CN107132463B - Short circuit preventing device for secondary winding of voltage transformer - Google Patents

Abstract

The anti-short-circuit device for the secondary winding of the voltage transformer provided by the invention is installed between the secondary winding of the voltage transformer and the measuring circuit of the sampling unit of the voltage transformer, and includes an air switch, a connecting terminal and a protection circuit board, and the protection circuit board includes a main circuit Resistors, protective resistors, light-emitting diodes and fuses; among them, the incoming line end of the air switch is connected to the live wire and neutral line of the secondary winding of the voltage transformer, the outgoing line end of the air switch is connected to one end of the main circuit resistance, and the main circuit resistance The other end is connected to one end of the fuse, and the other end of the fuse is connected to one end of the protective resistor or the positive pole of the light-emitting diode while connected to the incoming terminal of the terminal, and the other end of the protective resistor or the negative pole of the light-emitting diode is connected to the terminal The incoming line end of the terminal block is connected to the live line and neutral line of the measuring circuit of the voltage transformer sampling unit. The invention can eliminate the potential safety hazard of the short circuit of the secondary winding of the voltage transformer caused by the short circuit of the test loop.

Description

Anti-short circuit device for secondary winding of voltage transformer

technical field

The invention belongs to the technical field of electrical engineering, and in particular relates to a short-circuit prevention device for a secondary winding of a voltage transformer.

Background technique

Capacitive equipment insulation on-line monitoring system is mainly to measure tgδ, Cx (pF) of 220kV main transformer bushing, current transformer, coupling capacitor and other capacitive equipment, as well as resistive current and full current of zinc oxide arrester, and analyze the above data by comparison Comprehensively judge the insulation status of capacitive equipment.

The capacitive equipment insulation on-line monitoring system mainly measures the bus voltage vector and the leakage current vector flowing through the tested product through the voltage transformer sampling unit and the tested equipment sampling unit, and then inputs all test signals into the host through the cable channel for data processing and Analysis calculated. However, when measuring the secondary voltage of the voltage transformer through the sampling unit of the voltage transformer, due to factors such as external force damage to the signal channel, human misoperation, and test instrument failure, etc., the secondary winding short circuit of the voltage transformer often occurs. If there is a fault, the secondary winding will generate a large short-circuit current and burn the voltage transformer, seriously affecting the stability and safety of the system.

Contents of the invention

The technical problem to be solved by the present invention is to provide a secondary winding anti-short circuit device of a voltage transformer to solve the problem of burning the voltage transformer due to a short circuit of the secondary winding of the voltage transformer.

The anti-short-circuit device for the secondary winding of the voltage transformer provided by the invention is installed between the secondary winding of the voltage transformer and the measuring circuit of the sampling unit of the voltage transformer, and includes an air switch, a connecting terminal and a protection circuit board, and the protection circuit board includes a main circuit Resistors, protective resistors, light-emitting diodes and fuses; among them, the incoming line end of the air switch is connected to the live wire and neutral line of the secondary winding of the voltage transformer, the outgoing line end of the air switch is connected to one end of the main circuit resistance, and the main circuit resistance The other end is connected to one end of the fuse, and the other end of the fuse is connected to one end of the protective resistor or the positive pole of the light-emitting diode while connected to the incoming terminal of the terminal, and the other end of the protective resistor or the negative pole of the light-emitting diode is connected to the terminal The incoming line end of the terminal block is connected to the live line and neutral line of the measuring circuit of the voltage transformer sampling unit;

