DE2519579A1 - Anti-arcing control for electric train pickup - has current monitoring control on primary current converter - Google Patents

Abstract

The electric traction vehicle with overhead power supply has a current monitoring system in the high voltage input side of the transformer. The primary transformer current operates on threshold level switches which are coupled to solid stage control circuits. These operate the protection loops which prevent damage to the drive system if the pick-up contacts start to lift off the conductors e.g. at high speed. The system is more responsive than relay protection in the secondary circuits of the transformer.

Description

Device for the rapid detection of pantograph jumps The invention relates to a device for the rapid detection of pantograph jumps in electrical Propulsion vehicles with the help of the measurement of the primary current consumed by the vehicle.

In the case of electric traction vehicles, their energy via pantographs received from a contact line (or busbar), especially with larger ones Travel speeds pantograph jumps occur. Under such a jump one does not understand a mere lifting of the pantograph from the contact line where the power supply is maintained via an electric arc; the arc voltage drop is usually negligible compared to the contact line voltage.

One speaks of a pantograph jump only when if the connection between the contact line and the moving locomotive is interrupted. After the pantograph has been reconnected to the contact line, switch-on processes occur that the electrical equipment - i.e. machines, especially the traction motors, as well as apparatus - endanger the vehicle and lead to damage. this applies particularly to vehicles with a recuperation brake. The duration of the jumps is normally so short (approx. 30 ms - 1 half-wave at 16 2/3 Hz to approx. 1s) that the zero voltage relay does not drop out due to its time delay.

A quick detection of a pantograph jump for the purpose of initiation of measures to avert a risk to electrical equipment when it is re-installed the pantograph therefore appears to be desirable.

As previous practice has shown, voltage measurement can be used Do not clearly detect the jump between pantograph and rail. In the case of test railcars, with a thyristor AC power controller in the field circuit of the brake motors in the Recuperation circuit was equipped to record the jumps Parallel resonant circuit used.

This is matched to the mains frequency 16 2/3 Hz and is used with fed by an auxiliary operating voltage from the transformer.

In normal operation, this resonant circuit takes to cover his losses a little stream. In the event of sudden changes in tension, such as those when jumping off arise, a larger equalizing current occurs, which signals a jump. A higher harmonic content in the contact line voltage has a disadvantageous effect, so that jumps are incorrectly reported. A high harmonic content arises in particular from commutation notches in power converter traction vehicles.

After a pantograph jump, the vehicle can be on the drive during a few tenths of a second or even longer a residual voltage remains, so that the detection of the zero voltage is not reliable. This residual stress can originate from the recuperation circuit and e.g. aperiodic (decaying direct voltage element) or decay as a dampened oscillation. The residual stress then continues to run a damped oscillation if the traction vehicle transformer is only asynchronous feeds (e.g. transformer oil pump).

After all of this, the above-mentioned devices were able to record the pantograph jumps do not fully satisfy.

The invention is based on the disadvantages of the known Avoiding arrangements. This is achieved in that in the case of the aforementioned Device that detects the jump by measuring what is recorded by the vehicle Primary current by measuring the current with the primary current transformer, which is on the high voltage side the transformer primary winding is located, and that for the detection of the jump accordingly a zero value of the primary current a threshold device is provided whose The response threshold is made dependent on the value of the current before the jump has flowed through the primary winding of the current transformer.

The invention will now be explained in more detail with reference to FIGS. First of all, it should be noted that the vehicle to be detected when operating a traction unit Primary current moves within very wide limits; the primary current can reach the maximum Reach twice the nominal current of the vehicle transformer, the smallest value is the Transformer no-load current at undervoltage.

In view of such a large area of zero current detection via current transformers, it is necessary to explain the static and transient behavior of these transformers in somewhat more detail. ) For the current transformers used for measuring purposes, the error limits are defined in the various accuracy classes. The details of the error limits contain the maximum permissible current errors (f in%) and incorrect angles (oPin angular minutes). For current measurements, only the current errors are of interest, the error angles only have an influence on power measurements. The table below shows the current error limits assigned to each class depending on the primary rated current IN. Class current error + f in 96 at 1.2 IN l, o IN 0.5IN o, 2 IN o, l 1N o, lo, lo, lo, 16 o, 2 o, 25 o, 2 o, 2 o, 2 o, 29 o, 35 o, 5 o, 5 o, 5 o, 5 0.66 o, 75 l, o 1 l, ol, o - 1.5 2.0 3 3.0 3, o 3, o - - In Fig. 1 the current transformer error limits for the various accuracy classes (0.1 to 3) are shown graphically. These error limits apply at nominal frequency and for loads between the nominal load and a quarter of the nominal load with a load power factor cos p = 0.8, for class 3 between 0.5 and 1 times the nominal load (8 is again the current error in%, tN the primary nominal current ).

