JP2702961B2 - Ground fault line selection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for specifying a ground fault line due to deterioration of equipment of an ungrounded distribution line, and particularly relates to a zero-phase current transformer provided on a distribution line. The present invention relates to a ground fault line device capable of specifying a ground fault line using only phase current.

[Conventional technology]

According to the "High Voltage Receiving Equipment Guideline" issued by the Japan Electrical Association, the high voltage distribution lines in Japan are generally tree-like systems, and the neutral point of the receiving transformer is ungrounded. And each phase electric wire of the line has a part whose geometrical arrangement is asymmetric with respect to the ground. For this reason, the ground capacitance of each phase becomes unbalanced, and the residual zero-phase current I _0r
And the capacitance to ground increases with the increase of the insulated wires.

On the other hand, for ground fault protection, generally, the zero-phase voltage obtained from the grounding transformer and the zero-phase current obtained from the zero-phase current transformer installed in each distribution line are input. A ground fault directional relay that identifies the This detection sensitivity improves the efficiency of maintenance and inspection work for security and track equipment,
It is desired to detect the insulation degradation section with high sensitivity in order to improve the supply reliability. However, the detection sensitivity is limited by the existence of the residual zero-sequence voltage, the existence of the residual zero-sequence current, and the decrease of the zero-sequence voltage due to an increase in the ground capacitance. Further, when the detection sensitivity is set to be equal to or higher than the detection sensitivity allowed by the residual voltage and the current, the result of the determination becomes erroneous.

FIG. 2 shows an outline of conventional ground fault protection of an ungrounded distribution line. In FIG Te at, F ₁ to F ₃ are respectively connected to the bus BUS via a distribution line was and disconnection device CB ₁ to CB _3, is connected to a further main transformer MT. Meanwhile grounded directional relay DG ₁ ~DG ₃ is zero-phase current transformer respectively corresponding ZCT ₁ ~ZCT _3, and inputs the electrical signal output by the ground transformer GPT common installation, the zero-phase voltage V ₀ and zero-phase When the currents I _{01 to} I ₀₃ are equal to or more than a predetermined value and the phase relationship is within a predetermined phase angle, an operation output is derived,
Actuates one of the corresponding to and disconnection device CB ₁ to CB ₃ is opened.

The configuration and operation of the earth fault directional relay DG ₁ ~DG ₃ of FIG. 2 will be described with reference to FIG. 3 and FIG. 4. FIG. 3 is an example of a ground fault direction relay, where PT is a transformer for converting the output zero-phase voltage V ₀ of the grounding transformer GPT into an electric quantity suitable for the level detection circuit 1, and CT is Output zero-phase current I _{0 of} zero-phase current transformer ZCT
Is a transformer for converting into a quantity of electricity suitable for the level detection circuit 3. The level detection circuit 1 derives a predetermined level or more of V ₀ to the square wave circuit 2. On the other hand, the level detection circuit 3 derives a predetermined level of I ₀ or more to the square wave circuit 4. The phase comparison circuit 5 receives the square waves output from the square wave circuits 2 and 4 as inputs, and determines the weight angle of these square waves as the operation determination angle (about the electrical angle).
90 ° C.) or less, the determination output is derived to the output circuit 6, and the output circuit 6 receives the pulse signal of the phase comparison circuit 5,
Detecting that the pulses have continued for a predetermined number of times, the corresponding pulse generators CB _{1 to} CB ₃ are output with a pulse disconnect command.

FIG. 4 shows waveforms a, b, c, and d of the respective parts in FIG.
The phase difference angle θ between the zero-phase voltage V ₀ and the zero-phase current I ₀ is determined by the phase comparison circuit 5
The operation output is derived below the operation determination angle of. FIG. 5 shows the third
In the phase characteristic diagram showing the operation and non-operation area of V ₀ and I ₀ of the ground fault directional relay shown in the figure, the operation judgment angle of the phase comparison circuit 5 is set to about 90 ° in electrical angle. If discrimination overlaps angle to V ₀ and I ₀ is less than 90 degrees, i.e. (180-
θ) <π / 2, no operation is performed, and when (180−θ)> π / 2, operation is performed.

Then 1-line ground fault G to G point of the distribution line F ₁ strains of Figure 2
There is assumed that occurred, the operation of the earth fault directional relay DG ₁ ~DG _3.

