JP2015023707A - Protection control device, protection control method, and protection control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform higher-precision and higher-reliability protection with excellent economical efficiency by the same configuration, without reference to a protection object.SOLUTION: According to an embodiment, a protection control device includes a calculation part that calculates the sum total, associated with a plurality of terminals, of electric power based on a value obtained by sampling each of electric currents and voltages of the plurality of terminals of an electric power system set as a protection object, and a determination part that determines the presence or absence of the occurrence of an accident in the protection object by comparing the sum total, calculated by the calculation part, with a predetermined threshold.

Description

  Embodiments described herein relate generally to a protection control device, a protection control method, and a protection control program.

Generally, in a protection control device that protects a power system, a typical method for protecting power transmission lines, transformers, and buses is a current differential protection method.
The protection control device to which this method is applied uses the Kirchhoff's law to determine the sum of the currents of all terminals that wrap the protection target as the operation amount of the relay. Determine whether or not.

Yoshifumi Ohura, Protection Relay System Engineering, The Institute of Electrical Engineers of Japan, 131-134

The current differential protection method used in the above-described protection control device is a method for performing current differential protection based on Kirchhoff's current law, for example, based on the following equation (1).

  In Equation (1), b is the number of terminals to be protected, and k in Equation (1) is the sensitivity of the relay considering current measurement error.

  This formula is widely applied to the protection of power transmission lines, transformers, buses, motors, etc., and the formula (1) is obtained by adding the data obtained by sampling synchronized alternating current values at all terminals to the instantaneous value of AC current. The left side of is obtained. Of course, even when the object to be protected is a DC circuit, Kirchhoff's current law holds, and therefore, the equation (1) can be applied.

  On the other hand, in recent years, distributed power systems such as solar power generation and wind power generation are increasing. In this system, the power source to the inverter is a DC circuit, and the inverter to the power system is an AC circuit.

  When providing a protective circuit in a distributed power supply system that protects a DC / AC mixed circuit in which one terminal is DC current and the other terminal is AC current, the DC circuit, inverter, AC circuit Generally, a protection circuit is provided individually. However, in the unlikely event that these protection circuits fail, Equation (1) does not hold for the entire system, so a protection device that backs up the protection circuit at low cost and protects the entire distributed power supply system collectively. The current differential protection according to Kirchhoff's current law cannot be used to achieve this.

  The problem to be solved by the present invention is to provide a protection control device protection control method and a protection control program capable of performing highly accurate protection regardless of the protection target.

  According to the embodiment, the protection control device includes: a calculation unit that calculates a sum of a plurality of terminals of power based on values obtained by sampling currents and voltages of a plurality of terminals of a power system to be protected; and a calculation unit And a determination unit that determines whether or not an accident has occurred in the protection target by comparing the sum calculated by the above and a predetermined threshold value.

  According to the present invention, high-precision protection can be performed regardless of the object to be protected.

The block diagram which shows the structural example for taking in the electric current of the protection control apparatus in 1st Embodiment, a voltage, and relay determination. The flowchart which shows an example of the operation | movement procedure by the protection control apparatus in 1st Embodiment. The block diagram which shows the structural example used for protection of the direct current alternating current system in the protection control apparatus in 1st Embodiment. The block diagram which shows the structural example used for protection of the transformer in the protection control apparatus in 1st Embodiment. The flowchart which shows an example of the operation | movement procedure for protection of the transformer by the protection control apparatus in 1st Embodiment. The figure which shows an example of the (phi) -i curve for demonstrating the protection of the inrush in the transformer protection by the protection control apparatus in 1st Embodiment. The figure for demonstrating protection of the inrush in the transformer protection by the protection control apparatus in 1st Embodiment. The figure which shows the structural example at the time of using a communication path between the both terminal relays of the power transmission line in the protection control apparatus in 1st Embodiment. The flowchart which shows an example of the operation | movement procedure at the time of using a communication path between the both terminal relays of the power transmission line by the protection control apparatus in 1st Embodiment. The figure which shows the structural example used for protection of the bus-line in the protection control apparatus in 1st Embodiment. The flowchart which shows an example of the operation | movement procedure for protection of the bus-bar by the protection control apparatus in 1st Embodiment. The block diagram which shows the structural example for taking in the electric current of the protection control apparatus in 2nd Embodiment, a voltage, and relay determination. The flowchart which shows an example of the operation | movement procedure by the protection control apparatus in 2nd Embodiment. The figure which shows the structural example of the protection control apparatus in 3rd Embodiment. The flowchart which shows an example of the operation | movement procedure by the protection control apparatus in 3rd Embodiment. The figure which shows the structural example of the power transmission line model for calculating a compensation term with the protection control apparatus in 3rd Embodiment. The figure which shows the structural example in the case of the amount of phasors in a power transmission line model. The figure which shows the structural example of the inverter circuit model for calculating the compensation term concerning the direct-current alternating current mixed system in the protection control apparatus in 3rd Embodiment. The figure which shows the structural example of the protection control apparatus in 4th Embodiment. The flowchart which shows an example of the operation | movement procedure by the protection control apparatus in 4th Embodiment. The figure which shows an example of the waveform of the electric current and voltage in the protection control apparatus in 5th Embodiment. The flowchart which shows an example of the operation | movement procedure by the protection control apparatus in 5th Embodiment.

  Hereinafter, embodiments will be described with reference to the drawings.

(First embodiment)
First, the first embodiment will be described.
FIG. 1 is a block diagram illustrating a configuration example for capturing current and voltage and determining a relay in the protection control device according to the first embodiment.
As shown in FIG. 1, in the first embodiment, the protection control device 1 includes a voltage input conversion unit 3, a current input conversion unit 4, a voltage analog-digital (A / D) conversion unit 5, and a current analog-digital. (A / D) A conversion unit 6 and a digital arithmetic processing unit 7 are provided.

