CN1617408A

CN1617408A - Device for preventing secondary loop open circuit of mutual inductor

Info

Publication number: CN1617408A
Application number: CN 200310110012
Authority: CN
Inventors: 王选文
Original assignee: HUARUI POWER AUTOMATION EQUIPMENT CO Ltd CHANGCHUN
Current assignee: HUARUI POWER AUTOMATION EQUIPMENT CO Ltd CHANGCHUN
Priority date: 2003-11-12
Filing date: 2003-11-12
Publication date: 2005-05-18

Abstract

This invention relates to a device for preventing secondary circuit open-circuit of mutual inductor used in a protection device of automatically making short-circuit secondary loop when the mutual inductor loads open-circuit at the secondary side in power system, which parallels an AC electronic switch with a voltage discriminator at either end of the inductor secondary coil formed by connecting a two-way or single-way thyristor with a diode bridge circuit or by two single-way thyristor in parallel reversely, a trigger diode or a Zener diode is used in the discriminator.

Description

Prevent the device of transformer secondary circuit open circuit

Technical field:

The present invention relates to a kind of device that prevents the transformer secondary circuit open circuit, especially for the protective device of the energy automatic short-circuit current transformer secondary circuit when secondary is surveyed load open circuit of the current transformer CT in the power system operation.

Background technology:

Be used for the electric power system current transformer at present, its primary winding is connected in the test line, and 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 owing to serial connection in 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 highly saturated bearing; 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, even influence the normal operation of electrical network, in addition at secondary circuit; remanent magnetism in the iron core also can influence the service precision of current transformer; so it is the open circuit that should guarantee to cause secondary circuit that current transformer is in operation, yet, at present; there is not special protective device, but by tightening the secondary circuit open circuit that measures such as terminal screw prevent instrument transformer.

Summary of the invention:

The object of the present invention is to provide a kind of device that prevents the transformer secondary circuit open circuit, in case with regard to the device in energy automatic short-circuit instrument transformer secondary coil loop, operating current transformer can not opened a way owing to a variety of causes does not cause secondary circuit when the secondary circuit both end voltage arrives certain value.

Of the present invention be achieved in that employing at the 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 present invention is simple and reliable for structure, and is on-the-spot easy to use, easy to utilize, solved the problem that open circuit takes place present ubiquitous secondary loop of mutual inductor.

Description of drawings:

Fig. 1 is an electrical schematic diagram of the present invention;

Embodiment:

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 ZCTS1 of voltage checker.The CT secondary coil two end load impedances that are in operate as normal are very little. so both end voltage is very low; when certain reason makes secondary circuit; load this moment infinity; two terminal voltages are very high; because the bidirectional triode thyristor as electronic AC switch is attempted by CT secondary coil two ends; therefore; be added with high pressure between the anode of this bidirectional triode thyristor and the control utmost point; just the bidirectional trigger diode wave height is pressed triggering and conducting; the bidirectional triode thyristor conducting that also is triggered like this. ending until alternating current zero crossing, more than is positive half cycle situation, when ac signal is negative half period; repeat said process too. also be; in case the secondary circuit of CT open circuit, 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 CT is generally less than or equals 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, only when the CT secondary circuit is opened a way, 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, be generally about 1-1.5V, power consumption is within 10W, based on above-mentioned principle, CT secondary coil two terminal voltage maximums are no more than the trigger voltage of bidirectional trigger diode, the equipment and the person all there is not influence, when the CT 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 CT secondary coil two ends is bordering on infinity, and the loop is not had influence, does not influence in the loop and measure and control precision, bidirectional triode thyristor is selected for use withstand voltage greater than 100V, electric current is greater than the specification of 5A, and installs radiator additional, and 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, as the anode of the bidirectional trigger diode 2CTS2 of voltage checker and one-way SCR with control the utmost point and be connected, its operation principle is described below.During current transformer CT operate as normal; CT 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; the high pressure that be added on the bidirectional trigger diode this moment makes its conducting; thereby trigger the one-way SCR conducting, the load impedance of CT secondary coil two ends is still diminished, reach 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 ZCTS3,2CTS4 or form by two steady district pipes, 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.

Claims

1, a kind of device that prevents the transformer secondary circuit open circuit, it is characterized in that at Current Transformer Secondary coil two ends electronic AC switch that has voltage checker in parallel, two ends of the bidirectional trigger diode of voltage checker with as the anode A of the bidirectional triode thyristor of electronic AC switch with control utmost point G and be connected;

2, the device that prevents the transformer secondary circuit open circuit as claimed in claim 1, it is characterized in that by single-phase silicon-controlled with by the DI-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;

3, the device that prevents transformer secondary circuit open circuit as claimed in claim 1 is characterized in that 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.