JPS6142211A - Insulating spacer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to cable electrical circuits, particularly high voltage, large size,
This relates to a cable tray for parallel installation.

[Background of the invention]

In conventional large-sized cable trays, three cables (for three-phase circuits) are laid in parallel. At this time, since the distances between the three phases are different in the cable tray, it is possible that current flows and heats the cable tray, so a PR plate was inserted as a spacer between the cable tray and the support material.

However, recently, as the performance of high-voltage circuit breakers has improved and the cut-off time has become faster, the spikes at the time of turning on and turning off have become larger.At the same time as the spikes, the potential of the cable tray also rises due to capacitive coupling, and the potential reaches the ground potential. Somehow, sparks started to occur with the support material.

[Purpose of the invention]

The present invention aims to prevent abnormal voltage generation in the cable tray by discharging the abnormal voltage generated in the cable tray.

[Summary of the invention]

Since it has been confirmed that abnormal voltage occurs in the cable tray and sparks occur, the present invention incorporates an abnormal voltage suppressor into the insulating spacer installed to insulate the tray as a means to eliminate this abnormal voltage. The purpose was to prevent this from happening.

[Embodiments of the invention]

FIG. 1 shows an example of application of the present invention.

A spacer according to the present invention is inserted between the cable tray and the support.

Figure 2 shows the overall diagram. Lay three thick cables in parallel and connect them for a long time. FIG. 3 is a diagram showing the parts in use of this electric circuit, and the part 1 corresponds to this.

This circuit is a 3-phase circuit, so three cables make up one circuit, but if there is insufficient capacity for one line/phase, one circuit can be configured with two lines/phase (6 cables in total). However, here we will proceed with the explanation based on Article 1/Phase.

1 in Figure 3 is this cable.As shown in Figure 4, because they are laid in parallel, the distances between the three cables and the cable tray are different, so that r, )r, >'s. There is.

Therefore, the strength H of the magnetic field created by the current i flowing in each cable is H = i / 2 tcr (AT/m), and the distance r between each cable seen from 98 points is r, ~ Since it is different from r3, even if the vectorial current sum 3I='+ +12 +'s =0, it occurs at point a.

Since the cable tray is made of iron, voltage is induced,
A current flows through the support material and a heating phenomenon occurs. This situation is shown in FIG.

(The cross material of the tray is aluminum.) Part (a) in the graph shows the temperature rise of the support material (standing) 4 when no insulating material is inserted.

Moreover, (b) shows the temperature rise at the same point when an insulating material corresponding to that shown in FIG. 1 is inserted.

As is clear from the graph, the temperature rise reaches saturation in about 4 hours, but there is a difference of about 5 deg between the two.

This temperature increase is expected to include a local increase in K, such as contact resistance, and to prevent this, it is common to insert the above-mentioned insulating spacer.

Therefore, in order to prevent this problem, a spacer made of an insulating material as shown in FIG. 5 has been inserted between the cable tray and the support to insulate the cable tray and the support.

One end of the tray was grounded to provide a single point of grounding, keeping the entire structure at ground potential.

In this operating state, where a steady current is flowing, no problem occurs, but recently the breaker has been changed from a conventional magnetic breaker to a vacuum breaker, as shown in Figure 3, to reduce space and improve reliability. The format has been changed.

Vacuum circuit breakers have good breaking performance, and because of this, surge voltage is generated when a load is turned on or cut off due to cutting current, and it is now possible to apply surge voltage to the power cable, which was not previously generated.

The equipment 16 connected to the circuit is designed to withstand this spike voltage and will not cause any problems, but this time, we have added a new cable between the cable tray attached via this insulating plate and its support. A phenomenon occurred in which sparks were generated when the circuit breaker was activated. (See FIG. 6) The cause of this is considered to be the electrostatic coupling shown in FIG. 7, and electromagnetic coupling due to current is added to this.

In other words, during normal operation or at rest, the cable tray and the cable conductor are coupled with each other with a certain capacitance.

In this state, if a spike in potential suddenly occurs within the cable, the potential of the cable tray will also increase while remaining in this coupled state.