On traction vehicles, the rated current of the primary current transformer is in usually above the primary rated current of the transformer. There the Transformer no-load current is relatively small, result on the transformer secondary side theoretically very small current values. In practice they are even smaller because the Primary currents are below 0.1 IN of the current transformer and larger in this area negative current errors can occur.

To explain the origin of the current error in the converters and the Figures 2a to 2c (a) serve to influence the transient behavior Connection scheme, b) the substitute scheme and c) a vector diagram). For the replacement scheme of the current transformer, the transformer replacement scheme can be in a somewhat simplified form be applied. As can be seen from the vector diagram, the current error will be ß I caused by the no-load current 1o of the current transformer (the vector diagram is not a measure).

If the primary current I1 is now zero in the event of a pantograph jump, so this does not usually lead to the current transformer secondary current becoming zero at the same time I2, because the magnetizing current 1µ still decays over the load. Because in general the current 1Fe of the iron losses is less than I µ / u and thus Io (no-load current) I µ is, the secondary current 12 ru -I after the switch-off / u. This magnetizing current is approx. 0.1 to several% of the translated current and depends on the used Core material, the design of the current transformer as well as from the connected Burden. The decay of this residual magnetization current (direct current) takes place with a time constant (T = L / R) from a few tenths of a second to a few seconds.

The reference symbols still missing in the legend to FIG. 2 are: II Primary current, converted on the secondary side U2 Secondary voltage Z Load AI Current error or Error angle g Load angle When measuring and monitoring currents by means of Electronic devices are usually still small for electrical isolation Intermediate current transformers are used, which are connected on the primary side by the main current transformer (secondary 5A) and their secondary side transfers the current to one for the electronics appropriate smaller value translated. These intermediate current transformers behave analogously the main current transformer, although the no-load currents and thus also the current error are relatively larger. By connecting the main and intermediate current transformers in series The magnetizing currents add up after the primary current has been switched off about the on the Secondary side of the intermediate current transformer connected Burden flow. It is advisable to use an intermediate current transformer for the pantograph jump-off device to be used with a lower no-load current.

For example, toroidal cores with highly permeable silicon iron alloys can be used or nickel iron alloys can be used, which have a large induction range have a high permeability.

As already noted, is in terms of the behavior of the current transformer the detection of the jump is required by a threshold device whose The response threshold depends on the value of the current that passed through the primary winding of the current transformer before the jump has flowed. This response threshold must take into account the parallel to Load switched no-load impedances of the main and the intermediate current transformer as well as the intended current range (guide value approx. 5 ... 30 %).

The burden of the intermediate current transformer is achieved via a rectifier arrangement fed, the approximately constant rectifier voltage drop occurs with small currents noticeable (resulting load impedance increases), so that the magnetizing current increases sharply. With small currents, the current transformer becomes an inductive one Shunt, since Io> I2 (Fig. 2). With such an arrangement no larger current range can be achieved.

For this reason, in the circuit of the jump device according to Fig. 3 to an ohmic resistor 1 (fed via an intermediate current transformer 2) a AC voltage proportional to the current obtained and a logarithmic amplifier 3 supplied. The logarithmic characteristic is achieved by means of 2 Zener diodes 4 (es a special log amplifier could also be used) via a diode bridge 5 are fed.

In parallel, there is a high-resistance resistor 6 to limit the Gain for small currents I1.

This facilitates the zero point adjustment of 3 and the oscillation avoided at 11: 0. The output voltage UlOg of the logarithmic amplifier 3 is in the range of I1 = 10 mA .... 1ob proportional to log I1, in the range of 11 = 1 ... 10 mA approximately proportional to log I1 (11 is, as can be seen, the primary current of the intermediate current transformer 2).

The logarithmic voltage is rectified (bridge 7 in Fig. 3) and after deducting a constant voltage (forward voltage drop across the diodes 8 and 9) a reference value (at the RC element 10, 11) is formed, which now represents the threshold value.

In the following, operated as a comparator amplifier 16 is the Instantaneous value of Ulog compared with the threshold value.

The voltage U3 is obtained as a digital signal at the output of 16. This is positive (e.g. U3 = + 10 .... 12V) at I1D, O (Instantaneous value of 11 greater than the threshold value) and negative (e.g. U3 = - 10 .... 12V) at IlrV0 (Instantaneous value of 1 less than 3 1 1 than the threshold value). Via a small time delay element 12,13,14,15 the output signal U4 is obtained. During normal operation of the vehicle, i.e. if the pantograph is in contact with the contact wire, U4S is 0, if the pantograph jumps off becomes Um0. This signal is used to control a thyristor actuator and thus used to protect endangered equipment parts (e.g. traction motors, apparatus).

In order to test the proposed device, pantograph jumps were made arbitrarily simulated; the magnetizing current of the intermediate current transformer sounds approximately exponentially from (: L, which in U has a linear decrease in function R), log of time. If the interruption of 11 occurs at its maximum value, where the instantaneous value of the magnetizing current I µ is small, then UlOg is also small. With every zero crossing) U log of I1, the output voltage U3 becomes negative for a short time, while the output variable (jump signal) U4 at the normal zero crossings from I1 positive, with a jump after approx. 10 ms (Y6 a period of 16 2/3 Hz) becomes negative.

