JPH01264530A - Ground fault circuit selector - Google Patents

Abstract

PURPOSE:To specify a ground-fault circuit without being influenced by the amplitude of a residual current normally by comparing the phases of higher order zero-phase except the fundamental wave component of the zero-phase current by means of zero-phase current transformers provided to respective wirings. CONSTITUTION:When a ground-fault trouble occurs, a current is applied to a ground-fault channel selector DG through zero-phase current transformers ZCT1-ZCTn, and currents of specific order components are removed by filters 1-1-1-n. Since the logic circuit 32-1 of a phase discriminator 3 inputs the signals of a phase inverter 31-1 and waveform shapers 2-1-2-n, its superposed angle is output with a predetermined width. Further, waveform measuring circuits 33-1-33-n output pulse waveforms since the output of the circuit 32-1 has a width of approx. 180 deg. of an electric angle. Then, an output circuit 4 outputs an operation command to a corresponding circuit breaker CB when the output pulse of the circuit 33-1 becomes a predetermined value.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a device for identifying a ground fault line due to equipment deterioration of an ungrounded power distribution line, and in particular to a device for identifying a ground fault line caused by equipment deterioration of an ungrounded power distribution line. The present invention relates to a ground fault line selection device that can identify a ground fault line using only phase currents.

[Conventional technology]

According to the "High Voltage Power Receiving Equipment Guidelines" published by the Japan Electric Association, Japan's high voltage power distribution lines are generally dendritic systems, and the neutral point of the power receiving transformer is ungrounded. Each wire assembly on the line has a portion whose geometrical arrangement is asymmetrical with respect to the ground. Therefore, the ground capacitance of each phase becomes unbalanced, and the residual zero-sequence current Ior
exists, and as the number of insulated wires increases, the ground capacitance also increases.

On the other hand, for ground fault protection, the zero-sequence voltage obtained from the grounding transformer and the zero-sequence current obtained from the zero-sequence current transformer installed on each distribution line are input, and the phase relationship between the two is determined and the ground fault circuit is detected. A ground fault directional relay is used to identify the ground fault. This detection sensitivity is desired to detect insulation deterioration sections with high sensitivity in order to improve the efficiency of maintenance and inspection work for railway equipment and to improve supply reliability. However, detection sensitivity is limited due to the presence of the residual zero-sequence voltage, the presence of residual zero-sequence current, and a decrease in zero-sequence voltage due to an increase in ground capacitance. Furthermore, if the detection sensitivity is set to be higher than the allowable residual voltage and current, the determination result will be erroneous.

FIG. 2 shows an overview of conventional ground fault protection for ungrounded power distribution lines. In this figure, F1 to F3 are connected to bus line B via circuit breaker CB l-CB s on the distribution line.
It is connected to US and further connected to main transformer MT. On the other hand, the ground fault direction relays DG1 to DGa are connected to the corresponding zero-phase current transformers ZCT1 to ZCT3 and the grounding transformer CI) which is commonly installed.
o and the zero-sequence current lot~I03 are greater than a predetermined value and the phase relationship is within a predetermined phase angle, an operating output is derived, and one of the corresponding circuit breakers CB]~CB3 is operated and opened.

The configuration and operation of the ground fault direction relays D 01 to D G 3 shown in FIG. 2 will be explained using FIGS. 3 and 4.

Figure 3 shows an example of a ground fault directional relay, where PT is
CT is a transformer that converts the output zero-sequence voltage Vo of the grounding transformer GPT into an amount of electricity suitable for the level detection circuit 1. It is a transformer that converts electricity into electricity. Level detection circuit 1
outputs Vo above a predetermined level to the square wave circuit 2. On the other hand, the level detection circuit 3 outputs Io at a predetermined level or higher to the square wave circuit 4. The phase comparator circuit 5 inputs the output square waves of the square wave circuits 2 and 4, and outputs a judgment output to the output circuit 6L when the weight angle of these square waves is equal to or greater than the operation judgment angle (approximately 90'C in electrical angle). The output circuit 6 receives the pulse-like signal from the phase comparator circuit 5, detects that a predetermined number of pulses are consecutive, and outputs the corresponding breaker C1.
Outputs a shutoff command to 3r to CB s.

Figure 4 shows the waveforms of each part in Figure 3: i'l + b + c+
d, and the operating output is derived when the phase difference O between the zero-sequence voltage Vo and the zero-sequence current Io is −3=difference angle is equal to or greater than the operation determination angle of the phase comparator circuit 5. Figure 5 shows the Vo of the ground fault direction relay shown in Figure 3.
This is an example in which the operation determination angle of the phase comparator circuit 5 is approximately 90 degrees in electrical angle in the phase characteristic diagram showing the operating and non-operating regions between Vo and Io. is 90″
If it is smaller, that is, when θ<π/2, it is inactive, and when θ>π/2, it is active.

