JPH0729700Y2 - Directional short circuit relay - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Application This invention is for protection in a power line linking system that shares a power system supplied from a power company and a private power generation system supplied by a customer by private power generation. Directional short circuit relay used in.

(B) Conventional technology In recent years, a CGS that drives a generator from a prime mover such as a gas engine or gas turbine to supply electric power to a premises load, and uses exhaust heat of the prime mover for heating, hot water supply, or cooling
(Co-Generation System) is spreading. This CGS
The power generation capacity of does not cover the total power consumption of consumers, but is used together with the amount of power supplied from the power company, and the power lines of the power grid and the private power grid are linked. In this power supply system, power supply reliability, power quality,
To ensure the safety of the public and workers and the maintenance of electrical equipment, not only operate the circuit breaker at the receiving end in the customer premises accident (short circuit / power failure), but also detect it in the power system and power failure to generate electricity. It is necessary to disconnect the machine from the grid. Applicant is developing a protection system to perform these functions. The directional short circuit relay is one of the devices adopted in this protection system.

The directional short-circuit relay detects the voltage of the power supply line and outputs an output when the detected voltage is below the set value, and the current of the power supply line, and the detected current is above the set value. An overcurrent detection unit that outputs an output, a phase determination unit that outputs an output when the direction of the current flowing through the power supply line is a predetermined direction by phase determination of the detection voltage and the detection current, and In response to the logical product output of each output of the current detection unit, the undervoltage detection unit and the phase determination unit,
It consists of an output circuit that drives a relay that disconnects the circuit breaker of the power supply line.For example, if a short-circuit accident occurs on the power system side, from the generator side to the power system,
Since an overcurrent flows and the voltage drops, in this direction short-circuit relay, the undervoltage detection unit detects that the voltage has dropped, and the overcurrent detection unit detects that a short-circuit current has flowed,
Furthermore, the phase determination unit determines that the current is from the generator to the power system, and if these logical product conditions are satisfied, the occurrence of a short circuit accident in the power system is known, and the output circuit is activated to turn on the relay. , Turn off the circuit breaker to stop the power supply from the generator to the power grid.

(C) Issues to be solved by the invention The distance between electric power companies and consumers varies. Therefore, the place where the short circuit accident occurs in the power system may sometimes be a short distance from the power receiving end or a long distance from the power receiving end. When the location of the accident is a short distance, an excessive current flows and the voltage drops relatively large, so that the directional short-circuit relay that operates under the conditions of the excessive current, the undervoltage and the phase can also operate. However, when the location of the accident is a long distance, the voltage does not drop so much, so the above three conditions may not be satisfied and the operation may not be performed. That is, in the direction short-circuit relay, it may not be possible to detect the occurrence of a long-distance short-circuit, and it may not be possible to protect it. When the switch is turned off and the backflow is requested to be prevented, there is a problem that the request cannot be met.

Therefore, it is possible to use the detected voltage only for phase discrimination without installing the undervoltage detector, and to operate only by overcurrent detection and phase discrimination, but the undervoltage detection was added to the condition most. Some of the power supplies of customers have phase-advancing capacitors for power factor improvement,
If the load is lightened with such a power source, the current will be on the leading side, and the phase relationship will be the same as if the current were flowing from the generator side to the power system, and the relay may operate. In this case, if the undervoltage detection is used as a condition, the voltage rather rises when the load becomes lighter, and malfunctions can be avoided. Therefore, it is generally desirable to set the undervoltage detection as an operating condition.

The present invention has been made in view of the above problems, and an object thereof is to provide a directional short-circuit relay capable of selecting whether or not to include undervoltage detection in the operating conditions according to the situation.

(D) Means and Actions for Solving the Problem The directional short-circuit relay of the present invention detects the voltage of the power supply line and outputs an output when the detected voltage is less than or equal to a set value, and an electric power supply. By detecting the current of the line, the overcurrent detection unit that outputs when the detected current is equal to or more than the set value, and the phase discrimination between the detected voltage and the detected current,
In response to a logical product output, a phase determination unit that outputs an output when the direction of the current flowing through the power supply line is in a predetermined direction, and each output of the overcurrent detection unit, the undervoltage detection unit, and the phase determination unit, An output circuit that drives a relay that disconnects the circuit breaker of the power supply line.The undervoltage detection unit forcibly outputs a signal indicating undervoltage detection depending on whether or not there is a setting, or the output of the undervoltage detection unit. Is characteristically provided with an undervoltage detection function exclusion setting means for selecting whether or not to correspond to the detection state.