Fig. 4 shows the short-term negative of the output voltage U3 at each zero crossing of the primary current I1. If the alternating current I1 - as shown in the figure - is sinusoidal, the threshold value x can be determined by measuring this short 11 zero time11 t according to the following relationship: In a circuit according to FIG. 3, there is a considerable area in which the threshold value x is constant. Outside this range, the transmission behavior of the circuit deviates from the logarithmic curve, which is expressed by changing the threshold value.

So that with the normal zero crossings of the current II, there is still no jump-off signal is output, the already mentioned delay element must be at the output of the circuit 12,13,14,15 are provided. The jump signal U4 in the present circuit becomes negative approx. 10 ms after the power interruption.

In order to get to the ones provided on the locomotive as quickly as possible after a jump Initiate protective measures (e.g. peeling), this delay time should be as short as possible. This requires a relatively low threshold value x. on the other hand opposed to this is the decaying residual magnetization current.

For the intermediate current transformer 2 used in the circuit the no-load current is measured and recorded as a function of the current transmitted (Fig. 5). As a possible combination became that of the main current transformer H with two different loads Z1 and Z2 with the intermediate current transformer ZSW, the corresponds to the mentioned intermediate current transformer 2 (IN is the secondary current of the main current transformer H or the primary current II in the intermediate current transformer 2, see Fig. 3). By drawing in the threshold value curve S of the jump device can be the current range for a perfect Determine function. For the combination H (Z1) + intermediate current transformer 2 results E.g. in the illustrated case a current range of 1.3.10 1NbiS2.2 IN IN (range 1: 170).

From this representation it can be seen that with a low threshold value the functional area is reduced. For the use of the jump-off device in the In practice, it is therefore advisable to determine the functional area with regard to the areas to be protected Objects (traction motor or auxiliary power circuits) as well as the intervention options (electronic or electromechanical switching devices) and the threshold value taking into account to determine the intended current transformer. The delay element is then corresponding 12,13,14,15 to adapt.

By changing the number of diodes 8 in the circuit of FIG the threshold value can be gradually adjusted according to the table below: Number Diodes 8 threshold value x O approx. 50% 1 approx. 22% 2 approx. 9 8 3 approx. 4% the The circuit described was made with a view to use with a thyristor AC power controller for the recuperation brake on existing locomotives with 16 2/3 Hz single-phase collector motors developed. However, the device can also be used in power converter traction vehicles.

Claims (6)

Claims Device for the quick detection of pantograph jumps in the case of electrical Traction vehicles with the help of the measurement of the primary current consumed by the vehicle, characterized in that the current measurement is carried out with the primary current transformer, which is on the high voltage side of the transformer primary winding, and that to detect the jump corresponding to a zero value of the primary current a Threshold device is provided, the response threshold of which depends on the value of the current is made dependent on the transformer before jumping through the primary winding has flowed. 2. Apparatus according to claim 1, in which for the purpose of measurement and monitoring of currents by means of electronic devices for galvanic isolation still small, be used on the primary side of the main current transformer fed intermediate current transformers can, characterized in that the response threshold of the threshold device taking into account the no-load impedances of the connected in parallel to the load Main current transformer and - if necessary, the intermediate current transformer and the intended one Current range is determined. 3. Device according to claim 1 or 2 with at least one intermediate current transformer, whose burden is fed via a rectifier arrangement, so that with small Currents make the approximately constant rectifier voltage drop noticeable and the magnetizing current increases sharply, characterized in that for the purpose of achieving a larger current range in the circuit of the jump-off device on an ohmic one Resistance obtained an alternating voltage proportional to the current and a logarithmic one Amplifier is fed. 4. Apparatus according to claim 3, characterized in that the logarithmic Characteristic curve is achieved by means of 2 Zener diodes, which are fed via a diode bridge and that there is a high resistance parallel to it. 5. Apparatus according to claim 3, characterized by the use of a special log amplifier. 6. Apparatus according to claims 3 to 5, characterized by a rectifier arrangement (7, Fig.3), in which the logarithmized voltage (UlOg) is rectified, a Means (8,9) for generating a constant voltage, the ion of the logarithmic Voltage (log) is subtracted, and a RC element (10,11), the The resulting voltage is obtained and forms a reference value that corresponds to that of the primary current represents the threshold value dependent on the current transformer, further characterized by a subsequent comparator amplifier (16) in which the instantaneous value of the logarithmic Voltage U1) is compared with the threshold value, and by a time delay element (12,13,14,15), which converts the output signal (U3) of the comparator amplifier (16) delayed a desired time, so that a signal at the output of the delay element (U4) appears, which is positive in normal operation of the vehicle, in the event of a pantograph jump on the other hand, which signal for resetting a thyristor actuator is negative and thus serves to protect endangered pieces of equipment.