CN1010154B - Protection circuit for predetecting short-circuit by carrier-frequency signal - Google Patents

Abstract

The present invention relates to is a protection circuit for a carrier frequency preview short circuit, which is mainly composed of an oscillator, a detecting loop, an identifying loop, a locking loop, an automatic detection circuit and an electric switching-on circuit, wherein the oscillator can generate carrier frequency signals before power is transmitted, and the signals are transmitted to an electric network as a detection signal source of impedance; whether a short circuit is generated can be judged by detecting the change of the impedance by detecting the network electric network. When the electric network generates a short circuit, input impedance is largely reduced. The circuit is locked by the locking loop, and power can be transmitted until a short circuit spot is relieved. When a line is in a normal state, the electric switching-on circuit can drive a chopper for closing. The circuit has the advantages of long protection distance, high safety and reliability, and is suitable for the short circuit protection of mine power supply networks.

Description

Protection circuit for predetecting short-circuit by carrier-frequency signal

The present invention is a kind of circuit that does not have electric carrier frequency preliminary examination short-circuit protection aspect about the Alternating Current Power Supply networking.

For mine and contain power supply network in the explosion gas environment, the short trouble of cable causes very big threat to safety.At present; though many short-circuit protection methods occurred; its effect and the reliability part that still has some deficits; can not satisfy the needs of power supply safety; a kind of phase sensitive short circuit protection circuit that provides as british patent document GB2065394; distinguish according to the phase place of short circuit current and electric motor starting electric current is different, then short circuit line is carried out disjunction.Its shortcoming is that break-time is long, causes the temperature of short dot to rise and generation naked light accident thus.Can cause short trouble not eliminate in addition and secondary send the electricity danger.The ZB12-II type flame proof coal drill transformer integrated protection device that provides of " the electric coal borer integrated protection " the 74th page published of Coal Industry Press and for example, this is high-frequency signal to be sent into electrical network do the signal that detects impedance, judges the networking state according to impedance variation.When the networking was short-circuited, input impedance descended, and executive circuit is received short-circuit signal, prescinds power supply.The shortcoming of this protective circuit is: adopt high-frequency generator, export 25 khz frequencies, this high-frequency signal is input to the power supply network of long distance and does the signal that detects impedance, then can produce reflected wave on the line, and it is unclear that the networking state is differentiated, and promptly resolution ratio is very low.Therefore this short-circuit protection circuit only is applicable to the protection less than 300 meters electric coal borer supply line of 127 volts of voltages, circuit.

The objective of the invention is to overcome shortcoming of the prior art, and propose the short-circuit protection of the power supply network of various different voltages in a kind of suitable mine, the short-circuit protection distance detects short trouble automatic blocking, and the networking just often can be delivered automatically.

Task of the present invention is finished by following scheme:

By oscillator 1, detect loop 2, differentiate loop 3, self-locking circuit 4, automatically deliver loop 5 and power transformer 6 compositions, it is characterized in that described oscillator 1, form the parallel oscillation tank circuit by inductance coil L1 and capacitor C 1, the centre tap of L1 connects the collector electrode of amplifier tube BG1, positive feedback coil L2 one termination BG1 base stage, another termination dividing potential drop electricity group R1, the mid point of R2, by the excitation power supply of BG1 amplification as tank, high-frequency bypass capacitor C2 is in parallel with resistance R 2, autobias circuit R3, C3 also connects back one termination BG1 emitter, other end connecting to neutral, the two ends of inductance coil L3 meet isolated component C4 respectively, R4 is as the oscillation power output, and its output frequency is 0.1～8 kilo hertz.

Advantage of the present invention has:

1, detection range is extensive, is applicable to different low-voltage power supply networkings.

2, detect distance, can satisfy the needs at mine power supply networking.

3, safe and reliable, because be the detection carried out under the electroless state before sending electricity, simultaneously latching circuit is arranged again, as long as short dot is arranged, the circuit breaker on the main line just can't closure, has avoided the danger of forced power transmission.

4, can realize delivering automatically.

Accompanying drawing 1 is carrier frequency preliminary examination circuit theory diagrams of the present invention.

Accompanying drawing 2 is automatic delivery circuit theory diagrams of the present invention.