In addition, the preferred solution is that the voltage transformer includes a first secondary winding, a second secondary winding and a third secondary winding, the first secondary winding includes live wire A and neutral wire N, and the second secondary winding includes The live wire B and the neutral wire N, the third secondary winding includes the live wire C and the neutral wire N; the measurement circuit of the voltage transformer sampling unit includes the first measurement circuit, the second measurement circuit and the third measurement circuit, and the first measurement circuit includes the live wire a and neutral wire n, the second measurement circuit includes live wire b and neutral wire n, the third measurement circuit includes live wire c and neutral wire n; the air switch includes the first, second, third and fourth circuits; terminal blocks Including the first hole, the second hole, the third hole and the fourth hole; the main circuit resistance includes the first main circuit resistance, the second main circuit resistance and the third main circuit resistance; the protection resistance includes the first protection resistance, the second protection resistance resistance, a third protection resistor and a fourth protection resistor; the fuse includes a first fuse, a second fuse and a third fuse; the light-emitting diode includes a first light-emitting diode, a second light-emitting diode and a third light-emitting diode; the The incoming line end of the first path is connected to the live wire of the first secondary winding, the outgoing line end of the first path is connected to one end of the first main circuit resistance, and the other end of the first main circuit resistance is connected to one end of the first fuse. The other end of the first fuse is connected to the incoming line end of the first hole and connected to one end of the first protective resistor, the other end of the first protective resistor is connected to the positive pole of the first light emitting diode, and the negative pole of the first light emitting diode is connected to the first light emitting diode. One end of the four protection resistors is connected, the other end of the fourth protection resistor is connected to the inlet end of the fourth hole, the outlet end of the fourth hole is connected to the neutral wire of the first measurement circuit, and the live wire of the first measurement circuit is connected to the first The outlet end of the hole; the inlet end of the second circuit is connected to the live wire of the second secondary winding, the outlet end of the second circuit is connected to one end of the second main circuit resistor, and the other end of the second main circuit resistor is connected to the second fuse Connect one end of the fuse, the other end of the second fuse is connected to the incoming line end of the second hole and one end of the second protection resistor, the other end of the second protection resistor is connected to the anode of the second light-emitting diode, and the second light-emitting diode The cathode of the diode is connected to one end of the fourth protective resistor, the other end of the fourth protective resistor is connected to the incoming line end of the fourth hole, the outgoing line end of the fourth hole is connected to the neutral line of the second measurement circuit, and the second measurement circuit’s The live wire is connected to the outgoing end of the second hole; the incoming end of the third road is connected to the live wire of the third secondary winding, the outgoing wire of the third road is connected to one end of the third main circuit resistance, and the other end of the third main circuit resistance One end is connected to one end of the third fuse, the other end of the third fuse is connected to the incoming line end of the third hole and connected to one end of the third protection resistor, and the other end of the third protection resistor is connected to the anode of the third light-emitting diode connection, the negative pole of the third light-emitting diode is connected to one end of the fourth protective resistor, the other end of the fourth protective resistor is connected to the incoming line end of the fourth hole, and the outgoing line end of the fourth hole is connected to the neutral line of the third measuring circuit. The live wire of the third measurement circuit is connected to the outlet end of the third hole; the inlet end of the fourth circuit is respectively connected to the neutral wire of the first secondary winding, the second secondary winding and the third secondary winding, and the The outgoing line end is connected with the incoming line end of the fourth hole through a wire.

In addition, the preferred scheme is that the rated currents of the first fuse, the second fuse and the third fuse are all 0.5A; the resistance values of the first main circuit resistance, the second main circuit resistance and the third main circuit resistance are all The resistance value of the first protection resistor, the second protection resistor and the third protection resistor is 2400Ω, and the resistance value of the fourth protection resistor is 120Ω; the work of the first light-emitting diode, the second light-emitting diode and the third light-emitting diode The current is 20mA.

Furthermore, the preferred solution is that the anti-short circuit device for the secondary winding of the voltage transformer also includes an epoxy resin board installed in the terminal box of the voltage transformer, and the air switch, the terminal block and the protection circuit board are respectively fixed on the epoxy resin board .

Through the above design scheme, the present invention can bring the following beneficial effects:

1. Eliminate the potential safety hazard of the short circuit of the secondary winding of the voltage transformer caused by the short circuit of the sampling unit of the voltage transformer, thereby improving the safety of the system operation.

2. The current of the measuring circuit of the quick-break voltage transformer sampling unit of the fuse is effectively limited to prevent the secondary winding of the voltage transformer from reducing insulation and shortening life due to excessive current.

Description of drawings

The present invention will be further described below in conjunction with accompanying drawing and specific embodiment:

Fig. 1 is the schematic diagram of the circuit structure of the voltage transformer secondary winding anti-short circuit device of the present invention;

Fig. 2 is the equivalent circuit diagram when the voltage transformer secondary winding anti-short circuit device of the present invention is shorted between A and B phases;

Fig. 3 is the equivalent circuit diagram when the A phase short circuit of the voltage transformer secondary winding anti-short circuit device of the present invention;

Fig. 4 is a circuit diagram of a light-emitting diode loop in the secondary winding anti-short circuit device of a voltage transformer according to the present invention.

