CN201181321Y - Earthing detection circuit of locomotive control circuit - Google Patents

Abstract

The utility model discloses a grounding detection circuit of a locomotive control loop, which comprises a positive bus, a negative bus, a load resistor and line-to-ground insulating resistors of the positive bus and the negative bus. Two detection branch circuits are respectively connected between the positive bus and the ground and between the negative bus and the ground, wherein one branch circuit is formed by connecting the known resistors and the other branch circuit is formed by connecting in series the known resistors and a switch. The grounding detection circuit determines the presence of the grounding fault in the locomotive control loop by detecting the insulating resistance of line-to-ground insulating resistors of the positive bus and the negative bus, overcomes the problems of the conventional method, realizes the early alarm of the grounding fault, eliminates the potential safety hazard of the grounding fault to the normal operation of the locomotive, and increases the service efficiency of the locomotive.

Description

The grounded inspection circuit of locomotive control loop

Technical field

The utility model relates to the grounding monitor circuit of locomotive control loop.

Background technology

Locomotive 110V direct supply is the working power of locomotive control unit, signal and communication system, relay protection loop and other aut.eq..Because the locomotive operation environment is abominable; the insulation damages of 110V electrical equipment or lead usually can cause the earth fault of circuit; though the single-point grounding fault can not exert an influence to the operation of locomotive; but during as if the multipoint earthing fault more than appearance two places or two places; circuit may produce short circuit and scaling loss equipment and lead, thereby has a strong impact on the security and the reliability of the normal operation of locomotive.Therefore the research to locomotive D.C. isolation monitoring method seems very important.

At present, the control loop earthing protecting method of using on locomotive mainly contains two kinds:

1. the control loop earthing protecting method on the DC locomotive

DC locomotive control loop ground protection principle as shown in Figure 1, L+ and L-are the both positive and negative polarity of control loop, R _LBe the pull-up resistor of control loop, Q is the ground connection automatic switch, and R is the ground connection current-limiting resistance, and K is a grounding relay, and the control loop L-utmost point is by the parallel circuit ground connection of Q, R and K.When L+ utmost point ground connection, the control loop both positive and negative polarity is by the Q short circuit, and because of the action current value of Q is very little, so automatic switch Q moves disconnection immediately, the control loop power supply acts directly on R _L, on R and the K, K inhales and action, and chain output ground fault signal is to locomotive control, the generation alerting signal.The R limiting short-circuit current is kept locomotive and is operated with failure.Widespread use on the DC locomotives such as present this ground protection mode changes at SS4, SS4B.

This method is simple; do not need too many components and parts; but there is obvious defects in this method: if certain point has also taken place by ground connection on the L-negative pole; this ground protection mode lost efficacy; L+ and L-direct short-circuit; cause the locomotive DC control system to work, the electrical equipment on the severe patient possibility scaling loss control loop.

2. bridge method

The principle that electric bridge method detects locomotive control loop earth fault is: two resistance with direct current both positive and negative polarity insulation against ground resistance and setting are arbitrarily formed electric bridge, wherein insulation resistance is a physical quantity of weighing medium insulating property quality, be used for herein, the negative pole insulation degree over the ground of promptly making a comment or criticism, it is numerically equal to the resistance value that medium has.System just often, bridge balance.When control loop some ground connection was taken place, the electric bridge out of trim produced alerting signal.Used this earthing protecting method on the locomotives such as China Star, Olympic star, Ha Che and Lan Jian at present.

This method is simple, but has obvious defects:

1. when the both positive and negative polarity insulation resistance is impartial descend or numerical value near the time, even surpassed alarm limit, this method can't detect earth fault;

2. when both positive and negative polarity insulation against ground resistance value all in normal range, but when differing greatly, this method can produce false alarm.

The utility model content

Defective at above-mentioned prior art existence, the utility model aims to provide a kind of grounding detection circuit for locomotive control loop based on unbalanced electric bridge, can real time on-line monitoring DC power system positive and negative busbar insulation resistance over the ground, eliminate the potential safety hazard that earth fault is brought to locomotive operation.

For achieving the above object, the technical solution adopted in the utility model is, a kind of grounding detection circuit for locomotive control loop, comprise positive bus-bar, negative busbar, pull-up resistor and positive and negative bus insulation resistance over the ground, all be connected with two detection branch between described positive and negative bus and the ground, article one, be made of known resistance, another is made of known resistance and change-over switch series connection.

In sum, the utility model provides grounding detection circuit for locomotive control loop to judge the earth fault that locomotive control loop exists by detecting positive and negative busbar insulation resistance size over the ground, overcome the deficiency of classic method, earth fault is reported to the police in advance, eliminate earth fault and give the locomotive potential safety hazard that normal operation brings, improve the normal service efficiency of locomotive.

