JP4033136B2 - Overcurrent protection system - Google Patents

Description

  More particularly, the present invention relates to an overcurrent protection system having a function of locking an operation output of a connection protection relay based on phase determination of a system current.

  FIG. 3 shows a configuration diagram of a general power distribution system. In FIG. 3, 100 is a distribution substation, 101 is a power source (showing a power transformer connected to a host system not shown), 102 is a bus, Ry1 is a protection relay, CB1 is a circuit breaker, and 200 is a distribution. An electric wire (feeder), 201 is a bus near the power receiving point of the consumer 300, Ry2 is an overcurrent protection relay, CB2 is a circuit breaker, 300 is a consumer, and 301 is a private power generation facility in the consumer 300.

  The distribution substation 100 receives power from the upper system (66 [kV] to 110 [kV]), and steps down the voltage by the power transformer as the power source 101 in the substation 100 and supplies it to the distribution line 200. There are a plurality of power transformers, and power is distributed to 4 to 12 distribution lines 200 per transformer via the bus 102. In FIG. 3, these are collectively shown as one impedance.

In a typical example, the voltage on the primary side of the power transformer in the distribution substation 100 is 66 [kV] (may be 77 [kV] depending on the region), and the secondary side is 6 .6 [kV] system. Normally, a system of 6.6 [kV] or less is called a power distribution system.
This power distribution system is a non-grounded system, and a zero-phase resistor and a zero-phase voltage generated at the time of a ground fault are inserted by inserting a zero-phase resistor on the secondary side of a grounding transformer (GPT) not shown in order to detect a ground fault. The current is detected and the protective operation is performed by the ground fault protection relay.

  Such a power distribution system is intended to distribute power to the customer 300, and usually a large power source (short-circuit power source) is not provided on the customer side. Even if a power source is provided, there is only a private power generation facility 301 as shown in FIG. 3, and no current is supplied from the customer 300 to the distribution system side, and the configuration is a radial system. Therefore, it is not connected to the distribution line at the end. That is, the private power generation equipment 301 in the customer 300 has a system configuration that can be connected to the distribution line 200, but this type of power generation equipment 301 is provided for use during maintenance and abnormal situations.

  The protection and control system for the power distribution system is designed in consideration of such system conditions, and includes the following protection system including the electric equipment in the customer 300.

(1) Protection in the event of a short-circuit accident In a three-phase distribution line, the case where two or three of the three phases come into contact is called a short-circuit accident. Normally, an overcurrent protection relay with inverse time characteristics is used for such a short-circuit accident. As is well known, overcurrent protection relays with inverse time characteristics have characteristics such that when a current greater than the rated current flows through the distribution line, the current value and the time until operation are inversely proportional. It is a protection relay.

  In FIG. 3, when a short circuit accident occurs at a point F <b> 3 in the customer 300, a short circuit current flows from the distribution substation 100. In the illustrated example, since there is no branching in the middle, short-circuit currents of the same value flow through the relays Ry1 and Ry2. Usually, another customer is also connected between the distribution substation 100 and the customer 300. Therefore, in the case of an accident in a specific customer 300 such as this accident, the vicinity of the customer 300 is blocked. It is desirable to shut off only the container CB2, and this will reduce the influence because other customers will not be interrupted.

  For this reason, a difference is intentionally provided in the operation time between the relay Ry1 in the distribution substation 100 and the relay Ry2 on the customer 300 side, and the relay Ry1 is 0.2 in comparison with Ry2. It is set to operate with a delay of about 0.5 seconds. This time is a numerical value with some allowance in the time until the short circuit current stops when the relay Ry2 detects this when the short circuit accident occurs at the point F3 and operates the circuit breaker CB2. It takes at least about 150 [ms] before the relay operates to open the circuit breaker).

  Thus, if a certain difference is provided in the operation time of the relays Ry1 and Ry2, the breaker CB2 on the customer 300 side always operates before the breaker CB1 on the substation 100 side, and the short-circuit accident is solved. For this reason, the circuit breaker CB1 does not operate. This is the same when a short-circuit accident occurs in any customer connected to the distribution line 200 or the bus 201.