In this directional short circuit relay, if the undervoltage detection function exclusion setting means does not exclude the undervoltage detection function, the overcurrent detection unit detects overcurrent, the undervoltage detection unit detects undervoltage, and the phase When the discriminator detects a current from the generator side to the power system side, the output circuit operates on the condition of the logical product of these and turns on the relay to disconnect the breaker.
On the other hand, when the undervoltage detection function exclusion is set, the output of the undervoltage detection unit is forcibly set to the output state indicating the undervoltage regardless of the magnitude of the voltage. Therefore, the output circuit operates under the conditions of the overcurrent detection and the reverse current detection by the phase determination circuit, and the relay is turned on to disconnect the breaker.

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

FIG. 1 is a circuit block diagram of a directional shorting relay showing an embodiment of the present invention. This directional short-circuit relay 1 consists of a three-phase power supply line 2, a power transformer PT and a current transformer CT.
A voltage component and a current component of three phases are taken in via the, and the undervoltage detection unit, the overcurrent detection circuit unit, and the phase determination circuit are individually provided for each phase.

The R-phase undervoltage detection unit 4 _R sets the input transformer 11 _R , the over-input protection circuit 12 _R , the voltage amplification circuit 13 _R , the delay circuit 14 _R , the absolute value amplification circuit 15 _R , the inoperative voltage, and the settling non-setting. Inoperative voltage settling circuit 16 _R , which outputs a logical "0" when the operating voltage is higher than the operating voltage, and outputs a logical "1" when the operating voltage is lower than the settling inoperative voltage
It is composed of a waveform shaping circuit 17 _R.

The R-phase overcurrent detection unit 5 _R includes an input transformer 21 _R , an overinput protection circuit 22 _R , and an operation current settling circuit 2 that outputs a status signal of logic “1” when the detected current is equal to or more than the settling operation current.
3 _R , current amplification circuit 24 _R , waveform shaping circuit 25 _R , absolute value amplification circuit 26 _R, and waveform shaping circuit 27 _R.

An output of the waveform shaping circuit 27 _R undervoltage detector 4 _R, the output of the waveform shaping circuit 27 _R of the overcurrent detection unit 5 _R is inputted to the AND circuit 31 _R.

Further, from the delay circuit 14 _R undervoltage detector 4 _R, it derives a voltage component derives current component from the waveform shaping circuit 25 _R of the overcurrent detection unit 5 _R, to determine the current of the phase with respect to voltage division The phase discrimination circuit 32 _R is provided. In the power supply line 2, if the current flows in the electric power system side from the generator side, in response to the phase determination circuit 32 _R determination result, from the generator side of the phase discriminating circuit 32 _R to the power mains It outputs a signal of logic "1" indicating that it is a current. The output of the AND circuit 31 _{R and} the output of the phase determination circuit 32 _R are input to the AND circuit 33 _R. Therefore, these AND circuits 31 _R and 33 _R take a logical product of the three conditions of undervoltage detection, overcurrent detection, and reverse current to check the coincidence. Although the description is omitted, the circuit configurations for the other S and T phases are similar.

The output of the AND circuit 33 _R goes through the OR circuit 35 to set the operating time.
It has been entered in 36. The outputs of the AND circuits 33 _S and 33 _T (not shown) of the other phases are similarly input to the OR circuit 35. The operation time settling circuit 36 is a circuit which, when a signal matching the above three conditions is input from the OR circuit 35, outputs the signal after the settling time. An output circuit that receives an operation signal from the operation time settling circuit 36 after the operation time settling circuit 36.
37, an output relay 38 driven by the output circuit 37 and an operation indicator lamp 39.

The directional short-circuit relay 1 also includes a noise removing circuit 5 for removing noise of the battery voltage input from the battery 3.
1. A constant voltage circuit 52 for converting the battery voltage into a constant voltage and supplying it to each circuit is provided.

