JP3331867B2 - Capacitor abnormality detection device in capacitor equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting an abnormality of a capacitor in a power capacitor equipment for improving a power factor or the like.

[0002]

2. Description of the Related Art An abnormality detection method for a capacitor in a power capacitor equipment such as power factor improvement is roughly classified into a mechanical detection method and an electric detection method. The mechanical detection method includes a method of detecting the expansion of the case containing the capacitor and a method of detecting the internal pressure.The electrical detection method includes an open delta method, a voltage differential detection method, and a neutral detection method. There are a point voltage detection method, a double neutral point detection method, an overcurrent detection method, and the like.

FIG. 3 to FIG. 5 are diagrams showing a schematic configuration of an example of a capacitor abnormality detecting device using an electric detection system. FIG. 3 shows an overvoltage detection system using a three-phase system, and FIG. FIG. 5 shows an overvoltage detection system using an unbalanced type. The example shown in each figure is for a single capacitor. Hereinafter, the example shown in each figure will be briefly described.

In each of the figures, C, C1, and C2 denote an aggregate of capacitors (hereinafter, referred to as “capacitors”).
In the example shown in FIG. 3, the capacitor C is connected to the three-phase power system R
Phase, S phase, and T phase, each capacitor C
Are connected to each other (neutral point). Discharge coils DC are connected to both ends of each capacitor C, and secondary coils of each discharge coil DC are connected in series and connected to an overvoltage relay. In this case, if a short circuit occurs in any of the capacitors C, an overvoltage occurs and the voltage is detected by the overvoltage relay.

In the example shown in FIG. 4, the R-phase of the three-phase power system,
Capacitors C1 and C2 inserted in each of the S-phase and the T-phase represent capacitors C shown in FIG. 3 divided in series by an equal capacity, and a discharge coil DC is connected to both ends of each of the capacitors C1 and C2. The secondary coil of each discharge coil DC is connected in series with the polarity inverted for each phase and connected to the overvoltage relay. In this case, if a short circuit occurs in any of the capacitors C1 and C2, an overvoltage occurs and the voltage is detected by the overvoltage relay.

In the example shown in FIG. 5, the R-phase of a three-phase power system,
Capacitors C1 and C2 inserted in each of the S-phase and T-phase represent capacitors C shown in FIG. 3 which are divided in parallel by equal capacitance, and the connection points (neutral points) of capacitors C1 of each phase. A current transformer CT is inserted in a connection line connecting the capacitor C2 of each phase and a connection point (neutral point) of each other, and is connected to an overcurrent relay. In this case, if a short circuit occurs in any of the capacitors C1 and C2 of each phase, an unbalanced current flows between the neutral points, and the current is detected by the overcurrent relay.

[0007]

However, in the conventional capacitor abnormality detection system as described above, in the mechanical type, since the dielectric of the capacitor has an all-film structure, the internal pressure has increased. There is a problem that detection sensitivity cannot be sufficiently obtained. Further, in the electrical detection method, the sensitivity can be increased. However, in the case where a plurality of single capacitors are connected in parallel, the following problem occurs.

That is, in the open delta or voltage operation system, a voltage transformer for detecting the terminal voltage of the capacitor connected to the three-phase power system is required. It is necessary to extract a neutral point, so that there are many bushings and the like, which not only complicates the structure but also increases the cost.

In the double neutral point detection system, it is necessary to draw out a neutral terminal from each of the capacitors connected to the three-phase power system connected in parallel, and similarly, there are many bushings and the like, which complicates the structure. Not only that, general-purpose products cannot be operated, which is expensive.

The overcurrent detection method has a problem that the larger the number of parallel connected single capacitors, the smaller the overcurrent multiple at the time of failure and the higher the detection sensitivity.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and enables a capacitor to be electrically detected with a simple configuration, and is particularly effective when a plurality of capacitor units are used. An object of the present invention is to provide a capacitor abnormality detection device in a capacitor facility.

