DE19545928A1 - Selective network monitoring system for switchgear - Google Patents

Abstract

The network monitoring system detects the electrical post- arc currents and following the zero current and compares them with a given limiting current value, for operation of a power cut-out switch for the switch appts when the limit current value is exceeded. Pref. the post-arc current is measured after the first zero-crossing of the opened switch pole, with the limiting current value lying within the range of 5 to 15 A. Pref. the operation of cut-out switches (21,22) for parts of the supply system are monitored for operation of a main cut-out switch (2).

Description

The invention relates to a method for selective Network monitoring in switchgear. In addition, the Invention also to carry out the associated arrangement of the procedure.

In power distribution systems is one of the most important in the In the event of accidents occurring in practice, a short circuit in the sub-distribution networks that lead to short-circuit currents, which in general more than an order of magnitude above the nominal currents in the network lie. Such short circuits can not only cause local damage the one that generally arises when a short circuit occurs Arcing lead, but also affect the safety unit and function of the higher-level network. Therefore be Circuit breakers used in sub-distribution networks to in the event of faults in the network, the affected part of the network, d. H. the sub-distribution with related consumers, from separate the remaining area and thus an unimpaired To ensure the function of the overall system. This performance switches have the task of the short-circuit current after only to interrupt a few current half-waves in order to occur To minimize damage and impairments to the network. she generally consist of a fixed and a relatively movable contact, which by mechanical Disconnect the contacts a previously closed current open circle.

In exceptional cases, the lei may fail switch come when, for example, the end of the Lifetime of the switch contacts is reached. In this case a higher-level circuit breaker must have a corresponding major part of the subordinate network from the rest of the network separate. The problem here is the failure of the  orderly circuit breaker with high security and very to be recognized early in order to allow a sufficiently short time delay delay in triggering the higher-level circuit breaker. Especially with vacuum switches when so-called named late failures, d. H. Events where the Circuit breaker first successfully disconnects, but then failed by reigniting an arc, diagnosing the Switching behavior is very important in order to safely switch off solution of the higher-level circuit breaker.

In practice, methods have been used that one Detect short circuit due to the current amplitude in the network and if necessary, a corresponding signal to trigger the Generate higher-level circuit breaker. It must be in generally measured over several current half-wave periods to a sufficiently high signal-to-noise ratio in particular against false triggers. A disadvantage of this The method is that - especially in the event of failure of the under ordered switch - the short-circuit current several half-waves must flow long in order to be recognized with certainty. This measure is necessary to prevent operational overcurrents distinguishable from short circuits. This allows but damage already occurs at the location of the short circuit and the disturbance can spread over large parts of the energy distribution network.

With the US-PS 4 811 154 was already the short early detection by simultaneous analysis of the current rate of increase proposed in addition to the current amplitude. Out etz, Vol. 112 (1991), p. Finally, 718-722 is a procedure for early short-circuit detection using digital Already known algorithms. This is a short circuit early already in the rising part of a half-wave at comparatively low instantaneous current possible. The Failure a circuit breaker is only in combination here nation with evidence of an insufficiently long arc permanently detectable in the counter concerned. Especially with more  pole switching devices must therefore the arc duration in be measured in all poles. A corresponding diagnosis like the early detection of short circuits itself is therefore very much complex and cost-intensive. In particular, late delays sager only recognized when they occurred and therefore at least cannot be predicted.

The object of the invention is therefore a method and propose associated arrangement, which is an improved Selectivity in network monitoring for switchgear enables light.

The task is solved with the following features:

• - Electrical aftercurrents after zero current are recorded,
• - The electrical wake currents are specified with a Limit value compared and
• - If the limit is exceeded, a signal is sent to Triggering of a higher level in the switchgear Circuit breaker generated.

In the associated arrangement, in which the network of a switching plant at least one higher-level circuit breaker and has several subordinate circuit breakers is one Facility in place that has the subordinate performance switches are monitored and, if necessary, the parent Circuit breaker trips. The facility consists of Include condition detection and current measurement units Lich the post-current detection of the circuit breakers on the one hand and from a trigger for the higher-level performance scarf ter.

