JP2002311061A - Processor for electric power - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure accuracy of condition monitoring of an alternating current or protective measurement in an electric power system and electric power equipment by detecting an alternating current flowing in and an alternating voltage of a conductor such as a bus of the electric power system and an electric wire of the electric power equipment via a small, light and inexpensive structure free of an iron core saturation phenomenon at high current detection. SOLUTION: This processor for electric power comprises a current sensor 14 comprising an air core coil through which a conductor 1 passes, a voltage sensor 17 formed by a voltage dividing series connection of a capacitor 15 and a resistor 16 between the conductor 1 and a reference potential point, a means for extracting a differential signal of current from an output signal of the sensor 14 and extracting a differential signal of voltage from an output signal of the sensor 17, and a means for using both differential signals as detection signals of current and voltage to execute condition monitoring or protective measurement according to both differential signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power processing apparatus used for monitoring or protecting the power of a power system or power equipment.

[0002]

2. Description of the Related Art Conventionally, a low power type protection and measuring device which is an example of this type of power processing device is formed at a transformer input shown in FIG.

[0003] This transformer input protection and measurement device comprises an instrument current transformer (CT) having a ring-shaped core through which a conductor 1 such as a bus of an electric power system or a wire of electric equipment such as GIS penetrates in a main circuit. It has a current sensor 2 and a voltage sensor 3 consisting of an instrument transformer (PT) having a primary winding provided between the conductor 1 and a ground point as a reference potential point.

When a commercial alternating current of 60 Hz or 50 Hz flows through the conductor 1, the current sensor 2 detects the current and outputs a 5A or 1A analog current detection signal ai in a steady state of the detected current waveform. The voltage sensor 3 detects the voltage of the conductor 1 and outputs a detected voltage waveform of 110 V from the secondary winding in a steady state.
Is detected.

The detection signals ai and av are supplied to an auxiliary current transformer (AuxCT) 5 and an auxiliary transformer (Aux) provided in a main unit (protection / measurement unit) 4 of a computer configuration.
PT) 6, and is supplied to a signal selection multiplexer 9 via low-pass filters (LPFs) 7 and 8 for preventing aliasing noise of high-frequency digital processing.

The multiplexer 9 is operated by a timing clock having an appropriate frequency of the fundamental frequency of the commercial alternating current, and alternately selects the detection signals ai and av to perform A / D conversion.
Output to converter 10.

The A / D converter 10 converts each of the detection signals ai and av based on the timing signal into, for example, N digital data d per one cycle of the commercial AC.
A / D-converted to i and dv and sent to CPU11.

The CPU 11 executes a Fourier calculation waveform analysis of the data di and dv based on the measurement processing program of the measurement unit 12 to determine the current, voltage or fundamental wave of the commercial AC fundamental wave flowing through the conductor 1. The voltage, current, and harmonic current and voltage are separated into waveforms and extracted. Changes in the extracted current, voltage amplitude, and phase are monitored to detect the presence or absence of a ground fault, short-circuit fault, etc. Perform protection measurement of system and electrical equipment.

When a system fault or the like occurs and the current and voltage of the commercial alternating current flowing through the conductor 1 become abnormal, the CPU 1
Under the control of 1, the protection unit 13 outputs a trip command to a circuit breaker (CB) of a power device such as a substation or GIS, and opens the circuit breaker to protect the power system and the power device.

At the same time, an open circuit breaker notification or the like is sent from the measuring section 12 to a manned central monitoring station or the like via a transmission device (not shown) to notify the occurrence of a protection operation.

When only the status of the AC flowing through the conductor 1 is monitored, the CPU 11 detects the presence or absence of an abnormality such as a system accident, and monitors the status of the AC flowing through the conductor 1.
The monitoring result is sent to the above-mentioned central monitoring station.

[0012]

In the case of this type of conventional power processing apparatus, the current sensor 2 and the voltage sensor 3 are:
It is composed of a large, heavy and expensive CT and PT each containing a so-called iron core.

In addition, the detection signals ai, a
“v” is a current signal of 5 A or 1 A (at a steady state) and a voltage signal of 110 V (at a steady state) according to the CT and PT standards, and a signal for sending information on the current and voltage flowing through the conductor 1 to the main unit 4. These are signals of a large current and a large voltage more than necessary, and it is necessary to adjust the signal level using the auxiliary current transformer 5 and the auxiliary transformer 6 so as to be compatible with the subsequent signal processing.

