JP2015104297A - Electric leak monitoring and protection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent unnecessary cutoff of a cable by using power information on the cable in power generation of a distribution type power supply, regardless of a grounded system or non-grounded system.SOLUTION: An electric leak monitoring and protection system comprises: a first cable Dand second cable Dwhose primary sides are connected to the secondary side of a distribution transformer and which branch out; first open/close means Efor performing opening operation when electric leak occurs in the first cable; second open/close means Efor performing opening operation when electric leak occurs in the second cable; effective power calculation means H based on voltage and current in the first cable; direction determination means I for outputting an operation delay instruction Sby determining inverse load flow power made from effective power flowing toward a branch point of the first and second cables; and delay means J for making the opening operation of the first open/close means be later by prescribed time than the opening operation of the second open/close means, by using the operation delay instruction S. A first load to which power is supplied from a power system and a distribution type power supply interconnected with the power system are connected to the first cable; a second load to which power is supplied from the power system is connected to the second cable.

Description

  The present invention relates to a leakage monitoring and protection system for preventing a circuit in which leakage has not occurred from being unnecessarily interrupted in an AC distribution system in which various distributed power sources are interconnected.

FIG. 6 shows a conventional leakage monitoring and protection system in a low voltage distribution system.
In FIG. 6, reference numeral 10 denotes a distribution transformer whose primary side is connected to the power system, and whose secondary side is grounded, and is branched by a point a via a wiring breaker 20. , 22 are respectively connected.
A load 51 is connected to the wiring breaker 21 via a line 31, and a load 52 is connected to the wiring breaker 22 via a line 32. The circuit breaker 21 for wiring is driven by the earth leakage relay 21R to which the detection signal of the zero-phase current transformer 41 on the line 31 is input, and the circuit breaker 22 is detected by the zero-phase current transformer 42 on the line 32. It is driven by a leakage relay 22R to which a signal is input.
An earth leakage breaker may be used instead of the circuit breakers 21 and 22 and the earth leakage relays 21R and 22R.

Now, in the state where all the circuit breakers 20, 21 and 22 for wiring are turned on, for example, when a leakage occurs at the point (accident point) F of the line 32, the leakage current _Ig1 becomes as shown by the solid line in the figure. It flows through the circuit breakers 20 and 22 for wiring and the ground. This leakage current _Ig1 is detected by the zero-phase current transformer 42 to operate the leakage relay 22R and the circuit breaker 22 is cut off, so that the fault circuit, that is, the line 32 and the load 52 are cut off from the system. become. At this time, no leakage current flows from the power system to the line 31 side, and the circuit breaker 21 for wiring is kept closed, so that power can be supplied to the load 51 without any problem.

Next, FIG. 7 is an example in which the same leakage monitoring protection system as that in FIG. 6 is applied to a low-voltage distribution system in which distributed power sources are interconnected.
In FIG. 7, a distributed power source 60 is connected to the line 31 in addition to a load 51. The distributed power source 60 is, for example, an engine generator, a solar power generator, a wind power generator, or the like, and is connected to the power system via the line 31, the circuit breakers 21 and 20, and the distribution transformer 10. . Note that power monitoring devices 71 and 72 for monitoring active power, reactive power, and the like are connected to the lines 31 and 32, respectively.

In this low-voltage distribution system, if leakage occurs at the point F of the line 32 when all the circuit breakers 20, 21, 22 are turned on, the leakage current _Ig1 flows through the same path as described above. 22 operates and the line 32 and the load 52 are disconnected from the system.
Further, in this system configuration, since the leakage current _Ig2 flows from the distributed power supply 60 on the line 31 side to the circuit passing through the point F through the lines 31 and 32 until the wiring breaker 22 is interrupted, The circuit breaker 21 for wiring is also interrupted by the operation of the earth leakage relay 21R. That is, since no electric leakage has occurred on the line 31 side, the circuit breaker 21 for wiring performs an unnecessary breaking operation even though power can be continuously supplied from the power system to the load 51.

