JP2005354882A - Protector and protecting method of distribution system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protector and a protection method of distribution system in which arrangement of a load-break switch can be simplified. <P>SOLUTION: When a decision is made that power flows into premises (forward power flow), a control section 35 excites a trip coil 25 to open a load-break switch 17. When a decision is made that power flows out from premises (reverse power flow), the control section 35 does not excite the trip coil 25 but sustains throw-in of the load-break switch 17. Consequently, unnecessary opening of the load-break switch 17 due to generation of an eddy current caused by short circuit failure on the outside of premises can be suppressed in a distribution line 11 linked with a distributed power supply 15 in the premises. Furthermore, an operating power supply voltage on the consumer load 14 side is employed as a reference voltage for judging power flow direction. Since power flow direction is judged based on the phase of a load current I<SB>R</SB>for a control power supply voltage Vp, an extra voltage sensor is not required in the load-break switch 17. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power distribution system protection device and a power distribution system protection method for protecting a power distribution system connected to a distributed power source.

  Conventionally, a control device for a load switch having an overcurrent protection function (for example, a SOG type high voltage load switch) has an overcurrent (or short circuit current) exceeding a set value (lock current value of the load switch) on the consumer side. When this occurs, the load switch is locked to prevent opening during overcurrent. After the protective relay of the substation operates and selectively cuts off the abnormal section, the power line is cut off by disconnecting the distribution line, and after the overcurrent disappears due to the power outage (that is, the distribution line is in a no-voltage state) Later, the load switch of the customer who caused the accident is opened. After a predetermined time has elapsed, the distribution line is reclosed. Since power is supplied to customers other than the customer who has the cause of the accident and the service line of the customer having the cause of the accident remains open by the load switch, the power outage continues in the customer premises. After that, the cause of the accident is removed, and the load switch is turned on manually to recover.

  By the way, in recent years, a distributed power source (in-house power generation device) is provided on the premises, and the number of consumers who use it in combination with the power supply of the commercial power source is increasing and the power generation capacity of the consumer tends to increase. In addition, since the power generation capacity of the distributed power source that can be linked to the power distribution system is defined to be less than 2000 kW (kilowatts), for example, the current supplied from the distributed power source is overcurrent level (the load switch lock current value (Exceeding level) has occurred. However, the conventional load switch control device operates on the premise that the consumer only receives power supply from the power company. For this reason, when an accident occurs outside the customer's premises, a reverse power flow occurs from the distributed power source to the distribution line, and this reverse power flow is regarded as an overcurrent, so no accident has occurred in the customer's equipment. In some cases, the load switch was opened despite the fact that it was a long service line.

  In detail, if an accident occurs outside the customer's premises, the distribution line will be out of service due to a trip at the substation. However, current flows from a consumer having a distributed power source to the distribution line side, that is, reverse power flow occurs. This reverse power flow becomes an overcurrent level, and the control device detects this overcurrent, locks the opening operation of the load switch after a predetermined lock time (for example, 0.1 seconds), and performs the opening operation to the no-voltage state. Set to the standby state. As a facility standard, a distributed power source is obliged to be stopped within a predetermined stop time (about 2 seconds) after the occurrence of a power failure when a distribution line is interrupted. In general, the stop time of the distributed power supply at the time of distribution line power failure is longer than the lock time of the load switch. For this reason, the control device detects the reverse power flow as an overcurrent, detects the non-voltage state of the distribution line by stopping the distributed power supply, and automatically opens the load switch.

  Therefore, if the circuit breaker of the substation is cut off (tripped) due to an accident in another customer or the power distribution line (accident outside the customer's premises) and this circuit breaker is turned on again, an accident will occur. The load switch of the customer who installed the distributed power supply that is not used is open. For this reason, when the circuit breaker is turned on again, the power failure state continues in the customer premises even though power is supplied to the distribution line again. In addition, in order to turn on the load switch in the open state, a corresponding recovery procedure such as inspection and return operation by a qualified person is necessary, and it takes time to turn on the load switch. Thus, since the load switch restoration work on the customer side is complicated, it is preferable that the load switch in the customer premises is opened without any darkness despite the accident outside the customer premises. There wasn't. It has been desired to open the load switch only when an accident (short circuit) is detected on the customer premises.

  Furthermore, even though there is no distributed power supply installed, even customers who use large induction motors (loaders) as loads will experience power outages due to trips at substations due to accidents outside the customer's premises. When this happens, the induction motor tries to keep current flowing due to regeneration, and reverse power flow occurs. The control device detects this reverse power flow as an overcurrent and detects the non-voltage state of the distribution line by disconnecting the induction motor from the premises system, and the load switch is automatically opened. Similar to the case where the distributed power source is installed, the load switch opens in spite of the accident outside the customer's premises, so it is desired to take the same measures. That is, it has been necessary to prevent the load switch from being opened by a current from a distributed power source or a current from a large motor during a power failure in the distribution line.