Further, regarding the current sensor 2, the conductor 1
Even when the current flowing through is a large current in the fault current range, which is several tens of times the steady state, so that the core saturation does not occur,
It is also necessary to suppress the saturation phenomenon as much as possible by making the iron core sufficiently large.

For this reason, in the conventional apparatus, miniaturization,
There is a problem that weight reduction and cost reduction cannot be achieved.

The present invention is a compact, lightweight, inexpensive, superconducting state monitor or power system based on the detection of alternating current and voltage flowing through a conductor without causing iron core saturation when detecting a large current. Another object of the present invention is to enable protection measurement of power devices.

[0017]

According to a first aspect of the present invention, there is provided an electric power processing apparatus comprising: an air-core coil through which a conductor such as a bus of an electric power system or an electric wire of an electric appliance penetrates; Sensor, a voltage sensor formed by connecting a voltage dividing capacitor and a resistor in series between the conductor and the reference potential point, and a differential signal of the current flowing through the conductor from the output signal of the current sensor. Means for extracting and extracting a differential signal of the conductor voltage from the output signal of the voltage sensor, and monitoring the state of alternating current flowing through the conductor based on the two differential signals as detection signals of the conductor current and voltage. Or means for performing protection measurement of the power system and power equipment.

In this case, the power sensor is composed of an air-core coil, and the voltage sensor is composed of a series circuit of a voltage dividing capacitor and a resistor. It is small, lightweight and inexpensive, the output signal is at a level suitable for signal processing, and there is no need to adjust the signal level using an auxiliary current transformer or an auxiliary transformer.

Moreover, since an air-core coil having no iron core is used for the current sensor, the conventional iron core saturation phenomenon does not occur even in an accident current region where the current flowing through the conductor is large.

Since the current sensor outputs a differential signal of the current and the voltage sensor outputs a differential signal of the voltage, both the current and the voltage of the alternating current flowing through the conductor are both detected by the original detection amplitude. (Ω is the angular frequency of current and voltage), and the differential waveform is equally shifted by 90 °.

Therefore, the two differential signals are treated as detection signals of the AC current and voltage flowing through the conductor, and the presence or absence of the AC short circuit, ground fault system fault, etc. can be determined from changes in the amplitude and phase of the two differential signals. Detecting and monitoring the AC status or the power system,
Protection measurement of power equipment can be performed.

Therefore, compared with the case where the conventional CT and PT are used as the current sensor and the voltage sensor, the conductor flows through the conductor with a very small, lightweight and inexpensive configuration without causing the problem of the saturation phenomenon of the iron core. It is possible to accurately monitor the state of alternating current or protect and measure the power system and power equipment.

Next, in the case of the second aspect, the differential signal of the current and voltage of the conductor extracted from the output signals of both sensors is given by:
The amplitude variation based on the frequency variation of the alternating current flowing through the conductor is corrected, and the corrected differential signals are used as the current and voltage detection signals to monitor the status of the alternating current flowing through the conductor or the power system and power. Perform protection measurement of equipment.

In this case, the frequency of the alternating current flowing through the conductor fluctuates for some reason.
2. Even if the amplitude of the voltage differential signal fluctuates, the amplitude fluctuation is corrected, and based on the corrected amplitude and phase of the two differential signals, the AC state flowing through the conductor with higher accuracy than in the case of claim 1. Monitoring or protection measurement is performed.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. In this embodiment, as shown in FIG. 1, an air-core coil current sensor 14 is used in place of the conventional CT current sensor 2, and this sensor 1
4 penetrates the conductor 1.

The air-core coil of the sensor 14 forms a Rogowski CT of a primary conductor penetrating type, and its output is an analog of a 60 Hz or 50 Hz fundamental wave current (primary current) of commercial AC flowing through the conductor 1. Is the differential signal Ai.

At this time, Rogowski CT has no iron core, is lightweight, small and inexpensive, and has a magnetic saturation even when a large current of several tens times the steady current such as an accident current flows through the conductor 1. Does not occur, and no abnormal high voltage is generated due to the opening of the secondary circuit.

The frequency characteristic of the air-core coil of the current sensor 14 is, for example, as shown by a solid line in FIG.
60Hz or 50Hz angular frequency ω _{0 of} commercial AC flowing through
The level (amplitude) of the output signal (differential signal Ai) changes linearly in a wide frequency range including the region of (= 2πf ₀ , f ₀ is the fundamental frequency).