  As described above, the unnecessary circuit breaker operation of the circuit breaker 21 occurs because the distributed power source 60 connected to the line 31 is generating power, and on the line 31 side when the distributed power source 60 is not generating power. This is because, in consideration of the occurrence of leakage, the leakage relay 21R has the same level of operation sensitivity, operation time limit, etc. as the leakage relay 22R.

Here, as a prior art for preventing an unnecessary circuit breaker operation of a circuit breaker of another circuit in a low voltage distribution line, for example, those shown in FIGS. 8 and 9 are known.
FIG. 8 is a configuration diagram of the leakage detection protection device described in Patent Document 1, wherein 11 is a distribution transformer whose secondary side is grounded, 43 is a zero-phase current transformer, 81 is a ground phase by a voltage dividing capacitor, voltage detector for detecting a ground voltage V _e, 82 is the zero-phase voltage detector for detecting a zero-phase voltage V ₀ by dividing capacitors, 91 is leakage relay.
In this prior art, the leakage relay 91 subtracts the charging current for the ground-phase ground capacitance obtained from the ground-phase voltage V _e and the zero-phase voltage V ₀ from the zero-phase current I ₀ and leaks the resistance component. The current I _gr is detected, and when the detected leakage current I _gr exceeds the set level, it is determined that the load side of the circuit has a ground fault and the circuit breaker is operated to perform a predetermined protection operation.

FIG. 9 is a block diagram of the insulation monitoring device described in Patent Document 2, wherein 12 is a distribution transformer whose secondary side is ungrounded, 13 is a grounding transformer (EVT), and 43 is a zero-phase current transformer. , 82 is a zero-phase voltage detector composed of a voltage dividing capacitor, 83 is a phase voltage detector also composed of a voltage dividing capacitor, and 92 is an insulation monitoring unit.
In this prior art, the insulation monitoring unit 92 performs a vector calculation using the zero-phase voltage detection value, the phase voltage detection value, and the zero-phase current I ₀ to calculate the insulation resistance value and the resistance component leakage current I _gr at the point F. Display output and so on.

  Furthermore, as another conventional technique, there are a monitoring device and a monitoring system having a function of monitoring a leakage current and insulation of a line as well as monitoring a power and an electric energy of a plurality of load circuits by detecting a voltage and a current of a distribution system. It is described in Patent Documents 3 and 4.

JP 2001-352663 A (FIG. 7 etc.) JP 2006-10608 A (FIG. 5 etc.) JP 2012-132812 A (FIG. 3 etc.) Japanese Patent Laying-Open No. 2005-304148 (FIG. 1 etc.)

In the prior art described in Patent Documents 1 and 2, a zero-phase voltage detector is required to determine the direction of leakage current with reference to the zero-phase voltage, and in particular, Patent Document 2 targeting a non-grounded system. Then, since it is necessary to install a transformer for grounding, these have caused an increase in circuit size and cost. In addition, initial setting of the phase line system (three-phase three-wire system, etc.) of the line is complicated.
Furthermore, Patent Documents 3 and 4 do not show the idea of effectively using the power information obtained for monitoring the state of circuits and facilities for monitoring leakage and insulation.

  Therefore, the problem to be solved by the present invention is to detect the power of the own line by using the power information of the line at the time of power generation of the distributed power source without detecting the zero-phase voltage, regardless of the grounded system or the non-grounded system. An object of the present invention is to provide a leakage monitoring and protection system that prevents unnecessary interruptions.

In order to solve the above problems, the leakage monitoring and protection system according to claim 1 is configured as follows.
That is, as shown in FIG. 1, the leakage monitoring and protection system according to the present invention is connected to the secondary side of the distribution transformer B whose primary side is connected to the power system A via the main switching means C and is branched from each other. The first line D ₁ and the second line D ₂ , the first opening / closing means E ₁ installed on the first line D ₁ and opening when a leakage occurs, and the second line D ₂ The second opening / closing means E _{2 that} is installed and opens when leakage occurs, the active power calculating means H that calculates the active power from the voltage and current of the first line D ₁ , and this active power is the first opening / closing. A direction discriminating means I for discriminating that it is a reverse power flow toward the branch point of the first line D ₁ and the second line D ₂ via the means E ₁ and outputting an operation delay command S _TD ; the command _{S TD,} open the first opening operation of the opening and closing means _{E 1} of the second switching means _{E 2} And a delay means J for delaying a predetermined time than work, the first line D _1, the first and the load F ₁ fed from the electric power system A through the first switching means E _1, the a dispersion type power source G for interconnection to the power system a through the first switching means E _1, is connected to the second line D _2, power from the electric power system a through the second switching means E ₂ second load F ₂ is characterized in that it is connected to be.