At the same time as the accident occurred, each DG _{1 to} DG ₃ is different from normal
V ₀ is applied, whereas, when viewed for I _0, commensurate ivy zero-phase current I ₀₁ in the fault point in DG ₁ current I _g is applied from ZCT _1. DG ₂ is the current corresponding to the charging current I _C2 of the ground capacitance C ₂
A current I _{03 corresponding} to the ground capacitance C ₃ is applied to I ₀₂ and DG ₃ . Current direction of each distribution line as shown in FIG. 2, the F _2, F ₃ in the direction F ₁ flows out from the bus BUS, approximately 180 ° position in this example and summer and direction flowing to bus Has a difference. That DG ₃ fault line DG ₂ of F ₂ when the phase determination that there was line summer in order to the operation direction DG ₁ of F _1, F ₃ becomes possible to select the fault line to become inoperative.

Next, always, the residual zero-sequence voltage V _0r and the residual zero-sequence current I _0r
An example in which a ground fault accident has occurred in a system where a fault has occurred will be described. The zero-phase voltage by connexion occurs a ground fault V _{0 s,} the zero-phase current of the fault line I _0S1, the zero-phase current of the healthy line When I _0S2 first 6 DGR terminal input zero-phase voltage as shown in FIG. Is V
As _0s1 or V _0S2, when this value causes a ± phi phase shift than the true V _{0 s} which I connexion generated a true failure becomes a vector synthesis of V _{0 s} and V _0r is equal magnitude of V _{0 s} and V _0r The resultant zero-phase voltage has a phase difference of ± 45 ° with respect to V _0s . The generation phase of the residual zero-phase voltage V _0r is in the range of 360 ° from the same phase depending on the system conditions, and the phase characteristic indicating the operating range of the DGR is equal to the phase shift angle φ of the zero-phase voltage as shown in FIG. phi ₁ to the reference signature S of _{0 s,} it causes a shift of phi ₂ phase. On the other hand, the terminal input zero-phase current of the relay
I ₀₁ and I ₀₂ of the healthy line are vector composites of the residual currents I _0r1 and I _0r2 generated in the respective lines and the true zero-phase currents I _0s1 and I _0s2 flowing in the respective lines generated at the time of the accident. Become. Range of inoperative in relation to the the DG accident line phase characteristics B and I ₀₁ at this time, the healthy line DG, there is a range that operation in relation to the phase characteristics B and I _02.

Next, the relationship between the zero-sequence voltage at the time of occurrence of the one-line ground fault and the capacitance to the ground will be described with reference to FIG. Fig. 7 shows 1
The phase voltage E, which is an equivalent circuit when a line ground fault occurs, the zero-phase voltage generated when the capacitance of the entire system to ground is C ₀ , and the fault point resistance R _g is
The relationship between V ₀ and the phase voltage can be expressed by equation (1).

That is, as shown in the vector diagram in FIG. 8, _g R
_g is the voltage applied to the fault point Is equivalent to the zero-phase voltage V ₀ , and it can be seen that V ₀ when R _g is constant becomes smaller in a system having a large ground capacitance C ₀ .

On the other hand, ground faults due to aging insulation deterioration of equipment constituting the distribution line of the system occur intermittently due to minute ground faults, and become continuous over time. The conventional ground fault directional relay determines this by determining that a ground fault has occurred continuously for a predetermined time.

[Problems to be solved by the invention]

As described above, the conventional earth-fault directional relay has a zero-phase current (I ₀ ) obtained from a zero-phase current transformer (ZCT) provided at the outlet of the distribution line, and a grounding transformer (I ₀ ) connected to the bus. GPT) is used to select a line by performing phase discrimination with the zero-phase voltage (V ₀ ) obtained from the GPT). The basic principle of performing phase discrimination is a reference other than the zero-phase current I ₀ flowing through each line. Quantity of electricity (in this example,
V ₀ ).

On the other hand, the detection sensitivity is always
In a system with residual voltage or residual current, the phase is discriminated by using the vector composite amount of the residual electric amount and the zero-phase electric amount generated by the ground fault as input.
In particular, in the event of a micro-ground fault near the operating limit (high-resistance ground fault), phase discrimination will be erroneous. To prevent this, the detection sensitivity is restricted by the amount of residual electricity, for example, the detection sensitivity is increased so as not to be affected by the residual zero-sequence voltage or residual current. In addition, in order to ensure the determination of a ground fault, a method is used to confirm that the ground fault has continued for a predetermined period of time. Was.

According to the present invention, only a zero-phase current obtained from a zero-phase current transformer installed in each distribution line is input, and a ground fault line can be selected from the phase relationship between the zero-phase currents. It is an object of the present invention to provide a ground fault line selecting device capable of determining a minor ground fault without being influenced by the magnitude of the current.

