JP2568092B2 - Power cable accident section detection method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for detecting a faulty section of a power cable in a cross-bond grounding type three-phase power cable line.

[Prior Art] In the case of FIG. 3, when a ground fault occurs at an accident point 12 of the cable line 10, a surge current 14 progresses left and right.

It is detected by CT16 at both ends of the cable line 10,
The accident point is located based on the difference in arrival time.

[Problems to be Solved by the Invention] However, this method has problems in that the mechanism is complicated, the cost is high, and the versatility is not.

[Means for Solving the Problems] As shown in FIGS. 1a and 1b, the present invention is as follows: (1) Insulating the cable sheath 24 of each ordinary junction box 41 to form an insulated junction box, and cut the cable sheath. 24 wires are connected by a bond wire 52, and an intermediate point of each bond wire 52 is grounded collectively by a ground wire 40. (2) Left and right between the connection point to the ground wire 40 and the cable sheath 24 (left and right are drawings. The current sensor 56 is provided on the same side (for example, right side) of one of the power supply lines (for example, 26) of the bond wires 52 of each phase of (1), and the magnitude of the fault current flowing through each current sensor is provided. By measuring each of them and comparing and discriminating them, the accident zone can be reliably located.

[Embodiment] In FIG. 1a, 20 is the whole cable, 22 is a cable conductor, and 24 is a cable sheath.

 26 and 28 are power supplies.

31,32,33, --- are insulation junction boxes. In addition, A,
When it is necessary to distinguish each phase of B and C, insulation junction box
31A, insulation junction box 32B, etc.

 30 is a cross bond line.

 41, 42, 43, --- are normal junction boxes, and 40 is a ground wire.

 The part of the ordinary junction box (41, etc.) is shown in Fig. 1b.

Ordinary junction box with edge cut 50 on each cable sheath 24
Convert 41 into an insulated junction box.

The cable sheaths 24 on both sides of the edge cut portion 50 are connected by bond wires 52.

The midpoint of each bond wire 52 is grounded together at the grounding point 40.

For each of the left and right bond wires 52 between the connection point to the ground wire 40 and the connection point to the cable sheath 24, on the same side (for example, the right side) as viewed from one power supply (for example, 26), the fault current is detected. Each of the current sensors 56 (for example, CT, etc.) is attached.

There are three current sensors 56 for each ordinary junction box 41. If it is necessary to distinguish them for each of the A, B and C phases, they will be indicated as current sensors 56A and 56B, for example.

[Operation] In order to make it easier to understand how the fault current flows, FIG. 2 is shown with the cable 20 omitted.

 Reference numeral 58 is an optical fiber for signal transmission, 62 is a transmission device (slave station), and 64 is a master station.

For example, in the line of the power supply on both sides as shown in Fig. 2,
Assume that a ground fault has occurred at an accident point 66 between the insulated junction boxes 35 to 36.

 The fault currents I and I ′ flow like arrows.

The fault current I flowing to the left side, after passing through the current sensor 56C of the ordinary junction box 42, is evenly shunted by the ground wire 40 and becomes approximately I / 3 (impedance on the ground side >> impedance on the cable shield side). Therefore, it hardly flows to the ground side).

Therefore, in the ordinary junction box 42, the current value detected by the current sensor 56 is as follows.

In the ordinary junction box 41 on the power supply 26 side, the current values of all the current sensors 56 are the same and are almost equal to I /
It becomes 3.

Further, the accident current I ′ flowing from the accident point 66 to the right side (power supply 28 side) also changes in the same manner.

In this case, however, in the ordinary junction box 43 that is encountered for the first time, the current is divided into about 1/3 by the ground wire 40 and then measured by each current sensor 56.

Therefore, each current sensor 56 in this ordinary junction box 43
The current value detected by is as follows.

Therefore, the current sensor 56 that detects the maximum fault current
It can be seen that an accident occurred in the cross-bond section of the cable 1 connected to the bond wire side where was attached.

[Effect of the invention] The accident section can be surely understood.

[Brief description of drawings]

 FIG. 1a is an explanatory view of an embodiment of the present invention, FIG. 1b is an enlarged explanatory view of a portion of an ordinary junction box, FIG. 2 is an explanatory view of a fault current flowing through a sheath, and FIG. 3 is an explanatory view of a conventional technique. 10: Cable line, 12, 66: Accident point 14: Surge current, 16: CT 20: Cable, 22: Cable conductor 24: Cable sheath 26: Power supply, 28: Load 30: Cross bond wire 31, 32, 33, − ---: Insulation junction box 41, 42, 43, -----: Normal junction box 40: Ground wire, 50: Edge cut portion 52: Bond wire, 56: Current sensor 58: Optical fiber 62: Transmission device (slave station) ) 64: Master station

Claims (1)

(57) [Claims] 1. In a cross-bond grounding type three-phase power cable line, the cable sheath 24 of each ordinary junction box is insulated to form an insulated junction box, and a bond wire 52 is provided between the edge-cut cable sheaths 24.
And ground the intermediate point of each bond wire 52 collectively with the ground wire 40, and of the bond wires 52 of each of the left and right phases between the connection point to the ground wire 40 and the cable sheath 24. A method for detecting a fault section of a power cable, characterized in that current sensors 56 are provided on the same side as viewed from one power source, and the magnitude of a fault current flowing through each current sensor is measured and compared to determine.