The voltage input conversion unit 3 is provided at each of one end and the other end of the protection target 2 and takes in the voltage at both ends of the protection target detected by the PT (transformer) 9.
The current input conversion unit 4 is provided at each of one end and the other end of the protection target 2, and takes in the current at one end and the other end of the protection target 2 detected by the CT (current transformer) 8.

  The voltage analog-to-digital (A / D) converter 5 is provided corresponding to the voltage input converter 3. The A / D converter 5 performs A / D conversion of the voltage taken in by the corresponding input converter 3.

  The current analog-to-digital (A / D) converter 6 is provided corresponding to the current input converter 4. The A / D conversion unit 6 performs A / D conversion of the current taken in by the corresponding input conversion unit 4.

  The digital arithmetic processing unit 7 uses the voltage / current values from the voltage analog-to-digital (A / D) converter 5 and the current analog-to-digital (A / D) converter 6 to cause an accident to occur in the protection target. The relay is determined whether or not it exists.

The digital arithmetic processing unit 7 includes a calculation unit 7a and a determination unit 7b.
The calculation unit 7a performs necessary calculations for relay determination. The determination part 7b performs relay determination using the calculation result by the calculation part 7a.

Next, the operation of the protection control device in the first embodiment will be described.
FIG. 2 is a flowchart illustrating an example of an operation procedure performed by the protection control device according to the first embodiment.
First, on one end side and the other end side of the protection target 2, the current input conversion unit 4 acquires the analog current value data detected by the CT 8 that is the connection destination (step S1).
On one end side and the other end side of the protection target 2, the voltage input conversion unit 3 acquires the analog voltage value data detected by the connection destination PT9 (step S2).
On one end side and the other end side of the protection target 2, the current A / D converter 6 calculates digital current value data by digitally converting the analog current value data acquired by the current input converter 4 ( Step S3).
The voltage A / D conversion unit 5 calculates the digital voltage value data by digitally converting the analog voltage value data acquired by the voltage input conversion unit 3 on one end side and the other end side of the protection target 2. (Step S4).

Based on the digital current value data and the digital voltage value data, the calculation unit 7a of the digital arithmetic processing unit 7 obtains the instantaneous power for each observation point as the operation amount of the relay, and calculates the absolute value of these sums ( Step S5). The determination unit 7b performs relay determination as to whether or not an accident has occurred in the protection target 2.
When the protection target accident has occurred (YES in step S6), the digital arithmetic processing unit 7 operates the trip circuit and outputs a trip command to the circuit breaker (step S7).

  Next, details of relay determination will be described. In this embodiment, the digital arithmetic processing unit 7 uses the Telegen's theorem to perform relay determination using the sum of products of currents and voltages at arbitrary points in time at each observation point to be protected. .

Telegen's theorem is a theorem that means that the sum of the products of the current flowing through each branch and the potential difference between the branches in the electrical circuit is zero, as shown in the following equation (2).

Here, the current and voltage observation points are b.
This formula (2) has non-time dependence. For example, the digital processing unit 7 column _V 1 of the potential difference across the _protected, V 2, ..., column _{I 1,} I 2 of _{V N} and a current, ..., the same time the sampling of _{I N} in each column In this case, the potential difference and the current sampling time do not affect the stored information. Therefore, the digital arithmetic processing unit 7 can detect the internal accident of the protection target 2 by performing a differential calculation using the following formula (3) as a determination formula.

K in the equation (3) is a threshold for relay determination, and is a relay sensitivity in consideration of a current measurement error.
This equation (3) can be applied to power transmission lines, transformers, and buses to which current differential relays are conventionally applied, and can also be applied to power systems in general such as AC / DC mixed systems including inverters and converters.

  It can be said that the basic formula of the Telegen theorem (formula (2)) expresses the energy conservation law in the electric circuit. It can be said that this equation represents a power conservation law when considered in unit time. For values obtained from the sum of products of current and voltage at different sampling sequences, the basic formula of Telegen's theorem is a quasi-power conservation law as a generalization of the power conservation law. Represents.

  The energy conservation law is a law that the total amount of energy in an isolated system does not change. Taking FIG. 1 as an example, if power consumption and storage in the protection target 2 is negligible due to the characteristics of the relay, in normal operation, the power entering the protection target 2 and the protection target 2 The output power is considered to be approximately equal.

  On the other hand, when an accident occurs inside the protection target 2, power is consumed greatly in the form of heat or light. For this reason, the difference between the power entering the protection target 2 and the power exiting from the protection target 2 increases. The digital arithmetic processing unit 7 performs protection by detecting this difference using the above equation (3).

FIG. 3 is a block diagram illustrating a configuration example used for protection of a DC / AC mixed system in the protection control device according to the first embodiment.
In the example shown in FIG. 3, the protection target is the inverter 11. A PV module (solar power generation module) 10 is provided in the DC circuit as one end of the inverter 11. CT8 and PT9 are provided in the DC circuit as one end of the inverter 11 and the AC system as the other end.

  In the first embodiment, the expressions for input and relay determination are the same regardless of whether the protection target is an AC circuit, a DC circuit, or an AC / DC mixed circuit (see FIG. 3). As a result, the reliability and economy of relay determination are improved.

  That is, regardless of whether the object to be protected is a power transmission line, a transformer, or a bus, or an AC / DC mixed system that cannot be protected by the conventional current differential protection system, the configuration shown in FIG. Differential protection can be realized. Here, the power consumption due to the resistance of the transmission line is sufficiently small, and the accumulation of power due to inductance and capacitance is small enough to be ignored.