Although not shown, the contact connection terminals _Xa , _Xb , _Xc of the output relay 38 are connected to a trip coil driven by a battery. An alarm device is connected to the contact connection terminals a, a. The terminals M ₁ and M ₂ are function exclusion terminals of the undervoltage detectors 4 _R , 4 _S and 4 _T , and when these terminals M ₁ and M ₂ are short-circuited with a push button switch or a lead wire, the voltage amplification circuit
13 _R , 13 _S , 13 _T are internally short-circuited, waveform shaping circuit 17 _R , 1
7 _S, a signal indicating an undervoltage detection from 17 _T is forcibly output. That is, the function of the undervoltage detection unit is excluded by the short circuit of the terminals M ₁ and M ₂ , and is ignored from the operating condition.

In the above-mentioned directional short-circuit relay 1, when normal power is supplied to the power supply line 2, the taken-in voltage is not less than the settling non-operation voltage and the current is not more than the settling operation current. Therefore, any output of the waveform shaping circuit 27 _R undervoltage detector 4 _R of the waveform shaping circuit 17 _R and the overcurrent detection unit 5 _R is logic "0", therefore, the AND circuit 31 _R, 33 _R output Also becomes a logical "0". That is, the operation signal is not output.
Therefore, the output circuit 37 does not operate, the operation indicator lamp 39 does not light, and the output relay 38 does not turn on. In this case, since the relay contact 38a remains the normally closed contact _Xb , no current flows in the trip coil.

When a short circuit accident occurs on the power system side of the power supply line 2,
Short-circuit current flows from the generator side to the short-circuit accident point,
The voltage also drops. Therefore, the undervoltage detection unit 4 _R detects a voltage equal to or higher than the settling inoperative voltage, and outputs a logic “1” from the waveform shaping circuit 17 _R. Further, the overcurrent detection unit 5 _R detects an overcurrent equal to or more than the settling operation current.
Outputs logical "1" from _R. Further, the phase determination circuit 32 _R that compares the phase of the voltage component from the delay circuit 14 _R and the phase of the current component from the waveform shaping circuit 25 _R outputs a logic “1” because it is a current for the power system from the generator side. . Therefore, the three conditions of undervoltage detection, overcurrent detection, and direction determination match, and the AND circuits 31 _R and 33 _R output logic “1”. That is, the operation signal is output. In this case, this operation signal is input to the output circuit 37 via the operation time settling circuit 36, and the output circuit 37 operates to turn on the output relay 38 and turn on the operation indicator lamp 39. ON the output relay 39, the relay contact 38a is put into the normally open contact X _a, current flows through the trip coil, thereby interrupt the breaker of the power supply line 2. Further, since the normally open contact of the relay contact 38b is also turned on, the alarm device also operates.

Even if the power is supplied from a far distance from the power receiving end, and even if a short circuit accident occurs at a long distance, if it is necessary to monitor the occurrence of the above accident with this directional short circuit relay,
Short-circuit terminals M ₁ and M ₂ . Due to this short circuit, the voltage amplification circuits 13 _R , 13 _S , 13 of the undervoltage detectors 4 _R , 4 _S , 4 _T
T is forced so that the detected output voltage becomes 0 regardless of the input, and therefore the waveform shaping circuit 17 _R , 1
7 is _S, 17 _T, is always a logic "1". In this state, if a short-circuit accident occurs at a point far from the power receiving end and overcurrent flows from the generator side to the power system side, but the voltage does not drop too much, the undervoltage detectors 4 _R , 4 _S , 4 _{Even if the} voltage input to _T is higher than the settling inoperative voltage, the waveform shaping circuit 17
_Since the output of _R , 17 _S , and 17 _T is forced to “1”, the waveform shaping circuit of the overcurrent detector 5 _R , 5 _S , and 5 _T is input because of the overcurrent input.
The output of 27 _R , 27 _S , and 27 _T is logic "1", and the current flows from the generator side to the power system.
2 _R , ... Outputs a logical “1”, and therefore the AND circuit 31 _R ,
The inputs of 33 _R are all "1", the operation signal is output, the output circuit 38 operates, the output relay 38 is turned on, the current is passed through the trip coil, and the generator side of the power supply line 2 and the power system. Turn off the switch on the side. Even if the undervoltage is not detected due to a long-distance short-circuit accident, the directional short-circuit relay operates only by detecting the overcurrent and the current direction.