Further, leakage monitoring protection system according to claim 2, in claim 1, said main switching means C is, the main switching means C, a branching point of the first line D ₁ and the second line D _2, It opens when a line leakage occurs between the two.

Leakage monitoring protection system according to claim 3, the effective power computing means H and the direction determining means I in claim 1 or 2, constitutes a part of a power monitoring device for monitoring a first power line D ₁ It is characterized by.

Leakage monitoring protection system according to claim 4, the delay unit J in claim 1 or 2, leakage relay for interrupting the first switching means E ₁ by detecting the leakage of the first line D ₁ one It comprises the part.

According to the present invention, regardless of the method of detecting the zero-phase voltage, it is determined that the effective power of the own line to which the distributed power source is connected is reverse power flow, and the occurrence of leakage in the other line is detected. The operation of the opening / closing means for the own line can be delayed to prevent unnecessary blocking operation. This eliminates the need for a zero-phase voltage detector or a grounding transformer in a non-grounded system, and can eliminate an unnecessary breaking operation with a simple circuit configuration regardless of grounding or non-grounding.
In addition, the detection of reverse power flow by calculating active power and determining its direction can be easily realized by using the functions originally possessed by existing power monitoring devices that monitor active power, reactive power, etc. of the line. Can be provided.

It is a block diagram corresponding to claim 1 of the present invention. 1 is a configuration diagram of a leakage monitoring and protection system according to an embodiment of the present invention. It is a block diagram of the principal part of FIG. It is operation | movement explanatory drawing at the time of the electric leakage generation | occurrence | production in FIG. It is operation | movement explanatory drawing at the time of the electric leakage generation | occurrence | production in FIG. It is explanatory drawing of the conventional electric leakage monitoring protection system in a low voltage | pressure distribution system. It is explanatory drawing of the conventional electric leakage monitoring protection system in a low voltage | pressure distribution system. It is a block diagram of the earth-leakage detection protection apparatus described in patent document 1. It is a block diagram of the insulation monitoring apparatus described in patent document 2.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 2 is a configuration diagram of an embodiment of the present invention that embodies the leakage monitoring and protection system shown in FIG. 1. Components having the same functions as those in FIG. 7 are denoted by the same reference numerals. .

In FIG. 2, the difference from FIG. 7 will be mainly described. A zero-phase current transformer 43 is provided on the load side of the circuit breaker 20 connected to the distribution transformer 10, and its detection signal is used for wiring. It is input to a leakage relay 20R for operating the circuit breaker 20.
Further, the leakage relay 110 that operates the circuit breaker 21 for the line 31 and the power monitoring device 120 that monitors the active power, reactive power, etc. of the line 31 are connected to the leakage relay 21R and the power monitoring device 71 shown in FIG. Each of the functions to be described later is added. The power monitoring device 120 is connected to a voltage detector 44 that detects the voltage of the line 31 and a current detector 45 that similarly detects a current.
Here, the voltage detector 44 is not indispensable, and is not necessary when the voltage of the line 31 can be directly input to the power monitoring device 120. In some cases, an instrument transformer is used instead of the voltage detector 44. The voltage of the line 31 may be input to the power monitoring device 120 using (PT).