[0012]

An object of the present invention is to provide a single capacitor having a capacitor connected to each phase of a three-phase power system, and a capacitor inserted between the capacitor and each phase of the three-phase power system. A current transformer and an overcurrent relay for connecting the current transformer in parallel and inputting an output thereof; a plurality of the capacitor units are connected in parallel to the three-phase power system ; Any or each of the current transformers
However, the plurality of capacitor units connected in parallel are different.
This is achieved by providing a capacitor abnormality detection device in a capacitor facility, which is distributed and attached to a single capacitor unit .

According to the above-mentioned feature of the present invention, when all the capacitors are normal, the currents flowing through the respective current transformers have the same value and are equal to each other.
Since a current having a phase difference of 0 ° flows, the composite value on the secondary side of the current transformer is zero amperes. When a failure occurs in a capacitor of any one of the capacitor units, an unbalanced current flows between the three phases in the failed capacitor unit. The total value of each phase of the current flowing through the failed capacitor unit becomes zero ampere, but the total value between different capacitor units does not become zero ampere, and the current flows through the overcurrent relay. The relay can detect a fault by setting to detect this current.

In the case where two current transformers are connected in parallel, for example, the capacitors of one of the current transformers are connected to the R-phase and the S-phase out of the three phases, and the remaining one is a single capacitor. When three current transformers are distributed and attached to the T phase, the current transformers are divided into R, S, and T phases for each capacitor. In each case, the number of current transformers is three, and the number is small, and it can be installed between the capacitor and each phase of the three-phase power system. Therefore, the structure of a single capacitor should be simple. Can be.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an example of a capacitor abnormality detecting device in a capacitor facility according to the present invention will be described with reference to FIGS. FIG. 1 shows an abnormality of a capacitor in the capacitor equipment according to the present invention when two single capacitors (capacitor groups housed in one capacitor case) are connected in parallel to the R, S, and T phases of a three-phase power system. FIG. 2 is a circuit diagram of a detection device. FIG. 2 is a circuit diagram of a capacitor abnormality detection device in a capacitor facility according to the present invention when three capacitor units are connected in parallel to the R, S, and T phases of a three-phase power system. FIG.

(1) An abnormality detecting device for a capacitor when two capacitor units are connected in parallel to the R, S, and T phases of a three-phase power system, as shown in FIG. Current transformers CT are attached to the R and S phases of the SCA, and current transformers CT are attached to the T phase of the remaining single capacitor SCB, and the secondary coils (primary is The input line of the capacitor unit is connected in parallel and connected to the overcurrent relay 1. In this case, there are three current transformers CT for three phases, a single capacitor SCA and a single capacitor S
Each is distributed to the CB and attached to a different phase.

In the capacitor abnormality detecting device thus constructed, the current flowing through each current transformer CT has the same value and a current having a phase difference of 120 ° flows in a normal state. The combined value on the secondary side of CT is zero amperes. If a failure occurs in any of the capacitors C1 and C2 of the single capacitors SCA and SCB, for example, the internal of the capacitor connected to the R phase of the single capacitor SCA When a short-circuit or the like (a capacitor C1 shown by an arrow in FIG. 1) occurs in a part of the capacitor, an unbalanced current flows between the three phases in the capacitor unit SCA.

In this case, the failed capacitor unit SCA
The total value of each phase of the current flowing through the capacitor becomes zero ampere, but the total value between the single capacitor units SCB does not become zero ampere, and the current flows through the overcurrent relay 1 to detect a failure.

The currents flowing through the phases of the single capacitors SCA and SCB, and the currents during normal times and faults will be described below using equations. In the expression, I and V are vector quantities and are omitted in the expression. A and B respectively denote the single capacitors SCA and SCB, and R, S, T
Indicates the R, S, and T phases of the three-phase power system.