  Here, FIG. 4 is a diagram illustrating an example of the operation time characteristic and the operation time accuracy of the overcurrent protection relay having the inverse time characteristic. The relationship between the operating time and the input current value (generally the ratio to the rated current) is similar, but the absolute value of the operating time can be set in 0.1 steps (about) up to 10 with a standard value of 1. This is called a lever.

Relays Ry1 and Ry2 shown in FIG. 3 are relays having the same characteristics, and the operation time is adjusted by changing the setting of the lever. That is, assuming that the input current at the time of complete short-circuiting (when the resistance at the short-circuiting point is zero) in the power distribution system of FIG. 3 is 500%, the operating time difference between the relays Ry1 and Ry2 is about 0.5 seconds at this current value. The lever settings have been changed.
Note that the vertical axis n on the right side of the operating time characteristic in FIG. 4 indicates the settling value of the operating time.

(2) Voltage control In recent years, distributed power sources based on renewable energy have become widespread due to trends in the liberalization of power and increased awareness of environmental issues. When a large-capacity distributed power source is connected in the current distribution system, if the current flowing through the distribution line (hereinafter referred to as tidal current) greatly changes depending on the amount of generated power, the voltage at a specific point falls within the specified value. However, it is becoming difficult to maintain the voltage value at the prescribed 101 ± 6 [V] throughout the distribution system.

  In a long distribution line, even when only the load is connected, it is difficult to maintain the terminal voltage at the specified 101 ± 6 [V] due to the voltage drop due to the impedance of the distribution line. An automatic voltage regulator referred to as SVR is installed, and the voltage on the load side is increased by tap control of the transformer to maintain the voltage value within a specified range. This voltage regulator detects the voltage on the power supply side (distribution substation side) and controls the voltage on the load side, and has no function of controlling the voltage on the reverse side, that is, the power supply side.

For example, when the voltage becomes higher than the target value, the voltage value is changed by controlling the tap of the transformer, but the voltage hardly changes and remains at the lower limit value. On the contrary, when the voltage becomes lower than the target voltage, the voltage is controlled to increase and remains at the upper limit value.
Under such a voltage control system, when such a distributed power source is connected to the load side, it has become difficult to maintain an appropriate voltage value over the entire distribution system.

Due to the above circumstances, it is difficult to maintain the voltage value in the distribution system. As a countermeasure, the two distribution lines are connected at the end in order to increase the capacity of the distribution line and reduce the influence of the distributed power supply. Operation to do is considered.
FIG. 5 shows an example of this type of interconnected system (loop system), which has a configuration in which two distribution lines are interconnected via a bus at a power receiving point of a consumer.

In FIG. 5, the description will focus on the differences from FIG. 3. 120 is a distribution substation, 121 is a power source (power transformer), 122 is a bus, Ry3 is an overcurrent protection relay, CB3 is a circuit breaker, and 220 is The distribution line, 221 is a bus, Ry4 is an overcurrent protection relay for connection (connection protection relay), CB4 is a circuit breaker, and the bus 201 on the distribution line 200 side and the bus 221 on the distribution line 220 side It is connected via the circuit breaker CB4. Reference numeral 501 denotes a connection line.
In such an interconnection system, the current per distribution line is reduced, so that the voltage drop in the line is reduced and the voltage in the distribution line can be easily maintained.

However, the above interconnection system has the following problems on the protection system.
First, when this type of system is protected by a conventional protection system, the operation time of the relay Ry2 is normally about 0.2 seconds (due to time coordination according to the system configuration in the customer 300 premises, the operation time is roughly It is about 0.5 to 0.2 seconds, but is assumed to be 0.2 seconds below).
In contrast, the operation time of the relays Ry1 and Ry3 in the distribution substations 100 and 120 is set to about 0.5 to 1 second (hereinafter assumed to be 0.5 seconds), and the relay Ry4 is Since it is on the load side, it is assumed that it is set to 0.2 seconds like the relay Ry2.

  Now, at the time of a short circuit accident at the point F3 in the customer 300 premises, it is required that the nearby circuit breaker CB2 operates and the other circuit breakers do not operate. At this time, the relay Ry2 operates in about 0.2 seconds, and the accident disappears when the circuit breaker CB2 is turned off. Further, since the relays Ry1 and Ry3 have a long operation time as described above (0.5 seconds), the circuit breakers CB1 and CB3 do not operate.