[Means for solving the problem]

In order to achieve the above object, according to the present invention, in a ground fault line selection device for detecting a ground fault accident of an ungrounded distribution line having a plurality of lines, a high order frequency component of a zero-phase current of each line is derived. The frequency deriving means, the output signal from the higher-order frequency deriving means of a predetermined line in the plurality of lines, and the phase relationship between the output signal from the higher-order frequency deriving means of another line, the predetermined phase range A phase determining means for deriving a determination output; and an output determining means for determining that the determination output of the phase determination means has reached a predetermined value within a predetermined time.

[Action]

In an ungrounded dendritic distribution line, the zero-phase current at the time of a one-line ground fault occurs,
On the accident line side, the air flows in the direction flowing into the bus (BUS) and flows out from the bus. This value is a composite value of the current due to the ground charge of the healthy line and the current due to the value leakage resistance. (Generally, the ground leakage current is very small compared to the ground charging current, so it may be omitted.) Therefore, the zero-phase current obtained from the zero-phase current transformer installed in each distribution line is divided into the DC component and The phase relations of the currents are compared with each other via a high-pass filter that blocks the fundamental wave component and passes the second harmonic wave or more, and the current directions of the other plural lines and the own line become opposite phases. Is determined, and the line having the opposite phase relationship is specified as the faulty line.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described.

FIG. 1 shows an embodiment of an apparatus for selecting a ground fault line of a distribution line according to the present invention. The connection of the present invention differs from FIG.
It is not necessary to take in the zero-phase voltage (V ₀ ) obtained from the grounding transformer GPT connected to the bus (BUS), and the secondary side current of the zero-phase current transformers (ZCT _{1 to} ZCT _m ) installed in each distribution line (I ₀₁ , i ₀₂ …
i _0n ), and the rest is the same.

In FIG. 1, MT is a power receiving transformer, CB ₁ , CB ₂ , and CB _n are distribution line breakers F _{1 to} F _n , and ZCT ₁ , ZCT ₂ , and ZCT _n are fault point currents (I _g ) or The zero-phase current transformers C ₁ , C ₂ , and C _n that convert the currents (i ₀₁ , i ₀₂ , i _0n ) corresponding to the ground charging currents (I _C2 , I _Cn )
The ground capacitance of the distribution line concerned, DG is a ground fault line selection device of the present invention, OT ₁ is F ₁ , OT ₂ is F ₂ , OT _n is an accident line selection output signal output corresponding to F _n FIG. 9 shows an example of the configuration of the DG shown in FIG. In FIG. 9, 1-1, 1-2, 1-n are ZC
A filter which receives a secondary current i ₀₁ , i ₀₂ , i _0n of T as an input and allows a specific order of this current to pass through, 2-1,2-2,2-n is 1-
A waveform shaping circuit corresponding to the output of 1, 1-2, 1-n and converting this into a square wave, 3 receives an output signal of the waveform shaping circuit as an input, and derives an output when a predetermined phase relationship is established. (31-1, 31-2, 31-n) is a phase inverting circuit for inverting the output of the corresponding waveform shaping circuit, (32-1, 32-2, 32-
n) is an AND circuit for inputting the output of the phase inversion circuit of the own line and the output of the waveform shaping circuit of another circuit, (33-1, 33-2,
33-n) is a waveform measuring circuit which receives the output of the corresponding AND circuit as an input and outputs when the input waveform forms an electrical angle of π / 2 + α or more of a specific order, and 4 designates that the output of the waveform measuring circuit is a predetermined value. measures that has decreased to a predetermined amount in time, constitute such an output circuit tripping to the corresponding to and disconnection device CB ₁ to CB _n instructs at least a predetermined value.

 The operation of this configuration will be described below.

For example, assuming that a ground fault in the G ₂ points of the bus (BUS) is generated in the first view, ground charging s flow I of each distribution line
_C1 ~I _Cn charging s flowing in the distribution line flows in the fault point G ₂ is the corresponding ZCT ₁ ~ZCT _n This commensurate ivy zero-phase current i from
_{01 to} i _0n and applied to DG. In the DG, the phase of a specific harmonic number component current of a higher-order harmonic current component other than the fundamental wave of this current is determined. In the case of this failure, the direction of the ground charging flow is almost the same for all the lines in the direction in which each distribution line flows into the common bus side. This relationship is shown in FIG.
In the AND circuit (31-1, 31-n) of the phase discriminating circuit 3, since the outputs of all the waveform shaping circuits are all in phase and only the own line is inverted, the output is almost zero. Becomes Accordance connexion, indicating that the output signal of this theory circuit is the circuit in the subsequent stage of the circuit case zero total all of the line output OT ₁ ~OT _n is applicable becomes zero because it does not work is sound.