In order to solve such problems, conventionally, a load switch that uses the current flow direction of the line current as the judgment material and prohibits the opening operation of the load switch for reverse power flow from the distributed power source has been used. It has been proposed (see, for example, Patent Document 1). That is, the load switch control device detects the phase voltage and the load current when a power failure occurs, determines the flow direction from the phase difference between the detected phase voltage and the load current, and detects the flow direction and the overcurrent detection means. The overcurrent direction is detected by the signal. Since it is possible to specify whether the overcurrent accident has occurred on the premises or on the premises, the opening operation of the load switch due to the overcurrent caused by the accident on the premises is prevented. For this reason, after the circuit breaker of the substation is turned on again, electric power is smoothly supplied to the customer through the load switch that maintains the input state.
JP 2003-158820 A

  However, in the conventional load switch control device, it is necessary to provide a phase voltage detection sensor for detecting the phase voltage. Since the phase voltage is indispensable for determining the flow direction of the line current, it is difficult to omit the phase voltage detection sensor, which is one factor that hinders the simplification of the configuration of the load switch and its control device. It was.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a distribution system protection device and a distribution system protection method capable of simplifying the configuration of the load switch. .

  The invention according to claim 1 provides power separately from power supplied from the distribution line to a consumer load connected to the distribution line via a service line and a load switch provided on the service line. In a protection device for a distribution system having a distributed power supply to be supplied, a load current detection unit that detects a load current of any one of the three phases of the distribution line, and the load current detection unit An overcurrent detection unit that determines whether or not the load current is at an overcurrent level, and a phase difference calculation unit that calculates a phase difference between the load current detected by the load current detection unit and a control power supply voltage in the customer premises And a flow direction determination unit that determines a flow direction of the incoming line based on the phase difference calculated by the phase difference calculation unit, a determination result by the overcurrent detection unit, and a determination result by the flow direction determination unit The And summarized in that and a control unit for opening or turned maintain serial load break switch.

  The invention according to claim 2 is the invention according to claim 1, wherein the power flow direction of the distribution line is newly determined by the power flow direction determination unit when the power distribution line is reclosed after a power failure. The gist is that a determination unit is provided and a storage unit for storing the determination result is provided.

  The invention according to claim 3 provides power separately from power supplied from the distribution line to a consumer load connected to the distribution line via a service line and a load switch provided on the service line. In a protection device for a distribution system having a distributed power supply to be supplied, a load current detection unit that detects a load current of any one of the three phases of the distribution line, and the load current detection unit An overcurrent detection unit for determining whether or not the load current is at an overcurrent level, and a control power supply current for detecting one of a control power supply built in the load switch and a control power supply on the customer side A detection unit, a phase difference calculation unit that calculates a phase difference between the current obtained by the control power supply current detection unit and the load current detected by the load current detection unit, and a level calculated by the phase difference calculation unit. Based on phase difference A power flow direction determination unit that determines a power flow direction of the distribution line, and a control unit that opens or maintains the load switch based on a determination result by the overcurrent detection unit and a determination result by the power flow direction determination unit. This is the summary.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the control power source built in the load switch and the control power source in the customer premises are each a control power source transformer, and the control power source The gist of the present invention is that the current detector is a current transformer provided on the secondary side of the control power transformer.

  The invention according to claim 5 is the load current detected by the load current detection unit in the invention according to claim 3 or claim 4, when the distribution line is reclosed after a power failure. And a current difference obtained from the control power supply current detection unit are newly calculated by the phase difference calculation unit, and a storage unit for storing the calculation result is provided.

  The invention according to claim 6 provides power separately from power supplied from the distribution line to a consumer load connected to the distribution line via a service line and a load switch provided on the service line. In a protection method for a distribution system including a distributed power supply to be supplied, a step of determining whether a load current of any one of three phases of the distribution line is at an overcurrent level; and the load current Calculating the phase difference between the power supply voltage and the control power supply voltage in the customer premises, determining the flow direction of the distribution line based on the calculated phase difference, and whether the load current is at an overcurrent level And a step of opening or maintaining the load switch based on the determination result and the determination result of the flow direction of the distribution line.

  The invention according to claim 7 provides power separately from power supplied from the distribution line to a consumer load connected to the distribution line via a service line and a load switch provided on the service line. A method of protecting a power distribution system including a distributed power source to supply, determining whether or not a load current of any one of the three phases of the distribution line is at an overcurrent level; and Detecting a current of one of a control power supply built in a container and a control power supply in a customer premises, calculating a phase difference between the current obtained by the current detection and the load current, The step of determining the flow direction of the distribution line based on the calculated phase difference, the determination result of whether or not the load current is an overcurrent level, and the determination result of the flow direction of the distribution line Open or close the switch And summarized in that and a step of introducing maintained.