At this time, the cable tray must be grounded at one end. If this grounding is sufficient, this ground voltage current will flow from the tray and an abnormal potential rise in the tray will not occur. However, in the case of high frequency such as spike voltage, the cable tray Because it is long, the equivalent ground resistance becomes extremely large, and sufficient current cannot flow through it.

Therefore, discharge occurs in the gap between the insulating plate portions located at a close distance.

Therefore, in order to prevent this, the present invention provides a spacer with a voltage suppressor shown in FIG. 8, which discharges when the voltage exceeds a certain level and prevents an abnormal voltage rise in the tray.

In FIG. 8, 5 is a spacer made of the same insulating material as the conventional one.

This spacer has fixing bolt holes 6.

9 is a voltage suppressor according to the present invention, which generally uses a Zener diode.

There are various types of diodes, each having discharge voltage characteristics depending on needs.

An example of the discharge characteristics is shown in FIG.

Reference numeral 8 denotes an electrical conductor, which is provided with a large area to improve electrical contact with the cable tray and tray support.

This mounting state is illustrated isometrically as shown in FIG. 10.

In other words, in a steady state, the magnetic field from the cable is at the applicable frequency and the ground resistance is low, so no voltage is generated in the tray, so this diode has no particular role, but if an abnormal voltage is applied to the cable tray at one end, When this happens, the voltage reaches a voltage determined by the characteristics of the diode, and at the same time,
Discharge begins, and current flows through the support of the cable tray, which is the grounding body, to prevent pressure build-up.

In this installation state, as shown in Figure 10, the support is grounded at regular support pitches of 3 m, and because conventionally one end is grounded, it can be grounded at a value that is sufficiently proportionate to the high frequency equivalent resistance equivalent to the tray length of over 100 m. It turns out.

Furthermore, on the ground end side of the cable tray, a conventional insulating spacer can also be used.

In particular, electronic components such as Zener diodes are small and do not have sufficient mechanical strength.

Therefore, as in the present invention, by incorporating the spacer in a spacer having mechanical strength and sandwiching it between the tray and the support, it is possible to prevent falling objects and damage due to carelessness.

Although there is a method to attach the diode directly to the cable tray, it is inevitably exposed to the outside, and as mentioned above, there is a large possibility of damage, so it cannot be said to be sufficient.

In the future, in nuclear power plants, there is a movement to replace conventional magnetic circuit breakers with vacuum circuit breakers in order to save space, create a vacuum, and because the circuit breakers are compact.

In this case, it is necessary not only to replace the circuit breaker, but also to prevent abnormal voltage from occurring in the cable tray.

Therefore, by using the spacer of the present invention, it is possible to deal with this problem simply by replacing the conventional spacer.

〔Effect of the invention〕

According to the present invention, in a device that is insulated from earth and needs to suppress the voltage during an abnormality to a predetermined value or less, the effect of suppressing abnormal voltage can be provided by simply replacing the insulating spacer.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing how the cable tray is installed;
The figure is a perspective view showing a wide area of Fig. 1, Fig. 3 is a single circuit showing a target circuit where large cables are laid in parallel, and Fig. 4 is a perspective view of Fig. 1.
An explanatory diagram showing the distance between the cable tray and three cables, Fig. 5 is a perspective view of a conventional spacer, Fig. 6 is a partial view showing the spark point in a cross section showing the installation situation of the conventional cable tray, FIG. 7 is an explanatory diagram showing a situation where the cable and the cable tray are electrostatically coupled, FIG. 8 is a plan view and a cross-sectional view of a spacer according to an embodiment of the present invention, and FIG. 9 is a Zener diode. Figure 10 shows the electrical connection between the tray and the top and bottom when the spacer according to the embodiment of the present invention is installed. Fig. 11 is an electrical connection diagram showing the entire length of the tray with a spacer installed, and Fig. 12 is a diagram showing the difference in m degree rise in support with and without an insulating spacer. It is.

Claims (1)

[Claims] 1. For spacers used to insulate electrical circuits such as cable trays, when abnormal voltage occurs in the electrical circuit, the specified spacers are used to prevent danger to the human body and to prevent noise from affecting instrumentation cables in nearby rooms. An insulating spacer having a built-in voltage suppressor that connects an electric path to ground under voltage, and having electrical conductors on both surfaces to ensure sufficient contact between the electric path and a grounding body.