JP2745621B2 - Switch control device - Google Patents

Description

The present invention relates to an SOG (Storage Overcurrent Ground) type switching control device.

(B) Conventional technology In general, an overcurrent and a ground fault current are detected by coupling to a three-phase load, and when the ground fault current exceeds a predetermined level, a current is supplied to the trip coil by the detection and the switch is turned off. There is an SOG-type switch control device in which an overcurrent is detected and a switch is turned off by supplying a current to a trip coil on condition that power is turned off.

Conventionally, this type of switch control device has a zero-phase current detector,
A ground fault is detected by a ground fault signal detector such as a zero-phase voltage detector, and the detected ground fault signal (see A in FIG. 3) is input to a filter circuit 24 including an operational amplifier, and high frequency noise is reduced. 3 (see FIG. 3B), and further, for example, a full-wave rectifier circuit 25.
(See C in FIG. 3), and the level is converted by a level conversion circuit and taken into the CPU.

(C) Problems to be Solved by the Invention In the above-described conventional switch control device, a filter circuit is passed through in order to remove high-frequency noise of the detected zero-phase signal. In such a case, the 0V potential fluctuates, and the fluctuation becomes a detection error. Therefore, there is a problem that the switch control device cannot be operated with high accuracy when the ground fault signal truly reaches the set value.

It is an object of the present invention to provide a switch control device capable of correcting an offset error and operating accurately with a set value by taking the above problem into consideration.

(D) Means and Action for Solving the Problems A switch control device according to the present invention has an electric quantity detector for detecting a zero-sequence current or a zero-sequence voltage, and receives an output of the electric quantity detector to remove a high frequency component. A filter circuit including an operational amplifier, a rectifier circuit for rectifying an output signal of the filter circuit, means for taking in an output of the rectifier circuit, and determining whether or not the output value is equal to or higher than a preset set value. Means for shutting off the switch of the bus in response to a determination output that the determination result by the determination means is equal to or greater than the set value, wherein a switch between the output of the electric quantity detector and the input of the filter circuit is provided. Is turned on during monitoring and turned off during testing.
Switching means, which is turned off during monitoring and turned on during testing to short-circuit the input side of the operational amplifier of the filter circuit, and an offset value which captures and stores the offset output level of the rectifier circuit at the time of this short-circuit A storage unit; and a correction unit that corrects the output level of the quantity of electricity output from the rectifier circuit with the offset storage value during monitoring.

In this switch control device, the first switching means is turned off during the test, and the signal from the electric quantity detector is not input to the filter circuit. Then, during this test, the second switching means is turned on, and the input side of the operational amplifier of the filter circuit is short-circuited. Therefore, the output of the rectifier circuit has an offset level where no signal is present, and this offset level is taken in and stored in the offset value storage means. At the time of monitoring, the first switching means is turned on, and a signal from the electric quantity detector is taken into the settling operation determination means via the filter circuit and the rectifier circuit. In the detection signal to be taken, the already taken offset level is corrected. Therefore, without causing offset error,
It always operates with the set value with high accuracy.

(E) Examples Hereinafter, the present invention will be described in more detail with reference to examples.

FIG. 2 is a block diagram of an SOG type switch control device in which the present invention is implemented. In FIG. 1, a zero-phase current detector (zero-phase current transformer) 2 and a zero-phase voltage detector 3 are connected to a 6600 V power supply system 1, and a zero-phase current and a zero-phase voltage are detected, respectively. It has become. The zero-sequence current detected by the zero-sequence current detector 2 is converted into a voltage signal, and the voltage is input to an input transformer 21, an over-input protection circuit 22, a test switching circuit 23, a filter circuit 24, a full-wave rectifier circuit 25, and a level conversion circuit 26. Via the CPU 4. Similarly, the zero-sequence voltage detected by the zero-sequence voltage detector 3 is converted into a voltage converter 3a, an input transformer 31, an over-input protection circuit 32, a test switching circuit 33, a filter 34, a full-wave rectifier circuit 35, and a level converter. The data is input to the CPU 4 via the circuit 36.

The over-input protection circuits 22 and 32 are circuits having a function to suppress the detected zero-phase current and the zero-phase voltage when they exceed the detected level, and the test switching circuits 23 and 33 are over-input during normal monitoring. The zero-phase current detection signal and the zero-phase voltage detection signal from the protection circuits 22 and 32 are input to the filter circuits 24 and 34, and a test signal is input to the filter circuits 24 and 34 instead of the detection signal at the time of the self test. Since the filter circuits 24 and 34 correspond to the main parts of the present invention, the details will be described later. The filter circuits 24 and 34 are provided for removing harmonic components. The full-wave rectifier circuits 25 and 35 are circuits for converting a detection signal or the like into a DC component, and the level conversion circuits 26 and 36 are circuits for converting the detection signal or the like into a signal suitable for being taken into the CPU 4. The rectified signal received by the CPU 4 via the level conversion circuits 26 and 36 is further subjected to a smoothing process. Phase pulse circuit 27,
Reference numeral 37 denotes a case where a pulse signal corresponding to the zero crossing point of the output of the filter circuits 24 and 34 is input to the CPU 4 as a phase pulse signal, and a phase difference is detected in each of the zero-phase current detection system and the zero-phase voltage detection system. Used for

The settling circuit 5 is a circuit for setting the set value of the zero-phase current I ₀ , the set value of the zero-phase voltage V ₀ , and the set time T. The DG test switch 6a is a manual switch for performing a ground fault test. SO
The test switch 6b is a manual switch for performing an overcurrent test. On the display unit 7, V ₀ level display, power indicator, and a forecast display. The output unit 8 has a DG
It has a display, an SO display by overcurrent, and a trip relay at the time of ground fault, a trip relay at the time of overcurrent, a forecast relay, an abnormal relay, and the like.