  Further, when the protection target is an AC / DC mixed system, it is assumed that the power consumption and storage in the inverter (see FIG. 3) and the converter are small enough to be ignored here. This is because many inverters already have an efficiency of 90% or more. In the future, since the number of DC-AC mixed power systems will increase, the application of this embodiment will be more effective.

Although Equation (2) and Equation (3) represent instantaneous power, Telegen's theorem also holds for the amount of phasor, so even if the following Equation (4) using the value of phasor is applied: The structure and effect remain the same.

In formula (4), I _α and V _α represent phasor values of current and voltage, respectively.
When the protection target is a transformer and the transformer is protected by the conventional current differential protection method, the protection control device malfunctions due to the inrush waveform when the transformer is turned on. As a countermeasure, focusing on the fact that there are many second harmonics in the inrush current, it is possible to determine that the second harmonic is above a certain value by a filter and lock the output of the current differential relay. It has been used for some time.

  This system requires a lock circuit for locking the output of the current differential relay. For this reason, in addition to the current differential protection of the transmission line protection described above, different filtering and logic sequences are further required. Therefore, the same current differential protection method as the transmission line protection is required, but different software implementation is required. It becomes.

  In addition, since the second harmonic contained in the fault current has increased due to changes in the power system in recent years and the second harmonic component contained in the inrush waveform has decreased, the inrush waveform In this conventional detection method, there is a concern about malfunction due to an internal accident in the transformer and malfunction due to an external accident.

FIG. 4 is a block diagram illustrating a configuration example used for protection of the transformer in the protection control device according to the first embodiment.
As shown in FIG. 4, when the protection target is the transformer 12, the iron loss and copper loss inside the transformer 12 can be ignored at all times. Further, since the exciting current itself of the transformer 12 is small, the energy accumulated in the reactance of the winding of the transformer 12 can be ignored. Further, when the transformer 12 has an internal accident, a large amount of effective power is consumed due to dielectric breakdown. For these reasons, an internal accident can be detected using the above formula (3) or formula (4).

By the way, when inrush at the time of voltage application occurs, the iron core enters the saturation region, and the energy accumulated in the reactance also changes. However, since the average value of the instantaneous power to the transformer 12 is almost zero, if inrush occurs if the following equation (5) is used instead of the above equations (3) and (4): There is no malfunction of the differential protection relay. If this equation (5) is used, a harmonic detection circuit is not required, and the configuration shown in FIG. 1 improves the reliability and economy, and the transformer 12 can be protected.

The left side of Equation (5) represents a value obtained by summing the average value of the instantaneous voltage for each of the observation points in an interval of N periods (N is an integer of 1 or more) of the AC fundamental frequency. In this equation (5), i _α and v _α are values sampled at the same time.

FIG. 5 is a flowchart illustrating an example of an operation procedure for protecting the transformer by the protection control device according to the first embodiment.
First, analog current value data acquisition, analog voltage value data acquisition, digital current value data calculation, and digital voltage value data calculation are performed through S1 to S4 described above.

Next, the calculation unit 7a of the digital arithmetic processing unit 7 obtains an average value of the instantaneous power for each observation point as an operation amount based on the digital current value data and the digital voltage value data, and calculates the absolute sum of these values. A value is calculated (step S5A). The determination unit 7b performs relay determination as to whether or not an accident has occurred in the protection target 2 using Expression (5) based on the calculation result.
When the protection target accident has occurred (YES in step S6), the digital arithmetic processing unit 7 operates the trip circuit and outputs a trip command to the circuit breaker (step S7).

Next, the fact that the average value of the instantaneous power to the transformer 12 becomes almost zero will be described in detail.
The voltage applied to the transformer 12 and _{V (t) = V m sin} (ωt), the residual magnetic flux at t = 0 and phi _r, the magnetic flux of the iron core at time t is represented by the following formula (6) It is.

N in Equation (6) is the number of turns of the primary winding. When the above equation (6) is rewritten by the unit method (Per Unit method) using V _m and Nω as base quantities, the voltage V (t) and the magnetic flux φ (t) are expressed by the following equations (7-1) and (7 -2).
V (t) = sin (ωt) Expression (7-1)
φ (t) = φ _r (1-cos (ωt)) Equation (7-2)
FIG. 6 is a diagram illustrating an example of a φ-i curve for explaining inrush protection in transformer protection by the protection control device according to the first embodiment.
When the saturation magnetic flux of the iron core in the phi-i curve shown in FIG. 6 and phi _s, the exciting current i _m is given by the following equation (8). Here, m is the reciprocal of the slope of the φ-i curve.

i _m (t) = m (φ _r −cos (ωt)) φ> φ _s
= 0 φ ≦ φ _s Equation (8)
However, the saturation magnetic flux φ _s is set to 1 for simplification.
Therefore, the following formula (9) is established.
p (t) = v (t) i _m (t)
= Msin (ωt) (φ _r −cos (ωt)) φ> φ _s
= 0 φ ≦ φ _s (9)
FIG. 7 is a diagram for explaining inrush protection in transformer protection by the protection control device according to the first embodiment.
As shown in FIG. 7, when the average value of p (t) is one cycle, the power generated in inrush is zero.

  As described above, compared to the conventional current differential protection method, the current and voltage inputs are required in this embodiment, but the same arithmetic expression can be applied without depending on the configuration of the protection target. There is. According to Telegen's theorem, it is not necessary to sample current and voltage at the same time when using equations (3) and (4).