Next, a single-line ground fault G occurs at point G of distribution line F1 in the system shown in Figure 2.
Assuming that a ground fault directional relay DG'z~DG3
The operation will be explained.

At the same time as the accident occurs, Vo, which is different from the normal state, is applied to each of D'G 1 to D G s. On the other hand, looking at Io, in D G 1, a zero-sequence current IO'l corresponding to the fault point current Ig is applied. is applied from ZCTl. ``DG2 is the current I02 corresponding to the charging current IC2 of the ground capacitance C2.
．． DG3 is a current l113 commensurate with the ground capacitance C3.
is applied. As shown in Figure 2, the current direction of each distribution line is 17z, F8 in the direction in which Fl flows out from the bus bar BUS.
In this case, the inflow direction is 14= with respect to the generatrix, and in this example, there is a phase difference of approximately 18°. That is, if phase determination is performed to set DG 1 of faulty line F1 as the operating direction, DG2 of F2. F8
DGs becomes inoperable, making it possible to select a faulty line.

Next, an example will be described in which a ground fault occurs in a system in which a residual zero-sequence voltage V Or +residual zero-sequence current Ior always occurs in the system. Assuming that the zero-sequence voltage generated by a ground fault is Vos, the zero-sequence current of the faulty line is ■oss, and the zero-sequence current of the healthy line is I052, the DGR is as shown in Figure 6.
The terminal input zero-sequence voltage of , like Vosz or VO52, is a solid combination of Vos and When the magnitudes are equal, the composite zero-sequence voltage will have a phase difference of ±45° with respect to Vos. The generation phase of the residual zero-sequence voltage V 6 r ranges from the same phase to 360° depending on the system conditions, and the phase characteristic indicating the operating range of the 'DGR is Vos equal to the phase shift angle φ of the zero-sequence voltage, as shown in Figure 6. φ■, φ2 for the reference characteristic S of
This causes a phase shift. On the other hand, the terminal human power zero-sequence current of the relay is Io1 of the failed line, and the residual current Ior1 of the healthy line is Ior1. I. ,
2 and the true zero-sequence electricity 'Jr(, 'rosl, I O32) flowing in the line A that occurred at the time of the accident.In the DG of the fault line at this time, the phase characteristics B and No. The range of non-operation in the relationship, healthy line D
In G, there is a range of operation depending on the relationship between the phase characteristics I3 and Ioy.

Next, the relationship between the zero-sequence voltage and the ground capacitance when a one-wire ground fault occurs will be explained with reference to FIG.

Figure 7 shows the equivalent circuit when a one-wire ground fault occurs, and the relationship between the zero-sequence voltage VO and the sum voltage E is It can be expressed by equation (1).

That is, as shown in Figure 8, it can be seen that Vo, which corresponds to the zero-sequence voltage Vo when R6 is constant, becomes smaller in a system where the ground capacitance C is large.

On the other hand, ground faults caused by insulation deterioration over time in the equipment that makes up the power distribution lines of a power system occur intermittently as small ground faults, and become more continuous over time. Conventional ground fault directional relays use this detection method to determine that ground faults have occurred continuously for a predetermined period of time.

[Problem to be solved by the invention]

As mentioned above, conventional ground fault directional relays use not only the zero-sequence current (Io) obtained from the zero-sequence current transformer (ZCT) installed at the outlet of the distribution line, but also the grounding transformer (Io) that is connected to the busbar. G.P.
The line is selected by phase discrimination with the zero-sequence voltage (V o ) obtained from T), and the basic principle of performing phase-side valve is based on the zero-sequence current Io flowing through each line as well as the reference electrical quantity. (In this example, Vo) is always taken in.

-Force detection sensitivity is determined by the difference between the residual electricity quantity and the zero-sequence electricity quantity generated by a ground fault accident in the system M1 where residual voltage or residual current always exists in the conventional ground fault directional relay.
Since the phase is discriminated by inputting the combined amount of signals, the phase discrimination may be incorrect, especially in the case of a slight ground fault (high resistance ground fault) near the operating limit. In order to prevent this, the detection sensitivity is set very high so that it is not affected by the residual zero-sequence voltage or residual current, and the setting of the detection sensitivity is restricted by the amount of residual electricity. In addition, in order to ensure the determination of ground faults, the method is to confirm that a ground fault has continued continuously for a predetermined period of time, so there are cases where intermittent and minor ground faults cannot be detected. Ta.

The present invention uses only the zero-sequence current obtained from the zero-sequence current transformer installed in each distribution line by hand, makes it possible to select the ground fault line from the mutual phase relationship of these zero-sequence currents, and furthermore, To provide a ground fault line selection device capable of determining even a minor ground fault accident without being influenced by the magnitude of current.