Here, the distribution transformer 10 in FIG. 2 is the same as the distribution transformer B in FIG. 1, the circuit breaker 20, the zero-phase current transformer 43 and the earth leakage relay 20R are the same as the main switching means C, and the lines 31 and 32 are the same. first, to the second line _D 1, _{D 2,} circuit breaker 21, zero-phase current transformer 41 and the earth leakage relay 110 in the same first switching means _{E 1,} circuit breaker 22, zero-phase the Nagareki 42 and earth leakage relay 22R is also second switching means _{E 2,} the load 51 and 52 correspond similarly each of the first, the second load _F 1, _{F 2.} 2 also functions as the active power calculation means H, the direction determination means I, and the delay means J in FIG.

  Next, FIG. 3 is a configuration diagram of a leakage monitoring and protection device 100 including the leakage relay 110 and the power monitoring device 120. The leakage monitoring and protection device 100 includes the active power calculation means H and the direction determination means of FIG. I and delay means J are realized.

In FIG. 3, a leakage relay 110 includes a leakage current detection unit 111 connected to the zero-phase current transformer 41, a level determination unit 112 that outputs a leakage detection signal when a leakage current detection value exceeds a set level, a timer 113 for a predetermined time (delay time) delays the detection signal by the operation delay command S _TD, and includes an output section 114 for outputting an opening command S _CB for circuit breaker 21 based on the output signal. Here, the delay time set in the timer 113 is longer than the time from when the leakage occurs in the line 32 of FIG. 2 to when the circuit breaker 22 is disconnected by the operation of the leakage relay 22R. Yes.

In addition, the power monitoring device 120 includes a voltage detector 121 that detects the voltage of the line 31 based on the output signal of the voltage detector 44, a current detector 122 that detects the current of the line 31 based on the output signal of the current detector 45, The active power calculation unit 123 that calculates the effective power of the line 31 using the detection values of these detection units 121 and 122, and the direction (polarity) of the active power is not the load 51 side but the reverse direction (for wiring in FIG. 2) And a direction discriminating unit 124 for detecting that so-called reverse power flow is generated. Here, the occurrence of reverse flow power can be easily detected based on the polarity of active power calculated using current and voltage as vectors, as is well known. Note that the voltage detector 44 is not indispensable as described above.
The active power calculation unit 123 and the direction determination unit 124 can use functions originally included in a power monitoring device that monitors active power, reactive power, and the like of the line 31.

Next, the operation of this embodiment will be described with reference to FIGS.
As shown in FIG. 4, a case is assumed in which leakage occurs at a point F on the line 32 close to the load 52 in a state where all the circuit breakers 20, 21, and 22 are turned on. In this case, since the leakage current _Ig1 flows from the distribution transformer 10 through the line 32 and the point F in the same manner as in FIG. 7, the circuit breaker 22 for wiring operates and the line 32 and the load 52 are disconnected from the system. Blocked.

At this time, if the distributed power source 60 of the line 31 is generating power, a leakage current flows from the lines 31 and 32 through the point F during the period until the circuit breaker 22 is cut off. Thus, FIG. 3, the power monitoring device 120 of FIG. 4, by the direction determination unit 124 the polarity of the effective power effective power calculating unit 123 in FIG. 3 is computed is determined, the backward flow power P _R is generated Can be detected.

As a result, the operation delay command S _TD is output from the direction determination unit 124 to the timer 113, and the timer 113 outputs the leakage detection signal output from the level determination unit 112 due to the leakage current flowing through the line 31 for the delay time. The output is delayed and sent to the output unit 114 in the leakage relay 110. For this reason, the output unit 114 outputs the interruption command _SCB after the delay time has elapsed since the leakage was detected. However, before the delay time elapses, the wiring breaker 22 for the line 32 is output. by but the cutoff operation, since leakage current or backward flow power P _R of the line 31 disappears, the output and operation delay command S _TD of level determination unit 112 is reset, it shuts off command S _CB is output from the output unit 114 Never happen.
Therefore, the circuit breaker 22 for wiring disconnects only the line 32 in which leakage has occurred from the power system, and the line 31 in which leakage does not occur continues to feed the load 51 from the power system without operating the circuit breaker 21. It becomes possible to do.