FIG. 8 is a diagram illustrating a configuration example when a communication path is used between both terminal relays of the power transmission line in the protection control device according to the first embodiment.
In FIG. 8, the example which applied this embodiment to transmission line protection is shown. The configuration of the relay of both terminals is almost the same as the configuration shown in FIG. However, the digital arithmetic processing unit 7 is provided on one end side and the other end side of the transmission line, respectively, and the digital arithmetic processing unit 7 sends current and voltage to the counterpart terminal via the communication path 13 to perform differential protection. .

  In the conventional differential protection, it is necessary to synchronize the amount of electricity sent between the two terminals, but in the present embodiment, synchronization between the current and the voltage is not necessarily required. Therefore, even when either current or voltage data is lost due to a transmission failure or the like, differential protection calculation can be performed using current and voltage data acquired at other timings.

FIG. 9 is a flowchart illustrating an example of an operation procedure when a communication path is used between both terminal relays of a power transmission line by the protection control device according to the first embodiment.
First, the current input conversion unit 4 on one end side and the other end side of the power transmission line acquires analog current value data detected by the connection CT8 (step S1).
The voltage input conversion unit 3 on one end side and the other end side of the power transmission line acquires analog voltage value data detected by the connection destination PT9 (step S2).
The current A / D conversion unit 6 on one end side and the other end side of the transmission line digitally converts the analog current value data acquired by the current input conversion unit 4 to calculate digital current value data (step S3). ).
Further, the voltage A / D converter 5 on one end side and the other end side of the power transmission line calculates the digital voltage value data by digitally converting the analog voltage value data acquired by the voltage input converter 3 ( Step S4).

  The digital arithmetic processing unit 7 on one end side of the transmission line outputs the digital current value data and digital voltage value data on one end side to the digital arithmetic processing unit 7 on the other end side of the transmission line via the communication path 13. Further, the digital arithmetic processing unit 7 on the other end side of the transmission line outputs the digital current value data and digital voltage value data on the other end side to the digital arithmetic processing unit 7 on one end side of the transmission line via the communication path 13. (Step S11). Thereby, the digital arithmetic processing unit 7 on one end side and the other end side of the transmission line can obtain digital current value data and digital voltage value data on both ends of the transmission line.

Next, the calculation unit 7a of the digital arithmetic processing unit 7 obtains the instantaneous power for each observation point as the operation amount based on the digital current value data and the digital voltage value data, and the absolute value of the sum of the obtained values. Is calculated (step S5). The determination unit 7b performs relay determination as to whether or not an accident has occurred in the protection target 2.
When the protection target accident has occurred (YES in step S6), the digital arithmetic processing unit 7 operates the trip circuit and outputs a trip command to the circuit breaker (step S7).

FIG. 10 is a diagram illustrating a configuration example used for protecting the bus in the protection control device according to the first embodiment.
FIG. 10 shows an example in which this embodiment is applied to busbar protection. In this example, PT9 and CT8 are provided at a plurality of locations on the bus. The voltage and current of the bus are acquired by the input converters 3 and 4 via PT9 and CT8, and then converted into digital quantities by the A / D converters 5 and 6. The digital arithmetic processing unit 7 uses the LAN 14 in the substation premises to perform a differential protection operation in a relay connected to the same LAN.

  In this configuration example, the current and voltage in the substation can be easily acquired using the LAN. Therefore, the differential protection using both current and voltage proposed in this embodiment can be easily realized as compared with the conventional case.

  Further, even when data loss occurs in either the current or voltage data in the LAN 14, it can be replaced with current and voltage data acquired at other timing as in the above-described transmission line protection. Therefore, a highly reliable protection relay can be provided.

FIG. 11 is a flowchart illustrating an example of an operation procedure for protecting a bus by the protection control device according to the first embodiment.
First, the current input conversion unit 4 at each location of the bus bar acquires analog current value data detected by the CT 8 as a connection destination (step S1).
The voltage input conversion unit 3 at one end side and the other end side of the busbar acquires the analog voltage value data detected by the connection destination PT9 (step S2).
The current A / D converter 6 at each location on the busbar calculates the digital current value data by digitally converting the analog current value data acquired by the current input converter 4 (step S3).
The voltage A / D converter 5 on one end side and the other end side of the busbar calculates digital voltage value data by digitally converting the analog voltage value data acquired by the voltage input converter 3 (step). S4).
The digital arithmetic processing unit 7 inputs the calculated digital current value data and digital voltage value data via the LAN 14 (step S12).

Next, the calculation unit 7a of the digital arithmetic processing unit 7 obtains the instantaneous power for each observation point as the operation amount based on the digital current value data and the digital voltage value data, and the absolute value of the sum of the obtained values. Is calculated (step S5). The determination unit 7b performs relay determination as to whether or not an accident has occurred in the protection target 2.
When the protection target accident has occurred (YES in step S6), the digital arithmetic processing unit 7 operates the trip circuit and outputs a trip command to the circuit breaker (step S7).

(Second Embodiment)
Next, a second embodiment will be described. In addition, description of the same part as what was shown in FIG. 1 among the structures in each following embodiment is abbreviate | omitted.
FIG. 12 is a block diagram illustrating a configuration example for capturing current and voltage and relay determination of the protection control device according to the second embodiment.
As shown in FIG. 12, in the second embodiment, a digital arithmetic processing unit 7-2 is provided instead of the digital arithmetic processing unit 7 shown in FIG.
The digital arithmetic processing unit 7-2 includes an operation amount calculation unit 7-2a, a suppression amount calculation unit 7-2b, and a determination unit 7-2c.

The operation amount calculator 7-2a calculates the operation amount to be protected. The suppression amount calculation unit 7-2b calculates the suppression amount of the protection target. The determination unit 7-2c performs relay determination based on the determination results by the operation amount calculation unit 7-2a and the suppression amount calculation unit 7-2b, that is, whether or not a protection target accident has occurred.
In the second embodiment, the following equation (10) is used as an equation for determination by the digital arithmetic processing unit 7-2.