Further, since the operation time of the interconnection protection relay Ry4 is 0.2 seconds, it operates with no time difference from the relay Ry2 (the current value flowing through the relay Ry2 is larger than Ry4, so that the time-limited characteristics) Relay Ry4 is likely to operate later than Ry2).
In order to prevent the relay Ry4 from operating reliably, it is necessary to ensure a time difference of about 0.2 seconds with respect to the relay Ry2 in consideration of an accident current value or the like. In addition, it is necessary to coordinate the time between the relay Ry4 and the other relays Ry1 and Ry3. As a result, the operation time of the relays Ry1 and Ry3 becomes longer than the present time.

On the other hand, when a short circuit accident occurs at the point F2 on the distribution line 220, the relays Ry3, Ry4 and the circuit breakers CB3, CB4 should operate, and the other relays should not operate. However, in the current time setting, first, after the operation of the relays Ry4 and Ry2, the circuit breakers CB4 and 2 are operated (OFF) in about 0.2 seconds, and thereafter (about 0.5 seconds later), the relays Ry3 and circuit breakers are operated. CB3 operates (OFF). Therefore, the circuit breaker CB2 operates unnecessarily.
In order to avoid this, it is necessary to operate the circuit breaker CB4 earlier than CB2. However, as described above, in an accident at the point F3 in the customer 300 premises, the circuit breaker CB2 should be operated with priority over CB4. Therefore, it is difficult to set the operation time that is optimal for any of the accident points F2 and F3.

Here, the conventional overcurrent protection relay with inverse time characteristics is an electromagnetic type, based on the principle that the mover rotates faster when the current value flowing through the coil is large, and rotates slowly when the current value is small. In addition, various characteristics are realized by mechanically adjusting the rotation time of the mover.
On the other hand, in recent protection relay technology, a digital data obtained by A / D (analog / digital) conversion of current input is processed by a data processing device such as a microcomputer to realize a desired function. Digital relays that achieve a predetermined performance by combining these are becoming widespread, and are gradually being supplied at low cost by mass production.

In FIG. 5, the problem that appropriate protection coordination cannot be achieved depending on the accident point is that the operation time of the protection relay cannot be changed. To solve this problem, the operation time is set according to the accident occurrence point. It is sufficient if there is a function that can change the value flexibly, and this function may be realized by a digital relay.
Therefore, for example, for the relay Ry2 in the vicinity of the customer 300, when it is determined that the accident has occurred because the current exceeds the set value, the current after the accident is the same as the current before the accident. When it is in phase, it is judged as an accident in customer 300 (accident point F3), and it is operated instantaneously in a short time of about 0.2 seconds, and when it is in reverse phase (accident point F2), it is judged as an external accident. The operation time of the connection protection relay Ry4 (breaker CB4) provided between the distribution line 200 and the other distribution line 220 is set to be short as described above while being operated in a long time period of about 0.7 seconds. It is conceivable to set the time between the long time and the long time (about 0.4 to 0.5 seconds).

However, this requires a timed coordination in three stages: relay Ry2, relay Ry4, and relays Ry1 and Ry3 in distribution substations 100 and 120, so the operating time of relays Ry1 and Ry3 is slightly longer, Delay from 0.5 seconds to 0.7 seconds. Further, depending on the system constants and configuration, there are cases where it is not possible to cope only by delaying the operation time, and there is a limit to delaying the operation.
In such a case, a means for shortening the delay time required for cooperation is required by taking time cooperation in two stages as in the present situation.

For the purpose of preventing multi-stage overcurrent protection coordination by preventing unnecessary protection operations, when a signal based on overcurrent detection in a system lower than the self is received, the self-protection operation is performed by the operation of the determination means. An overcurrent protection device that locks the command output operation is described in Patent Document 1 below.
Further, Patent Document 2 below discloses a protective relay system in which operation characteristic data can be transmitted and received between the upper relay and the lower relay, and the respective operation characteristics can be freely set.

Japanese Patent Laid-Open No. 11-206008 (Claims 1-3, FIG. 2, etc.) JP-A-7-87658 (Claims 1 to 3, FIG. 1 etc.)

