CN2087394U

CN2087394U - Open circuit protector for secondary circuit of current mutual-inductor

Info

Publication number: CN2087394U
Application number: CN 91215300
Authority: CN
Inventors: 刘运中
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-04-05
Filing date: 1991-04-05
Publication date: 1991-10-23

Abstract

The utility model discloses an open circuit protector for the secondary circuit of a current mutual-inductor, which is a protector that in the open circuit of the secondary side load of the current mutual-inductor in the operation of a power system, and the secondary circuit of the current mutual-inductor can be automatically in the short circuit. An AC electronic switch with a voltage arbiter are connected in parallel with the two terminals of the secondary coil of the current mutual-inductor, the AC electronic switch can be connected by a bidirectional controlled silicon or by a unidirectional controlled silicon and a diode bridge circuit, or can be connected in parallel by two unidirectional controllable silicon reversely, and the voltage arbiter can be composed of a bidirectional trigger diode or a voltage stabilizing diode. The utility model has the advantages of simple structure and convenient operation.

Description

Open circuit protector for secondary circuit of current mutual-inductor

The utility model relates to a kind of protective device that is used for current transformer C, the T energy automatic short-circuit current transformer secondary circuit when the secondary side load open circuit of power system operation.

Be used for the electric power system current transformer at present; its primary winding is connected in the test line; secondary coil is connected in series all kinds of relays and the transmitter of various instrument and protection system control loop and forms secondary circuit; because the device impedance of above-mentioned serial connection is all very little; so current transformer is when normal operation; secondary side approaches short-circuit condition; voltage on the secondary coil is also very low; but because the serial connection of above-mentioned plurality of devices; any one loose contact or open circuit can cause that the secondary loop of mutual inductor impedance increases; even open circuit; in case secondary circuit is opened a way; the number of ampere turns of primary winding will all be used for excitatory; make iron core be in the height saturation condition; make core loss and temperature excursion; can respond to very high voltage in the secondary coil this moment; jeopardize various device and the operator safety of string at secondary circuit; even influence the normal operation of electrical network; in addition, the remanent magnetism in the iron core also can influence the service precision of current transformer, is the open circuit that should guarantee to cause secondary circuit so current transformer is in operation; yet; at present, do not have special protective device, face is by tightening the secondary circuit open circuit that measures such as terminal screw prevent instrument transformer.In case the purpose of this utility model makes operating current transformer can owing to a variety of causes not cause the open circuit of secondary circuit with regard to device that can automatic short-circuit instrument transformer secondary coil loop with a kind of secondary circuit both end voltage during to certain value.

Technical scheme of the present invention, employing is at two ends of Current Transformer Secondary coil electronic AC switch that has voltage checker in parallel, electronic AC switch can be formed by connecting by double silicon control or by one-way SCR and diode bridge, also available two one-way SCRs oppositely and connect and form, voltage checker is with bidirectional trigger diode or use voltage stabilizing didoe.

The utility model embodiment is illustrated in conjunction with the accompanying drawings.

Fig. 1 the utility model electrical schematic diagram;

Fig. 2 is embodiment 1 accompanying drawing;

Fig. 3 is embodiment 2 accompanying drawings;

Fig. 4 is embodiment 3 accompanying drawings.

By shown in Figure 1,1 is electronic AC switch, and it is in parallel with secondary coil two ends of current transformer, with 1 join 2 for voltage checker.

Embodiment 1:

By shown in Figure 2, be connected with control utmost point G with anode A as the bidirectional triode thyristor SCR1 of electronic AC switch as the two ends of the bidirectional trigger diode 2CTS1 of voltage checker.By Fig. 1; shown in 2; be in the C of operate as normal; T secondary coil two end load impedances are very little; therefore both end voltage is very low; when certain reason makes secondary circuit; load this moment infinity, two terminal voltages are very high, owing to be attempted by C as the bidirectional triode thyristor of electronic AC switch; T secondary coil two ends; therefore; the anode of this bidirectional triode thyristor and control are added with high pressure between the utmost point, and just bidirectional trigger diode is by the high pressure triggering and conducting, the bidirectional triode thyristor conducting that also is triggered like this; end until alternating current zero crossing; more than be positive half cycle situation, when ac signal is negative half period, repeat said process too; also be; in case C; the secondary circuit open circuit of T, when open circuit voltage is higher than as the trigger voltage of the bidirectional trigger diode of voltage checker, this diode current flow; trigger the bidirectional triode thyristor conducting, thereby reach the purpose of protection.Because C, T are generally less than or equal 100VA, and secondary loop current＜5A.So the voltage on the secondary coil just often is not more than 20V, after multiply by 1.414 times, crest voltage is not more than 30V, so when the two-way trigger tube trigger voltage is selected for use greater than 30V, therefore, the conducting that can not be triggered all the time at ordinary times of bidirectional triode thyristor electronic switch is only at T, during the secondary circuit of C open circuit, two terminal voltages of two-way trigger tube are during greater than 30V, the bidirectional trigger diode conducting, thereby trigger the conducting of bidirectional triode thyristor electronic switch, its pressure drop is very little like this, is generally about 1-1.5V, power consumption is within 10W, based on above-mentioned principle, C, T secondary coil two terminal voltage maximums are no more than the trigger voltage of bidirectional trigger diode, and the equipment and the person are not all had influence.When C, T operate as normal, secondary coil two terminal voltage deficiencies are so that bidirectional triode thyristor electronic switch triggering and conducting, so this electronic switch resistance at C, T secondary coil two ends is bordering on infinity, the loop there is not influence, do not influence in the loop and measure and control precision, bidirectional triode thyristor is selected for use withstand voltage greater than 100V, and electric current is greater than the specification of 5A, and installing radiator additional, the bidirectional trigger diode trigger voltage is preferably selected for use between the 30V-60V.

Embodiment 2:

By shown in Figure 3; electronic AC switch by single-phase silicon-controlled SCR2 be formed by connecting by the D1-D4 diode bridge; bidirectional trigger diode 2CTS2 as voltage checker is connected with the control utmost point with the anode of one-way SCR; its operation principle is described below: current transformer C; during the T operate as normal; C; T secondary coil two ends are because load impedance is very little; so two terminal voltages are very low; the electronic switch resistance that be made up of bridge circuit and one-way SCR this moment is bordering on infinity; former loop there is not influence; in case certain reason makes the secondary circuit open circuit; load is similar to infinity; two terminal voltages raise, and the high pressure that be added on the bidirectional trigger diode this moment makes its conducting, thereby trigger the one-way SCR conducting; make C; the load impedance of T secondary coil two ends still diminishes, and reaches the purpose of protection secondary coil.

Embodiment 3:

By shown in Figure 4, by two one-way SCRs oppositely and be connected into electronic AC switch, voltage checker is by two bidirectional trigger diode 2CTS3,2CTS4 or form by two voltage-stabiliser tubes, its operation principle is the same with the first two embodiment, when secondary circuit is opened a way, load is in infinity, two terminal voltages of secondary circuit raise, when to certain voltage, make bidirectional trigger diode or voltage-stabiliser tube conducting, thereby trigger unidirectional controllable silicon S CR3 conducting, then make secondary coil two end load impedances become very little, reached the purpose that prevents the secondary coil open circuit, the burning voltage of voltage stabilizing didoe is selected for use between 30V-60V.

The utility model is simple and reliable for structure, and is on-the-spot easy to use, easy to utilize, solved the problem that present ubiquitous secondary loop of mutual inductor can not be opened a way.

Claims

1, a kind of open-circuit protector for secondary loop of mutual inductor is characterized in that, at Current Transformer Secondary coil two ends electronic AC switch that has voltage checker in parallel.

2, open-circuit protector for secondary loop of mutual inductor according to claim 1 is characterized in that, is connected with control utmost point G with anode A as the bidirectional triode thyristor of electronic AC switch as two ends of the bidirectional trigger diode of voltage checker.

3, open-circuit protector for secondary loop of mutual inductor according to claim 1; it is characterized in that; by single-phase silicon-controlled with by the D1-D4 diode electronic AC switch that is formed by connecting, as the anode of the bidirectional trigger diode of voltage checker and one-way SCR with control the utmost point and be connected.

According to the open-circuit protector for secondary loop of mutual inductor of claim 1, it is characterized in that 4, by two one-way SCRs oppositely and be connected into electronic AC switch, voltage is declared device and is made up of two bidirectional trigger diodes.