Therefore, the current sensor 14 is formed to be lighter, smaller and less expensive than the conventional current sensor 2, and detects a commercial AC current flowing through the conductor 1 without magnetic saturation even for a large current. The differential signal Ai is output.

Next, the conventional PT voltage sensor 3 is not provided, but a voltage sensor 17 in which a voltage dividing capacitor 15 and a resistor 16 are connected in series is provided between the conductor 1 and a ground point which is a reference potential point. Can be

At this time, assuming that the capacitance of the capacitor 15 is C and the resistance value of the resistor 16 is R, the resistor 16 has a low resistance value of (1 / ω ₀ · c) に お い て R at the angular frequency ω ₀ . A shunt resistor is formed, the commercial AC voltage of the conductor 1 is differentiated by the capacitor 15 and the resistor 16, and a differential signal Av of the commercial AC voltage is output from a connection point therebetween.

The CR of the capacitor 15 and the resistor 16
The frequency characteristic of the voltage dividing circuit is, for example, as shown by a solid line in FIG. 3, and, like the frequency characteristic of the air-core coil, the output is obtained in a wide frequency range including the region of the angular frequency ω ₀ of the commercial AC flowing through the conductor 1. The level of the signal (differential signal Av) changes linearly.

Accordingly, the voltage sensor 17 is formed by a differentiating circuit of the capacitor 15 and the resistor 16 to be lighter, smaller and cheaper than the conventional voltage sensor 3 using PT, and is similar to the differential signal Ai of the current of the current sensor 14. And outputs a differential signal Av of the commercial AC voltage.

The output signals of the two sensors 14 and 17 are not large current and voltage signals like the output signals of the conventional CT and PT sensors 2 and 3, but are the commercial AC current flowing through the conductor 1. , A voltage signal of an appropriate level as a voltage information signal, for example, several mV to several V.

Therefore, the output signals of the two sensors 14 and 17 are not passed through the auxiliary transformers such as the auxiliary current transformer 5 and the auxiliary transformer 6 of the conventional device, and the low-pass filters 7 and 8 of the conventional main unit 4 are not used. Are directly supplied to the low-pass filters 19 and 20 of the main unit 18 having a computer configuration corresponding to
Digital processing aliasing is eliminated.

Further, the output signals of the two sensors 14 and 17 passed through the low-pass filters 19 and 20 are supplied to a multiplexer 21 corresponding to the conventional multiplexer 9, and the multiplexer 21 outputs a commercial AC signal formed by a PLL oscillator or the like. Based on the timing signal of the transmission frequency of the fundamental frequency (60 Hz or 50 Hz)
Are alternately selected and sent to the A / D converter 22.

The output signals of the sensors 14 and 17 are converted by the A / D converter 22 into N digital data Di and Dv per commercial AC cycle.

Further, the CPU 23 forms means for extracting the differential signals Ai and Av from the output signals of the sensors 14 and 17 based on the measurement program of the measuring section 24, and performs a Fourier transform of the data Di and Dv, similarly to the CPU 11 of the conventional device. The waveform analysis is performed to digitally separate and extract the differential signals Ai, Av included in the data Di, Dv.

At this time, the voltage of the fundamental wave of the commercial alternating current flowing through the conductor 1 is V, the current is I, and their angular frequency is ω.
Then, the voltage V is V = Vm · sin ω · t, the current I is I = Im · sin (ωt + α), (Vm and Im are the maximum amplitude, and α is the phase difference of the current I with respect to the voltage V), and is extracted. The differentiated signals Ai and Av are Ai = dI / dt = Im.
ω · cos (ωt + 2), Av = dV / dt = Vm · ω
・ Cosωt.

The extracted differential signals Ai and Av are signals obtained by multiplying the amplitudes Vm and Im by ω with respect to the original current I and voltage V by 90 °, and the amplitude is ω times the original. However, the phase does not change. In other words, the voltages I and V are both differentiated and detected with an amplitude of ω times.

Therefore, the CPU 23 uses the extracted differential signals Ai and Av as detection signals of the current I and the voltage V, and forms means for monitoring the state of the commercial AC or measuring the protection based on the two differential signals Ai and Av.