As described above, there is a limit to delaying the operation time of the relay for time coordination, and there is a problem that appropriate protection coordination cannot be achieved by the method of adjusting the set value according to the accident occurrence point.
In addition, the protection systems described in Patent Documents 1 and 2 lock the relay operation of the upper system by transmission / reception between the load-side lower system without power supply and the upper system with power supply, or the upper or lower system. However, in this case, if the relay operates at one location of the lower system, the fault point is always on the lower side of the relay, so the upper system relay that should be locked is naturally It will be decided.
However, if there is a power supply (distributed power supply) in the lower system, the upper relay to be locked may change depending on the operating state of the distributed power supply. In the interconnection system as shown in FIG. There are two relays Ry1 and Ry3 in the upper system with respect to the lower relay Ry2, and the lower relay Ry2 cannot determine which relay should be locked depending on the accident point. In any case, it is difficult to specify the upper relay to be locked only by the information that the lower relay is operated.
Furthermore, in the prior art of Patent Document 1, since a lock signal is passed between a higher-order relay and a lower-order relay that are far away from each other, the signal transmission distance is long, and a large-scale transmission device is required, resulting in an increase in cost. .

  Therefore, the present invention pays attention to the fact that the current flowing through the relay Ry2 in the vicinity of the customer 300 is in phase with the current before the occurrence of the accident in the premises accident of the customer 300. Unnecessary operation of the relay Ry4 is prevented by locking the operation of the connection protection relay Ry4 in the power receiving facility. Also, the relay Ry2 (and the relay Ry4) and relays in the distribution substations 100 and 120 The time coordination in two stages of Ry1 and Ry3 is taken.

  In the interconnection system of FIG. 5, the relay Ry <b> 4 operates even if an accident occurs in any of the distribution lines 200 and 220 except for a premises accident of the customer 300. For this reason, it is possible to determine whether the current state of the current flowing through the relay Ry2 in the vicinity of the customer 300 is the same or opposite before and after the occurrence of the accident. In other words, in the case of a customer premises accident, unnecessary operation of the relay Ry4 can be prevented by locking the operation of the relay Ry4.

The relay Ry4 operates even in a local accident at the distribution substations 100 and 120. However, in this internal short-circuit accident, the circuit breaker CB1 or CB3 is opened (OFF) by an instantaneous element of the relay Ry1 or Ry3, so about 0.2 seconds. If there is a period of time, there is no possibility that the relay Ry4 will operate unnecessarily due to erroneous determination.
In such a system, it is necessary to transmit a signal to detect the current of the relay Ry2 and lock the operation of the relay Ry4. However, both of the relays Ry2 and Ry4 are usually in the power receiving facility of the customer 300. In general, the switchboard is centrally installed in one place, so that transmission by wiring is possible. Even if the locations of both relays are separated, there is no problem because the communication means can be configured relatively inexpensively.

Therefore, the invention described in claim 1 is an interconnection system in which two distribution lines are interconnected via a circuit breaker having an interconnection protection relay, and operates when a customer's premises accident occurs. In the interconnection system including a protection relay for detecting a local accident and a circuit breaker, the protective relay for detecting a local accident is:
The phase judgment function that detects whether the current phase before and after the accident is the same phase or the opposite phase to determine internal accidents and external accidents within the customer premises, and the current phase before and after the accident occurrence are the same phase. A relay function that obtains an operation output instantly when an overcurrent is detected, a relay function that obtains an operation output when the current phase before and after the occurrence of the accident is in reverse phase and the overcurrent continues for a predetermined period, and a current phase before and after the occurrence of the accident And means for outputting an in-phase detection signal indicating that they are in phase,
The interconnection protection relay has a function of locking an operation output for a predetermined period when the in-phase detection signal is received.

According to the present invention, it is possible to prevent unnecessary operation of the relay by locking the operation output of the interconnection protection relay when a customer's premises accident occurs, and to shorten the transmission distance of the lock signal. Simplification and cost reduction of the transmission device and the like can be achieved. In addition, in the event of an accident on the distribution line, the connection protection relay is the first by setting the operation time in two stages: the relay near the customer and the protection relay for the connection, and the relay in the distribution substation. It is possible to perform time cooperation such that the relays in the vicinity of the customer are operated, and then the time delay required for the cooperation can be minimized. Furthermore, by comparing the phase of the current before and after the accident, there is an effect that it is possible to determine whether or not there is a power supply in the lower system (more precisely, whether or not the lower power supply affects the protection determination).
In general, in a distribution system in which distributed power sources are interconnected, appropriate protection coordination of an overcurrent protection system including a relay on the customer side can be achieved, and the applicable range can be greatly expanded. In particular, a protection system having such a determination function can be realized at a relatively low cost due to recent advances in electronic technology.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a power distribution system to which this embodiment is applied, and the system configuration itself is substantially the same as FIG.