(Function)
According to the invention described in claim 1 or claim 6, it is determined whether or not the detected load current is at an overcurrent level, and then the load current and the control power supply voltage in the customer premises are calculated. The tidal direction is determined from the phase difference. The load switch is controlled to open and close based on the determination result of the flow direction. When it is determined that the flow direction is the forward direction (that is, the load side of the load switch; the premises), the load switch is opened. When it is determined that the power flow direction is reverse power flow (that is, the power supply side of the load switch; off-premise), the load switch is turned on and maintained. For this reason, in the distribution system in which the distributed power sources on the premises are connected, it is possible to suppress unnecessary opening of the load switch due to the occurrence of an overcurrent due to an off-site accident. In addition, since the control power supply voltage in the customer premises is used as a reference voltage for determining the tidal direction, it is not necessary to separately provide a voltage detection sensor in the load switch, for example. Therefore, simplification of the configuration of the load switch, and consequently simplification of the configuration of the protection device of the distribution system can be achieved.

  According to the invention described in claim 2, in addition to the action of the invention described in claim 1, the load detected by the load current detection unit at the time of power recovery after the distribution line is re-closed after a power failure. The phase difference between the current and the control power supply voltage in the customer premises is newly calculated by the phase difference calculation unit, and the calculation result is stored. Therefore, the phase difference between the load current when the load current is determined to be an overcurrent level and the control power supply voltage in the customer premises is stored at the time of power recovery when the distribution line is re-closed after a power failure. The tidal direction can be determined to be a reverse tidal current when the phase difference has changed significantly (for example, about 180 degrees). However, this assumes that the power flow direction at the time of power recovery is a forward power flow. Therefore, it is not necessary to input the phase of the control power supply voltage into the phase difference calculation unit in advance. In other words, it is not necessary to input whether the phase of the control power supply voltage is in phase with each line voltage in the distribution line or their reverse phase voltage.

  According to the invention described in claim 3 or 7, either one of the current of the control power source built in the load switch and the current of the control power source in the customer premises is detected by the control power source detector. The In addition, it is determined whether or not the detected load current is at an overcurrent level, and then the flow direction is determined based on the phase difference between the load current and the current obtained by the control power source detection unit. . The load switch is controlled to open and close based on the determination result of the flow direction. When it is determined that the flow direction is on the premises (that is, the load side of the load switch), the load switch is opened. When it is determined that the flow direction is off-premise (that is, the power supply side of the load switch), the load switch is turned on and maintained. For this reason, in the distribution system in which the distributed power sources on the premises are connected, it is possible to suppress unnecessary opening of the load switch due to the occurrence of an overcurrent due to an off-site accident. Thus, by using the control power supply built in the load switch or the control power supply on the customer side, there is no need to separately provide a voltage detection sensor in the load switch, for example. Therefore, the structure of the load switch can be simplified, and the structure of the protection device for the distribution system can be simplified.

  According to the invention described in claim 4, in addition to the operation of the invention described in claim 3, the current flowing in the secondary side of the control power transformer is provided on the secondary side of the control power transformer. The current is converted by the current transformer. The direction of the power flow is determined based on the phase difference between the current obtained by this current conversion and the load current (phase current).

  According to the invention described in claim 5, in addition to the operation of the invention described in claim 3 or claim 4, at the time of power recovery when the distribution line is re-closed after a power failure, the load current detection unit The phase difference between the detected load current and the current obtained by the control power supply current detection unit is newly calculated by the phase difference calculation unit, and the calculation result is stored in the storage unit. For this reason, the phase difference between the load current when the load current is determined to be an overcurrent level and the current obtained by the control power supply current detection unit is the power restored after the distribution line is cut off. The tidal direction can be determined as a reverse tidal current when the phase difference memorized at the time has changed significantly (for example, about 180 degrees). However, this assumes that the power flow direction at the time of power recovery is a forward power flow. Therefore, it is not necessary to input the phase of the control power supply voltage into the phase difference calculation unit in advance. In other words, it is not necessary to input how many times the phase of the control power supply current is deviated from the phase of each line voltage in the distribution line.

  According to the present invention, for example, it is not necessary to separately provide a voltage detection sensor in the load switch, so that the configuration of the load switch can be simplified.

<First Embodiment>
Hereinafter, a first embodiment in which the present invention is embodied in a protection device for a distribution system in which distributed power sources are connected will be described with reference to FIGS. 1, 2A, and 2B.

  As shown in FIG. 1, a consumer load 14 is connected to a distribution line 11 on the power company side via a lead-in line 13, and power from the distribution line 11 outside the customer premises is consumed by the customer load during normal power reception. 14 is supplied as a forward current. On the distribution line 11, a distributed power source 15 is connected to the power source side of the customer load 14, and the power generated by the distributed power source 15 can be supplied to the customer load 14. In the present embodiment, the distributed power source 15 is a generator.

  On the distribution line 11, a customer premises control power transformer 16 is provided on the power source side of the customer load 14. Both ends of the primary side winding of the customer premises control power transformer 16 are connected to the S phase and T phase of the lead-in line 13 as an example, and both ends of the secondary side winding are respectively connected to the control device 18. It is connected. An electromotive voltage is generated in the secondary winding of the customer premises control power transformer 16 in accordance with the turn ratio with the primary winding.

