JPH04183219A - Power cable line and partial discharge detecting method therefor - Google Patents

Abstract

PURPOSE:To facilitate detection of partially discharging phase by providing means for switching a connection, which cross bonds the cable sheath at a joint of a power cable from one phase to another phase, from one end to the other end of the cable sheath in same phase. CONSTITUTION:Cable sheaths 1-3 disposed at the joints of a power cable are connected at a plurality of joint boxes(JB) T1-T4. JBJ1, J4 are grounded at a normal. joint NJ connected with sheaths on the opposite sides whereas JBJ2, J3 are insulation jointed IJ where the sheaths on the opposite sides are insulated each other. JBJ2, J3 are provided with link boxes 40 containing switches 41-43. Connections 11, 21, 31 with insulated joint boxes 1A-3A and connections 12, 22, 32 provided with CTs 51-53 and connected with insulated joint boxes 1B-3B are connected with the switches thus switching between the NJ and the IJ. According to the constitution, partially discharged phase can be detected easily and repaired quickly.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a power cable line that is optimal for detecting partial discharges in each phase in a power cable line that employs the cross-bond method, and a partial discharge detection method thereof. Regarding.

[Prior Art] Generally, as a measure to reduce the sheath potential, a cross-bond grounding system with a sheath connection as shown in FIG. 4 is adopted for long high-voltage cable lines.

In this cross-bond method, the joint box is grounded every two sections, and the joint box other than the grounding point has a fourth
As shown in figure (a), the sheaths 1.2.3 of each phase are insulated junction boxes IA, 1B (2A, 2B).

3A, 3B) and are cross-bonded. In this method, if the cable section lengths are made the same, the vector sum of the sheath potentials in the three sections will be approximately zero, and the sheath circuit loss can be reduced.
In addition, since the sheath is connected continuously over the entire length of the cable, most of the earth return current in the event of a system ground fault flows through the sheath, which has the advantage of reducing induced current to the outside. .

On the other hand, Fig. 4(a) shows a method for detecting partial discharge in cables.
, (b), there is a method of attaching a clamp-type current detector (CT) to the cross bond line and detecting the pulse current caused by partial discharge without cutting the line. In the same figure (b), IC, 2C, and 3C are the conductors of the power cable, and ID, 2D, and 3D are the sheaths 1.2.3.
Each edge section, X indicates a partial discharge.

[Problem to be solved by the invention] By the way, as described above, the clamp type current detector (CT)
When detecting a partial discharge in a cross bond line using Since the partial discharge also propagates to the phase and is detected, it is not possible to identify the phase in which the partial discharge is occurring. Therefore, the defective part cannot be repaired quickly.

[Object of the Invention] The present invention has been made in view of these conventional drawbacks.
It is an object of the present invention to provide a power cable line and a method for detecting partial discharge thereof, which can identify the phase in which a partial discharge occurs in a power cable line employing a cross-bond method, and enable quick repair thereof.

[Means for Solving the Problems] The power cable of the present invention that achieves the above object has cross bond connection between one side of one cable sheath and the other side of the cable sheath of the other phase at the connection part of the power cable. In this power cable line, a switching means is provided between the connections to connect one side of one cable sheath to the other side of the cable sheath of the same phase.

Further, the method for detecting partial discharge in a power cable of the present invention provides a method for detecting partial discharge in a power cable line in which one side of one cable sheath is cross-bonded to the other side of the cable sheath of the other phase at the connection part of the power cable. When detecting partial discharge, a detection means for electrically detecting partial discharge is attached to the connection, and the connection between the sheaths is switched so that one side of each cable sheath is connected to the other side of the cable sheath of the same phase. , which detects partial discharge.

[Operation] The connection of the sheaths at the connection portion of each power cable is switched from an insulated connection in which the sheaths on both sides are insulated to a normal connection in which the sheaths on both sides are connected by the switching means. Thereafter, the partial discharge is electrically detected by a detection means provided on the cross bond line.

In this case, the connections of the power cables for each phase are normal connections, so there is no risk of partial discharge current flowing to or from other cables via the cross bond wire, and the defective cable can be identified. can.

[Example] Hereinafter, a power cable line and a partial discharge detection method thereof according to the present invention will be described based on an example shown in the drawings.

FIG. 1 shows a power cable line according to the invention, connected by cable sheaths 1.2.3 or several joint boxes. Of these, joint box J1
, J4 is a normal connection (NJ
) and the joint box J2 other than the ground point,
J8 etc. have an insulated connection (IJ) in which the sheaths on both sides are insulated.