In the figure: QF-air switch, J-terminal, R1-first main circuit resistance, R2-second main circuit resistance, R3-third main circuit resistance, r1-first protection resistance, r2-second protection resistance , r3-the third protection resistor, r4-the fourth protection resistor, F1-the first fuse, F2-the second fuse, F3-the third fuse, L1-the first light-emitting diode, L2-the second light-emitting diode, L3 - third light emitting diode.

Detailed ways

The anti-short-circuit device for the secondary winding of the voltage transformer provided by the present invention is installed between the secondary winding of the voltage transformer and the measuring circuit of the sampling unit of the voltage transformer, and is used to cut off the voltage transformer when the measuring circuit of the sampling unit of the voltage transformer is short-circuited. The sampling unit measures the line between the circuit and the secondary winding of the voltage transformer to prevent the secondary winding of the voltage transformer from burning out the voltage transformer due to excessive current.

The epoxy resin board installed in the terminal box of the voltage transformer, the air switch, the terminal block and the protection circuit board are respectively fixed on the epoxy resin board

The anti-short-circuit device for the secondary winding of the voltage transformer includes an epoxy resin board, an air switch, a terminal block and a protection circuit board. The air switch, connection terminals and protection circuit board are all fixed on the epoxy resin board, and the epoxy resin board is installed In the terminal box of the transformer, the epoxy resin board is cheap, has excellent insulation performance and wear resistance, and is easy to design and install. Therefore, the present invention uses the epoxy resin board as the board for fixing the positions of the electrical components.

The protection circuit board is connected between the air switch and the terminal. The protection circuit board specifically includes the main circuit resistance, protection resistance, light-emitting diodes and fuses; wherein, the incoming line end of the air switch is connected to the live wire and Neutral line, the outlet end of the air switch is connected to one end of the main circuit resistance, the other end of the main circuit resistance is connected to one end of the fuse, and the other end of the fuse is connected to the input end of the terminal block and one end of the protection resistor or The positive pole of the light-emitting diode is connected, the other end of the protection resistor or the negative pole of the light-emitting diode is connected to the incoming line end of the terminal, and the outgoing line of the terminal is connected to the live line and neutral line of the measuring circuit of the voltage transformer sampling unit.

The fuse is used to cut off the line between the secondary winding of the voltage transformer and the measuring circuit of the sampling unit of the voltage transformer when the current flowing through it exceeds its own rated current.

The air switch is used to ensure that there is no voltage on the line when replacing fuses and other operations.

The light-emitting diode is used to display the working status of the fuse. When the fuse is not blown, the light-emitting diode lights up, indicating that there is no short circuit in the measurement circuit of the voltage transformer sampling unit; when the fuse is blown, the light-emitting diode is off, indicating that the voltage transformer There is a short circuit in the measuring circuit of the sampling unit.

The main circuit resistance is used to ensure that the fuse can blow quickly.

The connecting terminal is used to protect the circuit, and the original wiring of the measuring circuit of the sampling unit of the sampling voltage transformer is not changed.

The voltage transformer includes at most three secondary windings, and each secondary winding corresponds to a measurement loop, and the number of measurement loops of the voltage transformer sampling unit is determined by the number of secondary windings of the voltage transformer. The secondary winding and the measuring circuit respectively include a live wire and a neutral wire. Taking the voltage transformer including three secondary windings as an example, the secondary winding anti-short circuit device of the voltage transformer of the present invention is described in detail. When the voltage transformer includes one secondary winding and two secondary windings, the anti-short circuit device for the secondary winding of the voltage transformer can be obtained in the same way.

Fig. 1 shows the circuit structure of the secondary winding anti-short circuit device of a voltage transformer provided by the present invention.