The solution according to the invention is therefore based on the measurement of Aftercurrents through structural elements of the circuit breakers. This is especially for vacuum switches over the steam screens possible. The height of the wake is a measure of the dielek tric consolidation of a switching tube after success rich shutdown of a short-circuit current at the end of a  Current half-wave. With extensive series of tests be demonstrated that above an experimentally be confirmed, sharply defined limit of the wake after the Zero current crossing even when the scarf is initially successful with high probability with the failure of the affected switching tube must be expected. Against it guarantee a safe separation behavior below this limit accomplishes. The absolute location of this limit depends on the design, is, however, in one for vacuum interrupters Measurements easily accessible range from about 5 to 15A.

When using the invention for vacuum interrupters in particular also a prediction about the time behavior Switching tubes with a screen connected on one side, d. H. at electrical connection between steam screen and one of the two electrodes, even if the switching tube failed only after a few 100 ms due to a late failure.

Further details and advantages of the invention emerge from the following figure description of execution examples based on the drawing. Show it

Fig. 1 is a graphical plot of the maximum aftercurrent specifically applied when opening vacuum switches on the arc duration,

Fig. 2 is a schematic representation of a vacuum switch in which the measurements of Fig. 1 were carried out,

Fig. 3 shows an arrangement for selective network monitoring for a special single-pole circuit breaker and

FIG. 4 shows a modification of the arrangement according to FIG. 3 with a bus system.

A procedure is proposed in which especially with vacuum switches, the current after the first current zero crossing of the opening switching pole measured and analyzed is set to when a preset value is exceeded  Threshold value a signal to trigger the higher-level To produce circuit breakers. So the sub-area of the network with the failing circuit breaker very early early, in the case of late failures it may already be before the actual failure, disconnected from the network will. This is not possible with previous methods security achieved in power distribution networks. Ins special damage and hazards are caused by the in the Be range of the short circuit arcing occurs reduces and consequential costs and emissions, such as noise or Arc products, minimized.

Fig. 1 shows the results of extensive studies. Experimentally measured aftercurrents are shown, which lead to new ignitions or late failures as a function of the arc duration, which is indicated by filled symbols, or the aftercurrents, which were measured when opened correctly without reignitions, which is indicated by open symbols. The magnitude of the aftercurrents is in the range of approximately 5 to 15 A, the measuring times in the range of ms. It can be seen from the illustration in FIG. 1 that there is a limit below which a safe Trennver is guaranteed, while above the limit even if the switch-off has occurred with high probability of failure of the affected switching tube.

The measurements for the representation according to FIG. 1 were carried out specifically on a vacuum interrupter, which is shown schematically in FIG. 2. 1 means the fixed power supply pin and 2 the movable power supply pin, which at its ends carry a fixed contact 11 on the one hand and a movable contact 21 on the other. The contacts are arranged inside the outwardly hermetically sealed switching tube 30 , which consists of a vapor shield 31 , which likewise forms the casing and is connected to the fixed power supply bolt 1 , an insulator 32 and a bellows 33 . Such switching tubes are known in practice with many variations.

In FIG. 3, a transmission system is shown, are protected by an upstream circuit breaker in which a number of sub-distributors or consumers, each inlet by its own subordinate circuit breakers or can be switched off. The superordinate circuit breaker Lei is designated 2, while the two subordinate circuit breakers shown in Fig. 3 have the reference numerals 21 and 22 and the downstream consumers have the reference numerals 31 and 32 .

In the event of a short circuit in one of the sub-distributions, the associated sub-circuit breaker 21 or 22 must open in order to avoid a fault in the other sub-distribution networks. If the corresponding circuit breaker 21 or 22 fails, the higher-level circuit breaker 2 must separate the total amount of the sub-distributions assigned to it from the rest of the network. He receives the necessary trigger signal from a device 5 for selective network monitoring, which is described in detail below.

Referring to FIG. 3 5 comprises the means for selective network monitoring two main parts: a diagnostic portion 6 consisting of a unit 7 voltage to Schalterzustandserken and a unit 8 for current measurement, as well as an off solver 9 with corresponding intelligence to evaluate the diagnostic from the Part 6 information received.

