Mobile high voltage network

A mobile high voltage network supplies electrical consumer units connected via a plug-in connector and can be switched on and off by means of mechanical switches, with a fuse responding in the event of a short circuit. The high voltage network carries a direct voltage and to each electrical consumer unit (8; 10) a separate diagnostic and protection monitoring system is assigned which is activated when it is switched on and/or off. Such a direct voltage and high voltage network in conjunction with the diagnostic and protection monitoring system makes it possible, before starting up any circuit of consumer units, to effect a self-diagnosis of the protection monitoring system, to ensure that all components are fully functional. Without this, self-diagnosis with proof of functionality the relevant circuit of consumer units is not switched on.

BACKGROUND OF THE INVENTION

The invention relates to a mobile high voltage network to supply an electrical consumer unit connected by a plug-in connector and which can be actuated by means of mechanical switches, with a fuse responding in the event of a short-circuit.

So far, few applications have been known for the mobile use of electrical networks of high power transmission. Basically, the conditions and solutions which have become known from stationary high voltage networks have been taken as the basis for this. With such networks, for which only alternating voltages are customary, cable breakage and the separating of connection couplings under load on account of the zero passage of the voltage gradient cause no problems. With a view to the greatest possible flexibility, a high degree of efficiency, a low expenditure on components, as well as a reasonably priced solution, including the expenditure on power electronics, the loss through the power electronics, as well as the expenditure for the stabilization of the network frequency and the network voltage, it has thus far been uneconomic for power transmission by means of high voltage networks based on alternating or direct current.

In the mobile field, electronically controlled and monitored technical devices have become known already which are capable of self-diagnostic checking. That means that during operation, faults which occur are detected and appropriate actions are instigated.

The task of the invention lies in creating a mobile high voltage network of the type described in the introduction hereto, that is economic to operate and to monitor.

This task is solved by the fact that the mobile high voltage network carries a direct voltage, and a separate diagnostic and protection monitoring system is assigned to each electrical consumer unit or load. Such a mobile high voltage network, in conjunction with the diagnostic and protection monitoring makes it possible, before the starting up of any consumer circuit, to carry out the protective monitoring so as to ensure that all the components are fully operational. Without this self-diagnostic check with proof of the capacity to operate, the relevant consumer circuit is not connected.

The diagnostic and protective monitoring device detects insulation faults and faults of the electrical connection. The diagnostic and protective monitoring device also prevents any separation of the electrical connector when live. In the event of too high electrical current, a fuse prevents the overloading of the diagnostic and protective monitoring device and the electrical line connections and junctions.

The diagnostic and protection monitoring is, however, also used to regulate the switching off of the consumer so that the network connection can be separated. For this, the consumer is disconnected from the high voltage network and the remaining network circuits are monitored to see if they are live. In particular, consumers with stored energy—electrical accumulators or also machines, which on stopping still feed current into the consumer—are transferred via a short-circuit connection into the safe condition with no voltage and no current. As soon as the consumer has definitely reached the condition where there is no voltage, the protection monitoring releases the plug-in connection for the separation.

This allows a separation of components carrying D.C. voltage, without the surrounding medium being ionized and without any arc occurring. The current can therefore be safely interrupted. In this way, no special protection medium, (e.g. hydrogen) is needed in the contact area and devices to blow out arcs. The operational reliability is increased many times more that with so far customary devices which use protection gas and arc blow-devices. The occurrence of an arc is excluded by the proposed solution. There is, therefore, no burning off of the contacts, nor is any device needed to extinguish arcs. Over the whole lifespan, without any additional measures the operational reliability of the diagnostic and monitoring, protection is therefore guaranteed. Through the monitoring of insulation faults, line breakage, or too great a flow of power, it is guaranteed that no danger arises when using electronically operated machines through the high voltage network.

The parallel circuit of a mechanical switch and a power switch makes it possible to use the advantageous properties and characteristics of these components to the base advantage. Thus, electronic power switches are in a position to by-pass relatively large potential differences with arc formation, whilst mechanical switches are very prone to this.

On the other hand, electronic power switches, unlike mechanical switches, exhibit high losses. When following the stated method of switching both when switching on and switching off the consumer, due to the effective electronic power switches, on the mechanical switch, there is a very slight voltage difference, which cannot adequately ionize the environment so as to cause no arcs. In addition, with the consumer switched on, only a slight drop in power is detected at the switches. The degree of effectiveness of the switching device is higher, and the thermal incidence, which is slight on account of the reduces loss of power, can be dissipated to the environment without additional cooling devices.

The features of the invention bring about on the mechanical switches certain preset voltage levels, which make it possible to establish the proper function of the switches. In addition, the current path takes over the dissipation of the slight leakage current of the power switches, in order to definitely exclude burning off on the contacts.

Due to the features of the invention, the plug-in connector cannot be separated when it is under electrical voltage. Therefore, any danger from the occurrence of an arc or contact with live components is excluded. Only in the state where there is no current and no voltage can the connector be disconnected.