As shown in Figure 1, the secondary windings of the voltage transformer are the first secondary winding, the second secondary winding, and the third secondary winding. The live wire of the first secondary winding is called phase A, and the live wire of the second secondary winding The live wire is called phase B, the live wire of the third secondary winding is called phase C, and the neutral wires of the first secondary winding, the second secondary winding and the third secondary winding are all called N phase; the voltage transformer sampling unit measures The circuits are the first measurement circuit, the second measurement circuit and the third measurement circuit respectively. The live wire of the first measurement circuit is called phase a, the live wire of the second measurement circuit is called phase b, and the live wire of the third measurement circuit is called phase c , the zero lines of the first measurement circuit, the second measurement circuit and the third measurement circuit are all called n-phase; the air switch is a four-way air switch, which are the first, second, third and fourth way, The first and secondary windings, the second and second secondary windings, and the neutral phase N of the third and secondary windings are twisted into one strand and connected to the fourth circuit, the live wire A phase of the first secondary winding, and the live wire B phase of the second secondary winding The live wire C phase of the third and secondary windings is connected to the first, second and third circuits respectively; the terminal is a four-hole terminal, which is the first hole, the second hole, the third hole and the fourth hole , the zero line n phases of the first measurement circuit, the second measurement circuit and the third measurement circuit are twisted into one strand and connected to the fourth hole, the live line a phase of the first measurement circuit, the live line b phase of the second measurement circuit and the third measurement The phase c of the live wire of the circuit is respectively connected to the first hole, the second hole and the third hole.

The main loop resistance includes a first main loop resistance R1, a second main loop resistance R2 and a third main loop resistance R3.

The protection resistors include a first protection resistor r1, a second protection resistor r2, a third protection resistor r3 and a fourth protection resistor r4.

The fuses include a first fuse F1, a second fuse F2 and a third fuse F3; the light emitting diodes include a first light emitting diode L1, a second light emitting diode L2 and a third light emitting diode L3.

The input terminal of the first circuit is connected to the live wire A phase of the first secondary winding, the outgoing terminal of the first circuit is connected to one end of the first main circuit resistance R1, and the other end of the first main circuit resistance R1 is connected to the first fuse One end of F1 is connected, the other end of the first fuse F1 is connected to the incoming line end of the first hole and one end of the first protection resistor r1 is connected, and the other end of the first protection resistor r1 is connected to the anode of the first light-emitting diode L1 , the cathode of the first light-emitting diode L1 is connected to one end of the fourth protective resistor r4, the other end of the fourth protective resistor r4 is connected to the incoming line end of the fourth hole, and the outgoing line end of the fourth hole is connected to the zero of the first measuring circuit. Line n, live line a of the first measurement circuit is connected to the outlet end of the first hole.

The incoming line end of the second circuit is connected to the live wire B of the second secondary winding, the outgoing line end of the second circuit is connected to one end of the second main circuit resistance R2, and the other end of the second main circuit resistance R2 is connected to the second fuse F2 One end of the second fuse F2 is connected to the incoming line end of the second hole and connected to one end of the second protection resistor r2, and the other end of the second protection resistor r2 is connected to the anode of the second light-emitting diode L2, The negative electrode of the second light-emitting diode L2 is connected to one end of the fourth protective resistor r4, the other end of the fourth protective resistor r4 is connected to the incoming line end of the fourth hole, and the outgoing line end of the fourth hole is connected to the neutral line of the second measurement circuit n, the live wire b of the second measurement circuit is connected to the outlet end of the second hole.

The incoming line end of the third circuit is connected to the fire wire c of the third secondary winding, the outgoing line end of the third circuit is connected to one end of the third main circuit resistor R3, and the other end of the third main circuit resistor R3 is connected to the third fuse F3 One end of the third fuse F3 is connected to the incoming line end of the third hole and connected to one end of the third protective resistor r3, and the other end of the third protective resistor r3 is connected to the anode of the third light-emitting diode L3, The negative electrode of the third light-emitting diode L3 is connected to one end of the fourth protective resistor r4, the other end of the fourth protective resistor r4 is connected to the incoming line end of the fourth hole, and the outgoing line end of the fourth hole is connected to the neutral line of the third measurement circuit n, the live wire c of the third measurement circuit is connected to the outlet end of the third hole.

The incoming wire end of the fourth road is respectively connected to the zero line n of the first secondary winding, the second secondary winding and the third secondary winding, and the outgoing wire end of the fourth road is connected to the incoming wire end of the fourth hole through a wire .