Now earth fault in G ₁ point F ₁ is assumed to be generated at the first view, ground charging s flow i _02, i _0n flow in a direction flowing into the bus side, the fault point G ₁ I _g1 flows out of the bus. This I _g1 is almost _C2 + _Cn and the dominant charging current of the healthy line to the ground is dominant, and the phase difference between this I _g1 and I ₀₂ and I _0n is about 180 °. This current is applied to the DG is converted into this through ZCT ₁ ~ZCT _n in commensurate ivy i ₀₁ through i _0n. FIG. 11 shows the waveform of each part in this case. The logic circuit 32-1 of the phase discriminating unit 3 receives the signals of the phase inverting circuit 31-1 and the shape shaping circuits 21-2 and 21-n as inputs and outputs the weight angle thereof. It is output with a predetermined width like a waveform. Since the other AND circuits 32-2 and 32-n are ANDed with the output of 2-1, this output becomes zero. The waveform measuring circuits 31-1 to 31-n derive a Pal waveform as shown at 33-1 in FIG. 11 because the output of the AND circuit 32-1 has a width of approximately 180 degrees in electrical angle. Next, the output circuit 4 confirms whether or not the output pulse of 33-1 has reached a predetermined value within a predetermined time, and when this value reaches a predetermined value, issues an operation command to the corresponding CB. Output.

According to the embodiment of the present invention described above, there is an effect that the ground fault line can be specified without being influenced by the magnitude of the residual current only by the zero-phase current obtained from the zero-phase current transformer installed in each distribution line.

 Next, another embodiment will be described.

The present invention is different from FIG. 9 only in the method of determining the output circuit 4 shown in FIG. Generally, in the insulation deterioration of the equipment of the distribution line, in the initial stage of the deterioration, a minute current flows and the generation is intermittent and irregular, and the generation interval becomes short with time.

Accordingly, the output circuit of the present embodiment employs a determination method suitable for this generation mode, and is capable of detecting a change with time of insulation deterioration.

This circuit compares the amount of the output pulse of the waveform measuring circuits 33-1 to 33-n with the amount of the pulse before a predetermined time and the current amount of the pulse. According to the embodiment of the present invention, it is possible to determine the deterioration of the distribution line over time.

〔The invention's effect〕

According to the present invention, only a zero-phase current obtained from a zero-phase current transformer provided in each distribution line is input, a filter is provided to eliminate a residual current constantly generated in the system, and a mutual connection of the zero-phase current of each line is provided. for was scheme to identify the accident line from the phase relationship, V ₀ obtained from ground transformer are carried out conventionally
Unlike the method of discriminating the phase from the zero-phase current obtained from the zero-phase current transformer, without being affected by the magnitude of the residual current at all times, and without paying attention to the unique waveform and magnitude of the zero-phase voltage, Ground fault line can be specified. Further, there is an effect that the apparatus can be simplified.

[Brief description of the drawings]

FIG. 1 is a system connection diagram of one embodiment of the present invention, FIG. 2 is an example of a conventional line selection system using a ground fault directional relay, FIG.
FIG. 4 is a diagram illustrating the operation of a conventional DG, FIG. 5 is a phase characteristic diagram,
FIG. 6 is a vector diagram, FIG. 7 is an equivalent circuit at the time of one-line ground fault,
FIG. 8 is a vector diagram corresponding to FIG. 7, FIG. 9 is a principle configuration diagram of one embodiment of the present invention, and FIG. 10 and FIG. MT: Power receiving transformer, CB _{1 to} CB _n … Shiya breaker, ZCT _{1 to} ZCT _n
…… Zero-phase current transformer, F _{1 to} F _n …… Distribution line, G ₁ , G ₂ …… Fault point, C _{1 to} C _n …… Capacity to ground, DG …… Ground fault line selection device, 4 …… Output circuit, OT _{1 to} OT _n …… Output signal.

Claims (2)

(57) [Claims] 1. A ground fault line selecting device for detecting a ground fault accident on an ungrounded distribution line having a plurality of lines, wherein a high-order frequency deriving means for deriving a high-order frequency component of a zero-phase current of each of the lines. Compare the phase relationship between the output signal from the higher-order frequency deriving means of the predetermined line in the plurality of lines and the output signal from the higher-order frequency deriving means of the other lines, and determine the discrimination output when a predetermined phase range is reached. A ground fault line selecting device, comprising: a phase determining means for deriving; and an output determining means for determining that a determination output of the phase determining means has reached a predetermined value within a predetermined time. 2. The ground fault line selecting device according to claim 1, wherein said output judging means receives said judgment output of said phase judging means and judges a judgment value within a predetermined time and a judgment within a predetermined time before a predetermined time. A ground fault line selecting device, comprising: means for comparing the value with a value to determine whether the comparison amount increases or decreases.