JPS6116756Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a static power protection relay device for the purpose of detecting a failure occurring in a component of a power system.

Due to the importance of protective relay devices intended for core systems, at least one of a constant monitoring device and an automatic inspection device is used in most cases to discover defects in the protective relay device itself.

Conventional continuous monitoring devices are primarily intended to detect defects in the transistor logic portion inside the protective relay by constantly monitoring the relay output. This is because conventional static protection relays generally consist of an auxiliary transformer for input conversion, some reactors, capacitors, resistive elements, and transistor (or IC) logic, but in most cases the failure is caused by transistor logic. This was a reasonable method as it was occurring in the area.

However, in recent years, the configuration of the input conversion section has become more complex.
As its main components began to include arithmetic circuits such as modulation/demodulation circuits for waveform transmission and filter circuits using operational amplifiers, failure detection in transistor logic by monitoring the output of the aforementioned relays became popular. However, it is no longer sufficient to detect defects in the input converter.

On the other hand, automatic inspection makes it possible to detect faults in the complicated input converter described above to a considerable extent by applying an input that simulates a system fault to the relay; however, it has disadvantages such as an increase in the scale of the equipment required for automatic inspection. It had

SUMMARY OF THE INVENTION An object of the present invention is to provide a protective relay device having a monitoring device for detecting defects in a transmitting/receiving section and an input converting section by simple means.

The present invention will be explained below with reference to the drawings. FIG. 1 shows a case in which the present invention is applied to a relay device that performs current differential protection of a two-terminal power transmission line by transmitting the waveform of one end to the other end. Note that this example representatively shows any one phase among the three phases.

In the figure, 1 is a current transformer CT that transforms the grid current _IA into a current Ia of a size suitable for inputting the protective relay device, and 2 is a current transformer CT that transforms Ia into a current of a size suitable for signal operation within the protective relay device. 3 is a transmitting device for transmitting the own end (A end) current waveform to the opposite end, 4 is a receiving device for receiving the transmitted current waveform at the opposite end, and these waveforms are Specific methods for transmission include current waveform transmission using pilot wires, pulse code modulation PCM,
Waveform transmission using frequency modulation FM is widely known. Further, 7 is a determination circuit that performs current differential determination using the current waveforms of the current end and the opposite end. Reference numerals 5, 6, and 8 are a DC component monitoring device, an AC component monitoring device, and a DC component blocking device, the functions of which will be explained in detail below, respectively.

First, the DC component monitoring device 5 will be explained. The excessive DC component is handled by the dynamic range of the operational amplifier circuit.
The direct current component monitoring device 5 is provided for the purpose of monitoring the failure of relays due to constraints on the transmission frequency bandwidth.

An embodiment of the DC component monitoring device 5 is shown in FIG. In Fig. 2, 9 and 9' are low-pass filters LPF that remove frequency components higher than the fundamental AC component and derive the DC component in Ia', and 10 and 10' are level detectors that detect the level of the DC component. It is a circuit.

The output of the LPFs 9 and 9' can be made sufficiently small at all times and in the event of a system failure. On the other hand, if a DC failure occurs in at least one of the input converter, transmitter, and receiver shown in Figure 1 (for example, it is sufficient to specify an increase in the drift of the operational amplifier).
It is detected as a defect by the above circuit.

Next, the AC component monitoring device 6 will be explained. This monitors only the alternating current component and can improve the accuracy of monitoring the alternating current component. In other words, in the case of a device that monitors both DC and AC components at once, an alarm may be issued due to the DC component error even if the error is tolerable when focusing only on the AC component, or conversely, the level at which an alarm is issued may be determined by the DC component error. Since the settings are made taking into consideration AC components, the accuracy of AC monitoring tends to decrease. The AC component monitoring device 6 described below eliminates these inconveniences and performs monitoring with less waste.

An embodiment of the AC component monitoring device 6 is shown in FIG.
In Figure 3, 11 is the sum Ia″+ of the two inputs Ia″ and Ib″
12 is a level detection circuit configured to continuously generate an output when the output of the addition circuit 11 exceeds a certain reference level; 13 is a level detection circuit configured to continuously generate an output when the output of the level detection circuit 12 exceeds a certain reference level; This is a timer circuit (on-day cycle circuit) that produces an output when the protection continues.If there is no fault in the protected system, I _A + I _B =0 holds true in FIG.
Therefore, Ia''+Ib''=0, and the AC component monitoring device 6 of FIG. 3 does not produce an output. If an accident occurs in the grid, Ia″+Ib″≠0, but after a certain period of time if the protective relay device operates normally and the accident is removed.
Ia″+Ib″ returns to a sufficiently small value. Therefore, by appropriately selecting the detection level of the level detection circuit 12 and the timer time of the timer circuit 13 shown in FIG. 3, it is possible to prevent the AC component monitoring device 6 from outputting any output at all times or in the event of a system failure.