When the measurement circuit of the voltage transformer sampling unit is working normally, the circuit current does not exceed 1mA, or even lower, which is similar to an open circuit state. Once the measurement circuit has a phase-to-phase short circuit or a single-phase ground fault, the current will increase sharply. In order to meet the requirement that the volume be as small as possible, the first fuse F1, the second fuse F2, and the third fuse F3 in the present invention choose the smallest 5*20mm fuse tube on the market, that is, the fuse with a rated current of 0.5A device.

When the current passing through the fuse is less than its rated current, the fuse will not blow. Only when the rated current exceeds its rated current and reaches the fusing current, the fuse will heat up and blow. The greater the current through the fuse, the faster the fuse will blow. Generally, when the current flowing through the fuse is twice the rated current, it should be blown within 30 seconds; when it is five times the rated current, it should be blown instantly. In order to ensure that when a phase-to-phase or single-phase grounding fault occurs, the fuse will be instantly and reliably blown and to avoid some malfunctions caused by inductive load startup, the present invention selects 2.5A current, which is 5 times the rated current.

When a phase-to-phase short-circuit fault occurs in the measurement circuit (such as a phase-to-phase short-circuit between A and B), its equivalent circuit diagram is shown in Figure 2:

Known Uab=100V, I=2.5A, get R1=R2=0.5*Uab/I=20Ω,

Among them: Uab is the effective value of the line voltage of the secondary winding of the voltage transformer; I is the fusing current value of the set fuse.

When a single-phase ground fault occurs in the measurement circuit (for example, phase A is grounded), its equivalent circuit diagram is shown in Figure 3:

Known Ua=58V, I=2.5A, get R1=Ua/I=23.2Ω,

Among them: Ua is the effective value of the phase voltage of the secondary winding of the voltage transformer; I is the fusing current value of the set fuse.

Combining the above two failure modes, select a 20Ω resistor (composed of two 10Ω resistors in series) as the main circuit resistance, that is, the resistance values of the first main circuit resistance R1, the second main circuit resistance R2, and the third main circuit resistance R3 are 20Ω.

In order to meet the requirement that the working current of the light-emitting diode is 20mA, the selection of the protection resistors r1, r2, r3, and r4 is shown in Figure 4:

It is known that I1=I2=I3=20mA, Uan=58V, r1=r2=r3,

Listable equation: Uan=I1*r1+3*I1*r4,

Select 2400Ω resistors as r1, r2, r3 according to the specifications and equation constraints of existing resistors in the market, and choose 120Ω resistors as r4.

Claims (3)