  One item on the left side of equation (10) is the amount of movement, and two items are the amount of suppression. If this equation (10) is used as a determination equation, it is possible to avoid a malfunction due to a large measurement error and an increased differential amount even when the current value to be protected is large.

Further, the basic configuration and effect can be obtained by using the power phasor amount I _α V _α or the average value of the instantaneous power for a certain period instead of using the instantaneous amount of electricity (power) i _α v _α in the equation (10). does not change. The basic configuration and effect are the same as so-called complex power in which either the phasor current or voltage is a conjugate complex number.

FIG. 13 is a flowchart illustrating an example of an operation procedure performed by the protection control device according to the second embodiment.
First, analog current value data acquisition, analog voltage value data acquisition, digital current value data calculation, and digital voltage value data calculation are performed through S1 to S4 described above.

  Next, the operation amount calculation unit 7-2a of the digital arithmetic processing unit 7-2 obtains the instantaneous power for each observation point as the operation amount based on the digital current value data and the digital voltage value data, and obtains this The sum of the values is calculated (step S21).

Based on the digital current value data and the digital voltage value data, the suppression amount calculation unit 7-2a calculates the absolute value of the instantaneous power for each observation point as the suppression amount for each observation point, and the sum of these values is expressed by the formula (10 ) calculates a value obtained by multiplying the constants _{k 1} shown in (step S22). The determination unit 7-2b performs relay determination as to whether or not an accident has occurred in the protection target 2, using Expression (10) based on the calculation results of the operation amount and the suppression amount.
When the protection target accident has occurred (YES in step S6), the digital arithmetic processing unit 7 operates the trip circuit and outputs a trip command to the circuit breaker (step S7).

(Third embodiment)
Next, a third embodiment will be described.
In the third embodiment, a configuration example is shown for a case where power consumption and storage in the inductance and capacitance within the protection target cannot be ignored.
FIG. 14 is a diagram illustrating a configuration example of a protection control device according to the third embodiment.
As shown in FIG. 14, in the third embodiment, a digital arithmetic processing unit 15 is provided instead of the digital arithmetic processing unit 7. The digital arithmetic processing unit 15 includes an operation amount calculation unit 15a, an accumulated power consumption calculation unit 15b, and a determination unit 15c.

An arithmetic expression for determination by the digital arithmetic processing unit 15 is the following expression (11). This expression (11) is an expression obtained by adding the compensation terms for the stored power and the power consumption to the expression (3) described in the first embodiment.

  Ps in the second term on the left side of Equation (11) is instantaneous power stored in the protection target, and Pc in Equation (11) is power consumed in the protection target.

  In the third embodiment, the accumulated power consumption calculation unit 15b is more accurate than the first embodiment even when the consumption and accumulation of power in the inductance and capacitance within the protection target cannot be ignored. Differential operation can be realized.

Hereinafter, the compensation term as the second term on the left side of Expression (11) will be described by giving an example in which the protection target is a power transmission line.
FIG. 15 is a flowchart illustrating an example of an operation procedure performed by the protection control device according to the third embodiment.
First, analog current value data acquisition, analog voltage value data acquisition, digital current value data calculation, and digital voltage value data calculation are performed through S1 to S4 described above.

  Next, the operation amount calculation unit 15a of the digital arithmetic processing unit 15 calculates the instantaneous power for each observation point as the operation amount based on the digital current value data and the digital voltage value data, and calculates the sum of the calculated values. Calculate (step S31).

Based on the digital current value data and the digital voltage value data, the accumulated power consumption calculation unit 15b subtracts the power Pc consumed in the protection target and the power Ps accumulated in the protection target from the operation amount calculated in S31. A value is obtained (step S32).
The determination unit 7c performs relay determination as to whether or not an accident has occurred in the protection target 2 using Expression (11) based on the calculation results of the operation amount and the suppression amount.
When the protection target accident has occurred (YES in step S6), the digital arithmetic processing unit 7 operates the trip circuit and outputs a trip command to the circuit breaker (step S7).

FIG. 16 is a diagram illustrating a configuration example of a transmission line model for calculating a compensation term by the protection control device according to the third embodiment.
First, the case where the instantaneous amount of electricity to be protected is used for determination will be described. In the power transmission line model shown in FIG. 16, a capacitor (C) 16 is provided at the first terminal and the second terminal, and a series circuit of a resistor 17 and a coil 18 is provided between the first and second terminals. . Also, the input current 19 to the first terminal is i ₁ , the input current 20 to the second terminal is i _2, and the resistor (R) 17 and the coil (L) from the first terminal to the second terminal The current 21 flowing in the 18 series circuits is i ₁₂ , the voltage 22 at the first terminal is v _1, and the voltage 23 at the second terminal is v ₂ .

In this model, the following equations (12), (13), and (14) hold.

Further, the following formula (15) is established.

The first term on the right side of Equation (15) corresponds to the power consumption Pc, and the second to fourth terms on the right side correspond to the stored power Ps.
The current and voltage across the protected object can be measured with a protection relay. Further, the constants of the resistor R, the capacitor C, and the coil L can be known from the line constant obtained in advance for the transmission line. Therefore, it is possible to calculate the power consumption Pc and the stored power Ps.

FIG. 17 is a diagram illustrating a configuration example in the case of the phasor amount in the transmission line model.
Next, the case where the electricity quantity of the phasor quantity to be protected is used for the determination will be described. In the power transmission line model of FIG. 17, an admittance 24 is provided at the first terminal and the second terminal, and an impedance 25 is provided between the first and second terminals. Further, the phasor value 26 of the input current to the first terminal and I _1, the 27 phasor values of the input current to the second terminal and I _2, the impedance 25 from the first terminal toward the second terminal the current 21 flowing to _{i 12.}

In this model, the following equation (16) is established.