Each phase current of the capacitor unit SCA is given by: IRA = ｛1- (YRA + a ² YSA + aYTA) /
(YRA + YSA + YTA)｝ VRYRA ISA = ｛a ² − (YRA + a ² YSA + aYTA) /
(YRA + YSA + YTA)｝ VRYSA ITA = ｛a- (YRA + a ² YSA + aYTA) /
(YRA + YSA + YTA) @VRYTA

Each phase current of the capacitor unit SCB is expressed as follows: IRB = ｛1− (YRB + a ² YSB + aYTB) /
(YRB + YSB + YTB)｝ VRYRB ISB = ｛a ² − (YRB + a ² YSB + aYTB) /
(YRB + YSB + YTB)｝ VRYSB ITB = ｛a- (YRB + a ² YSB + aYTB) /
(YRB + YSB + YTB)｝ VRYTB

Where a = -1 / 2 + j (route 3) /
^{2, a 2 = -1 / 2} -j ( root 3) / 2, VR =
aVS = a ² VT (phase voltage)

The three-phase total value of only the capacitor unit SCA is: IAT = IRA + ISA + ITA = 0

On the other hand, the input current of the overcurrent relay 1 depends on the R and S phases of the single capacitor SCA and the single capacitor SCB.
, The current IT flowing in the overcurrent relay 1 is given by IT = IRA + ISA + ITB = −ITA +
ITB (However, IRA + ISA = -ITA)

In a normal state, absolute value IRA = absolute value IRB = absolute value ISA = absolute value ISB = absolute value ITA =
Since it is the absolute value ITB, IT = 0.

At the time of failure, as shown in FIG. 1, the case where the capacitor C1 of the single capacitor unit SCA has a short-circuit failure is as follows. YRA = 2, 0 (pu) YSA = YTA = 1, 0
(Pu) YRB = YSB = YTB = 1, 0 (pu), VR =
1, 0 (pu) ITB = a = − ／ + j (route 3) / 2 ITA = −0, 75 + j (route 3) / 2 That is, IT = −ITA + ITB = 0, 25 (p.
u)

The rated current of the capacitor unit SCA is 1, 0
(Pu), the setting value of the relay should be determined with a margin for 25% of the rated current of one capacitor unit SCB, and the sensitivity to the total current of the two units can be increased.

(2) An abnormality detecting device for a capacitor when three single capacitors are connected in parallel to the R, S, and T phases of a three-phase power system, as shown in FIG. In the single unit SCA, the second capacitor unit SC in the R phase
Current transformers CT are attached to the B phase in the S phase and the third capacitor unit SCC to the T phase, and the secondary coils of each current transformer CT are connected in parallel and connected to the overcurrent relay 1. Be composed. In this case, there are three current transformers CT for three phases, which are respectively distributed to the single capacitor unit SCA, the single capacitor unit SCB, and the single capacitor unit SCC and attached to different phases.

The abnormality detecting device for a capacitor having the above-mentioned configuration is similar to the two devices described above, and the capacitor C1 of any one of the capacitor units SCA, SCB and SCC is used.
When a failure occurs in C2, for example, the capacitor unit SC
If a short-circuit or the like (a capacitor C1 shown by an arrow in FIG. 2) occurs in a part of the capacitor connected to the R-phase of A, the total value of the phases of the current flowing through the failed capacitor unit SCA becomes zero. However, the total value between the other capacitor units does not become zero amperes, but a current flows through the overcurrent relay 1 to detect a failure.

Hereinafter, similarly, the currents flowing through the respective phases of the single capacitors SCA, SCB, and SCC, and the currents in the normal state and the fault state will be described by using equations.
In the expression, I and V are vector quantities and are omitted in the expression. A, B and C are single capacitors SC
A, SCB, and SCC are shown, and R, S, and T show each of the R, S, and T phases of the three-phase power system.

Each phase current of the capacitor unit SCA is given by: IRA = ｛1− (YRA + a ² YSA + aYTA) /
(YRA + YSA + YTA)｝ VRYRA ISA = ｛a ² − (YRA + a ² YSA + aYTA) /
(YRA + YSA + YTA)｝ VRYSA ITA = ｛a- (YRA + a ² YSA + aYTA) /
(YRA + YSA + YTA) @VRYTA

Each phase current of the capacitor unit SCB is given by: IRB = ｛1- (YRB + a ² YSB + aYTB) /
(YRB + YSB + YTB)｝ VRYRB ISB = ｛a ² − (YRB + a ² YSB + aYTB) /
(YRB + YSB + YTB)｝ VRYSB ITB = ｛a- (YRB + a ² YSB + aYTB) /
(YRB + YSB + YTB)｝ VRYTB

