JPH04372520A - Ground directional relay - Google Patents

Abstract

PURPOSE:To provide a cheap and reliable ground directional relay for judging the grounding fault and of a nonearthed distribution line and its direction. CONSTITUTION:This is compose of a current transformer 3, which detects the grounding conductor current of a three-phase transformer 1, a zero-phase current transformer 4, and a ground directional relay 5. The judgment of grounding fault and the judgment of fault direction are performed by the phase difference between the grounding conductor current and the zero-phase current and the levels of both currents.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground fault direction relay device for detecting the direction of a ground fault fault in an ungrounded three-phase high voltage distribution line.

0002

2. Description of the Related Art As a device for determining a ground fault in a power distribution line up to the direction of the fault, a zero-phase current transformer 4 and a zero-phase current transformer 4 are used as shown in FIG.
Capacitors C9 and C1 are installed in each phase of the three-phase distribution line R, S, and T.
One end of the zero-phase voltage detection capacitor C0 is connected to the connection point where one end of C0 and C11 are connected and the other end is connected in common, and the other end of the capacitor C0 is connected to the ground. A zero-phase voltage detector b configured by connecting an isolation transformer Tr that steps down and outputs a low voltage, and the outputs of a zero-phase current transformer 4 and a zero-phase voltage detector 6 are input, and the level and phase angle are determined. It has generally been constructed with a ground fault direction relay 5 that determines the ground fault fault level and fault direction from the ground fault level.

0003

[Problem to be Solved by the Invention] In order to minimize the power outage section of the distribution line, it is necessary to install many ground fault direction relay devices on the distribution line, and therefore the above-mentioned zero-sequence voltage detection is required. Many zero-phase voltage detectors were also installed, which was a factor in reducing the reliability of high-voltage distribution lines. Moreover, it is also quite expensive in terms of cost.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inexpensive and highly reliable ground fault directional relay device that does not require installation of equipment for detecting zero-sequence voltage on a high-voltage distribution line.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the ground fault direction relay device of the present invention is a three-phase high-voltage power distribution line connected to the high-voltage side by a Y connection or a delta connection. A three-phase transformer consisting of three transformers or single-phase transformers, a current transformer that detects the grounding wire current of the transformer, a zero-phase current transformer that detects the ground fault current, and a It consists of a ground fault direction relay that inputs the detection output of a current transformer that detects ground current and the detection output of a zero-phase current transformer to determine the ground fault fault level and fault direction.

[0006]

[Operation] The grounding wire current of a three-phase transformer is due to the distributed capacitance between the transformer's primary winding and the iron core, and that capacity is equivalent to a three-phase Y connection. By utilizing the fact that the current level is proportional to the zero-sequence voltage and its phase is 90 degrees ahead of the zero-sequence voltage, the grounding wire current is detected by a current transformer, which allows the conventional zero-sequence voltage detector to It can perform the same function as .

[0007]

EXAMPLES Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing the configuration of the present invention, and 1 is a circuit diagram in which the high voltage side winding is connected to ungrounded three-phase high voltage distribution lines R, S, and T.
Connected by wire connection, with Δ connection on the low voltage side, R', S'
, T' are three-phase transformers that constitute a low voltage circuit. 2
is a grounding wire for the housing and iron core of the three-phase transformer 1, which is grounded to the earth as a type of grounding. Reference numeral 3 denotes a current transformer that detects the ground line current, and its secondary output is input to the earth fault direction relay 5. Furthermore, the output of the zero-phase current transformer 4 for detecting a ground fault fault current in the distribution line is also input to the ground fault direction relay 5. Note that the detection of the ground fault current may be performed not by the zero-phase current transformer 4, but by a method in which each phase current is detected by a current transformer and the three-phase composite zero-phase current component is determined from the detected value.