More specifically, the CPU 23 regards the extracted differential signals Ai and Av as the original detection signals of the current I and the voltage V based on the above-mentioned measurement program,
Monitoring and detecting the presence or absence of a short circuit of the commercial alternating current flowing through the conductor 1 or a system fault due to a ground fault from the changes in ω, Vm · ω and the phase ω, and monitors the state of the commercial alternating current.

At this time, the amplitude and phase of the differential signals Ai and Av may be monitored as they are, but if the frequency of the commercial AC flowing through the conductor 1 fluctuates for some reason, the differential signal Ai
Since the amplitudes of Im and ω and Vm and ω of i and Av fluctuate under the influence of the frequency fluctuation and may cause erroneous detection, in this embodiment, an auxiliary voltage sensor or the like (not shown) is used. The voltage V of the commercial alternating current flowing through the conductor 1 is measured, and when the frequency changes by Δf from the original fundamental frequency f ₀ of 60 Hz or 50 Hz, the extracted differential signals Ai, A
The amplitude of v is corrected by multiplying by f ₀ / (f ₀ + Δf).

Then, the CPU 23 calculates the differential signal A after the correction.
Based on changes in the amplitude and phase of i and Av, erroneous detection due to frequency fluctuations of the commercial AC is prevented, and the state of the commercial AC is accurately monitored.

Further, in this embodiment in which the protection measurement is performed, when a commercial AC system accident or the like flowing through the conductor 1 occurs, the CPU 23 performs protection similarly to the CPU 11 of the conventional device based on the above-described state monitoring. A trip command is output from the section 25 to a circuit breaker of a power station such as a transformer station or a GIS to protect the power system and the power apparatus, and at the same time, the central monitoring of manned from the measuring section 24 via a transmission device (not shown). A notification of opening of the circuit breaker or the like is sent to a place or the like to notify the occurrence of the protection operation.

Therefore, in the case of this embodiment, the current sensor 14 and the voltage sensor 15 are provided with an air-core coil having no iron core, CR
The voltage dividing circuit is small, light, and inexpensive, and does not cause a saturation phenomenon due to the detection of a large current in the current sensor 14.

Then, the sensors 14 and 15 detect the commercial AC current and voltage flowing through the conductor 1 with the differentiated signals Ai and Av of the same waveform dimension, and detect the differentiated signals Ai and Av as the commercial AC current and voltage. As a voltage detection signal, the conventional auxiliary current transformer 5,
There is no need to provide the auxiliary transformer 6 or the like.

Therefore, the main circuit side is significantly smaller, lighter, and cheaper than the conventional device, and the configuration for miniaturization, weight reduction, and cost reduction enables extremely accurate protection measurement of the power system and power equipment. it can.

When only the status of the commercial AC flowing through the conductor 1 is monitored, the protection unit 25 of the main unit 18 is omitted, and the information of the monitoring result and the system fault are sent from the measurement unit 24 to a manned central monitoring station or the like. What is necessary is just to make a report when such a situation occurs.

In the above embodiment, the reference potential point is the ground point, but the reference potential point is not limited to the ground point.

Further, the alternating current flowing through the conductor 1 is not limited to a commercial alternating current, but may be a so-called private power generation alternating current.

For example, when monitoring the state of three-phase alternating current or performing protection measurement, the configuration shown in FIG. 1 may be provided for each phase.

By the way, in order to solve the inconvenience of the conventional current sensor 2 and voltage sensor 3, it is conceivable to construct as shown in FIG.

In the case of FIG. 4, a current sensor 26 comprising an air-core coil similar to the current sensor 14 is used for detecting the current of the commercial alternating current flowing through the conductor 1, and the commercial alternating current flowing through the conductor 1 is Is differentially detected.

On the other hand, the voltage of the commercial alternating current flowing through the conductor 1 is a so-called voltage sensor 29 which is formed by connecting two voltage dividing capacitors 27 and 28 in series between the conductor 1 and a ground point. The voltage is detected by dividing the voltage by the capacitor voltage dividing method.

The sensors 26 and 29 have no iron core such as CT and PT, are small and lightweight, and the current sensor 26 does not cause a saturation phenomenon when detecting a large current.
The disadvantages of the conventional current sensor 2 and voltage sensor 3 are eliminated.

