JPH04138021A - Capacitor protector - Google Patents

Abstract

PURPOSE:To detect fault even in the case where a group of capacitors consist of odd sets of unit capacitors by connecting the neutral points of three or more odd sets of star connection capacitors with one another by conductors, and detecting the current flowing in this conductor so as to issue a signal. CONSTITUTION:When a group of capacitors are sound, three star connection capacitors 2 are all balanced, and a current does not flow to any part of the conductor 7, so an overcurrent relay 9 does not operate. But, if any one unit capacitor 3 goes wrong, unbalance occurs between the star connection capacitor 2, which contains the faulty unit capacitor 3, and a sound star connection capacitor 2, and a current flows to the conductor 7, which connects the neutral points 6. This current is largest at the part leading to the neutral point 6 of the star connection capacitor 2, which contains the faulty unit capacitor 3, and the value is defined as IA. A current transformer 8 detects this current IA, and the overcurrent relay 9 issue a signal, and a breaker 4 opens.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a capacitor protection device that detects a failure when it occurs in order to protect a group of capacitors.

[Conventional technology]

Figure 5 is a wiring diagram showing a conventional capacitor protection device. In the diagram, (1) is a capacitor group, (2) is a star-connected capacitor, and 0) is composed of one or more capacitor elements. It is a unit capacitor, and six unit capacitors (3) with the same function are used, and the unit capacitor (
3) Three sets of star-wired capacitors (2) are connected in a star-shaped configuration, and two sets of star-wired capacitors (2) are connected.
constitute a capacitor group (1). (A) Breaker, (9 is 3 sets of circuit connection terminals, 2 sets of star-shaped wired capacitors (2) are connected in parallel with each other at their line ends,
A), 3 sets of circuit connection terminals (9) are connected to the 3-phase AC circuit. (6) are 2 sets of star-shaped wired capacitors (2)
The neutral point of (7) is the conductor connecting between both neutral points (6),
8 is a current transformer that detects the current flowing through the conductor m, and (9) is an overcurrent relay that is operated by the secondary current of the current transformer and issues a signal, so that the breaker 4 is opened by the signal. It has become.

Next, the operation will be explained. When the capacitor group (1) is healthy, balance is maintained between both star-connected capacitors (2) and no current flows through the conductor opening connecting their neutral points (6), so the overcurrent relay is activated. (9) does not work.

However, if one considers the case where one of the unit capacitors B) has dielectric breakdown due to deterioration over time, an unbalance will occur between both star-connected capacitors (21), and the conductor m connecting the two neutral points (6) will A current ΔI flows through the unit capacitor (31
If the glue actance is X when healthy and X^ when faulty, and the rated current of capacitor group (1) when healthy is IR, then IΔ1
1 becomes. The current transformer (9) detects this current Δ, and the overcurrent relay (9) issues a signal, which opens the shield breaker (A) and disconnects the capacitor group (1) from the three-phase AC circuit.

By doing this, it is possible to prevent burnout caused by short-circuit current from spreading to other healthy parts and spreading the failure.
In oil-filled capacitors, which are often used in power capacitors, they are an extremely advantageous protection device for safe operation.

Note that although the case where one unit capacitor L31 fails has been explained above, capacitors are operated for a long period of time, and the possibility of failure of two or more unit capacitors (3) at the same time is extremely small. It is.

Further, when the capacitor group (1) consists of four or more sets of star-connected capacitors (2), two sets each are connected as shown in FIG. 5 for protection.

[Problem to be solved by the invention]

Since the conventional capacitor protection device is constructed as described above, it is necessary to divide the capacitor group into star-shaped connections of coefficient sets.

However, it is not always possible to divide a capacitor group into star-wired capacitors with coefficient sets; for example, when a capacitor group is constructed by reusing existing capacitors, or when adding to an existing capacitor group to expand the capacitor group. In some cases, an odd number of star-connected capacitors may be used, and in such cases there are problems such as the inability to provide protection as shown in Figure 5.

The present invention was made to solve the above-mentioned problems, and it is an object of the present invention to provide a capacitor protection device that can detect failures even when a capacitor group consists of an odd number of unit capacitors.

[Means to solve the problem]

The capacitor protection device according to the present invention connects the neutral points of three or more odd-numbered sets of star-shaped wired capacitors with a conductor,
It detects the current flowing through this conductor and generates a signal.