Oscillator 5 is formed the parallel oscillation tank circuit by inductance coil L1 and capacitor C 1, the centre tap of L1 connects the collector electrode of amplifier tube G1, positive feedback coil L2 one termination BG1 base stage, another termination divider resistance R1, the mid point of R2, by the excitation power supply of BG1 amplification as tank, high-frequency bypass capacitor C2 is in parallel with R2, autobias circuit R3, C3 also connects back one termination BG1 emitter, other end connecting to neutral, the two ends of inductance coil L3 meet isolated component R4 respectively, C4, as the oscillation power output, to the sinusoidal ac signal that detects 0.1～8 kilo hertz of any respective frequencies of loop output.

Form by inductance coil L3, L4, L6 and load resistance R4, capacitor C 4, C5, C6, C7, C8 and to detect loop 2, detection of grid impedance, amplitude, electrical network just often, the impedance height; During the networking phase fault, impedance is low.This loop is equivalent to L4 or the L6 Low ESR short circuit after by short circuit, and the secondary voltage of T1, T2 reduces greatly.A ' in the circuit, B ', 3 three contacts by intermediate relay ZJ of C ' are connected with three of main line respectively.

Discriminating loop 3 is made up of comparator Ic1, Ic2, voltage-stabiliser tube DW1, DW2, potentiometer W1, W2, diode D1, D2, resistance R 5, R6, capacitor C 9, C10, inductance coil L5, L7.When the networking does not have short trouble, detect loop output sinusoidal signal, through D1, D2 detection, Ic1, Ic2 positive input obtain high potential, because this signal is higher than the signal of adjusting that W1, W2 provide, then Ic1, Ic2 export high potential.

When there was phase fault at the networking, as A, B line to line fault, then L4 was by short circuit, and L5 exports reduction, and Ic1 positive applied signal voltage is lower than reverse inter-input-ing voltage, and Ic1 exports electronegative potential, and transistor base gets electronegative potential to be ended.

Self-locking circuit 4, form by comparator Ic3, diode D4, D5 and resistance R 7, R9, R10, capacitor C 11, C12, when any line to line fault in networking, Ic1 or Ic2 will export electronegative potential, clamp down at electronegative potential with door by diode D3 and resistance R 8 are that form, the latching circuit that diode D4 and comparator Ic3 form pins its electronegative potential, disconnect up to power transformer switch GK, could be with its self-locking releasing.Resistance R ₇, R ₉, capacitor C ₁₁It is to prevent that latching circuit is in the misoperation of moment of GK switch combined floodgate that charge circuit mainly acts on.

Automatically deliver loop 5 and be made up of three grades of timing circuits, first order element has Ic5, C17, R13, R14, R16, R17, D9; Second level element has Ic6, C18, J2, D10, R18, R19; Third level element has comparator Ic7; C19; R22; R23; D11; R13; C17 and R17; R18; C18 and R22; C19 is that time delay process is connected on each comparator input terminal respectively; divider resistance R14; the R5 series connection point meets Ic5; Ic6 normal phase input end and Ic7 inverting input; as the benchmark current potential; R19; D10 and R23; D11 is a capacitor C 18; the discharge loop of C19; a termination capacitor positive pole after connecting separately; another termination Ic5; the output of Ic6; D10; the D11 anode connects capacitance cathode; Ic5; the Ic6 output respectively through R17 and J2 coil be connected to+24 volts of power supplys on; its contact J2-1 is serially connected in the ZJ wire loop; the Ic5 inverting input connects 101 AND circuit, Ic7 output termination 102 protective circuit output stages.

Power transformer 6 is oscillators, delivers the power supply that loop and circuit breaker ZDJ provide different voltages automatically, and the primary side of transformer 6 is connected with the main line mains side by switch GK.

When the GK closure, power transformer 6 has electricity, 27 volts of interchanges through QL ₃24 volts of rectification, integrated voltage stabilizer Ic4 voltage stabilizing, output direct currents are supplied with oscillator loop, discriminating loop, are delivered ring current QL automatically ₂Export 18 volts of direct currents and supply with the J1 relay; Exchange 151 volts of pull-in winding ZDL that supply with vacuum circuit-breaker through the normally closed auxiliary contact of ZDL1, after the QL1 rectification as closing a floodgate with, ZDL adhesive, it is often opened auxiliary contact ZDL2 closure, the power supply of QL1 is changed to 24 volts, the normal phase adhesive of confession ZDL.ZDL and ZJ relay two normally closed contact ZDL3 and ZJ1 control an adhesive, then another disconnection each other.