However, while the output signal of the current sensor 26 becomes a differential signal of the current, the output signal of the voltage sensor 29 becomes the voltage detection signal itself, and becomes a signal having a different waveform dimension. 26 is integrated by the integrator 31 of the input unit 30 and converted into a current detection signal of the same dimension as the voltage detection signal.

Further, the current detection signal and the sensor 2
9 is converted into a current signal and a voltage signal similar to the output signals of the current sensor 2 and the voltage sensor 3, and the main unit 4
The output signal of the current sensor 26 via the integrator 31 is power-amplified by the amplifier 32 of the input unit 30, and the output signal of the voltage sensor 29 is supplied to the amplifier 3 of the input unit 33.
4 for power amplification. Then, by the main unit 4,
State monitoring or protection measurement is performed in the same manner as in the related art.

Therefore, in the case of the configuration shown in FIG. 4, although the current sensor 26 and the voltage sensor 29 can be reduced in size and weight, the input units 30 and 33 for amplifying the electric power are required. Auxiliary current transformer 5, auxiliary transformer 6
It is not possible to achieve a significant reduction in size and weight as in the case of the configuration of FIG.

The present invention can be applied to monitoring of the current state of various power systems and power devices or protection measurement.

[0061]

The present invention has the following effects. The power sensor 14 is composed of an air-core coil, and the voltage sensor 17 is composed of a series circuit of a voltage dividing capacitor 15 and a resistor 16. ， Lightweight and inexpensive,
Moreover, the output signals of both sensors 14 and 17 are at a level suitable for signal processing, and there is no need to adjust the signal level using an auxiliary current transformer or an auxiliary transformer.

Further, since an air-core coil without an iron core is used for the current sensor 14, even when a large current is detected in the fault current region, the conventional iron core saturation phenomenon does not occur.

Then, the conductors 1 and 2 are detected by the sensors 14 and 17.
Since both the alternating current and voltage flowing through the conductor 1 were detected as differential signals, the two differential signals were
Treat as a voltage detection signal, detect the presence or absence of the AC short circuit, ground fault, etc. based on changes in the amplitude and phase of the two differential signals, and perform the AC status monitoring or protection measurement of the power system and power equipment. Can be.

Therefore, compared to the case where the conventional CT and PT are used as current sensors and voltage sensors, the configuration is extremely small, light and inexpensive. Protection measurement of power system and power equipment can be performed accurately.

Next, in the case of claim 2, even if the frequency of the alternating current flowing through the conductor fluctuates for some reason and the amplitude of the differential signal of the current or voltage of the conductor fluctuates with this fluctuation,
This amplitude fluctuation is corrected, and the amplitudes of the corrected differential signals,
Based on the phase, the monitoring of the AC state or the protection measurement of the power system and the power equipment can be performed with higher accuracy than in the case of the first aspect.

[Brief description of the drawings]

FIG. 1 is a block connection diagram of an embodiment of the present invention.

FIG. 2 is a frequency characteristic diagram of an air-core coil forming the current sensor of FIG.

FIG. 3 is a frequency characteristic diagram of a CR voltage dividing circuit forming the voltage sensor of FIG. 1;

FIG. 4 is a block connection diagram of an apparatus using an air core coil current sensor and a capacitor voltage dividing type voltage sensor.

FIG. 5 is a block diagram of a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conductor 2,14,26 Current sensor 3,17,29 Voltage sensor 4,18 Main unit 15,16 Capacitor for voltage division, resistance

Claims (2)

[Claims] An electric power for monitoring the status of the alternating current or protecting and measuring the electric power system and the electric power device based on detection of an alternating current and a voltage flowing through a conductor such as a bus of an electric power system and a wire of an electric power device. A current sensor comprising an air-core coil through which the conductor penetrates; a voltage sensor formed by connecting a voltage dividing capacitor and a resistor in series between the conductor and a reference potential point; and the current sensor Means for extracting a differential signal of the current from the output signal of the voltage sensor, and extracting a differential signal of the voltage from the output signal of the voltage sensor; and using the two differential signals as the current and voltage detection signals,
Means for performing the state monitoring or the protection measurement based on the two differential signals. 2. A differential signal of current and voltage extracted from output signals of both sensors is subjected to a correction of an amplitude fluctuation based on a frequency fluctuation of an alternating current flowing through a conductor. 2. The power processing apparatus according to claim 1, wherein the detection of the AC current and the voltage includes monitoring of the AC state or protection measurement of the power system and the power equipment.