[Effect]

In the capacitor protection device according to the present invention, when a failure occurs in a unit capacitor, a current flows through the conductor connected between the neutral points, so it is possible to protect a group of capacitors by detecting this and issuing a signal.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a wiring diagram showing a capacitor protection device according to an embodiment of the present invention. In the figure, B) to (6) are the same as in the case of FIG. 5, and therefore their explanation will be omitted. (21 is a unit capacitor (3) 3 star-shaped wired capacitors connected in a star shape, (1) is a capacitor group consisting of 3 sets of star-shaped wired capacitors U, (7) is a star-shaped wired capacitor group of 3 sets. A conductor that connects the neutral points (6) of wired capacitors (2).It branches into three from a common point 0ω and connects to each neutral point (6).8 is the neutral point of each. (6) and common points (1
01, three current transformers detecting the current flowing in the conductor (7), (9) are three overload tffi relays which are actuated by the secondary current of the respective current transformer (to) and emit a signal; If any one of the overcurrent relays (9) issues a signal, the circuit breaker (2) opens.

Next, the operation will be explained. When the capacitor group is healthy, all three star-connected capacitors U are balanced and no current flows through any part of the conductor (2), so the overcurrent relay (9) does not operate.

However, if any one unit capacitor (3) fails, an imbalance will occur between the star-shaped wired capacitor (2) containing the failed unit capacitor (3) and the healthy star-shaped wired capacitor (to). A current flows through the conductor opening connecting the neutral point b). This current is greatest at the portion connected to the neutral point (6) of the star-shaped wired capacitor (2) including the failed unit capacitor (3), and its value is set as ΔIA.

If X, Open circuit.

FIG. 2 is a wiring diagram showing a capacitor protection device according to another embodiment of the present invention. Connect the neutral point (6) of each with the conductor port,
A current transformer and an overcurrent relay (9) are provided. In Fig. 3, the left and right star-connected capacitors are further connected by a conductor m, and a current transformer 8 and an overcurrent relay (9) are also provided for this. In the case of these figures 2 and 3, as in the case of figure 1, when a failure occurs in one unit capacitor (3), this can be detected and the circuit breaker (2) can be opened. .

In the above embodiment, the case where there are three sets of star-shaped wired capacitors (2) is shown, but it can also be implemented when there are five or more sets.
In Figure 0, which shows an example of this, two sets of star-shaped wired capacitors (2) on the left constitute the first detection section (11), and three sets of star-shaped wired capacitors (2) on the right constitute the first detection section (11). This constitutes the second detection section (12). The first detection section (11) is wired in the same manner as in the conventional example of FIG. 5, and the second detection section (12) is wired in the same manner as in FIG. 3. In this way, even in the case of an odd number of five or more sets of star-connected capacitors (2), connect two sets at a time and connect them as usual, and use the remaining three sets to connect them as shown in Figures 1 to 3. By doing so, a failure of the unit capacitor (3) can be detected.

Also, instead of Figure 4, there are 5 sets of star-connected capacitors! 2
By sequentially connecting all the neutral points (6) of 1, 5
Failure detection may be performed by grouping the sets of star-connected capacitors (2) together.

In the capacitor group (1), the unit capacitors (3) may be single-phase capacitors or single-phase capacitor groups housed in separate cases (not shown), or may be made of paper, film, aluminum ( A capacitor element or a group of capacitor elements (both not shown) made of foil or the like, and several star-connected capacitors may be housed in a common case. Further, in the above embodiment, the current is detected by the current transformer 6 to open the circuit breaker (a), but other current detectors, switches, etc. may be used. A meter etc. may also be used.

[Effects of the Invention] As described above, according to the present invention, the neutral points of odd-numbered sets of star-connected capacitors are connected by a conductor, and the current flowing through this conductor is detected and a signal is generated. Therefore, if a failure occurs in a unit capacitor, a current flows through the conductor and this can be detected.Therefore, there is an effect that a failure in a unit capacitor can be detected even when there is an odd number of capacitor groups.

[Brief explanation of drawings]

FIG. 1 is a wiring diagram showing a capacitor protection device according to one embodiment of the present invention, FIGS. 2 to 4 are wiring diagrams showing capacitor protection devices according to other different embodiments, and FIG.
The figure is a wiring diagram showing a conventional capacitor protection device. In the figure, (2) is a star-connected capacitor, (6) is a neutral point, (7) is a conductor, (to) is a current transformer, and (9) is an overcurrent relay. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent: Masuo Oiwa, Patent Attorney Figure 1, Figure 2: Star War Running Horoscope, Figure 3

Claims (1)

[Claims] A conductor connects the neutral points of three or more odd-numbered sets of star-connected capacitors connected to a three-phase AC circuit, and a signal is generated by detecting the current flowing through this conductor. Capacitor protection device.