[Means to solve the problem]

The zero-sequence current generated due to insulation deterioration in ungrounded dendritic distribution line equipment is mainly a charging current based on the ground capacitance of each distribution line, and its direction is They have almost the same phase, and the phase difference between the faulty line and the healthy line is opposite, that is, approximately 180 in electrical angle.
The phase difference is in the vicinity of °.

On the other hand, the relationship between failure mode and zero-sequence current is that the zero-sequence current that occurs due to pinholes in insulated cables or insulation deterioration of insulators becomes an intermittent, distorted wave flow that contains many harmonic components, and The fundamental wave component occupies most of the residual current generated due to the unbalance.

The present invention focuses on the above points, and the ZCT installed on each distribution line.
The fault line is identified by comparing the phase relationship of higher-order zero-sequence currents other than the fundamental wave component of the zero-sequence current to obtain the following.

[Effect]

In an ungrounded dendritic distribution line, when a one-line ground fault occurs, the zero-sequence current flows in the direction of the ground charging current on the healthy line side, flowing into the bus (BUS), and on the faulty line side. , flows in the direction outflowing from the bus bar. This value is the combined value of the ground charging current of the healthy line and the current due to the ground leakage resistance.

(In general, the ground leakage current is very small compared to the ground charging current, so it can be omitted.) Therefore, the zero-sequence current obtained from the zero-sequence current transformer installed in each distribution line is calculated as the DC component and the basic current. The phase relationship of this current is compared with each other through a bypass filter that blocks wave components and passes second harmonics and above, and it is determined that the current direction of the other multiple lines and the current direction of the own line are in opposite phase. The line with the opposite phase relationship is identified as the failed line.

In addition, this device has a method of increasing sensitivity by blocking the basic distribution of residual current through a bypass filter in order to detect minor ground faults.

〔Example〕

An embodiment of the present invention will be described below.

FIG. 1 shows an embodiment of a ground fault line selection device for a power distribution line according to the present invention. The difference between the connection of the present invention and that of Fig. 2 is that it is not necessary to take in the zero-phase voltage (Vo) obtained from the grounding transformer GPT connected to the bus (BUS), and the zero-phase voltage (Vo) obtained from the grounding transformer GPT connected to the bus The only difference is that the system takes in only the secondary current (jan, io2·l On) of the current transformer (ZCT+-ZCT,), and the rest is the same.

In Figure 1, MT is a power receiving transformer, and CB1.

CB2. CB is the circuit breaker for distribution lines F1 to F11, Z
CT t.

ZC'14, ZCT, l is the fault point current (rg) or the current (io) commensurate with the ground charging current (IC2, Icn).
n.

i 02110n) zero-phase current transformer, C1, CZ
.

C1 is the ground capacitance of the distribution line, I) G is the ground fault line selection device of the present invention, OTl is Fl, ○T2 is F2,
○Tn is a failure line selection output signal outputted corresponding to Fn, and FIG. 9 shows an example of the configuration of the DG in FIG. 1. 9th
In the figure, 1-1.1-2.1-n is 7. CT 2
Next current 101+ l OZ+ 1. With On as input,
A filter that passes a specific order of this current, 2-1
, 2-2, 2-n are 1. -1. ,,L-2,1-
3 is a waveform shaping circuit that corresponds to the output of n and converts it into a square wave; 3 is a phase discriminator that uses the output signal of the waveform shaping circuit manually and derives an output when a predetermined phase relationship is reached;
1-1, 31-2゜3l-n) is a phase inversion circuit that inverts the output of the corresponding waveform shaping circuit, (32-1, 3'2
-2゜32-n) is an AND circuit whose inputs are the phase inversion circuit output of its own line and the waveform shaping circuit output of another circuit;
(33-1, 33-2, 33-n) have the outputs of the corresponding AND circuits as inputs, and have a specific order.

A waveform measurement circuit that outputs when the input waveform is equal to or more than electrical angle π/2+α, 4 indicates that the output of the waveform measurement circuit has reached a predetermined amount within a predetermined time, and corresponds to a predetermined value or more. It consists of an output circuit that issues a trip command to the circuit breakers CBl-CBn.

The operation in this configuration will be explained below.

For example, assuming that a ground fault occurs at 62 points on the bus (BUS) in Figure 1, the ground charging currents ICI to Icn of each distribution line flow to the fault point Gz, and the charging currents flowing to each distribution line are: The phase of the corresponding zero-sequence current iox~iθ1° wave number component current is determined from the corresponding ZCTn~ZCTn.In this fault case, the direction of the ground-to-ground charging current is the direction in which it flows into the common bus side of each distribution line. Both lines are in approximately the same phase.

