JPH0743393B2 - Voltage detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a voltage detection device for contactlessly detecting a three-phase voltage in a charging part conductor in a substation equipment having a charging part conductor.

[Prior Art] FIG. 5 is a configuration diagram showing a conventional voltage detection device applied to a gas-insulated electric device. In the figure, 1 is a grounded outer skin of the gas-insulated electric device, 2 is the same outer skin 1. It is a live part conductor that is placed in the and to which a voltage is applied.
It is provided individually. Reference numeral 3 denotes a voltage detecting portion (antenna) arranged at a predetermined distance from each charging portion conductor 2 in the outer cover 1, and 4 denotes a voltage for converting an induced current drawn from the detecting portion 3 into a voltage. The input resistance (R ₀ ) of the detection device, 5 is an amplifier that obtains an output (voltage across both ends) from the input resistance 4, 6 is an insulating support that electrically insulates the detector 3 from the outer skin 1, and 10 is an amplifier from the amplifier 5. It is a display unit for displaying output, charging / non-charging of the charging unit conductor 2 for each phase (presence or absence of three-phase voltage), and the like.

Further, 21 is a resistor (R ₁ ) that connects the detection unit 3 and one end of the input resistor 4 in series for each phase, and the value R ₁ of this resistor 21 is
The value is sufficiently large with respect to the value R ₀ of the input resistance 4 and has a relationship of R ₁ + R ₀ ≈R ₁ . 22 to 24 are variable resistors (R _A , R _B , R _C ) connected in parallel to each resistor 21 and connecting the detection unit 3 and the other end of the input resistor 4 in series, and are provided for each phase. ing.

Next, the operation will be described. When a voltage is applied to each charging portion conductor 2, an electric field is generated in the grounded outer skin 1.
If there is an electrode electrically insulated from the grounded outer skin 1 in this electric field, an electrostatic induction current flows between the electrode and the ground (ground portion). This electrode is the detection section (antenna) 3 in the device shown in FIG. 5, and between each charging section conductor 2 and each detection section 3, it is inversely proportional to the distance and proportional to the area of each detection section 3. Capacitances C _A , C _B and C _C are obtained.

Capacitance obtained between each charging part conductor 2 and each detecting part 3
Since the impedances of C _A , C _B , and C _C are sufficiently large even if the resistance (R ₁ ) 21 is added in series with the input resistance 4 of the voltage detection device, the impedance of each charging unit conductor 2 and detection unit 3 is Electrostatic induction current
i _A , i _B , and i _C are determined by the capacitances C _A , C _B , and C _C , respectively.

Also, because of the relationship of R ₁ + R ₀ ≈R ₁ , the induced current of each phase
i _A , i _B and i _C are shunted by the relationship between the resistance value R ₁ and the variable resistance values R _A , R _B and R _C. Now, if the variable resistance value R _A of the A phase is made sufficiently larger than the resistance value R ₁ and the variable resistance values R _B , R _C of the _B and _C phases are adjusted to be equal to the resistance value R ₁ , the resistance of each phase is 21 The current flowing through the input resistor 4 through the current is i _A1 ≈i _A (i _A2 ≈0), i _B1 = i _B / 2 (= i _B2 ), i
_C1 = i _C / 2 (= i _C2 ) Due to this induced current, the input voltage of each phase (the voltage applied across the input resistor 4) is
_{Va = i A1 × R 0,} Vb = i B × R 0/2, Vc = i C × R 0/2, next, the input voltage Va of the phase A, the input voltage Vb, Vc of the other two phases 2 Doubled. However, since the induced currents i _A , i _B , and i _C have the same capacitance between the charging section conductor 2 and the detecting section 3 (C _A = C _B = C _C ), i _A = i _B = i _C. However, since the phase of each input voltage Va, Vb, Vc of the A, B, C phases is delayed by 120 degrees as shown in FIG. 6, the vector diagram of the input voltage Va, Vb, Vc is
As shown in FIG.