In equation (16), the second minute amount is ignored.
Further, in terms of complex power, the following formula (17) is established.

In equation (17), the minute amount is ignored.
The sum of the second term and the third term on the right side of the equation (17) is Pc + Ps. These values can also be obtained from measurements and prior line constants.

FIG. 18 is a diagram illustrating a configuration example of an inverter circuit model for calculating a compensation term relating to a DC / AC mixed system in the protection control device according to the third embodiment.
As shown in FIG. 18, when the protection target is an AC / DC mixed circuit, there are many DC circuits in a distributed power supply system such as photovoltaic power generation, and the DC is converted into AC by an inverter and linked to the power system. ing.
The protection of the DC circuit, the protection of the inverter, and the protection of the AC circuit up to the grid connection point have been performed by individual relays, MCCB (wiring circuit breaker) or fuse.

On the other hand, if the principle of the third embodiment is used, the DC circuit, the inverter, and the AC circuit are protected by a relay by taking the current voltage of the DC circuit and the current and voltage of the AC circuit, respectively, and taking the differential. Can be done at once. Thereby, it becomes possible to hold down cost compared with the conventional structure which requires a some relay.
In addition, there is an advantage that the blind spot on protection that can occur in the vicinity of the connection point of each circuit can be eliminated and the reliability is improved.

In the model of FIG. 18, the DC circuit is provided with a rectifier circuit including a switch 30 and a diode 31 and a DC voltage source 34.
The rectifier circuit is connected to one end of the AC circuit, and this end is connected to one end of the coil L. One end of a parallel circuit composed of a resistor R and a capacitor C is connected in series to the other end of the coil L, and the other end of the parallel circuit is connected to a rectifier circuit.

In this model, the current 19 flowing through the DC circuit is i ₁ , the voltage 22 at the DC circuit terminal is v ₁ , the current from the other end of the parallel circuit composed of the resistor R and the capacitor C is i ₂ , and the coil L of one end of the voltage 32 between the other end of the parallel circuit of the above and v _12, a current 33 flowing from one end of the coil L to the other end and i _12, resistor R and the voltage of the parallel circuit consisting of a capacitor C has a 23 and _{v 2.}

In the model of FIG. 18, it is assumed that the power consumption is negligibly small in switching. The following equation (18) holds.

Further, the following expressions (19), (20), and (21) are established.

_{i 12 + i 2 = i c} ... formula (21)
Therefore, the following formula (22) is established.

The left side of Equation (22) indicates the power at the output terminal of the model of FIG. The first term on the right side is equal to the input terminal power. The second term to the fourth term on the right side indicate the stored power Ps. i ₁₂ and v ₁₂ can be calculated by combining the above equations for the input and output terminals. Further, since the LC in the equation (22) is known from the circuit constant, the stored power Ps can be easily calculated.

The calculation of i ₁₂ and v ₁₂ will be further described. In the model of FIG. 18, the following formulas (23), (24), and (25) hold.

i ₁ v ₁ = (ic−i ₂ ) v ₁₂ (24)

A similar configuration can be applied to the protection of transformers, buses, and motors. However, the judgment formula for protection when inrush occurs in the transformer is the following formula (26). This equation (26) is an equation obtained by adding the compensation terms for the stored power and the power consumption to the equation (5) described in the first embodiment.

It should be noted that the basic configuration and effect are not changed even if the phasor amount I _a V _a or the average value for _a certain period is used instead of using the instantaneous electric amount i _a v _a in the formula (11).
By adopting the above-described configuration, it is possible to provide a protection device that can realize protection with the same configuration for various protection targets and is excellent in economy and reliability. In addition, high-precision protection can be performed by the compensation means described above.

Note that, similarly to the second embodiment, the following formula (27) obtained by adding a suppression amount to the formula (11) is established.

  The first term on the left side of Equation (27) is the amount of movement, and the second term is the amount of suppression. If this equation (27) is used for the determination, it is possible to avoid a malfunction due to a large measurement error and an increased differential amount when the current value to be protected is large.

(Fourth embodiment)
Next, a fourth embodiment will be described.
In the fourth embodiment, an example of protecting a symmetrical three-phase AC power system will be described.
FIG. 19 is a diagram illustrating a configuration example of a protection control device according to the fourth embodiment.
Assume that the input currents i ₁ , i _2, i ₃ of each phase of the configuration shown in FIG. 19 are expressed by the following equations (28) to (30).
i ₁ = I _a cos (ωt−φ) (28)
i ₂ = I _b cos (ωt−2π / 3−φ) Equation (29)
i ₃ = I _c cos (ωt−4π / 3−φ) Equation (30)
Assume that the output currents i ₄ , i _5, i ₆ of each phase of the configuration shown in FIG. 19 are expressed by the following equations (31) to (33).
i ₄ = I _{a '} cos (ωt−φ ′) (31)
i ₅ = I _{b ′} cos (ωt−2π / 3−φ ′) Equation (32)
i ₆ = I _{c ′} cos (ωt−4π / 3−φ ′) Equation (33)
Assume that the input voltages v ₁ , v _{2, and} v ₃ of each phase of the configuration shown in FIG. 19 are expressed by the following equations (34) to (36).
v ₁ = V _a cos (ωt) Equation (34)
v ₂ = V _b cos (ωt−2π / 3) Equation (35)
v ₃ = V _c cos (ωt−4π / 3) Equation (36)
Assume that the output voltages v ₄ , v _{5, and} v ₆ of each phase of the configuration shown in FIG. 19 are expressed by the following equations (37) to (39).
_{v 4 = V a'cos (ωt} -δ') ... formula (37)
v ₅ = V _{b ′} cos (ωt−2π / 3−δ ′) Equation (38)
v ₆ = V _{c ′} cos (ωt−4π / 3−δ ′) Equation (39)
As an example of Telegen's theorem, for a three-phase AC input, the instantaneous power sum p (t) is given by the following equation (40).
p (t) = i ₁ v ₁ + i ₂ v ₂ + i ₃ v ₃ Formula (40)
Similarly, regarding the output of the three-phase alternating current, the sum p (t) of the instantaneous power is expressed by the following formula (41).
p (t) = i ₄ v ₄ + i ₅ v ₅ + i ₆ v ₆ Formula (41)
By using the sum of these inputs and outputs as the left side of Equation (3) or Equation (10), it can be used to protect a three-phase AC circuit.
For example, the following formula (42) that does not use the suppression amount and the following formula (43) that uses the suppression amount hold.