The features of the invention make it possible for the diagnostic device to detect potential changes on the screening line, which occur in the event of damage in the insulation fitted between the line carrying current and the protection line through external effects or the interruption of the screening line. The network is then reliably switched off, so that there can be no danger from any damaged line. It is, therefore, guaranteed that the essentially higher probability of the occurrence of harmful effects on the lines in mobile use is not faced with a higher danger potential.

The features of the invention ensure the detection of insulation faults or line interruptions of lines from both the positive and negative pins.

Further advantageous details and features of the invention can be seen in the claims.

The invention is explained in greater detail hereinafter by reference to the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

InFIG. 1, only the positive pin P and the negative pin M of a mobile high voltage network can be fed by a suitable D.C. current generator, which is not shown. An electrical consumer8(seeFIG. 2) is connected to these pins, with a diagnostic and protection monitoring device accommodated in an insulated casing1. A plug-in connector2facilitates the connection of the electrical consumer8to the high voltage network. The plug-in connector2is secured against disconnection in situations which are not allowed by means of a mechanical lock3.

In a positive line between the positive pin P and a first contact4of a socket of the connector2, in series behind each other, there is a fuse Si1, an electronic power switch T1, a mechanical switch S2, and an ammeter device i. In a negative line between the negative pin M and a second contact5of the socket, in series behind each other, there is a fuse Si2, an electronic power switch T3, and a mechanical switch S4. A mechanical switch S1, S3is connected in parallel to each of power switches T1and T3. In the direction of the current flow behind the power switches between the positive line and the negative line, a power switch T2is located. The network further comprises a resistor series circuit consisting of three identical high-impedance resistors R3, R4, R5whereby the voltage between the resistors R3and R4is applied to the free contact of switch S2and a voltage between R4and R5is applied to the free contact of switch S4.

To generate a reference potential, there is a further resistance series circuit before fuses Si1and Si2between the positive line and the negative line consisting of two identical high-impedance resistors R1, R2. The reference potential is defined as the average potential occurring between the resistors, which is fed via the third contact6of the socket into the one protection line7of the connected consumer8. The other protection line7aof the consumer8is connected to a fourth contact13of the connector, from where there is an electrical connection for a diagnostic evaluation device9. The protection lines7and7aare surrounded by an insulating layer and this again surrounds the current-carrying lines leaving contacts4,5.

The consumer8may be located alone or in series with further consumer units in a consumer unit circuit. “In series” here does not mean an electronic series circuit, where an electric current flows through every consumer unit and a part of the mains voltage is dissipated. Instead, here it means an stacked arrangement of consumer units, where each connected consumer unit makes available a voltage source for a further consumer unit, as explained below in connection withFIG. 3.

The drawing shows, in the form of latched lines, control lines for the control of switches S1, T1, S3, T3, T2, S2, S4lines for the transmission of the measured values of the ammeter device i, as well as lines for the transmission of voltage values to the measuring points u1, u2, u3, u4, u5and u6of the protection monitoring system. These lines are connected to an evaluation device9, which makes the protection monitoring capable of self-diagnosis.

FIG. 3shows an electrical consumer10connected to the protection monitoring in accordance withFIG. 1by means of a further unit11, from which a still further electrical consumer can be supplied with electrical power via a plug-in connection12. The further electrical consumer11again includes a diagnostic and protection monitoring system of the same kind as described inFIG. 1. The reference potential generated by the resistors R1, R2ofFIG. 1is used in the further electrical consumer11so that in the event of a fault a high-impedance contact protection is guaranteed.

For the constant monitoring of protection line7by the evaluation device9(to check for continuous flow and passage), a reference potential is connected via the protection line7of a connected consumer unit10to the third contact6of the diagnostic and protection monitoring system which is in the further electrical consumer11. This reference potential is also connected to a normally closed contact S5. The normally closed contact S5is opened, if via the connector12a further consumer unit is connected, and closed, if the connector is disconnected.

In the open condition of the normally closed contact S5, that is if a further consumer unit is connected, the direct connection between protection lines7and7ais interrupted. A reference potential is connected from the third contact6of connector12to the evaluation unit9ofFIG. 3and via resistor R6and line7ato the fourth contact13ofFIG. 1and hence to the evaluation device9ofFIG. 1.

Method of Operation of the Diagnostic and Protection Monitoring System:

Switching on the Consumer Unit:

If the supply is guaranteed by the generator the positive and negative voltages are measured at measuring points u1, u2against the reference potential produced by the resistors R1, R2. If the fuse Si1, Si2are in order and switchers S1, S3are open, then the electronic power switched T1, T2and T3in the disconnected condition act like resistors in series between the + pin and − pin. Between measuring points u1and u3, u3and u4, as well as between u4and u2characteristic voltages can then be measured. If these voltages to zero, then power switches T1, T2and T3are safely disconnected.

Switches, S2S4are open if between measuring points u3and u5, as well as between u4and u6, the voltages corresponding to the resistance series circuit from resistors R3, R4and R5are present.

If this condition is present, then in the first instance switches S2, S4are closed. Now, the voltages between measuring points u3and u5, as well as between u4and u6, drop to zero volts. On the next opening of switches S2, S4, the voltages must rise again.