In the above configuration, when the high voltage side winding of the three-phase transformer 1 is Y-connected, the ground wire current of the three-phase transformer 1 flows through the three-phase high voltage distribution line as shown in the equivalent circuit shown in FIG. R,S
, T, between the transformer primary high voltage winding and the iron core, L1,
Inductive reactance of L2, L3 and C1, C2, C3
, C4. On the other hand, if the high voltage side winding is Δ-connected, as shown in the equivalent circuit shown in Fig. 3,
For three-phase high-voltage distribution lines R, S, and T, it consists of inductive reactance of L4, L5, and L6 and distributed capacitance of C5, C6, C7, and C8 between the primary high-voltage winding of the transformer and the iron core. be done. However, since the impedance of each inductive reactance is small for each distributed capacitance, if each inductive reactance is ignored, the equivalent circuits shown in FIGS. 2 and 3 can be expressed as the equivalent circuit shown in FIG. 4. . In other words, CR between the R phase and the iron core, and C between the S phase and the iron core.
Between the S and T phases and the iron core is composed of each composite capacitance of CT,
Each of the capacitances CR, CS, and CT is grounded to the earth via a grounding line 2. Note that the ground line current iG in FIG. 4 is the current iR flowing through CR and the current iS flowing through CS.
It is a composite current of the current iT flowing through the CT and the current iT flowing through the CT, and is zero when there is no ground fault. However, when a ground fault occurs, a grounding line current flows at a level corresponding to the zero-sequence voltage, but the phase of this grounding line current is 90 degrees ahead of the zero-sequence voltage.
The configuration shown in FIG. 5 functions based on the principle of the conventional zero-phase voltage detector system shown in FIG. However, whereas the conventional zero-phase voltage detector system shown in FIG. , since it is necessary to lower the impedance between ground, the ground wire current iG is transferred to the current transformer 3.
The detected output is detected through the ground fault direction relay 5 as the one corresponding to the zero-sequence voltage V0, and the phase is compared with the zero-sequence current i0 of the zero-sequence current transformer 4, and the detection of each current level is performed. , the ground fault fault determination and the ground fault fault direction are determined. With this configuration, the direction of a ground fault fault can be determined if the ground line current iG phase is zero-sequence voltage V
Since it is 90 degrees ahead of zero, if the zero-phase current i0 phase is within ±90 degrees with respect to the ground wire current iG, it is determined as a ground fault on the load side, otherwise it is determined as a ground fault on the power supply side. be.

[0009]

[Effects of the Invention] As is clear from the above description, according to the present invention, the following effects can be obtained.

(1) By detecting the ground wire current of a general three-phase transformer without installing a zero-phase voltage detector on the high-voltage distribution line, an output corresponding to the zero-phase voltage can be detected;
A ground fault direction relay device with a simple configuration can be realized.

(2) There is no need for high-voltage equipment such as zero-phase voltage detectors on the high-voltage distribution line, and even if a large number of them are installed, the reliability of the distribution line will not deteriorate.

(3) Due to the simple configuration, a low-cost earth fault direction relay device can be obtained.

[Brief explanation of drawings]

[Fig. 1] A circuit diagram of an embodiment of the ground fault directional relay device of the present invention.

[Figure 2] The primary side of the three-phase transformer of the same ground fault directional relay device is
Equivalent circuit diagram of the primary side in case of wiring

[Figure 3] Equivalent circuit diagram of the primary side of the same three-phase transformer when the primary side is Δ connection

[Figure 4] Equivalent circuit diagram of the primary side when the primary side of the same three-phase transformer is Y-connection or Δ-connection, ignoring the inductive reactance on the primary side.

[Figure 5] Circuit diagram of conventional ground fault directional relay device

[Explanation of symbols]

1 Three-phase transformer 3 Current transformer 4 Zero-phase current transformer 5 Ground fault direction relay

Claims (1)

[Claims] Claim 1: A first detection means for detecting the grounding line current of a three-phase transformer connected to an ungrounded three-phase high-voltage distribution line using a current transformer, and detecting a zero-sequence current of the three-phase high-voltage distribution line. a second detection means, which is a zero-phase current transformer or a current transformer provided in each phase that detects each phase load current for synthesizing each phase load current to obtain a three-phase composite zero-sequence current component; A ground fault direction relay device comprising a ground fault direction relay that determines the direction of a ground fault from the outputs of the two detection means.