However, the length of the distribution lines 200 and 220 is assumed to be about 3 [km] which is an average value assuming a standard Japanese distribution system. The power supply impedance of the distribution substations 100 and 120 is almost ωL (ω = 2πf, f: power supply frequency, L: inductance), and 0.33 [Ω]. In addition, the impedance of the distribution lines 200 and 220 is a value of ωL only and is 1.2 [Ω], and the resistance that actually exists is ignored.
In addition, in the short circuit accident of a distribution line, a complete short circuit is rare and it is often accompanied by arc resistance. In addition, the impedance varies depending on the aspect of the accident, current value, weather conditions, and the like, and also changes with time. Therefore, the normal failure calculation is performed only with ωL, and the set value is determined in consideration of the maximum resistance value.

Furthermore, the impedance Xd ′ of the private power generation equipment 301 provided in the consumer 300 and connected to the distribution line 200 is a value in less than 1 second from several tens [ms] at the time of the transient impedance accident. It will be about 5 [Ω]. This value increases with time, and becomes approximately Xd (80 [Ω]) when time elapses until the steady state. Therefore, Xd ′ (about 7.5 [Ω]) was used for the trial calculation of the short-circuit current.
The system impedance of the customer 300 is 0.1 [Ω].

  When the fault current is calculated based on this assumption, the following is obtained. The rated currents of the distribution lines 200 and 220 are 400 [A], the lead-in wires of the customer 300 are rated current 100 [A], and the voltage class is 6.6 [kV].

(1) Accident at the customer's premises In a three-wire short-circuit accident (accident point F3) at the premises of the customer 300, a short-circuit current flows from the distribution lines 200 and 220, and the current shown in Formula 1 is approximately the accident point for one phase. It flows into F3.
[Formula 1]
(6,600 [V] / √3) / {(power source impedance + distribution line impedance) / 2 + (premises system impedance)} ≈4.4 [kA]

For this reason, the currents at the installation points of the protection relays Ry1, Ry3, Ry4 are all about 2.2 [kA], and the ratio to the rated current is 550%. The current at the installation point of the protection relay Ry2 is 4.4 [kA] (4400% of the rated current).
Usually, in an area exceeding 20 times the rating, the instantaneous element of the relay operates at several tens [ms] (determined by the relationship with the overcurrent intensity with respect to the short-circuit current of the local equipment). Therefore, in this case, the relay Ry2 operates first, and the other relays Ry1, Ry3, and Ry4 may have an operation time of about 0.5 seconds.

In the above case, since the fault current value is large, the relay Ry2 operates instantaneously. However, when the fault point resistance (arc resistance) r of about 2 [Ω] enters the fault point F3, the current becomes as shown in Equation 2. Note that the combined impedance of the left-hand side denominator in Equation 2 is about 2.18 [Ω].
[Formula 2]
(6,600 [V] / √3) / {(power source impedance + distribution line impedance) / 2 + (local system impedance + r)} ≈1.75 kA

At this time, the currents at the installation points of the relays Ry1, Ry3, Ry4 are all about 0.82 [kA], and the ratio to the rated current is 205%, and the current at the installation point of the relay Ry2 is 1750%, That instantaneous element does not work.
Here, when the set value n = 1 in the digital overcurrent protection relay having the inverse time characteristic shown in FIG. 4, the relays Ry1, Ry3, Ry4 operate in about 1 second, and the relay Ry2 on the customer 300 side. Operates in about 0.25 seconds, so time coordination can be achieved.

