JPS622889Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This device is used to prevent open-phase failures that occur in three-phase distribution lines, and to prevent burnout accidents caused by open-phase operation of loads such as three-phase induction motors connected to these lines. The present invention relates to equipment, and aims to provide a phase failure detection and disconnection device for three-phase distribution lines that can prevent erroneous circuit disconnection in short-term phase failure conditions caused by human-induced work conditions. be. Below are drawings showing embodiments of the present application, Figures 1 to 4.
The diagram will be explained. 1 is a three-phase high-voltage line, 2 is a high-voltage cutout, 3 is a power transformer for power only, 4 is a three-phase fuse breaker, 5 is an open phase detection device, 6 is a three-phase induction motor illustrated as a load, A, B, C is three-phase induction motor 6
A indicates a three-phase distribution line that supplies power to the A, B indicates a phase A wire, B indicates a phase B wire, and C indicates a phase C wire. Next, the three-phase fuse breaker 4 will be described in detail. 10 is an insulating case, 11, 11 are small chambers provided in the insulating case 10, and 12 is a bridging chamber. 1
3, 14, 15 are power supply side terminals, 13', 14' are load side terminals, and 7A, 7B are fuse elements, both ends of which are connected to terminals 13, 13' and 14, 14'. Further, the fuse elements 7A and 7B pass through the small chambers 11 and 11 and are connected to the power supply terminal 15 at one end in the bridging chamber 12, and the other end is brought close to the terminal piece 7C located between these fuse elements. It is arranged like this. Also small rooms 11, 11
is filled with arc-extinguishing agent. (In this case, the arc extinguishing agent may be filled only in the small chamber 11 on the power supply side.)
Reference numeral 8 denotes a bimetallic piece exemplified as a bridging piece, which is disposed in the bridging chamber 12 in close proximity to the fuse elements 7A, 7B and the terminal piece 7C, and when heated, it curves and closes the fuse element 7A. , 7B and the terminal piece 7C. 17 indicates a heating member of the bimetal piece 8;
As clearly shown in FIG. 4, it is composed of a heat capacity body 18 connected to the base of the bimetal piece 8, and a heater 19 attached to the heat capacity body 18. heat capacity body 1
As for 8, the time from when the heater 19 starts generating heat until the heat is transmitted to the bimetal piece 8 through itself and the bimetal piece 8 deforms is, for example, about 5 minutes to 15 minutes depending on the application. things are used. (For example, about 200g). Also heater 19
is one that can appropriately deform the bimetal piece 8 without being affected by external influences, for example, 1000
(Ω), 40 (W) I = about 0.2 (A) is used. Next, the heating circuit 20 of the heater 19 will be explained. 21 is a resistor whose one end is connected to the three-phase distribution line,
A value that can supply appropriate power to the heater 19, for example, about 30 (Ω) is used. 22 is a three-phase full-wave rectifier circuit, and each diode 22a has a reverse peak withstand voltage of 400 (V) and a peak reverse peak withstand voltage of 500 (V).
(V) and a current capacity of about 2 (V) is used. 23 is an arrester, for example, a 250 (V) arrester is used. Next, 24 indicates a relay,
DC operated ones are used. This relay 2
4, 24a is a relay contact provided in the heating circuit 20, and 24b is a relay coil that operates the contact 24a. Furthermore, this relay 24
The withstand voltage of the contact is 200 (V) and the current is 0.5
(A) is used. Next, to explain the open phase detection device 5 in detail, CT is a detection current transformer, and _N1 is the number of four turns of the primary winding _N1 . ) T ₁ and T ₂ are both terminals of the primary winding N ₁ , T ₃
is the midpoint terminal, N ₂ is its secondary winding (the number of turns is N ₂ ),
T ₄ and T ₅ are output terminals from the secondary winding N ₂ for taking out the distribution line disconnection signal. Z ₁ and N ₂ are illustrated as phase shift elements, Z ₁ is a phase advancing element, and its component R ₁ is a resistance (its value is R ₁ , and the value is similarly shown in parentheses below) So, B phase wire B and terminal T ₁
is interposed between. Z ₂ is a slow phase element,
The components R ₂ and L ₂ are a resistor (R ₂ ) and a reactor (L ₂ ), which are connected in series and interposed between the A-phase electric wire A and the terminal T ₂ . The midpoint terminal _T3 is directly connected to the C phase electric wire C. The output terminals T ₄ and T ₅ of the secondary winding N ₂ are full-wave rectifier circuits 25
The relay coil 24b is connected so as to be able to supply current to the relay coil 24b via the relay coil 24b. For example, the full wave rectifier circuit is
250 (V) and 1 (A) are used. The values of the resistors R ₁ , R ₂ and reactor L ₂ are determined so as to substantially satisfy equation (1). R ₁ = √ ² ₂ + ( ₂ ) ² , R ₂ = WL ₂ /√3 ...(1) Here, W is the angular frequency of the power supply voltage (radian/
seconds). In the above configuration, the phase rotation direction is A,
It is assumed that three-phase balanced voltages in the order of B and C are supplied. At this time, the line voltages V〓 _AB , V〓 _BC , V〓 _CA are in an equilibrium state, and this voltage causes the detection current transformer CT to
The current I〓 _BC flowing between the primary side terminal T ₁ and the middle terminal T ₃ is as follows: I〓 _BC = V〓 _BC /R ₁ ...(2), and is in phase with V〓 _BC . On the other hand, the terminal
The current I〓 _CA flowing between T ₂ and the midpoint terminal T ₃ is determined by the condition of equation (1). however