Left side of _{p a} formula (42) or equation (43) is a phase of the instantaneous power of the three phases.
Further, if the transmission line is a protection target in the fourth embodiment, it is impossible to detect the accident of each phase as compared with the conventional current differential relay, but if it is not necessary to detect the accident of each phase, As described in the first embodiment, since it is not necessary to send the current and voltage at each location to the counterpart terminal, the amount of transmission can be reduced.

Here, the operation when the above equation (43) is used as a determination equation will be described. Here, the operation of the digital arithmetic processing unit 7-2 will be described. FIG. 20 is a flowchart illustrating an example of an operation procedure performed by the protection control device according to the fourth embodiment.
First, analog current value data acquisition, analog voltage value data acquisition, digital current value data calculation, and digital voltage value data calculation are performed through S1 to S4 described above.

  Next, the operation amount calculation unit 7-2a of the digital arithmetic processing unit 7-2 calculates the instantaneous power of the input of each phase of the three-phase alternating current as the operation amount based on the digital current value data and the digital voltage value data. The sum of the instantaneous powers of the sum and three-phase AC outputs is obtained, and the sum of the obtained values is calculated (step S41).

Based on the digital current value data and the digital voltage value data, the suppression amount calculation unit 7-2a calculates the sum of the instantaneous power of the input of each phase of the three-phase alternating current and the instantaneous power of the output of the three-phase alternating current as the suppression amount. It calculates the sum, and calculates the value obtained by multiplying a constant k ₁ shown in formula (43) to the absolute value of the sum of the calculated value (step S42).
The determination unit 7c performs relay determination as to whether or not an accident has occurred in the protection target, using Expression (43) based on the calculation results of the operation amount and the suppression amount.
When the protection target accident has occurred (YES in step S6), the digital arithmetic processing unit 7 operates the trip circuit and outputs a trip command to the circuit breaker (step S7).

(Fifth embodiment)
Next, a fifth embodiment will be described.
In the fifth embodiment, an example in which relay determination is performed by applying an operator to a digital current value or a digital voltage value will be described.
FIG. 21 is a diagram illustrating an example of current and voltage waveforms in the protection control device according to the fifth embodiment.
FIG. 21 shows a waveform of a current i, a waveform of a value obtained by differentiating the value of the current i, a waveform of a voltage v, and a waveform of a value obtained by differentiating the value of the voltage v.

  According to Telegen's theorem, voltage and current are not limited to instantaneous voltage and current amount for relay determination, and the result of calculating them may be used. It is known that the Telegen's theorem holds even when Kirchhoff's operator is applied to at least one of the current and voltage in the formula (2) indicating the Telegen's theorem.

Kirchhoff's operator refers to an operator that can satisfy Kirchhoff's law even if the operator is subjected to differentiation or integration. When this operator is Λ, the following equation (44) is established from the equation (2).

For example, an accident can be detected with high sensitivity regardless of the magnitude of the power flow by using the time differential value of the current for relay determination.
Further, by using the time differential value of the voltage for relay determination, an accident can be detected with high sensitivity even when the voltage does not sufficiently decrease due to an accident at the end of a short-distance transmission line, for example.
Further, by using the integrated value of voltage or current for a certain time for relay determination, the influence of harmonic current or surge generated in the event of a system fault can be filtered, and a highly reliable relay can be realized. The above effects can also be obtained by a combination of these.

FIG. 22 is a flowchart illustrating an example of an operation procedure performed by the protection control device according to the fifth embodiment.
First, analog current value data acquisition, analog voltage value data acquisition, digital current value data calculation, and digital voltage value data calculation are performed through S1 to S4 described above.

  Next, the calculation unit 7a of the digital arithmetic processing unit 7 obtains values obtained by applying the Kirchhoff operator to the instantaneous power for each observation point as the operation amount based on the digital current value data and the digital voltage value data. The sum total of the obtained values is calculated (step S51).

The determination unit 7b performs relay determination as to whether or not an accident has occurred in the protection target 2 based on the calculation result.
When the protection target accident has occurred (YES in step S6), the digital arithmetic processing unit 7 operates the trip circuit and outputs a trip command to the circuit breaker (step S7).