(2) A short circuit accident at the point F2 on the distribution line 220 will be examined in the setting of the protection relay in consideration of the above-mentioned customer premises accident. The current value in this case is as follows.
Current of distribution lines 200 and 220: (6,600 [V] / √3) / (power supply impedance + distribution line impedance) ≈2.49 [kA]
-Current from private power generation equipment 301 of customer 300:
(6,600V / √3) / (local system impedance + power supply impedance (impedance Xd ′ of private power generation equipment 301)) ≈0.50 [kA]

  That is, at the fault point F2 (no fault point resistance), the short-circuit current flowing from the distribution lines 200 and 220 is about 2.49 [kA], and the short-circuit current by the personal generator 301 of the customer 300 is about 0.2. Since it is 5 [kA], the total of these is about 5.48 [kA]. That is, approximately 2.49 [kA] (623%) flows through the relays Ry1 and Ry3, and approximately 2.99 (= 2.49 + 0.5) [kA] (748%) and relay Ry2 flows through the relay Ry4. Current of 0.5 [kA] (500%) flows through the current.

In such an accident, it is necessary for Ry4 to operate earlier than relays Ry1 and Ry3, and this operation time difference is also required to be at least 0.2 seconds. Moreover, about the relay Ry2 of the consumer 300 vicinity, it is necessary to set the operation time between the relays Ry1, Ry3, and Ry4.
As countermeasures, for example, the setting value n of the relays Ry1 and Ry3 is n = 2, the setting value n of the relay Ry4 is n = 1, and the setting value n of the relay Ry2 is n = 1.5. With the three-stage setting, the time delay required for cooperation increases.

  Therefore, in the present embodiment, by setting the setting values of the relays Ry1 and Ry3 to be the same (for example, n = 2) and setting the setting values of the relays Ry2 and Ry4 to be the same (for example, n = 1), two-step time coordination is achieved. It is possible to prevent unnecessary operation of the relay Ry4 by sending a signal from the relay Ry2 in the vicinity of the customer 300 to the connection protection relay Ry4 and locking the operation in response to a premises accident of the customer 300 I tried to do it.

FIG. 2 is a functional block diagram showing a schematic configuration of a relay (customer premises accident detection protection relay) Ry2 and a connection protection relay Ry4 in the vicinity of the customer 300.
In FIG. 2, the relay Ry <b> 2 near the customer 300 has a phase determination function 21, relay functions 22 and 23, AND functions 24 and 25 to which these outputs are added, and pulse generation means 26.

The phase determination function 21 is a function that compares the current current waveform input from the current transformer with the current waveform several cycles before and determines whether both phases are in phase or in phase. 1 outputs a judgment signal for the premises accident (internal accident) of the customer 300, and outputs a judgment signal for an external accident (for example, an accident at the point F2 on the distribution line 120 in FIG. 1) in the case of reverse phase.
Also, the relay function 22 is an overcurrent protection function that instantaneously generates an operation output when an overcurrent is detected, for example, and the relay function 23 is an overcurrent protection function that generates an operation output when an overcurrent is detected continuously for a predetermined time, for example. These outputs are input to the AND functions 24 and 25 together with the respective determination signals.

  As a result, an accident detection signal is output from the AND function 24 instantly when an internal accident is determined, and from the AND function 25 after a predetermined time has elapsed (after the operation of the interconnection protection relay Ry4) when an external accident is determined. An accident detection signal is output. Note that an output circuit for tripping the circuit breaker CB2 in FIG. 1 by these accident detection signals is not shown.

  The output signal of the phase determination function 21 is input to the pulse generation means 26, which outputs one internal accident detection pulse having a pulse width of about 100 [ms]. Here, the reason why the pulse width is set to about 100 [ms] is that, on the receiving side, a circuit that receives a contact signal such as an auxiliary relay cannot perform a latch operation unless this time is at least. On the other hand, the reason why the pulse has such a short width is to immediately respond to a case where there are a plurality of accident points such as progress accidents and multiple accidents or a change in the situation.

In the interconnection protection relay Ry4, the output signal of the pulse generating means 26 is applied to the pulse width expanding means 43. The expanding means 43 has a function of expanding the pulse width of the internal accident detection pulse to a certain time. Have. The pulse width expanding means 43 may be provided on the relay Ry2 side.
Further, the current of the interconnection line 501 input from the current transformer is applied to relay functions 41 and 42 that detect overcurrent, and these outputs are input to AND functions 45 and 46. Here, the relay function 41 has an overcurrent protection function that generates an operation output when an overcurrent is detected continuously for a predetermined time, and the relay function 42 is an overcurrent that instantaneously generates an operation output when an overcurrent is detected. Has a protective function.