The next step is that power switch T2is switched on. The voltage between measuring point u3and u4must now decrease with the voltage drop of power switch T2in the connected condition. If this happens, then power switch T2is in order and it is switched off again.

Power switches T1, T3can now be switched on, and the voltages between measuring point u1and u3, as well as between u4and u2must go typically from 2V to <4V in response to the voltage drop at the power switches T1and T3. Then, power switches T1and T3are again switched off and the voltages rise again.

Switches S1, and S3can now be switched on, and the voltages between measuring points u1and u3, as well as between u4and u2, must properly got to 0V.

Then switches S1and S3are switched off again, whereupon with perfect operation, the voltages rise again.

Now, switches S2and S4are closed, and power switch T3is switched on. The voltage between the measuring point u4and u2must decrease with the known voltage drop of power switch T3. This ensures that this switch is switched on. Now, switch S3, which has the task of minimizing the loss of power switch T3, is closed.

Power switch T1is now switched on again, and the voltage supply occurs on connector2and electrical consumer8, which is connected thereto. In order to minimize the power losses on power switch T1, switch S1is then switched on, and power switch T1is switched off.

The described procedure of switching on may only take place if protection lines,7,7afor the onward passage of the reference potential do completely allow passage and no interruptions occur.

Switching off the Electrical Consumer:

The switch-off procedure begins with the opening of switches S1and S3. Then, power switch T1is switched off and power switch T2is switched on. Since via the consumer, which can also work as a generator, voltage can be fed in, a short circuit is necessary via power switch T2, so that the voltage in this case does not rise too high, if there is no protection device for this in the consumer.

As soon as the ammeter device i establishes that no further current is flowing (consumer8no longer working as a generator), switches S2and S4are opened.

The switching off of switches S2, S4is checked by measuring voltage between measuring points u3and u5or u4and u6. If the switching off was unsuccessful, power switches T3and T2are switched off.

Power switch T1does not switch on:

This can be discovered when switching on by voltage measurement between measuring point u1and u3.Consequence: no switching on possible.Power switch T1does not switch off:

This can be discovered when a power switch T1is switched on and/or off. If a defect is found, then the switch-on procedure can not be affected.

When switching off, by short-circuiting the power switch T2, the voltage at measuring points u1, u3and u5collapses. The short-circuit current destroys the fuse Si1or Si2. As soon as it is no longer possible to establish any further current via ammeter device i, then complete switching off is effected. Consequence: no further switching on possible; by voltage measurement between measuring point u1and u3, it is possible to discover any defect of the fuse or defect of power switch T1.Power Switch T3does not Switch on:

This can be discovered when switching on by measuring voltage between measuring points u2and u4.Consequence: no switching on possible.Power switch T3does not switch off:

When testing a switching function it is already possible to discover whether power switch T3switches on and off. If a defect is found, then the switching-on procedure can no longer be effected.

When switching off, faulty operation can be discovered by measuring the voltage between measuring points u2and u4. If power switch T3does not switch off, then nonetheless connector2can be switched off, the network is separated safely by switches S2and S4.Consequence: no Switching on possible.Power switch T2does not switch on:

This can be discovered when switching on between measuring points u3and u4.Consequence: no switching on possible, when switching off the mains connection, with the consumers working as generators an intolerably high voltage may occur.Power switch T2does not switch off:

During the switch-on test or when switching off, this can be discovered by measuring between measuring points u3and u4.Consequence: no further switching on possible, since otherwise there is a short circuit. Safe switching off is possible.Fault on switch S1: corresponding fault on power switch T1.Fault on switch S3: corresponding fault on power switch T3.Fault on switches S2, S4:

This is checked during the switch-on test operation, and can be discovered via voltage between measuring points u3and u5or u4and u6.

Consequence: no further switching on possible; cannot be opened when switching on switches S2, S4, power switches T2and T3remain switched on.

Prevention of Arcs:

The on/off switching procedure is accomplished with electronic power switches T1, T3and mechanical switches S1, S2, S3and S4. The on/off switching procedure and the ammeter device prevent the occurrence of an arc on switches S1, S2, S3and S4either through reduction to very low switching voltages or very high-impedance current paths.

The occurrence of an arc in the connector is prevented by the fact that this can only be separated via a controlled locking device, if the mains voltage to the connector is switched off.

If an arc occurs through mechanical effects on the current-carrying line to consumer8, which is protected by protection line7, then this is detected by protection line7through a voltage drop or voltage rise of the reference voltage and the mains voltage is switched off.

Interruption of the Protection Line:

Protection line7is constantly monitored by the evaluation device9for full flow and passage. For this, the reference potential is connected via protection line7of a connected consumer8to the evaluation device9(FIG. 1). If, as shown inFIG. 3, a connected consumer10comprises a connector12and provides for the connection of a further consumer, then connection of all the connected consumers is assured.

In this case the connection of the protection line to the previously connected consumer10is to be cancelled and the last consumer unit in the series must make the connection to the evaluation device9.

As soon as an interruption of the protection line is discovered, evaluation device9switches off the mains for this circuit of consumer units.