Note that the methods described in the above embodiments are, as programs that can be executed by a computer, magnetic disks (floppy (registered trademark) disks, hard disks, etc.), optical disks (CD-ROMs, DVDs, etc.), magneto-optical disks. (MO), stored in a storage medium such as a semiconductor memory, and distributed.
In addition, as long as the storage medium can store a program and can be read by a computer, the storage format may be any form.
In addition, an OS (operating system) running on a computer based on an instruction of a program installed in the computer from a storage medium, MW (middleware) such as database management software, network software, and the like realize the above-described embodiment. A part of each process may be executed.
Furthermore, the storage medium in each embodiment is not limited to a medium independent of a computer, but also includes a storage medium that downloads and stores or temporarily stores a program transmitted via a LAN, the Internet, or the like.
Further, the number of storage media is not limited to one, and the case where the processing in each of the above embodiments is executed from a plurality of media is also included in the storage media in the present invention, and the media configuration may be any configuration. The computer in each embodiment executes each process in each of the above embodiments based on a program stored in a storage medium, and a single device such as a personal computer or a plurality of devices are connected to a network. Any configuration of the system or the like may be used.
In addition, the computer in each embodiment is not limited to a personal computer, and includes an arithmetic processing device, a microcomputer, and the like included in an information processing device, and is a generic term for devices and devices that can realize the functions of the present invention by a program. Yes.
Although several embodiments of the invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Protection control apparatus, 2 ... Protection object, 3 ... Voltage input conversion part, 4 ... Current input conversion part, 5 ... Voltage A / D conversion part, 6 ... Current A / D conversion part, 7, 7 -2, 15 ... digital operation processing unit, 7a ... calculation unit, 7b ... determination unit, 7-2a, 15a ... operation amount calculation unit, 7-2b ... suppression amount calculation unit, 7c, 7-2c, 15c ... determination unit 8 ... CT (current transformer), 9 ... PT (transformer), 10 ... PV module, 11 ... inverter, 12 ... transformer, 13 ... communication path, 14 ... LAN, 15b ... accumulated power consumption calculation unit, 16 DESCRIPTION OF SYMBOLS ... Capacitor, 17 ... Resistance, 18 ... Coil, 19 ... Current at power transmission end, 20 ... Current at power reception end, 21 ... Current flowing through R and L, 22 ... Voltage at power transmission end, 23 ... Voltage at power reception end, 24 ... Admittance, 25 ... Impedance, 26 ... Current phasor at power transmission end, 27 ... Current at power reception end 28 ... Voltage phasor at transmission end, 29 ... Voltage phasor at reception end, 30 ... Switch, 31 ... Diode, 32 ... Voltage in circuit, 33 ... Current in circuit, 34 ... DC voltage source, 35 ... Three-phase AC current input, 36 ... three-phase AC current output, 37 ... three-phase AC voltage input, 38 ... three-phase AC voltage output, 39 ... current waveform, 40 ... current differential value waveform, 41 ... voltage waveform, 42 ... voltage differential value Waveform.

Claims (13)

A calculation unit that calculates a sum of the plurality of terminals of the power based on values obtained by sampling currents and voltages of the plurality of terminals of the power system as the protection target; and
A protection control apparatus comprising: a determination unit that determines whether or not an accident has occurred in the protection target by comparing the sum calculated by the calculation unit with a predetermined threshold value. The calculation unit includes:
2. The protection according to claim 1, wherein a sum total of the plurality of terminals is calculated based on values obtained by sampling currents and voltages of a plurality of terminals of the power system to be protected at arbitrary times, respectively. Control device. The calculation unit includes:
The protection control device according to claim 1, wherein a sum total of the plurality of terminals of electric power based on values obtained by sampling currents and voltages of the plurality of terminals of the power system to be protected at the same time is calculated. . The calculation unit includes:
4. The sum total of the plurality of terminals of instantaneous power based on a value obtained by sampling currents and voltages of a plurality of terminals of the power system to be protected is calculated. 5. The protection control device described. The calculation unit includes:
4. The sum total of the plurality of terminals of the power based on a value obtained by sampling the phasor amount of the current and the phasor amount of the voltage of the plurality of terminals of the power system to be protected is calculated. The protection control device according to any one of claims. The calculation unit includes:
The total sum of the plurality of terminals of an average value of power in a predetermined cycle based on values obtained by sampling currents and voltages of a plurality of terminals of the power system to be protected at the same time is calculated. The protection control device according to any one of 1 to 3. The calculation unit includes:
The operation amount of the protection target as the sum of the plurality of terminals of the instantaneous power based on the values obtained by sampling the current and voltage of the plurality of terminals of the power system to be protected, and the calculated value to the sum The protection control device according to claim 1, wherein the suppression amount of the protection target is calculated. In the power system, a DC circuit and an AC circuit are mixed,
The calculation unit includes:
Sample DC current and DC voltage of at least one terminal of the power system to be protected, respectively sample AC current and AC voltage of at least one terminal of the power system, and instantaneous power based on these sampled values The protection control device according to claim 1, wherein a sum total of the plurality of terminals is calculated. The calculation unit includes:
The amount of operation of the protection target as the sum of the plurality of terminals based on the values obtained by sampling the current and voltage of the plurality of terminals of the power system to be protected at an arbitrary time, and the protection target The protection control device according to claim 1, wherein power stored in a power system and power consumed in the power system to be protected are calculated. The power system as the protection target is a symmetrical three-phase AC power system,
The calculation unit includes:
The protection control device according to claim 1, wherein a sum of an input current and an output of each phase of the symmetrical three-phase AC power system is calculated. The calculation unit includes:
A sum total of the plurality of terminals of instantaneous power obtained by applying a Kirchhoff operator to at least one of values obtained by sampling currents and voltages of a plurality of terminals of a power system to be protected is calculated. The protection control device according to 1. A protection control method for protecting a power system having a plurality of terminals as a protection target,
Calculate the sum of the plurality of terminals of the power based on the values obtained by sampling the current and voltage of the power system,
A protection control method comprising: determining whether or not an accident has occurred in the protection target by comparing the calculated sum with a predetermined threshold value. A program used for a computer operating as a part of the protection control device according to claim 1,
The computer,
A protection control program for causing the calculation unit and the determination unit to function.

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