Behind 24 volts of direct voltages of integrated voltage stabilizer Ic4 output, its positive pole charges to C17 by R13, comparator Ic5 output high potential charges to C18 between charge period, Ic6 output high potential between charge period, when the reverse input end of Ic6 was higher than positive input, Ic6 exported electronegative potential, relay J 2 adhesives, the J2-1 contact is connected ZJ relay coil, the adhesive of ZJ contact, detects the loop and drops into the networking detection.

There is not short trouble when detecting the networking, in case R13 is to the end of C17 charging process, when the Ic5 reverse input end is raised to greater than the positive input signal, Ic5 exports electronegative potential, and Ic6 exports high potential, and J2 discharges, ZJ discharges, and the high potential of Ic6 output charges to C19 through R22, makes Ic7 output electronegative potential.When the anodal current potential of C19 is charged to when being higher than Ic7 inverting input current potential, Ic7 could export high potential, and the electronegative potential of triode BG2 base stage blocks, and could remove, and BG2 could get high potential and saturation conduction, and relay J 1 ability adhesive begins to send to the networking.

When alternating signal transmits on remote limited non uniform transmission line, the reflected wave that produces on the circuit has a strong impact on line input impedance, make the impedance of short circuit and normal condition differentiate unclear, in order to improve the impedance magnitude resolution ratio of short circuit and normal condition, must avoid the standing wave influence that forms by reflected wave.

Networking normal relevant with the frequency of short-circuit condition resolution ratio and oscillator, relevant with Route Length.

A total cable length is the power supply network of 1972 meters of 2661 meters power supply maximum distances, wherein: 416 meters on 375 meters, 25 square centimeters cables of 35 square centimeters of cables, 689 meters on 1147 meters, 6 square centimeters cables of 10 square centimeters of cables.25 of QC83-80 type magnetic switchs are arranged in this electrical network; 2.5KVA 10 of dry-type transformers, 7 of QC81-60 starters.

The induction coil T of oscillator ₁The magnetic induction amount be that the frequency of oscillation of 14 milihenries, oscillator is 3KC, at this moment, the normal condition impedance of electrical network is 85 Europe; The impedance of short-circuit condition is 5.1 Europe, and resolution ratio is 17.(resolution ratio greater than 1.8 can offer a clear explanation line status)

Claims (2)

1; a kind of protection circuit for predetecting short-circuit by carrier-frequency signal; comprise oscillator 1; detect loop 2; differentiate loop 3; self-locking circuit 4; automatically deliver loop 5 and power transformer 6; it is characterized in that described oscillator 1; form the parallel oscillation tank circuit by inductance coil L1 and capacitor C 1; the centre tap of L1 connects the collector electrode of amplifier tube BG1; positive feedback coil L2 one termination BG1 base stage; another termination dividing potential drop electricity group R1; the mid point of R2; by the excitation power supply of BG1 amplification as tank; high-frequency bypass capacitor C2 is in parallel with electricity group R2; autobias circuit R3; C3 also connects back one termination BG1 emitter; other end connecting to neutral; the two ends of inductance coil L3 meet isolated component C4 respectively; R4 is as the oscillation power output, and its output frequency is 0.1～8 kilo hertz.

2; protection circuit for predetecting short-circuit by carrier-frequency signal according to claim 1; it is characterized in that described automatic delivery loop 5 is made up of three grades of timing circuits; first order element has Ic5; C17; R13; R14; R16; R17 and D9; second level element has Ic6; C18; J2; D10; R18; R19; third level element has Ic7; C19; R22; R23; D11; R13; C17 and R17; R18; C18 and R22; C19 is three grades of time delay processes; receive each comparator input terminal respectively; divide piezoelectricity group R14; the R5 series connection point meets Ic5; Ic6 normal phase input end and Ic7 inverting input; reference potential as a comparison; R19; D10 and R23; D11 is a capacitor C 18; the discharge loop of C19; a termination capacitor positive pole after connecting separately; another termination Ic5; the output of Ic6; D10; the anode of D11 connects capacitance cathode; Ic5; the Ic6 output respectively through R17 and J2 coil be connected to+24 volts of power supplys on; its contact J2-1 is serially connected in the ZJ wire loop; the inverting input of Ic5 connects 101 AND circuit, the output termination 102 protective circuit output stages of Ic7.