  On the lead-in line 13, a load switch 17 is provided on the power supply side from the connection point of the distributed power supply 15 and the customer premises control power transformer 16, and the load switch 17 is opened and closed by the control device 18. Be controlled. Moreover, the load switch 17 is installed on the responsibility demarcation point. The load switch 17 and the control device 18 constitute a protection device for the distribution system.

<Load switch>
As shown in FIG. 1, in the load switch 17, a switching unit 20, a zero-phase current transformer 21, and a zero-phase voltage detection are provided on a lead-in line 13 of each phase composed of an R phase, an S phase, and a T phase. A capacitor 22 and two current transformers 24r and 24t for detecting overcurrent are provided. The opening / closing unit 20 includes a plurality of switches 20r, 20s, and 20t provided in each phase of the lead-in line 13. The zero-phase current transformer 21 is provided on the power source side of the switching unit 20 and detects the zero-phase current (ground fault current) of the R-phase, S-phase, and T-phase of the lead-in line 13. The zero-phase voltage detection capacitor 22 is provided on the load side of the switching unit 20 and detects a zero-phase voltage for performing selective protection between a load-side ground fault and a power-side ground fault. On the lead-in line 13, two current transformers 24r and 24t are arranged on the load side of the zero-phase voltage detection capacitor 22. Both current transformers 24r and 24t are provided in the R phase and the T phase of the lead-in line 13, respectively.

  A trip coil 25 for automatically tripping (opening) the switching unit 20 is provided in the load switch 17. Incidentally, the automatic trip operation includes a ground fault trip operation and an overcurrent trip operation. The ground fault trip operation means that when a ground fault current flows through the lead-in line 13 due to a ground fault occurring on the load side, when the ground fault current is detected and the set value is exceeded, the trip coil 25 is excited. In this operation, the opening / closing part 20 is automatically opened. The overcurrent trip operation means that when an overcurrent exceeding a certain set value is detected in a short-circuit accident, the switching unit 20 is locked so as not to be automatically opened, and a circuit breaker (not shown) at the substation trips to cause the distribution line 11 and the lead-in line. This is an operation of exciting the trip coil 25 and automatically opening and closing the opening / closing unit 20 instantaneously after the path 13 is in a no-voltage state.

<Control device>
The control device 18 includes a control power supply unit 30, a ground fault current detection unit 31, an overcurrent detection unit 32, a phase difference calculation unit 33, a power flow direction determination unit 34, a control unit 35, and a control power supply voltage phase determination unit 36. .

  The control power supply unit 30 is connected to both ends of the secondary winding of the customer-premises control power supply transformer 16. The control power supply voltage Vp (AC100V) induced on the secondary side of the customer premises control power supply transformer 16 is input. The control power supply unit 30 supplies operating power to each unit of the control device 18.

  The ground fault current detection unit 31 detects the zero phase current (ground fault current) output from the zero phase current transformer 21 and outputs the detection result to the control unit 35. The overcurrent detector 32 detects the load current (more precisely, the load current flowing through the R phase and T phase of the lead-in line 13) output from the current transformers 24r and 24t, and the detected load current is the overcurrent. It is determined whether or not it is level (that is, whether or not the lock current value of the load switch 17 is exceeded), and the determination result is output to the control unit 35.

Both ends of the secondary winding of the customer premises control power transformer 16 are connected to the phase difference calculation unit 33 in a branched manner. Phase difference calculation unit 33 based on the value of the load current I _R detected by the induced control power supply voltage Vp and the current transformer 24r on the secondary side of the customer premises control power transformer 16, the control power It calculates the phase difference between the voltage Vp and the load current I _R, and sends the calculation result to the power flow direction determination unit 34.

The control power supply voltage phase determination unit 36 determines whether the control power supply voltage Vp is in phase with each of the line voltages V _RS , V _ST , V _TR in the distribution line 11 or any of these negative-phase voltages based on information input from the outside. Then, the determination result is sent to the tidal direction determination unit 34.

Flow direction determination unit 34, flow direction based on the phase of the control power supply voltage Vp from the phase difference and the control power supply voltage phase determining unit 36 of the control power supply voltage Vp calculated by the phase difference calculation section 33 and the load current I _R And the determination result is sent to the control unit 35.

  When the ground fault current is detected by the ground fault current detector 31, the controller 35 excites the trip coil 25 to automatically open the opening / closing part 20. Further, when the overcurrent detection unit 32 detects an overcurrent that is equal to or greater than a set value (the lock current value of the load switch 17), the control unit 35 switches the load on and off based on the flow direction determined by the flow direction determination unit 34. The container 17 is kept open or charged. That is, the control unit 35 determines whether the short-circuit accident has occurred outside the customer premises (the power source side of the load switch 17) or on the customer premises (the load side of the load switch 17). The switch 17 is opened or turned on.