Below in conjunction with drawings and Examples principle of work of the present utility model is described in detail:

Description of drawings:

Fig. 1 is existing DC locomotive control loop ground protection circuit theory diagrams;

Fig. 2 is a grounded inspection circuit schematic diagram described in the utility model.

Embodiment:

With reference to Fig. 2, L+ and L-are the positive and negative busbar of locomotive control loop,

Be ground terminal, RP and RN are respectively positive and negative busbar insulation resistance over the ground to be measured, and RC1, RC2, RC3 and RC4 are the precision resistance of measuring known resistance, and RC5 is load, and S1 and S2 are change-over switch.

If the line voltage of control loop is U, RP//RC3 is Rcp, and RN//RC4 is Rcn (" // " expression two resistance parallel connections), and Rcp, Rcn voltage-to-ground are respectively Ucp, Ucn.Wherein the size of Ucp and Ucn can get it by the voltage of gathering Rc3 and Rc4 two ends respectively.

When switch S 1, when S2 all disconnected, measure R C3 and RC4 both end voltage were Ucp0 and Ucn0, and as seen from the figure, Ucp0 that is surveyed and Ucn0 are respectively the voltage between this moment positive and negative busbar and ground, can get thus:

$\frac{\mathrm{Ucp}0}{\mathrm{Rcp}}=\frac{\mathrm{Ucn}0}{\mathrm{Rcn}}---\left(1\right)$

When switch S 1 closure, when S2 disconnects, then between positive bus-bar and ground, added a measuring resistance RC1, the voltage at measurement RC3 this moment and RC4 two ends, the voltage that obtains between positive and negative busbar and the ground is respectively Ucp1 and Ucn1, can get thus:

$\frac{\mathrm{Ucp}1}{\mathrm{Rcp}}+\frac{\mathrm{Ucp}1}{\mathrm{Rc}1}=\frac{\mathrm{Ucn}1}{\mathrm{Rcn}}---\left(2\right)$

Can obtain by (1) formula and the associating of (2) formula:

$\mathrm{Rcp}=\mathrm{RC}1(\frac{\mathrm{Ucp}0\·\mathrm{Ucn}1}{\mathrm{Ucp}1\·\mathrm{Ucn}0}-1)$

$\mathrm{Rcn}=\mathrm{RC}1\left(\frac{\mathrm{Ucp}0\·\mathrm{Ucn}1-\mathrm{Ucn}0\·\mathrm{Ucp}1}{\mathrm{Ucp}0\·\mathrm{Ucp}1}\right)$

Calculate the value of Rcp and Rcn by last two formulas,, therefore can calculate control loop positive and negative busbar insulation resistance Rp and Rn over the ground by the resistance principle of parallel because the resistance value of RC3 and RC4 is known.

When the Rp value of calculating gained during less than setting value, there is earth fault in system's judgement locomotive control loop positive pole;

When the Rn value of calculating gained during less than setting value, there is earth fault in system's judgement locomotive control loop negative pole.

By schematic diagram as can be known, below in two kinds of situations, also can be by above-mentioned deduction method controlled loop positive and negative busbar insulation resistance over the ground:

1. S1 and S2 all disconnect; S1 disconnects and the S2 closure;

2. the closed and S2 disconnection of S1; S1 disconnects and the S2 closure.

Further, based on above-mentioned observation circuit, the judgement of can also breaking the steps include:

The voltage that load RC5 upward gathers among the setting figure is U1 (line voltage); The voltage of the last collection of RC4 is U2.U1 and U2 are compared:

If 1. U1 is 0, judge at first that then L-disconnects;

2. when U1＞0V, under the normal condition, as seen from the figure, U1 is certainly greater than U2; If L+ disconnects, RC4 is equivalent to and RC3, the parallel connection of RC5 series circuit, U2＞U1 will occur, so when U2＞U1＞0V, can judge the L+ disconnection;

3. when U1＞0V, under the normal condition, the closed S2 of S1 disconnects; S1 disconnects the S2 closure, and both of these case causes detecting the voltage difference twice of U2 owing to the variation of resistance down, but works as

During disconnection, then can cause U2 voltage under the different situation of two kinds of resistances identical,, then judge so detect voltage not simultaneously when twice of U2

Disconnect.

Claims (1)

1, a kind of grounding detection circuit for locomotive control loop comprises positive bus-bar, negative busbar, pull-up resistor and positive and negative bus insulation resistance over the ground, it is characterized in that, all is connected with two detection branch between described positive and negative bus and the ground, and one is made of known resistance; Another is made of known resistance and change-over switch series connection.

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