The joint box other than the grounding point is further shown in Figure 2 (a).
As shown in (b), insulated junction boxes IA, 2A, 3A on one side of cable sheath 1.2.3 and insulated junction box IB on the other end.
, 2B, 3B are connected with wires 11.12.21.22.
Link box 4 with switching means via 31.33
0 is set. The link box 40 has a switch 41 as a switching means that selectively connects the connection 11 to the connection 12 or 22, and connects the connection 21 to the connection 22 or 3.
The switch 42 selectively connects the wire 31 to the wire 32 or the wire 12, and the switch 43 selectively connects the wire 31 to the wire 32 or the wire 12. Normally, as shown in FIG. 2(a), the insulated junction box IA on one side of the cable sheath 1 is connected to the insulated junction box 2B on the other side of the cable sheath 2, and the insulated junction box 2A on one side of the cable sheath 2 is connected to the insulated junction box IA on one side of the cable sheath 2. The insulated junction box 3B on the other side of the sheath 3 and the insulated junction box 3A on one side of the cable sheath 3 are connected to the insulated junction box IB on the other side of the cable sheath 1 in a cross-bond connection. When the box 40 is switched, the NJ connection is established in which one side and the other side of the cable sheath of the same phase are connected, respectively, as shown in FIG. 4(b).

Figure 3 (a) shows a simplified diagram of this NJ connection and the equivalent circuit.
) and (b). In addition, in the same figure (b), IC12C
13C is the conductor of the power cable, LD, 2D'.

3D indicates each edge section of the sheath 1.2.3, and X indicates a partial discharge location.

Clamp type current detectors (CT) 51, 52, 53 for detecting partial discharge current are attached to the connections 12, 22, 33, respectively. These CTs 51, 52, and 53 are each connected to a display device such as a synchroscope, a frequency analyzer, a level meter, etc. (not shown). These can further be connected to a microcomputer for data processing.

In such a configuration, normally the switches in the link boxes 40 of joint boxes J2 and J8 other than the ground point are connected as loss bond connections as shown in Fig. 2(a) to prevent sheath circuit loss and conduction to the outside. Efforts are being made to reduce current. At the time of partial discharge detection, the switch of the link box 40 is changed as shown in FIG. 2(b), and the sheath connection in each joint box is set to normal connection. Here, on any span of any cable, as shown in Figure 3 (
If there is a partial discharge point X as shown in b), a current due to partial discharge flows through the sheath connection at the connection point of that span of the cable, and this current flows as a partial discharge pulse at C.
Captured by T. The partial discharge pulse detected by the CT is displayed on a display device such as a synchroscope, the frequency distribution is measured by a frequency analyzer, and the pulse size is measured by a level meter.

Generally, partial discharge pulses vary depending on the distance from the detection unit.
Since the magnitude becomes smaller and the frequency also attenuates on the high frequency side, it is possible to further specify the partial discharge position within the span based on these intensity and frequency distributions.

[Effects of the Invention] As is clear from the above description, according to the power cable line and partial discharge detection method thereof of the present invention, the sheath connection at the connection part in the power cable line in which the cross-bond method is adopted can be replaced by IJ connection. Since partial discharge is detected after switching from NJ connection to NJ connection, partial discharge current will not propagate to other phases even if the power cable line employs the cross-bond system. Therefore, it is possible to identify the phase in which partial discharge occurs, and to quickly repair it.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of the power cable line of the present invention, Figure 2 (
a) and (b) are diagrams showing the state of the power cable line connections in Figure 1, respectively, and Figures 3 (a) and (b) are diagrams showing simplified NJ connections and their equivalent circuits, respectively. 4(a) and 4(b) are diagrams respectively showing a cross-bonded connection and its circuits when a partial discharge occurs. 1.2.3... Cable sheath 11.12.2
1.22.31.33... Connection IA, 2A, 3A.
... Insulated junction box IB, 2B, 3B on the - side... Insulated junction box 40 on the other side... Link box (switching means) 51, 52, 53... Clamp type current detector ( C
T) J1~J4...Joint Box Agent Patent Attorney Moritani - Yuku C axis

Claims (1)

[Claims] 1. In a power cable line in which one side of one cable sheath is cross-bonded to the other side of the cable sheath of the other phase at the connection part of the power cable, one cable sheath is connected between the connections. A power cable line characterized in that it is provided with a switching means for switching one side of the cable sheath of the same phase to the other side of the cable sheath of the same phase. 2. When detecting partial discharge in a power cable line in which one side of the cable sheath of 1 is cross-bonded to the other side of the cable sheath of the other phase at the connection part of the power cable, the partial discharge is electrically connected to the connection. The partial discharge is detected after the connection between the sheaths is switched such that one side of one cable sheath is connected to the other side of the cable sheath of the same phase. A method for detecting partial discharge in power cables.