Further, the CPU 4 is provided with a test signal generation circuit 9, a test circuit, and a diagnostic circuit 10. The test signal generation circuit 9 generates, for example, a four-stage self-test current signal I ₀ and a self-test voltage signal V ₀ . The current signal I ₀ is sent to the test switching circuit 23,
The voltage signal V ₀ is input to each of the test switching circuits 33.
The test signal generation circuit 9 further inputs a short-circuit command signal to the test switching circuit 23. The test circuit / diagnosis circuit 10
Various diagnostic and test functions executed by U4, such as a constant voltage check function, a contact check function, a TC check function, and an inertial function check, are collectively shown.

In addition, the switch control device includes a filter circuit 11, a constant voltage circuit 12, and constant voltage level conversion circuits 13 and 14 as its own power supply unit. A commercial power supply voltage is applied to the terminals P ₁ and P _2, and a trip coil for shutting off the switch of the power supply system 1 is connected between the terminals V _a and V _c . TC detection circuit 15 is a circuit for detecting that the terminal V _a, the trip coil to V _c are connected.

FIG. 1 shows a test switching circuit 23 of the switch control device of the embodiment.
3 shows a specific circuit of the filter circuit 24. In the figure, a test switching circuit 23 includes switching elements Tr ₁ , Tr ₂
Made, the switching element Tr ₁ is connected between excessive input protection circuit 22 and the filter circuit 24 is turned on by a command signal TS _1. Switching element Tr ₂ is filter circuit 2
4 is provided to short-circuit the input side of the
It is turned on by S _2.

Filter circuit 24, the positive and negative power source + V, an operational amplifier AM with -V, the capacitor C _1, C _2, and a resistor R _1, R _2, R ₃ Prefecture. Operational amplifier AM - input terminal and the positive input terminal by the switching element Tr ₂ as described above, is configured to be short-circuited.

At the time of monitoring, the switching element Tr ₁ is on and the switching element Tr ₂ is off, and the detection signal from the over-input protection circuit 22 is input to the filter circuit 24 via the switching element Tr, where high-frequency noise is removed, and the operational amplifier From the output of AM, it is input to the full-wave rectifier circuit 25 of the next stage.

Switching element Tr ₁ is turned off by a command signal TS ₁ in a test, also the switching element Tr ₂ is turned on at appropriate timing. That is, the input side of the operational amplifier AM is short-circuited by the switching element Tr _2. As a result, the output of the operational amplifier AM becomes the offset level, and this level is taken into the CPU 4 via the full-wave rectifier circuit 25 and the level conversion circuit 26.
The CPU 4 stores this level, and when monitoring is performed again, when the detection signal is received, the stored offset level is subtracted from the detection signal to perform level correction. By performing the level correction in this way, even if the operational amplifier
Even if the offset level of AM fluctuates, a correct detection signal can be always taken into the CPU 4, and the switch control can be performed with high accuracy.

(F) Effects of the Invention According to the present invention, the input of the operational amplifier of the filter circuit is short-circuited by the switching means during the test, and the obtained offset level is stored, and the level of the detection signal is corrected with this offset level during monitoring. With a simple configuration,
High-precision switch control can be performed.

[Brief description of the drawings]

FIG. 1 is a circuit connection diagram showing a specific circuit of a test switching circuit and a filter circuit of an SOG type switch control device according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of the SOG type switch control device. FIG. 3 is an overall block diagram illustrating input / output waveforms of a filter circuit and a full-wave rectifier circuit. 1: Power system, 2: Zero-phase current detector, 3: Zero-phase voltage detector, 4:
CPU, 9: Test signal generation circuit, 24 ・ 34: Filter circuit, 25 ・
35: Full-wave rectifier circuit, Tr ₁ : switching element (first), Tr
₂ : Switching element (second), AM: Operational amplifier.

Claims (1)

(57) [Claims] An electric quantity detector for detecting a zero-phase current or a zero-phase voltage, a filter circuit including an operational amplifier for receiving an output of the electric quantity detector and removing a high frequency component, and an output signal of the filter circuit A rectifier circuit for rectifying the output of the rectifier circuit, means for taking in the output of the rectifier circuit, and determining whether or not the set value is equal to or more than a preset set value. And a means for shutting off the switch of the bus in response to the first signal, which is provided between the output of the electric quantity detector and the input of the filter circuit, is turned on during monitoring, and turned off during a test. Switching means; second switching means which is turned off during monitoring and turned on during testing to short-circuit the input side of the operational amplifier of the filter circuit; A switch control device comprising: an offset value storage unit that captures and stores a power level; and a correction unit that corrects an output level of an electric quantity output from the rectifier circuit with the offset storage value during monitoring.