Next, as shown in FIG. 5, a case is assumed where a leakage occurs between the branch point a of the lines 31 and 32 and the circuit breaker 22 for wiring.
In this case, since the leakage current _Ig3 passing through the point F flows from the distribution transformer 10 via the wiring breaker 20 and the line 32, the leakage relay 20R is operated and the wiring breaker 20 is cut off. As a result, power is not supplied from the power system to the loads 51 and 52 side.

On the other hand, when the distributed power source 60 is generating power, a leakage current _Ig4 that passes through the point F flows through the line 31, the circuit breaker 21 for wiring, and the line 32. Since this leakage current I _g4 is generating the backward flow power P _R, as described above, to generate the operation delay command S _TD active power calculation unit 123 and the direction determination unit 124 of FIG. 3 is operated, then the output The circuit breaker 21 for wiring is cut off by the cut-off command _SCB .
In this case, there is a time delay from the occurrence of leakage at the point F until the circuit breaker 21 for the line 31 is cut off, but the delay time by the timer 113 in the leakage relay 110 is set to the minimum necessary. If this is the case, there will be no inconvenience in operation.

  In the present invention, the line 31 further branches in FIG. 2, and a power breaker, a load, a distributed power source, a leakage relay, and a power monitoring device are connected to the branch destination line. Therefore, the present invention can also be applied to a low voltage distribution system that supplies power to a plurality of loads. In this case, what is necessary is just to lengthen the delay time set to the timer in an earth-leakage relay as it goes from the lowest layer to the highest layer. Thereby, for example, even when leakage occurs at the point F on the line 32 side shown in FIG. 4, it is possible to avoid the situation where the uppermost circuit breaker 21 on the line 31 side is cut off first. It is possible to continuously supply power from the power system to the loads on each level.

  The present invention is applicable to a distribution system in which a load and a distributed power source are connected in parallel to some lines regardless of whether the secondary side of the distribution transformer is grounded or ungrounded.

A: Power system B: Distribution transformer C: Main switching means D ₁ : First line D ₂ : Second line E ₁ : First switching means E ₂ : Second switching means F ₁ : First Load F ₂ : Second load G: Distributed power source H: Active power calculation means I: Direction determination means J: Delay means 10: Distribution transformers 20, 21, 22: Circuit breakers 20R, 21R, 22R: Electric leakage Relays 31, 32: Lines 41, 42, 43: Zero-phase current transformer 44: Voltage detector 45: Current detector 51, 52: Load 60: Distributed power source 71A, 72: Power monitoring device 100: Leakage monitoring and protection device 110: Leakage relay 111: Leakage current detection unit 112: Level determination unit 113; Timer 114: Output unit 120: Power monitoring device 121: Voltage detection unit 122: Current detection unit 123: Active power calculation unit 124: Direction determination unit

Claims (4)

A first line and a second line that are connected to the secondary side of the distribution transformer, the primary side of which is connected to the power system, via the main switching means and are branched from each other;
A first opening / closing means that is installed in the first line and opens when an electric leakage occurs;
A second opening / closing means that is installed in the second line and opens when a leakage occurs;
Active power calculation means for calculating active power from the voltage and current of the first line;
Direction determining means for determining that the active power is reverse power flowing toward the branch point of the first line and the second line via the first opening / closing means and outputting an operation delay command;
Delay means for delaying the opening operation of the first opening / closing means by a certain time from the opening operation of the second opening / closing means by the operation delay command;
With
The first line includes a first load fed from the power system via the first switching means, and a distributed power source linked to the power system via the first switching means. , Is connected,
A leakage monitoring and protection system, wherein a second load fed from the power system is connected to the second line via the second switching means. In the leakage monitoring and protection system according to claim 1,
The leakage monitoring and protection system, wherein the main switching means opens when a leakage occurs in the line between the main switching means and the branch point of the first line and the second line. In the leakage monitoring and protection system according to claim 1 or 2,
The leakage monitoring and protection system, wherein the active power calculation means and the direction determination means constitute a part of a power monitoring device that monitors the power of the first line. In the leakage monitoring and protection system according to claim 1 or 2,
The leakage monitoring and protection system according to claim 1, wherein the delay means constitutes a part of a leakage relay for detecting leakage of the first line and interrupting the first switching means.

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