Specifically, the power flow direction determination unit 34 determines the phase difference between the control power supply voltage Vp (exactly voltage vector) and the load current I _R (exactly current vector), that is, the load current with respect to the control power supply voltage Vp. phase I _R may determine the forward power flow when 0 ° +180 degrees, determines that reverse flow when the 0 ° -180 °. Based on the determination result (forward / reverse power flow determination) of the power flow direction determination unit 34, the control unit 35 determines whether the customer premises short circuit accident or the premises short circuit accident. Then, the control unit 35 determines whether the load switch 17 is opened or maintained.

As shown in FIG. 2 (a), customer premises and off-premises load power factor of 100%, and when the control power supply voltage Vp is the line voltage V _ST and phase in the power distribution line 11, the load on the control power supply voltage Vp when the phase of the current I _R is 90 degrees, it is determined that the power flow direction determination unit 34 is the forward power flow. Also, as shown in FIG. 2 (b), when the phase of the load current I _R with respect to the control power supply voltage Vp is -90 degrees, determines that the power flow direction determination unit 34 is a reverse flow. Then, the control unit 35 performs the opening operation of the load switch 17 when it is determined as a forward power flow, and turns on and maintains the load switch 17 when it is determined as a reverse power flow.

<Operation of Embodiment>
Next, the operation at the time of a short-circuit accident of the protective device for the distribution system configured as described above will be described.
At the time of a short circuit accident inside or outside the customer premises, a short circuit current (current of an overcurrent level exceeding the lock current value of the load switch 17) flows through the lead-in line 13. This short circuit current is detected by the overcurrent detector 32. Each current transformer 24r, and the load current I _R of the R-phase detected by 24t, based on the control power supply voltage Vp is induced in the secondary side of the customer premises control power transformer 16, the phase difference calculation unit 33 calculates the phase difference between the control power supply voltage Vp and the load current I _R. Based on the phase difference between the load current IR calculated by the phase difference calculation unit 33 _{and the} control power supply voltage Vp and the phase of the control power supply voltage Vp from the control power supply voltage phase determination unit 36, the power flow direction determination unit 34 determines the tidal direction.

  If the tidal direction determination unit 34 determines that the tidal direction is forward tidal flow, the control unit 35 determines that a short-circuit accident has occurred in the customer premises and excites the trip coil 25 to open the load switch 17. . When the tidal direction determination unit 34 determines that the tidal direction is reverse tidal current, the control unit 35 determines that a short circuit accident has occurred outside the customer premises and turns on the load switch 17 without exciting the trip coil 25. maintain. That is, by determining whether a short circuit has occurred on either the power source side or the load side of the load switch, overcurrent occurs due to an external short circuit accident in the distribution line 11 connected to the distributed power source 15. Unnecessary opening of the load switch 17 due to is suppressed.

For example, when the customer side receives power from the distribution line 11, when a short circuit accident occurs on the premises, that is, on the customer side, the power from the distribution line 11 flows into the failure point. The load current I _R flowing into the fault point with determining the overcurrent detection unit 32 is overcurrent flow direction determination unit 34, the phase difference load current I _R that is calculated by the arithmetic unit 33 _{(overcurrent)} based on the phase of the control power supply voltage Vp from the phase difference and the control power supply voltage phase determining section 36 and the control power supply voltage Vp and to determine flow direction of the load current I _R. In this case, when the control power supply voltage Vp is the line voltage V _ST and phase in the power distribution line 11, the phase of the control power source voltage load on Vp current I _R becomes a range of +90 degrees from the 0 degree, flow direction determination unit 34 It determines that the flow direction of the load current I _R is forward power flow. In response to flow direction of the load current I _R is forward, the control unit 35 premises, that is, short circuit in the customer load 14 side is determined to be occurring. Then, the control unit 35 excites the trip coil 25 to open the switches 20r, 20s, and 20t of the opening / closing unit 20, respectively.

In addition, for example, when a short circuit accident occurs in another customer or the distribution line 11, the circuit breaker of the substation trips and the distribution line 11 fails, or when the distribution line 11 has an unexpected power failure, Electric power flows out to the distribution line 11 side. The current from the distributed power supply 15 as well as determined that the overcurrent detection unit 32 is overcurrent flow direction determination unit 34, calculated by the phase difference calculation unit 33 the load current I _R and the control power supply voltage based on the phase of the control power supply voltage Vp from the phase difference and the control power supply voltage phase determining unit 36 of the Vp, it determines flow direction of the load current I _R. In this case, when the power factor of 100% and the control power supply voltage Vp of off-premises load line voltage VST phase with the distribution line 11, the phase of the load current I _R with respect to the control power supply voltage Vp becomes -90 degrees, power flow direction determination part 34 flow direction of the load current I _R is determined to be reverse power flow. In response to flow direction of the load current I _R is reverse, the control unit 35 off-premises, i.e. it is determined that an accident has occurred in the power distribution line 11 side. And the control part 35 maintains each switch 20r, 20s, and 20t of the opening-and-closing part 20 in an ON state, respectively. Even when the switching unit 20 is locked in this way, the control unit 35 does not excite the trip coil 25 even if the circuit breaker of the substation trips and the distribution line 11 and the lead-in line 13 become a non-voltage state. Each switch 20r, 20s, 20t of the opening / closing part 20 is maintained in the on state.