In Fig. 3 the status detection has the task of recognizing the case of open switch contacts. When the contacts are open, a signal is sent to the trigger circuit. The current measurement pursues two goals in particular: First, a successful shutdown must be diagnosed, which can be done in the simplest case by detecting a current zero crossing. On the other hand, it must be recognized whether the aftercurrent flowing after the shutdown has occurred in the corresponding phase is above the critical current limit for the switching tube, beyond which, with high probability, a failure must be expected. If both prerequisites are met, ie if a shutdown has occurred and a too high aftercurrent has occurred, the trigger 9 receives a corresponding signal.

The trigger circuit then outputs a trigger signal to the higher-level circuit breaker when the two on output signals from status detection and current measurement are the same timely. This means that the parent Circuit breakers supplied sub-distributions from the network separated so that the branch with the failing performance switch is de-energized and the short circuit in the area of Sub-distribution not in spite of a failed circuit breaker continues to be supplied with energy.

In Fig. 3, the selective network monitoring is shown only once as a common unit 5 . In fact, each of the lower-level circuit breakers 21 and 22 involved must have its own monitoring. This can according to FIG. 3 be expedient to only the two functions "state recognition" and "current measuring" each switch 21, 22, separately allocate and a single trip unit to be used, which is associated with its parent power switch 2. A corresponding bus system can be available for communication.

In Fig. 4 the arrangement of Fig. 3 is modified such that the system of higher-level circuit breaker 2 and lower-level circuit breakers 21 , 22 , each with connected consumers 23 , 24, each assigned units 61 , 62 and 63 for current measurement, status detection and tripping are coupled to a unit 51 for selective network monitoring via a bus system 10 . This ensures comprehensive communication.

The procedure described and the associated arrangement was above specifically for a vacuum switch with a tens switching tube, d. H. for a single-phase network, darge poses. In the case of three-phase networks, each phase of the subordinate circuit breaker a separate current measurement be performed.

Apart from vacuum switches, the method can also be used other switching principles are used, provided there for the current also a comparable sharply defined Limit corresponding to an impending failure exists.

Claims (10)

1. Procedure for selective network monitoring in switchgear with the following features:

• - Electrical aftercurrents after zero current are recorded,
• - The electrical wake currents are compared with a predetermined limit
• - If the limit value is exceeded, a signal is generated to trigger a higher-level circuit breaker in the switchgear.

2. The method according to claim 1, characterized records that the current after the first current zero passage of the opening switching pole measured and analyzed becomes. 3. The method according to claim 1, characterized records that the limit for signal generation to trip the higher-level circuit breaker type is chosen dependent. 4. The method according to any one of claims 1 to 3, wherein the Switchgear vacuum switch with at least one vacuum contains switching tube, characterized records that the wake flows over structural elements the switching tube, preferably the steam screen, measured will. 5. The method according to claim 3 and claim 4, characterized characterized that the limit to the signal generation to trip the higher-level circuit breaker for vacuum interrupters in the range between 5 and 15 A.   6. Arrangement for selective network monitoring in switchgear using the method according to claim 1 or one of claims 2 to 5, wherein the network with the switchgear has a higher-level circuit breaker and several subordinate circuit breakers, marked net by a device ( 5 , 51 ), which monitors the subordinate circuit breakers ( 21 , 22 ) and triggers the higher-level circuit breaker ( 2 ) if necessary. 7. Arrangement according to claim 6, characterized in that the device ( 5 , 51 ) Diagnoseein units ( 6 , 61 , 62 , 63 ) for status detection and current measurement of the circuit breaker ( 2 , 21 , 22 ) are assigned. 8. The arrangement according to claim 6, characterized in that at least one trigger ( 9 ) for the higher-level circuit breaker ( 2 ) is present. 9. Arrangement according to claim 7 and claim 8, characterized in that each of the subordinate circuit breakers ( 21 , 22 ) of the switchgear separate diagnostic units ( 6 , 61 , 62 ) for status detection and current measurement are assigned and that a unit ( 9 ) to trip the higher-level circuit breaker ( 2 ) is available. 10. The arrangement according to claim 8, characterized in that a system for data transmission, in particular a bus system ( 10 ), is available.