This relationship is shown in FIG. In the AND circuit (31 to 1.3l-n) of the phase discrimination circuit 3, the outputs of each wave shaping circuit are all in the same phase, and only the own line is inverted in phase, so this output is almost zero. becomes. Therefore, when the output signal of this theoretical circuit is zero, the circuits in the subsequent stages of this circuit do not operate, so the outputs OT+ to OTo become zero, indicating that all the corresponding lines are healthy.

Next, in Figure '1, assuming that a ground fault has occurred at point 61 of Fl, the ground-to-ground charging current 102+ions flows in the direction of flowing into the bus bar side, and at the fault point GI, Igl flows in the direction of flowing out from the bus bar. flows to This Igx is
2+Icn and the ground charging current of the healthy line are dominant,
This ■□1 and 102. Ion's phase difference is approximately 180
° Nearby. This current is converted to a corresponding value of ]01 to ]0° via ZCT and applied to I)G. Figure 1j shows waveforms at various parts in this case. The logic circuit 32-1 of the phase discriminator 3 is a phase inversion circuit 3]-1
Since the signals of the shaping circuit 2]-2 and 21-n are inputted, the weight angle is outputted, and the output waveform of 31-1 in FIG. I++ <Output with a predetermined width. Since the other AND circuits 32-2 and 32-1 are ANDed with the output of 2-1, this output becomes zero. Waveform measurement circuit 31-1
Since the output of the AND circuit 32-1 has a width of approximately 180 degrees in electrical angle, a pulse waveform as shown in FIG. 33-1 is derived. Next, the output circuit 4 checks whether the output pulse of 33-1 reaches a predetermined value within a predetermined time, and when it reaches this value or a predetermined value, the corresponding CB
Outputs an operation command to.

According to the second embodiment of the present invention, it is possible to identify a ground fault line using only the zero-sequence current obtained from the zero-sequence current transformer installed in each distribution line, regardless of the magnitude of the residual current. .

Next, another embodiment will be described.

The present invention differs only in the determination method of the output circuit 4 shown in FIG. 9, and is otherwise the same as that shown in FIG. In general, when the insulation of power distribution line materials deteriorates, a small current flows in the early stages of deterioration, and the generation thereof is intermittent and irregular, and the interval between occurrences becomes shorter as time passes.

Therefore, the output circuit of the present embodiment employs a determination method that is appropriate to the appearance of this occurrence, and makes it possible to detect changes over time in insulation deterioration.

This circuit compares the amount of output pulses of the waveform measurement circuits 33-] to 33-n with the amount of the current pulses a predetermined time ago, and when the amount increases, issues a breaker command to the corresponding breaker. According to the embodiment of the present invention, which is a derivation method, it becomes possible to determine the deterioration of the distribution line over time.

〔Effect of the invention〕

According to the present invention, only the zero-sequence current obtained from the zero-sequence current transformer installed in each distribution line is input, and a filter is provided to eliminate the residual current that always occurs in the grid, so that the mutual zero-sequence current of each line is This method identifies fault lines based on the phase relationship between
Unlike the method of phase discrimination based on the zero-sequence current obtained from the zero-sequence current transformer, this method does not depend on the magnitude of the residual current at all times, and does not focus on the unique waveform and magnitude of the zero-sequence voltage. Can identify ground fault lines. It also has the effect of simplifying the device.

[Brief explanation of the drawing]

FIG. 1 is a system connection diagram of an embodiment of the present invention, FIG. 2 is an example of a line selection method using a conventional ground fault direction relay, and FIG.
Fig. 4 is an explanatory diagram of 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 in the case of a one-wire ground fault, and Fig. 8 corresponds to Fig. 7. The vector diagram and FIG. 9 are principle configuration diagrams of an embodiment of the present invention, and FIGS. 10 and 11 are waveform explanatory diagrams of each part. MT ・Power receiving transformer, CB 1 to CBn breaker, Z
CT 1-Z CT n/zero phase current transformer, F1~Fo
・・Distribution line, Gl, G2・Fault point, 01 to C0,・Ground capacitance, DG・Ground fault line selection device, 4・Output circuit, ○T1 to OTl, Output signal.

Claims (1)

[Claims] 1. In a ground fault line selection device for detecting a ground fault in an ungrounded distribution line having multiple lines, a first means for deriving a high-order frequency component of a zero-sequence current of each line; a second means for comparing the phase relationship of the output of the first means with the input signal of another line, and deriving a discrimination output when a predetermined phase range is reached;
and third means for determining whether the output of the second means reaches a predetermined amount within a predetermined time. 2. In the apparatus according to claim 1, the output of the second means is input, and the predetermined determination amount within a predetermined time and the predetermined determination amount within a predetermined time before a predetermined time are compared, and the comparison amount increases or A ground fault line selection device characterized by comprising fourth means for determining that the ground fault line has decreased.