In addition, the variable resistance value R _A of the A phase is made equal to the resistance value R _1, and B, C
If the variable resistance values R _B , R _C of the phase are adjusted to be sufficiently larger than the resistance value R ₁ , only the input voltage Va of the A phase is input voltage Vb, Vc of the other phase.
It is 1/2 times that of the vector, and its vector diagram is as shown in FIG.

As shown in Fig. 6, when the vector sum of the three-phase balanced voltage is taken directly, the voltage becomes zero, but as can be seen from the vector diagrams in Figs. 7 and 8, the voltage of each phase can be changed as described above. If the resistors 22 to 24 are used for adjustment, then | Va + Vb + Vc | = | Vb | or | Vc |, and | Va + Vb + Vc | = | Va | Will be equivalent. If the level detection value of the amplifier 5 is set to a value slightly smaller than the input voltage value for detecting one phase, the three-phase balanced voltage is detected in the same manner as the one-phase detection during the three-phase charging. Further, voltage detection is possible even if any one of the three phases, one phase or two phases, is not charged, that is, if one of the three phases is charged, the voltage detection can be performed. it can.

[Problems to be Solved by the Invention] Since the conventional voltage detection device is configured as described above, the gain adjustment, that is, the variable resistance values R _A , R _B , and R _C for each phase is performed.
Adjustment is required and the voltage is detected while applying a high voltage to each charging portion conductor 2, so that the above adjustment requires a great deal of labor and time. Further, in order to have a relationship of R ₁ + R ₀ ≈R ₁ , the resistance value R ₁ must be sufficiently large, and the resistance value R ₁ has a large resistance value equivalent to the resistance value R ₁ .
In addition, the variable resistors 22 to 24 having variable resistance values have a problem that the cost required for the device is extremely high and the like.

The present invention has been made to solve the above problems, and provides an inexpensive voltage detection device capable of reliably detecting a three-phase voltage while eliminating the need for gain adjustment for each phase using a variable resistor. The purpose is to get.

[Means for Solving the Problems] The voltage detection device according to the present invention rotates the phase of one phase or two phases of the voltage obtained by converting the electrostatic induction current from each detection unit by 180 degrees. A phase inversion circuit and an adder circuit for vector-synthesizing the output from the same phase inversion circuit and another two-phase or one-phase voltage that has not performed phase rotation and output the vector are provided.

[Operation] In the voltage detecting device according to the present invention, the phase inversion circuit inverts the phase of the electrostatic induction voltage for one phase or two phases out of the three phases, and then the addition circuit inverts the electrostatic induction voltage. The voltage and the other two-phase or one-phase electrostatic induction voltage that has not been inverted are vector-combined, and by detecting the vector-combined three-phase voltage in this way, gain adjustment for each phase as in the conventional case is performed. Is unnecessary.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings. First
FIG. 1 is a block diagram showing a voltage detecting device according to an embodiment of the present invention. In the figure, reference numerals 1 to 6 and 10 have the same structure as that of a conventional device, and therefore the description thereof will be omitted. In FIG. 1, 7a is an amplifier for converting the electrostatic induction current i _A from the A phase into an electrostatic induction voltage Va and amplifying it, and 7b is an electrostatic induction current i _B + i _C = i _BC from the B and C phases _. An amplifier for converting the electrostatic charge into a static induction voltage Vbc and amplifying it, 8 is an induction voltage Va amplified by the amplifier 7a
Is a phase inverting circuit that rotates the phase of 180 degrees and outputs it, and 9 is an adding circuit that performs vector synthesis of the output from the phase inverting circuit 8 and the output from the amplifier 7b and applies the result to one end of the input resistor 4. .

Next, the operation of the apparatus of this embodiment will be described.

The A-phase electrostatic induction current i _A is converted into the induction voltage Va by the amplifier 7a, and then the induction voltage Va ₁ whose phase is rotated 180 degrees by the phase inverting circuit 8 is obtained. On the other hand, the electrostatic induction currents i _B and i _C of the B and C phases join to become i _BC , and are converted into the induction voltage Vbc by the amplifier 7b. Then, the induced voltages Va ₁ and Vbc are vector-synthesized (see FIG. 2) in the adder circuit 9,
The synthesized Va ₁ + Vbc is further amplified by the amplifier 5, and after being detected as a level, a display such as charging / non-charging (presence / absence of three-phase balanced voltage) is displayed on the display unit 10.