Each phase current of the capacitor unit SCC is given by: IRC = ｛1− (YRC + a ² YSC + aYTC) /
(YRC + YSC + YTC)｝ VRYRC ISC = ｛a ² − (YRC + a ² YSC + aYTC) /
(YRC + YSC + YTC)｝ VRYSC ITC = ｛a- (YRC + a ² YSC + aYTC) /
(YRC + YSC + YTC)｝ VRYTC

The input current of the overcurrent relay 1 is the sum of the R phase of the single capacitor SCA, the S phase of the single capacitor SCB, and the T phase of the single capacitor SCC. Is IT = IRA + ISB + I
TC

In a normal state, the current IT becomes zero by the following equation. Absolute value IRA = absolute value IRB = absolute value IRC = absolute value I
SA = absolute value ISB = absolute value ISC = absolute value ITA = absolute value ITB = absolute value ITC

At the time of failure, as shown in FIG. 2, the case where the capacitor C1 of the capacitor unit SCA has a short-circuit failure is as follows.

YRA = 2, 0 (pu) YRB = YS
B = YSC = YSA = YTA = YRC = YSC = YTC
= 1, 0 (pu) VR = 1, 0 (pu) IRA
= 1,5 (pu) ISB = a = −1 / 2 + j (route 3) / 2 ITC = a ² = −1 / 2−j (route 3) / 2

The current IT flowing in the overcurrent relay 1 is as follows: IT = IRA + ISB = ITC = 0, 5 (pu)

As described above, the rated current of the single capacitor unit SCA is 1, 0 (pu) as in the case of two units in parallel, so that the set value of the overcurrent relay 1 is one of three capacitors. It is sufficient to determine the margin with respect to 50% of the rated current of the unit, and it is possible to obtain higher sensitivity to the total current of the three units.

It should be noted that two capacitor units are used in the three-phase power system.
In the above description, two and three capacitors are connected in parallel, but two and three capacitors are connected in parallel to the three-phase power system.
The present invention is not limited to the number of units, and failure detection is possible if this method is applied as four or more units connected in parallel.

[0041]

As described above, according to the present invention,
By adopting a structure in which current transformers are attached to different phases of the input section of a single capacitor unit connected in parallel, bushing etc. of the single capacitor unit are reduced and the structure is simplified.
An abnormality can be detected with high sensitivity using a minimum number of current transformers, and a capacitor abnormality detection device in a capacitor facility with reduced cost can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an apparatus for detecting an abnormality of a capacitor in a capacitor facility according to the present invention, in which two single capacitors are connected to a three-phase power system.
It is a circuit explanatory diagram at the time of connecting in parallel.

FIG. 2 shows a three-phase power system including three capacitor units in the capacitor abnormality detecting device in the capacitor equipment according to the present invention.
It is a circuit explanatory diagram at the time of connecting in parallel.

FIG. 3 is a configuration diagram of an example of a capacitor abnormality detection device in a capacitor facility.

FIG. 4 is a configuration diagram of an example of a capacitor abnormality detection device in a capacitor facility.

FIG. 5 is a configuration diagram of an example of a capacitor abnormality detection device in a capacitor facility.

[Explanation of symbols]

 1 Overcurrent relay SCA, SCB, SCC Single capacitor CT Current transformer R, S, T Each phase of three-phase power system

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02H 7/16

Claims (1)

(57) [Claims] 1. A single capacitor having a capacitor connected to each phase of a three-phase power system, a current transformer inserted between the capacitor and each phase of the three-phase power system, and the current transformer in parallel. An overcurrent relay for connecting and inputting the output thereof, wherein a plurality of the capacitor units are connected in parallel to the three-phase power system, and any one of the three-phase current transformers.
Or each of the plurality of capacitors connected in parallel
Distributed and mounted on different capacitors
Be Te abnormality detecting device of a capacitor in the capacitor equipment according to claim.