Thus, by determining the flow direction based on the phase of the load current I _R with respect to the control power supply voltage Vp, since short circuit can be identified whether it has occurred in any of the customer's premises or customer off-premises, the customer off-premises Unnecessary opening operation of the load switch 17 due to overcurrent caused by a power failure due to a short circuit accident or the like in the case is prevented. Therefore, after the circuit breaker of the substation is turned on again, power is reliably supplied to the consumer load 14 via the load switch 17 kept in the turned on state. Further, by the voltage reference for the control power supply voltage Vp to determine the flow direction of the load current I _R, the reference voltage is not necessary to separately provide a voltage detection sensor, for example, load break switch 17 for detecting.

<Effect of embodiment>
Therefore, according to the present embodiment, the following effects can be obtained.
When a short-circuit accident occurs, it is determined whether a short-circuit accident has occurred on the power supply side or the load side of the load switch 17 arranged on the lead-in line 13, and the load switch 17 is based on the determination result. Was kept open or charged. That is, when it is determined that the flow direction is the premises (forward flow; load side of the load switch 17), the control unit 35 excites the trip coil 25 and opens the load switch 17. When it is determined that the flow direction is off-premise (reverse flow; on the power supply side of the load switch 17), the control unit 35 turns on and maintains the load switch 17 without exciting the trip coil 25. For this reason, in the distribution line 11 in which the distributed power supply 15 on the premises is connected, unnecessary opening of the load switch 17 due to the occurrence of an overcurrent caused by a power failure due to an external short circuit accident or the like can be suppressed. That is, only the short-circuit accident on the customer load 14 side can be detected and the load switch 17 can be opened. In other words, it is possible to prevent the load switch 17 from being tripped unnecessarily by the current supplied from the distributed power source 15 at the time of a power failure in the distribution line 11. Furthermore, in the present embodiment, since the operating power supply voltage on the customer load 14 side is used as the reference voltage for determining the flow direction, it is not necessary to separately provide a voltage detection sensor in the load switch 17, for example. Therefore, the configuration of the load switch 17 can be simplified.

Second Embodiment
Next, a second embodiment of the present invention will be described based on FIGS. 3 (a) and 3 (b). This embodiment is different from the first embodiment in the method of determining the tidal direction. Therefore, the same members as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

<Use of built-in VT>
As shown in FIG. 4, in the case where the control power transformer 41 is built in the load switch 17, the control device 18 controls the control power transformer 41 rather than from the consumer premises control power transformer 16. Get the operating power from. The control power transformer 41 is provided on the downstream side of the current transformers 24 r and 24 t on the lead-in line 13. Both ends of the primary side winding of the control power source transformer 41 are connected to the S phase and T phase of the lead-in line 13, respectively, and the secondary side winding is also connected to the control power source unit 30.

A current transformer 42 is provided at one end of the secondary winding of the control power transformer 41. The secondary current of the control power transformer 41 is converted into a current Iv 1 by the current transformer 42, and the converted current Iv 1 is output to the phase difference calculator 33. Phase difference calculation unit 33, based on each value of the load current I _R detected by converted current Iv1 and current transformers 24r from the secondary side current of the transformer 41 for controlling the power supply described above, with the current Iv1 It calculates the phase difference between the load current I _R, and sends the calculation result to the power flow direction determination unit 34.

The control device 18 includes a control power supply current phase determination unit 37 instead of the control power supply voltage phase determination unit 36. The control power supply current phase determination unit 37 is configured to shift the phase of the current Iv1 or current Iv2 (control power supply current) with respect to the phase of each line voltage VRS, VST, VTR in the distribution line 11 by information input from the outside. And the determination result is sent to the tidal direction determination unit 34. Power flow direction determination unit 34 determines flow direction based on the power factor of the current Iv1 from the phase difference and controlling the power supply current phase determination unit 37 and a current Iv1 calculated by the phase difference calculation section 33 and the load current I _R.

Specifically, the power flow direction determination unit 34 has a phase difference between the current Iv1 (more precisely, current vector) and the load current I _R (more precisely, current vector), that is, the power factor of the current Iv1 is 100%. If, it is determined that the forward power flow when the phase of the load current _{I R} for current Iv1 is +180 degrees 0 degrees, determines that reverse flow when the 0 ° -180 °. Based on the determination result (forward / reverse power flow determination) of the power flow direction determination unit 34, the control unit 35 determines whether a customer premises short circuit accident or a premises short circuit accident. Then, the control unit 35 determines whether the load switch 17 is opened or maintained.

As shown in FIG. 3 (a), 100% is the customer premises and off-premises load power factor, and when the power factor of the current Iv1 is 100%, when the phase of the load current _{I R} for the current Iv1 is 90 degrees The tidal current direction determination unit 34 determines that the current is a forward tidal current. Also it determined, as shown in FIG. 3 (b), when the phase in the load current I _R for current Iv1 is -90 degrees, and the power flow direction determination unit 34 is a reverse flow. Then, the control unit 35 performs the opening operation of the load switch 17 when the forward flow is determined, and turns on and maintains the load switch 17 when the reverse flow is determined.