[Formula] In other words, these two currents have the same value and opposite polarity, so in the detection current transformer CT, each I〓 _BC
A magnetomotive force of N ₁ /2 and I = _CA N ₁ /2 (ampere turns) is generated, and these substantially cancel each other out, creating a voltage between the output terminals T ₄ and T ₅ on the secondary side. I won't let you. Therefore, since no current is supplied to relay coil 24b, this relay 24 does not operate. As a result, no power is supplied to the heater 19, so the bimetal piece 8 is not heated and the three-phase fuse breaker 4 is not activated. Next, if one of the high voltage cutouts 2 breaks for some reason, A
We will discuss the case where the phase becomes an open phase. In this state, the three-phase induction motor 6 receiving electric power is in single-phase operation, which is a dangerous state that may lead to a burnout accident. In this case, each line voltage is

[Table] 〓 〓 〓
V _BC =a ² V _AB1 +aV _AB2 〓………………………………
…(Four)
〓 〓 〓

Claims (1)

[Scope of utility model registration request] A three-phase distribution line and a detection current transformer to be connected thereto are provided, and the secondary winding of the detection current transformer is provided with an output terminal for taking out the distribution line disconnection signal, and the detection The midpoint terminal of the primary winding in the current transformer is connected to one phase line of the above-mentioned distribution line, and one of the terminals on both sides of the primary winding is connected to a phase shifter constructed with a resistor. The other terminal of the remaining primary winding is connected to the winding on both sides of the midpoint terminal in the detection current transformer. Connected to the remaining one phase line of the distribution line through another phase shift element consisting of a series circuit of a resistor and a reactor so that the normal magnetomotive force in the line has substantially the same value and opposite polarity, Furthermore, in the case of the above-mentioned three-phase distribution line circuit, a fuse element is interposed in at least two wires, and a bimetal piece that can be freely contacted is disposed adjacent to the fuse element, and the three-phase distribution line A terminal piece connected to the remaining line in the circuit is arranged in parallel to the fuse element so that the fuse element and the terminal piece can be bridged by the bimetal,
A heat capacitor is connected to the bimetal piece, and a heater is disposed close to the heat capacitor so as to be able to heat the heat capacitor, and the heater is connected to the three-phase distribution line via a relay contact. An open phase detection and cutoff device for a three-phase power distribution line, characterized in that a relay coil for activating the relay contact is connected to an output terminal of the detection current transformer.