Assuming that the input voltages Va, Vb, Vc of each phase are all equal in size and the phases are delayed by 120 degrees (see FIG. 6), the vector sum Va + Vb + Vc becomes zero. However, according to the apparatus of this embodiment, by rotating the phase of only one phase (A phase) by 180 degrees, as shown in FIG. 2, | Va + Vb + Vc | = 2 × | Va |, (2 × | Vb | |, 2 × | Vc |). Therefore, set the level setting value of the amplifier 5 to the voltage V of one phase.
If the level is detected by the amplifier 5 as a value slightly smaller than the magnitude of a, Vb, Vc, any one of the three phases,
The voltage can be detected even if the one-phase or two-phase charging portion conductor 2 is not charged, that is, if one of the three phases is charged, the voltage can be detected.

As described above, according to this embodiment, the phase inversion circuit 8 inverts the phase of the electrostatic induction voltage Va for the A phase, and the adder circuit 9 performs vector composition with the electrostatic induction voltages Vbc of the B and C phases. Therefore, the conventional variable resistor (reference numeral 22 to FIG.
It is possible to eliminate the need for gain adjustment for each phase using
The three-phase voltage can be detected reliably and easily, and the cost required for the device can be significantly reduced.

In the above embodiment, only the phase of the voltage Va of the A phase of the three phase voltage is inverted, but the phase may be inverted for two phases of the three phase voltage. For example, as shown in FIG. 3, three-phase electrostatic induction currents i _A , i _B and i _C are converted into induction voltages Va, Vb and Vc by an amplifier 7, respectively, and then two phase inversion circuits 8 and 8 are provided. To set the phase of voltage Va and Vb to 18
Rotate 0 degrees to obtain induced voltages Va ₁ and Vb ₁ . Then, the induced voltages Va ₁ , Vb ₁ , Vc are vector-combined in the adder circuit 9 (fourth
See the figure). As a result, as is apparent from FIG. 4, even when the phases of two phases of the three-phase voltage are inverted, the same effect as that of the above embodiment can be obtained.

[Effects of the Invention] As described above, according to the present invention, the phase inversion circuit inverts the phase of one phase or two phases of the three-phase voltage, and the addition circuit inverts the voltage of another two phases or one phase. Since it is configured to perform vector synthesis, it is not necessary to adjust the gain for each phase using a variable resistor as in the past, and the time and labor for this adjustment can be reduced, and the three-phase voltage can be reliably and easily Can be detected. In addition, since the device is configured by a commercially available phase inversion circuit and addition circuit without using a special variable resistor, maintenance of the device is facilitated and an inexpensive device can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a voltage detector according to an embodiment of the present invention, FIG. 2 is a vector diagram for explaining the operation of the above-mentioned embodiment, and FIG. 3 is a voltage according to another embodiment of the present invention. FIG. 4 is a configuration diagram showing a detection device, FIG. 4 is a vector diagram for explaining the action of the other embodiment, FIG. 5 is a configuration diagram showing a conventional voltage detection device, and FIGS. 6 to 8 are actions of the conventional device. 3 is a vector diagram for explaining FIG. In the figure, 2 ... charging section conductor, 3 ... detection section, 8 ...
Phase inversion circuit, 9 ... Addition circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A detection unit is arranged at a predetermined distance from each of the three-phase charging unit conductors, and electrostatic capacitance generated between each of the charging unit conductors and each detection unit causes the detection unit to be separated from each of the detection units. A voltage obtained by converting the electrostatic induction current flowing from the detection unit in the voltage detection device that converts the electrostatic induction current flowing to the ground unit into a voltage to detect the voltage at each of the charging unit conductors. Phase inversion circuit that rotates the phase of one or two phases by 180 degrees, and the output from the phase inversion circuit and the other two-phase or one-phase voltage that does not rotate the phase are vector-combined and output And a summing circuit for controlling the voltage.