Here, a specific circuit example for forcing the output level of the voltage amplifier circuit 13 _R (13 _S , 13 _T ) and its operation will be described. Voltage amplifier circuit
As shown in FIG. 2, 13 _R outputs a signal to the next stage via the path of the NAND circuit G ₁ , the resistor R ₂ , and the inverter N ₁ . The output side of the resistor R ₂ is connected to the + V power source via the resistor R ₃ and is also connected to the −V power source via the phototransistor PT of the photocoupler. A resistor R ₄ is connected between the terminal M ₁ and the + V power source in a series circuit of light emitting diodes L _D of the photocoupler, and the diode D ₁ is connected in parallel to the light emitting diode L _D. Terminal M ₂ is connected to the -V supply.

In this voltage amplifying circuit 13 _R, in the state where the terminal M _1, M ₂ is open, the output of the NAND circuit G ₁ is is being inverted output by the inverter N _1. That is, when the input voltage taken in is equal to or higher than the settling operation voltage, the NAND circuit G ₁ outputs a high (logic “1”) signal, which is inverted by the inverter N ₁ to be low (logic “0”). The signal is output. Conversely, if the input voltage is smaller than the settling voltage, that is, if it is undervoltage, NAND
A low signal is output from the circuit G ₁ , inverted by the inverter N ₁ , and a high signal is output.

When the terminals M ₁ and M ₂ are short-circuited, for example, by operating a push button switch, + V power supply → resistance R ₄ → light emitting diode L _D → terminal
Current flows in the path of M ₁ , M ₂ → -V power supply, and light emitting diode
L _D fires. Then, upon receiving the light from the light emitting diode L _D , the phototransistor PT is turned on. Therefore, the input side of inverter N ₁ is forced low, and inverter N ₁
Inverted, the output becomes high, that is, the logic "1" state, and while the terminals M ₁ and M ₂ are short-circuited, a signal indicating undervoltage detection is forcibly output regardless of the input voltage.

(F) Effect of the invention According to this invention, the undervoltage detection unit is forced to output a signal for undervoltage detection, or the output of the undervoltage detection unit is set according to the detection state, depending on whether or not there is a setting. Since it has an undervoltage detection function exclusion setting means for selecting
Depending on the distance from the power receiving end to the substation of the electric power company, undervoltage detection can be added to or removed from the conditions for short circuit accident determination, so the undervoltage detection function is excluded even for distant short circuit accidents. By doing so, an accident can be detected and the circuit breaker of the power supply line can be properly cut off to perform the protection function.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of a directional short-circuit relay showing an embodiment of the present invention, and FIG. 2 is a circuit connection diagram showing a connection relationship between a voltage amplification circuit of the same-direction short-circuit relay and an undervoltage detection function exclusion terminal. Is. 1: Direction shorting relay, 2: power supply _{line, 4 R · 4 S · 4} T: undervoltage _{detector, 5 R · 5 S · 5} T: overcurrent detection unit, 32 _R: phase discrimination circuit, 31 _R · 33 _R: the AND circuit, 37: output circuit, 38: output relay, M ₁ · M _2: undervoltage detection function excludes terminal.

Claims (1)

[Scope of utility model registration request] 1. An undervoltage detector that detects a voltage of a power supply line and outputs an output when the detected voltage is a set value or less, and a current of the power supply line is detected, and the detected current is a set value or more. An overcurrent detection unit that outputs an output, a phase determination unit that outputs an output when the direction of the current flowing through the power supply line is a predetermined direction by phase determination of the detection voltage and the detection current, and A directional short-circuit relay consisting of an output circuit that drives a relay that disconnects the circuit breaker in the power supply line in response to the logical product output of the outputs of the current detection unit, undervoltage detection unit, and phase determination unit. The undervoltage detection function exclusion setting means for selecting whether to output the signal indicating the undervoltage detection forcibly from the undervoltage detection unit or to set the output of the undervoltage detection unit according to the detection state is provided. Characteristic directional short circuit relay.