1. A voltage transformer secondary winding anti-short circuit device, installed between the voltage transformer secondary winding and the voltage transformer sampling unit measurement circuit, is characterized in that it includes an air switch (QF), a terminal (J) and A protection circuit board, the protection circuit board includes a main circuit resistance, a protection resistance, a light-emitting diode and a fuse; wherein, the incoming line terminal of the air switch (QF) is connected to the live wire and the neutral wire of the secondary winding of the voltage transformer The outlet end of the air switch (QF) is connected to one end of the main circuit resistance, the other end of the main circuit resistance is connected to one end of the fuse, and the other end of the fuse is connected to the The incoming line end of the connecting terminal (J) is connected to one end of the protective resistor or the anode of the light-emitting diode, and the other end of the protective resistor or the negative electrode of the light-emitting diode is connected to the connecting terminal (J) The incoming line end of the terminal (J) is connected to the live wire and neutral wire of the voltage transformer sampling unit measurement circuit; The voltage transformer includes a first secondary winding, a second secondary winding and a third secondary winding, the first secondary winding includes a live wire (A) and a neutral wire (N), and the second secondary winding including a live wire (B) and a neutral wire (N), and the third secondary winding includes a live wire (C) and a neutral wire (N); The voltage transformer sampling unit measurement circuit includes a first measurement circuit, a second measurement circuit and a third measurement circuit, the first measurement circuit includes live wire (a) and neutral wire (n), and the second measurement circuit includes live wire (b) and neutral wire (n), and the third measurement circuit includes live wire (c) and neutral wire (n); The air switch (QF) includes a first road, a second road, a third road and a fourth road; The connection terminal (J) includes a first hole, a second hole, a third hole and a fourth hole; The main circuit resistance comprises a first main circuit resistance (R1), a second main circuit resistance (R2) and a third main circuit resistance (R3); The protection resistors include a first protection resistor (r1), a second protection resistor (r2), a third protection resistor (r3) and a fourth protection resistor (r4); The fuses include a first fuse (F1), a second fuse (F2) and a third fuse (F3); The light emitting diodes include a first light emitting diode (L1), a second light emitting diode (L2) and a third light emitting diode (L3); The incoming line end of the first path is connected to the live wire (A) of the first secondary winding, the outgoing line end of the first path is connected to one end of the first main circuit resistance (R1), and the first The other end of a main circuit resistance (R1) is connected to one end of the first fuse (F1), and the other end of the first fuse (F1) is connected to the incoming line end of the first hole and connected to the first hole. One end of the first protection resistor (r1) is connected, the other end of the first protection resistor (r1) is connected to the anode of the first light-emitting diode (L1), and the cathode of the first light-emitting diode (L1) is connected to the anode of the first light-emitting diode (L1). One end of the fourth protective resistor (r4) is connected, the other end of the fourth protective resistor (r4) is connected to the incoming line end of the fourth hole, and the outgoing line end of the fourth hole is connected to the first A zero wire (n) of the measurement circuit, the live wire (a) of the first measurement circuit is connected to the outlet end of the first hole; The incoming line end of the second path is connected to the live wire (B) of the second secondary winding, the outgoing line end of the second path is connected to one end of the second main circuit resistance (R2), and the first The other end of the two main loop resistors (R2) is connected to one end of the second fuse (F2), and the other end of the second fuse (F2) is connected to the incoming line end of the second hole and connected to the second hole. One end of the second protection resistor (r2) is connected, the other end of the second protection resistor (r2) is connected to the anode of the second light-emitting diode (L2), and the cathode of the second light-emitting diode (L2) is connected to the anode of the second light-emitting diode (L2). One end of the fourth protective resistor (r4) is connected, the other end of the fourth protective resistor (r4) is connected to the incoming line end of the fourth hole, and the outgoing line end of the fourth hole is connected to the first The zero wire (n) of the second measurement circuit, the live wire (b) of the second measurement circuit is connected to the outlet end of the second hole; The incoming line end of the third path is connected to the live wire (C) of the third secondary winding, the outgoing line end of the third path is connected to one end of the third main circuit resistance (R3), and the first The other end of the three main circuit resistors (R3) is connected to one end of the third fuse (F3), and the other end of the third fuse (F3) is connected to the incoming line end of the third hole and connected to the third hole. One end of the third protection resistor (r3) is connected, the other end of the third protection resistor (r3) is connected to the anode of the third light-emitting diode (L3), and the cathode of the third light-emitting diode (L3) is connected to the anode of the third light-emitting diode (L3). One end of the fourth protective resistor (r4) is connected, the other end of the fourth protective resistor (r4) is connected to the incoming line end of the fourth hole, and the outgoing line end of the fourth hole is connected to the first The zero wire (n) of the three measurement circuits, the live wire (c) of the third measurement circuit is connected to the outlet end of the third hole; The incoming line end of the fourth path is respectively connected to the neutral line (N) of the first secondary winding, the second secondary winding and the third secondary winding, and the outgoing line end of the fourth path It is connected with the wire inlet end of the fourth hole through a wire. 2. The voltage transformer secondary winding anti-short circuit device according to claim 1, characterized in that: The rated currents of the first fuse (F1), the second fuse (F2) and the third fuse (F3) are all 0.5A; The resistance values of the first main circuit resistance (R1), the second main circuit resistance (R2) and the third main circuit resistance (R3) are all 20Ω; The resistance values of the first protection resistor (r1), the second protection resistor (r2) and the third protection resistor (r3) are all 2400Ω, and the resistance value of the fourth protection resistor (r4) is 120Ω ; The working current of the first light emitting diode (L1), the second light emitting diode (L2) and the third light emitting diode (L3) is 20mA. 3. The voltage transformer secondary winding anti-short circuit device according to claim 1, characterized in that: it also includes an epoxy resin board installed in the voltage transformer terminal box, the air switch (QF), the wiring The terminal (J) and the protective circuit board are respectively fixed on the epoxy resin board.

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