<Use of customer side transformer>
By the way, when the control power transformer 41 is not built in the load switch 17, for example, the control power is obtained from the customer premises control power transformer 16. At that time, a current transformer 43 is provided at one end of the secondary winding of the customer premises control power transformer 16. The secondary current of the customer premises control power supply transformer 16 is converted into a current Iv 2 by the current transformer 43, and the converted current Iv 2 is output to the phase difference calculation unit 33. Phase difference calculation unit 33, based on each value of the load current I _R detected by the current converted current Iv2 and current transformers 24r from control power transformer secondary current above, the load and the current Iv2 It calculates the phase difference between the current I _R, and sends the calculation result to the power flow direction determination unit 34. Power flow direction determination unit 34 determines flow direction based on the power factor of the current Iv2 from the phase difference and controlling the power supply current phase determination unit 37 and a current Iv2 calculated by the phase difference calculation section 33 and the load current I _R. Hereinafter, specific method of determining the flow direction by power flow direction determination unit 34 is similar to the case of determining based on the phase difference between the load current I _R and current Iv1 described above, a detailed description thereof is omitted . In the present embodiment, the current transformer 42 and the current transformer 43 each constitute a current converter.

Therefore, according to the present embodiment, the following effects can be obtained.
In the case where the control power transformer 41 is built in the load switch 17, a current transformer 42 is provided at one end of the secondary winding of the control power transformer 41. When the load switch 17 does not include the control power transformer 41, a current transformer 43 is provided at one end of the secondary winding of the customer premises control power transformer 16. The flow direction determination unit 34 includes a current Iv2 detected by current Iv1 or current transformer 43 which is detected by the current transformer 42, to determine the flow direction on the basis of the phase difference between the load current I _R did. Thus, by using the control power source transformer 41 or the customer premises control power source transformer 16 built in the load switch 17, for example, there is no need to separately provide a voltage detection sensor in the load switch 17. . Therefore, the configuration of the load switch 17 can be simplified.

  The control power supply current induced on the secondary side of the control power transformer 41 or the customer premises control power transformer 16 is converted into the current Iv1 or the current Iv2 by the current transformer 42 or the current transformer 43. . The converted current Iv1 or current Iv2 is taken into the phase difference calculator 33. For this reason, for example, compared with the first embodiment in which the control power supply voltage Vp is directly taken into the phase difference calculator 33, the insulation design for the phase difference calculator 33 is facilitated.

(Another embodiment)
In addition, you may implement each said embodiment as follows.
In the first and second embodiments, a voltage memory function may be provided. That is, the storage unit 60 is provided in the control device 18, and the voltage phase when the voltage phase can be detected is stored in the storage unit 60. The voltage phase stored in the storage unit 60 is updated every predetermined period. For example, when a short-circuit accident occurs in the vicinity of the customer, there is a risk that the voltage between the three phases disappears. In this case, the power flow direction determination unit 34 determines the power flow direction based on the voltage phase stored in the storage unit 60. Therefore, even when the voltage detected for some reason is extremely lowered and the voltage phase becomes undetectable, or when the voltage between the phases disappears, the voltage phase stored on the storage unit 60 is used. The direction of the tidal current can be determined.

  In the first embodiment, the phase difference between the load current detected by the current transformers 24r and 24t and the control power supply voltage Vp in the customer premises when the distribution line 11 is reclosed after a power failure. May be newly calculated by the phase difference calculation unit 33, and the calculation result may be stored in the storage unit 60. This eliminates the need for prior input of the control power supply voltage phase, and eliminates the need to input information to the control power supply voltage phase determination unit 36 and the control power supply voltage phase determination unit 36 from the outside.

  In the second embodiment, the load current detected by the current transformers 24r and 24t and the current obtained by the control power source current phase determination unit 37 when the power distribution line 11 is reclosed after a power failure. May be newly calculated by the phase difference calculation unit 33 and the calculation result may be stored in the storage unit 60. This eliminates the need for prior input of the control power supply current phase, and eliminates the need to input information to the control power supply current phase determination unit 37 and the control power supply current phase determination unit 37 from the outside.

· In the first and second embodiments, so as to determine the flow direction on the basis of the phase with respect to the load current I _R of the R-phase with respect to the control power supply voltage Vp, it may be as follows. That is, to detect the load current I _T of S-phase of the load current I _S or T phase instead of R-phase, the phase difference between the load current I _S or T phase of the load current I _T of S phase to control the power supply voltage Vp The direction of the tidal current is determined based on this.

  In the first embodiment, the control power is taken from the customer premises control power transformer 16. In the second embodiment, the control power is taken from the control power transformer 41 or the customer premises control power transformer 16. However, it may be as follows. That is, in the first and second embodiments, the control power supply may be taken from the power supply side of the load switch 17.

