JPH0532778Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a ground fault detection device for an ungrounded power distribution line.

BACKGROUND ART Conventionally, zero-phase current transformers have been used to detect ground faults in ungrounded distribution lines.

Problems that the invention aims to solve In the conventional method of using a zero-phase current transformer, the ground current to be detected is very small, so the size of the zero-phase current transformer used is unavoidably large. It was closed. Therefore, the zero-phase current transformer is also expensive and requires a considerable amount of space for its installation.

An object of the present invention is to solve the above-mentioned conventional problems and provide an inexpensive, small, and lightweight ungrounded distribution line ground fault detection device.

Means for solving the problem The ungrounded distribution line ground fault detection device according to the present invention has the following features:
The substation is equipped with the same first and second circular non-cut winding cores that collectively connect the three core non-grounding system pull-out cables and pass the grounding wire of the thin layer of the pull-out cables, and each of the circular non-cut windings The core is provided with a primary winding and a secondary winding, the primary winding of the first circular non-cut wound core and the primary winding of the second circular non-cut wound core. are connected in series with opposite polarities, and the secondary winding of the first circular non-cut winding core and the secondary winding of the second circular non-cut winding core have a rectifier and a resistor. are connected in series with opposite polarity through the primary windings, and a voltage corresponding to the zero-sequence voltage of the lead-out cable is applied between the ends of the series-connected primary windings through a capacitor and a variable resistor, A ground fault in the own line generates a positive output between the ends of the series-connected secondary windings, and a ground fault in another line generates a negative output.

Embodiments Next, the present invention will be described in more detail with regard to embodiments of the present invention based on the accompanying drawings.

FIG. 1 schematically shows an embodiment of the ungrounded distribution line ground fault detection device of the present invention. In this embodiment, each core wire 11, 12, and 13 of a three-core non-grounding system pull-out cable for a substation of 6,600 V or more is bundled, and each core wire 11, 12, and 13 is connected to a
A grounding wire 20 commonly connected to the grounding wires 17, 18, and 19 connected to each of the grounding wires 17, 15, and 16;
Two circular non-cut wound cores 21 and 22 are provided so as to penetrate through the cores 21 and 22. The first circular non-cut winding core 21 is provided with a primary winding 23 and a secondary winding 24, and the second circular non-cut winding core 21 is provided with a primary winding 23 and a secondary winding 24.
2 is provided with a primary winding 25 and a secondary winding 26. These first and second circular non-cut wound cores 21 and 22 may have the same specifications. 1
The secondary winding 23 and the primary winding 25 are connected in series with mutually opposite polarities. The secondary winding 24 and the secondary winding 26 are connected in series with opposite polarities via full-wave rectifiers 27 and 28 and a resistor R. The terminals of the series-connected primary windings 23 and 25 are connected via a capacitor C and a variable resistor R _A to the tertiary power of a grounded potential transformer (GPT) or a capacitor-type potential transformer (PD). Voltages, that is, zero-sequence voltages _VO and _VO ' are applied. In addition, the ground wire 20
The charging current Icg is designed to flow in the event of a ground fault.

Such a circuit constitutes a current reactive filter, and the first circular non-cut wound core 2
A voltage proportional to -V _O +Icg is generated in the secondary winding 24 of the second circular non-cut winding core 22.
A voltage proportional to V _O +Icg is generated in the next winding 26,
Therefore, the output terminal of the resistor R and the R end has a value proportional to 2Icg. Here, as shown in Figure 2,
By setting the phase difference between the zero-sequence voltage V _O and the charging current Icg as θ, considering the adjustment angle φ by the capacitor C and the variable resistor R _A , and selecting the resistance values of the resistors R and R appropriately, the resistance can be adjusted. The outputs of the output terminals at the R and R ends can be set to K Icg cos (φ−θ). Here, K is a proportionality constant.

If the electrical path is only a cable, a slight ground fault (incomplete ground fault) is unlikely, so the adjustment angle φ may be 90°.
In this case, the output of the resistors R and R end is KIcg
cos(π/2-θ)=K Icg sinθ, and if there is a ground fault in the own circuit, it will be a positive output, and if there is a ground fault in another line, it will be a negative output.

However, in the case of overhead lines, etc., there may be a slight ground fault, and in this case, the charging current Icg will be about 1/10,
The phase difference θ between the zero-sequence voltage V _O and the charging current Icg also becomes smaller, and sin θ also becomes about 1/10, so the output is reduced to 1/100.
It becomes difficult to detect. Therefore, in such a case, it is necessary to adjust the variable resistor R _A so that the adjustment angle φ is about 10°. In this way, if the adjustment angle φ of the current phase of the Vo circuit is about 10°, then 1/1
Sufficient detection output can be obtained for both 0 ground fault and 100% ground fault, and both can be easily detected.

Effects of the invention According to the configuration of the ungrounded distribution line ground fault detection device of the present invention, since the winding core is excited by the zero-sequence voltage V _O , it can be used in places where the initial magnetic permeability is small but the magnetic permeability is large. Therefore, even if the charging current Icg is very small, it can be made small, lightweight, and inexpensive. For example, a circular non-cut wound core (cross-sectional area 10 x 3, diameter
160) 21, primary winding 25 and secondary winding 2
By stacking the circular non-cut wound cores 22 having 6 and 6 to prevent magnetism and integrally molding them to form a through-type sensor, approximately
It can weigh about 800g. Further, since the grounding wire 20 is passed through the wound cores 21 and 22, it is possible to effectively detect a failure when it occurs inside.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an ungrounded distribution line ground fault detection device as an embodiment of the present invention, and Fig. 2 is a vector diagram showing the relationship between zero-sequence voltage and charging current in the device of Fig. 1. . 11, 12, 13... Pull-out cable core, 1
4, 15, 16...Shiyahei layer, 17, 18, 1
9,20...Grounding wire, 21,22,...Circular non-cut wound core, 23,25...Primary winding, 24,
26... Secondary winding, 27, 28... Full wave rectifier,
R...Resistor, C...Capacitor, R _A ...Variable resistance.

Claims (1)

[Scope of utility model claims] The substation is equipped with the same first and second circular non-cut winding cores that collectively connect the three core non-grounding system pull-out cables and pass the grounding wire of the thin layer of the pull-out cables, and each of the circular non-cut windings The core is provided with a primary winding and a secondary winding, the primary winding of the first circular non-cut wound core and the primary winding of the second circular non-cut wound core. are connected in series with opposite polarities, and the secondary winding of the first circular non-cut wound core and the second
The secondary winding of the circular non-cut wound iron core is connected in series with opposite polarity via a rectifier and a resistor, and a capacitor and a variable resistor are connected between the ends of the series-connected primary winding. A voltage corresponding to the zero-sequence voltage of the lead-out cable is applied, and a positive output is generated between the ends of the series-connected secondary windings due to a ground fault in the own line, and a negative output is generated due to a ground fault in the other line. An ungrounded distribution line ground fault detection device characterized by generating an output of