On the other hand, the input converter 2, the transmitter 3, and
At least one of the receiving devices 4 becomes defective,
(For example, consider a defect that changes the amplification degree of the amplifier circuit.) If there is a case where Ia″+Ib″≠0 even though I _A + I _B = 0, there is a certain After the time limit has elapsed, the AC component monitoring device 6 outputs an output and the defect can be known.

Next is the DC component blocking device 8, which is a device intended to prevent the AC component monitoring device 6 and the differential determination device 7 from receiving the DC component DC drift generated in the preceding stage. Possible DC drifts that occur include, for example, drifts that occur in an operational amplifier or the like in an input conversion section that uses an operational amplifier installed in the preceding stage, or a drift over time in carrier frequency in FM waveform transmission.

A circuit for removing the influence of such drift is realized by, for example, a transformer or a coupling capacitor.

This DC component blocking circuit 8 allows for more accurate determination of the operation of the relay, which is not affected by DC drift.

The above explanation has been made using current differential protection of a two-terminal power transmission line as an example. However, the present invention is not limited to this, and the present invention is equally applicable even when the power transmission line has three terminals or when the purpose is to protect equipment. In short, the amount of electricity obtained at each terminal can be transmitted to each other, or any one
It is sufficient if the protection calculations are performed by collecting the data in one place.
FIG. 4 shows an embodiment in which the present invention is applied to a three-terminal power transmission line, and the same parts as in FIG. 1 are designated by the same reference numerals.

Note that the DC component monitoring device 5 may use a low-pass film as shown in FIG. 3, but the sum of the current of each phase or the sum of voltage of each phase is always almost zero like the zero-sequence quantity. In this case, it can also be realized by combining timer circuits as shown in FIG.

In this case, the circuit configuration can be simplified compared to FIG. 3.

In Fig. 5, 15 is the input amount (in this figure, I
₁₆ is _{a level} detector. Since the quantity of electricity I _R ′+I _S ′+I _T ′ is always very small and in the range −ko<I _R ′+I _S ′+I _T ′<ko, the level detector 16 outputs “0”.
The value of ko can be chosen to yield a constant value of . If a defect that increases DC drift occurs in the input converter and the above inequality no longer holds true, the output of the level detector 16 becomes "1".

When a zero-sequence electrical quantity is generated due to a system failure, the output of the level detector 16 becomes a waveform in which "1" and "0" are intermittent, but the timer circuit 17 sets the timer time so that it becomes "0". By selecting , only DC drift defects can be monitored.

As described above, according to the present invention, by monitoring both the DC component and the AC component, defects in the input conversion section including the transmission line and transmitting/receiving section can be detected by applying external inspection input or controlling the other end. A protective relay device that can be detected by simple means without transmitting a signal can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention applied to a two-terminal power transmission line, Fig. 2 is a block diagram showing an embodiment of a DC monitoring device, and Fig. 3 is an implementation of an AC monitoring device. FIG. 4 is a block diagram showing an embodiment of the present invention applied to a three-terminal system, and FIG. 5 is a block diagram showing another embodiment of the DC monitoring device. 2...Input conversion device, 3...Transmission device, 4...
Receiving device, 5...DC component monitoring device, 6...AC component monitoring device, 7...Differential determination device, 8...DC component blocking device.

Claims (1)

[Scope of utility model registration request] An input conversion device that converts the amount of electricity obtained from the power system into an amount of electricity suitable for the protective relay device at each terminal, and an input conversion device that is installed at the other terminal and corresponds to the amount of electricity output from the input conversion device of the other terminal. a transmitting device for transmitting the signal toward its own terminal;
A receiving device that receives a signal transmitted from this transmitting device and outputs an amount of electricity corresponding to the received signal, and inputs the output amount of electricity of the input converter installed at the own terminal, and in that input amount of electricity. a first DC component blocking circuit that blocks the DC component and outputs the AC component;
a second device that inputs the output electrical quantity of the receiving device, blocks the DC component in the input electrical quantity, and outputs the AC component;
a DC component blocking circuit; a determination device that inputs the output electrical quantities of the first and second DC component blocking circuits and responds when the plurality of input electrical quantities reach a predetermined relationship; 2. Input the amount of electricity on the input side of the DC component blocking circuit, input the amount of electricity on the output side of the DC component monitoring device that responds to the DC component in the amount of electricity, and the first and second DC component blocking circuits. , and an AC component monitoring device that responds to the AC component in the input electrical quantity.