Further, the output of the pulse width expanding means 43 is input to the AND function 45 as it is, inverted by the NOT function 44 and input to the AND function 46. The outputs of the AND functions 45 and 46 are configured to trip the circuit breaker CB4 of FIG.
As described above, the set values of the operation times of the relays Ry2 and Ry4 are both set to n = 1, and the set values of the relays Ry1 and Ry3 in the distribution substations 100 and 120 are both n = 2. It is assumed that it is set to.

  In such a configuration, when a short circuit accident occurs in the premises of the customer 300, an internal accident detection pulse is output from the pulse generating means 26 in the relay Ry2, and the breaker CB2 is instantaneously output by the output of the AND function 24. The circuit is opened (in about 0.25 seconds). The internal accident detection pulse has its pulse width expanded by the pulse width expanding means 43 and is input to the AND function 46 via the NOT function 44. Therefore, regardless of the output of the relay function 42, the output of the AND function 46 becomes a low level, and the operation output of the relay Ry4 is locked.

Further, while the output of the pulse width expanding means 43 is at a high level, an operation output may be generated via the AND function 45 by the output of the relay function 41. However, as described above, there is an accident point resistance in an internal accident. The current of the relay Ry4 is 205% with respect to the rated current and the current of the relay Ry2 is 1750% with respect to the rated current. According to the characteristic diagram of FIG. 4, the relay Ry2 is more than the relay Ry4 when the set value n = 1. Since it operates as soon as possible and the accident is eliminated, there is no problem.
Therefore, it is possible to prevent the interconnection protection relay Ry4 from operating unnecessarily in the case of a premises accident of the customer 300.

  Further, in the case of a short circuit accident at the point F2 on the distribution line 120 (no accident point resistance), as described above, 623% of the rated current flows through the relays Ry1 and Ry3, 748% through the relay Ry4, and 500 through the relay Ry2. % Current flows. In this case, the relay Ry4 operates before the relays Ry1, Ry2, and Ry3 due to the characteristics shown in FIG. 4, and in this case as well, time coordination can be achieved by two-stage settling.

  In addition to the relay Ry2, the interconnection protection relay Ry4 receives a current phase determination signal (internal accident detection signal) from other relays in the vicinity of the customer and locks the operation output by these OR functions. It may have a function.

It is a lineblock diagram of a power distribution system to which an embodiment of the present invention is applied. It is a functional block diagram which shows the schematic structure of the relay for a customer premises accident detection and the protection relay for connection which concerns on embodiment of this invention. It is a block diagram of a general power distribution system. It is a figure which shows the operating time characteristic and operating time precision of the overcurrent protection relay of an inverse time characteristic. It is a block diagram of the interconnection system of two distribution lines.

Explanation of symbols

21: Phase determination function 22, 23: Relay function 24, 25: AND function 26: Pulse generating means 41, 42: Relay function 43: Pulse width expanding means 44: NOT function 45, 46: AND function 47: OR function 100, 120: Distribution substation 101, 121: Power supply 102, 122: Bus 200, 220: Distribution line 201, 221: Bus 300: Consumer 301: Private power generation facility 501: Interconnection line Ry1, Ry2, Ry3, Ry4: Protection Relay CB1, CB2, CB3, CB4: Breaker F1, F2, F3: Accident point

Claims (1)

Two distribution lines are connected to each other via a circuit breaker equipped with a connection protection relay, and includes a protection relay and a circuit breaker for detecting an on-site accident that operates when an on-site accident occurs in a consumer. In the interconnected system
The on-site accident detection protection relay is
A phase determination function that detects whether the current phase before and after the accident is the same phase or an opposite phase and determines an internal accident and an external accident on the customer premises,
A relay function that obtains an operation output instantly when an overcurrent is detected when the current phase before and after the accident is the same phase,
A relay function that obtains an operation output when the current phase before and after the accident is in reverse phase and the overcurrent continues for a predetermined period;
Means for outputting an in-phase detection signal indicating that the current phase before and after the occurrence of the accident is the same phase;
The interconnection protection relay has a function of locking an operation output for a predetermined period when the in-phase detection signal is received.

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