The schematic block diagram of the protection apparatus of the power distribution system in 1st Embodiment. (A) is a phase characteristic diagram showing the phase of the phase current with respect to the control power supply voltage in the customer premises during forward flow, and (b) is the phase showing the phase of the phase current with respect to the control power supply voltage in the customer premises during reverse flow. Characteristic diagram. (A) is a phase characteristic diagram showing the phase of the phase current with respect to the current converted from the secondary current of the control power transformer during forward power flow, and (b) is the secondary side of the control power transformer during reverse power flow. The phase characteristic figure which shows the phase of the phase current with respect to the electric current converted from the electric current. The schematic block diagram of the protection apparatus of the power distribution system in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Distribution line, 13 ... Service line, 14 ... Consumer load, 15 ... Distributed power supply,
16 ... Transformer for customer side control power supply,
17 ... Load switch constituting a protection device for the distribution system,
18 ... Control device constituting protection device of distribution system,
24r, 24t ... current transformers constituting the load current detection unit, 32 ... overcurrent detection unit,
33 ... Phase difference calculation unit, 34 ... Tidal direction determination unit, 35 ... Control unit,
36 ... Control power supply voltage phase determination unit, 37 ... Control power supply current phase determination unit,
41 ... Control power supply transformer, 42, 43 ... Current transformer constituting the control power supply current detector,
60: storage unit, I _R , I _S , I _T ... load current, Iv1, Iv2 ... current (control power supply current),
Vp: Control power supply voltage.

Claims (7)

Power distribution provided with a distributed power source that supplies power separately from power supplied from the distribution line to a consumer load connected to the distribution line via a service line and a load switch provided on the service line In the system protection device,
A load current detector for detecting a load current of any one of the three phases of the distribution line;
An overcurrent detection unit for determining whether or not the load current detected by the load current detection unit is at an overcurrent level;
A phase difference calculation unit for calculating a phase difference between the load current detected by the load current detection unit and the control power supply voltage in the customer premises;
A tidal direction determination unit that determines a tidal direction of the service line based on the phase difference calculated by the phase difference calculation unit;
A distribution system protection device comprising: a control unit that opens or maintains the load switch based on a determination result by the overcurrent detection unit and a determination result by the power flow direction determination unit.   When power is restored after a power failure in the distribution line, the phase difference between the load current detected by the load current detector and the control power supply voltage in the customer premises is newly calculated by the phase difference calculator. The power distribution system protection device according to claim 1, further comprising a storage unit configured to store the calculation result. Power distribution provided with a distributed power source that supplies power separately from power supplied from the distribution line to a consumer load connected to the distribution line via a service line and a load switch provided on the service line In the system protection device,
A load current detector for detecting a load current of any one of the three phases of the distribution line;
An overcurrent detection unit for determining whether or not the load current detected by the load current detection unit is at an overcurrent level;
A control power supply current detection unit for detecting a current of any one of a control power supply built in the load switch and a control power supply in a customer premises; and
A phase difference calculation unit that calculates a phase difference between the current obtained by the control power supply current detection unit and the load current detected by the load current detection unit;
A tidal direction determination unit that determines a tidal direction of the distribution line based on the phase difference calculated by the phase difference calculation unit;
A distribution system protection device comprising: a control unit that opens or maintains the load switch based on a determination result by the overcurrent detection unit and a determination result by the power flow direction determination unit. The control power source built in the load switch and the control power source in the customer premises are each a control power transformer,
The distribution system protection device according to claim 3, wherein the control power source current detection unit is a current transformer provided on a secondary side of the control power source transformer.   A new phase difference calculation is performed on the phase difference between the load current detected by the load current detection unit and the current obtained by the control power supply current detection unit at the time of power recovery after the distribution line has been shut down. The distribution system protection device according to claim 3, further comprising a storage unit configured to perform calculation in the unit and store the calculation result. Power distribution provided with a distributed power source that supplies power separately from power supplied from the distribution line to a consumer load connected to the distribution line via a service line and a load switch provided on the service line In the system protection method,
Determining whether the load current of any one of the three phases of the distribution line is at an overcurrent level; and
Calculating a phase difference between the load current and a control power supply voltage in a customer premises;
Determining a flow direction of the distribution line based on the calculated phase difference;
A method of protecting a distribution system, comprising: determining whether or not the load current is at an overcurrent level and opening or closing the load switch based on a determination result of a flow direction of the distribution line. Power distribution provided with a distributed power source that supplies power separately from power supplied from the distribution line to a consumer load connected to the distribution line via a service line and a load switch provided on the service line In the system protection method,
Determining whether the load current of any one of the three phases of the distribution line is at an overcurrent level; and
Detecting a current of one of a control power supply built in the load switch and a control power supply on the customer side; and
Calculating a phase difference between the current obtained by the current detection and the load current;
Determining a flow direction of the distribution line based on the calculated phase difference;
A method of protecting a distribution system, comprising: determining whether or not the load current is at an overcurrent level and opening or closing the load switch based on a determination result of a flow direction of the distribution line.

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