular time intervals, and converts them into digital signals, and a converter that converts the measured values into digital signals. Compare the voltage value at the time of comparison with the value obtained by multiplying the current value at the time of 90 electrical degrees delayed from the time of comparison by the reactance value of the shunt reactor, or The current value is compared with the voltage value, which is 90 degrees electrically advanced from the current value, divided by the reactance value, and when a difference of more than a set value occurs between the two, it is determined that an accident has occurred and an accident signal is output. The structure includes a section and a section.

That is, in the present invention, when the shunt reactor is normal, the relationship between the terminal voltage and the current is constant, and the value obtained by multiplying the inflowing current by the impedance of the shunt reactor and the terminal voltage value match each instantaneous value. By focusing on this, we aim to realize high-speed and high-performance fault detection.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an example of a power transmission system in which a shunt reactor is installed. Electrical stations G ₁ and G ₂ are connected via a power transmission line L, and the breakers CB ₁ to CB 1 to
CB ₆ is installed, and shunt reactors Sh ₁ to _{Sh 6} are installed. Taking shunt reactor Sh ₁ as an example, the impedance of the shunt reactor is
Z ₁ , the terminal voltage of the reactor is v _z(t) , and the current flowing into the reactor is i _z(t) , as shown in Figure 2, v _z(t) = i _z(t)・Z〓= It is expressed as I _z・X・Sin(ωt+π/2)...(1). Here ω is the angular frequency and i _z(t) = Iz.
Sinωt, and since the reactance value of the shunt reactor is large compared to its resistance value, assuming that the impedance Z ₁ is only the reactance, Z〓 ₁ = jX
It is as follows.

In other words, when the shunt reactor is normal, the terminal voltage value matches the reactor current advanced by 90 electrical degrees multiplied by the reactance value X, and when the reactor fails, these two values will not match.

FIG. 3 shows a configuration that concretely realizes this failure detection. The current flowing into the shunt reactor Sh ₃ is measured by the current transformer CT, the terminal voltage is measured by the voltage transformer PT, and the current and voltage values of the measurement results are transferred to the converter A/D.
The current value and voltage value are sampled at the same time and at regular time intervals and converted into digital signals, and this conversion result is sent to the judgment section.
It is sent to the CPU to make the following decisions. If an abnormality is detected in this judgment, in the example of shunt reactor Sh ₃ , shunt breaker CB ₃ and CB ₅
disconnect the shunt reactor Sh ₃ from the system.

Abnormality determination of the shunt reactor in the determination unit CPU is performed as follows. In other words, equation (1) is an equation that holds true when there are no various errors, but in reality there are errors in each measurement value, so the judgment equation is as follows:
Equations (2) and (3) are adopted.

i _z(t+ 〓 _/2) If >0, v _z(t) +ΔV＞i _z(t+ 〓 _/2)・X＞V _z(t) −ΔV ……(2) i _z(t+ 〓 _{/ 2)} In the case of <0, v _z(t) +ΔV＞i _z(t+ 〓 _/2)・X＜V _z(t) −ΔV ...(3) Here, ΔV is determined taking into account the error. is a constant, and i _z(t+ 〓 _/2) is π/2 radians, or 90
It shows the current at a time delayed by degrees. FIG. 4 shows an example of the waveform of the signals on each side of equations (2) and (3) when the shunt reactor is normal, and FIG. 5 similarly shows an example when the shunt reactor is abnormal. In both cases, the sampling time interval is 30 electrical degrees. Time t(1) in FIG. 5 indicates the time point at which the accident occurs, and time t(2) indicates the time point at which the abnormality is detected.

By doing so, when a change in voltage or current that is greater than a set constant ΔV occurs, an abnormality can be detected quickly and with high accuracy with a time delay of less than π/2 radians.

In equations (2) and (3), we explained an example in which a constant error term ΔV is added, but if i _z(t+ 〓 _/2) > 0, v _z(t)・k ₁ > i _z(t+ 〓 _/2)・X＞V _z(t)・k ₂ ……(4) i _z(t+ 〓 _/2) If <0, v _z(t)・k ₁ ＞i _z(t+ 〓 _{/2 ) , _ _ _}
k ₁ > 1, k ₂ < 1),
Similar performance can be obtained.

In addition, in the explanation so far, we have explained the example of advancing the current, but it is clear that the same effect can be obtained by delaying the voltage. Similar effects can be obtained by other methods.

In addition, when converting current and voltage into digital signals in the converter A/D in Fig. 3, when the maximum value of voltage is V _M and the maximum value of current is I _M , V _M = I _M ·X If A/D conversion is performed with scaling such that ...(6), multiplication processing and division processing in the determination unit CPU becomes unnecessary, and the processing becomes extremely simple.

Note that the protection of static capacitors installed in power transmission systems can also be handled using the same concept as the above-mentioned protection method.

As explained above, according to the present invention, (1) abnormality detection is possible within the range of the error term ΔV, or k ₁ and k ₂ , which is set in consideration of the errors of the voltage transformer and current transformer. This makes it possible to perform high-performance anomaly detection, (2) it becomes possible to detect anomalies within π/2 radians, making it possible to detect anomalies at high speed, and (3) sampling at the same time. Voltage,
Since the configuration only requires the provision of current information and a judgment circuit, there are advantages such as the ability to reduce the cost of the device.

[Brief explanation of drawings]

Figure 1 is a power transmission system diagram in which a shunt reactor is installed, Figure 2 is a voltage and current relationship diagram of the shunt reactor, Figure 3 is a configuration diagram of shunt reactor protection according to the present invention, and Figure 4 is a diagram of the shunt reactor's voltage and current relationship. FIG. 5 is a waveform diagram of each signal when the path reactor is normal, FIG. 5 is a waveform diagram of each signal when an abnormality occurs in the shunt reactor, and FIG. 6 is an explanatory diagram of abnormality determination when a conventional relay is used. G ₁ , G ₂ ... Electrical station, L ... Transmission line, CB ₁ to _{CB 6}
...Shunt breaker, Sh ₁ to _{Sh 6} ...Shunt reactor,
PT...Voltage transformer, CT...Current transformer, A/D
...Conversion section, CPU...Judgment section.

Claims (1)

[Claims] 1 In a shunt reactor protection device that detects and protects shunt reactors installed in power transmission systems from accidents, a current transformer and a voltage transformer that measure the current flowing into the shunt reactor and terminal voltage, and both measurement sides a conversion unit that samples the signals at the same time and at regular time intervals and converts them into digital signals;
The conversion results are sequentially input and the voltage value at the comparison point is compared with the current value at a point 90 degrees later in electrical angle than this comparison point multiplied by the reactance value of the shunt reactor, or The current value is compared with the voltage value obtained by dividing the voltage value at a point 90 electrical degrees ahead of this value by the reactance value, and when a difference greater than the set value is detected between the two, it is determined that an accident has occurred and an accident occurs. A shunt reactor protection device comprising: a determination section that outputs a signal.