DE1013759B - Protection circuit for electrical medium or low voltage distribution systems - Google Patents

Description

In medium and low voltage networks, which are generally operated ungrounded, one is content usually with the monitoring of the insulation condition, possibly in connection with optical or acoustic indication of an earth fault, upon which this, if necessary, is switched off manually will. This type of earth fault monitoring was previously also common in underground networks. One has however, recently based on measurements in underground networks found that in the case of a single-pole Earth fault in a three-phase system which is based on the line capacities of the healthy Phase closing earth fault current can reach a level at which the formation of ignitable Spark is possible. The single-pole earth fault may therefore pose a risk to underground operations The elimination of this danger is by simply switching on a trigger element for the main switch that disconnects the mains to the measuring circuit of the normally arranged on the main switch Network monitoring device possible if you switch off the entire network, including wants to accept its healthy parts in such a case. Usually, however, there is the requirement to limit the shutdown to the defective parts of the system and the supply of the not to interrupt healthy line sections and consumers. This is only possible if the Ab The fault is switched selectively. The use of selective protection common in high-voltage networks but is not allowed in underground networks for economic reasons. The usage of Summation current converters, however, is problematic in terms of sensitivity and therefore requires possibly the use of amplifiers. In addition, the selectivity can be called into question by the line capacities.

The invention is based on the object of providing full protection of the with simpler means to achieve the entire system against earth faults when the aforementioned requirement is met.

According to the invention, this is achieved in that, in the event of an earth fault occurring in the to be protected Network the insulation monitoring device switches off the main switch of the network at the beginning of the network, whereby the switches of the individual branches are opened and that after the return of the mains voltage the automatic closing of the switch of the faulty feeder by its protective device is blocked.

If the fault is in a branch, the main switch and the switches can all be healthy Lines are reinserted, however, the fault is in front of the switches of the individual branches, see above Protective circuit for electrical medium or low voltage distribution systems

Applicant:

Siemens-Schuckertwerke

Aktiengesellschaft,

Berlin and Erlangen,

Erlangen, Werner-von-Siemens-Str. 50

Kurt Wulsten, Berlin-Siemensstadt,
has been named as the inventor

the insulation monitoring device prevents the main switch from being switched on again at the beginning. In this way, it is easier to locate the fault or determine the defective power supply unit Way allows.

This network protection according to the invention can be supplemented and perfected in various points will. For example, it is possible to switch the main switch on again after a certain time has elapsed Time, e.g. B. 1 to 2 see, to be made automatically with the help of a timing relay. It is further possible to lock the switches of the individual branches against each other, so that it is, for example, at dependent conveyors od. Like. Is made impossible that only a part of such Downstream systems are put back into operation, which could cause malfunctions.

A further subdivision of the network can be done by means of switches between the main switch and the switches for the branches and are superordinate to associated consumers. In such cases, order various options for assigning the protective devices to the Switches, namely:

1. Both the switches for the feeders and the switches for the associated consumer groups are provided with protective devices.

2. Only the switches for associated consumer groups have protective devices Mistake.

3. Only the switches for the feeders are provided with protective devices.

An exemplary embodiment for the protection of a network according to the invention is explained below:

The transformer 1 feeds a line 2, which has a circuit breaker 3, which is z. B. to a Device with motor drive 4, key switch 5 and working

709 657/338

Actuate current release 6. may, on a line 7 converter 29, a rectifier 30, the z. B. can be switched in Graetz; 'which works in any type of interconnection, relays 31 and 32 as well as pushbutton switches may branch. In the example mentioned, 33 and 34 take place. As in the insulation monitoring, this is done in the form that the main line 7 is in the device 18 which divides lines 8 and 9 in the protective devices 17, fäie via switches 10 and 11 5 to 17 d DC voltage generated is a low voltage to which lines 12 and 13 can be connected. B-. the protective device 17a considered, NEN. Loads A, B, C, D are connected to these lines. The contactor coil 16 α is connected with the help of the voltage via contactors 14 α to 14 d . The single converter 29 a, the rectifier 30 α and the relay are fed according to the above-explained possibility 31 α and 32 α. The contact of the relay 31 α is only the consumers ^, E, C, D with protection io closed in normal operation, while the relay is provided facilities. To all lines of the 32 α de-energized or network belongs to the push button switches 33 α and 34 α. continuously earthed protective excitation. If the relay 32a is on the push button switch 15, which has only been energized at 34a to simplify the drawing, the contactor 14a is indicated in the required places. The contactors are switched on and the downstream Ver-14 a to 14 d are connected to load via trip coils 16 a to 16 d 15 A. This chip-operated disappears. The contactors include protective equipment for any reason, so the lines 17 α to 17 d open. - Relay 32 a its contact, making the contactor coil

At the beginning of the main line 7 is the insulation 16 a is de-energized and the contactor 14 a monitoring device 18. It is switched via a. As a result, the relay 31a via the auxiliary voltage converter 19, which is connected to the line 2, 20 contact 35a and the protective resistor 36 ä is closed, and a rectifier 20 -a direct line between contactor 14a and consumer A. generated that switches to "the terminals of the condenser.

sators 21 is pending. This voltage is These consumers are assumed to be motors,

preferably by a.-low voltage (65 V), in order to use the windings of the relays 31 with all three

No dangerous phases of the network are connected by the measuring voltage. Is through the

to generate contact voltages in the network. A galvanic circuit for the internal test circuit of the consumer

For purposes of this, this terminal tension cannot be given by simply connecting the three phases

circuitry measures, e.g. B. via Wick instead of the protective resistor 36 an arrangement

taps on the voltage transformer, used on both of three protective resistors, as shown in

for example 100 V can be increased. 30 of the insulation monitoring device 18 specified

In the event of an earth fault at any one is. The star point of this arrangement is in this one

Point in the network closes the earth fault measuring circuit when connected to auxiliary contact 35,

as follows: As a result of the repeat

-O ₁₁₁ j Tj .. οι r> 1 · 00 switching on the automatic switch 3 the mains voltage

Plus terminal of the capacitor 21, relays 22, .., ^ö. _TT , _r ..,. _Λ ... ^r , °

/ '■ m. 2. 00C1.L -j .L Jo ^ or λ oc 35 back and was the cause of the draw of the

Ohmmeter 23, protective resistor 24, 25 or 26, _o ,,. , _(i ο τ> j- 1 1 α τ> j τ ±

faulty phase of the network fault point self-switch 3 a ground fault, z. B. on the line

tenierDenaitete t-ftase of the! network, i <enierstene, _{between contactor 14a and} consumer A, so becomes

Earth, protective conductor 15, negative terminal of the condenser ..,, _c ji on c · ""

-; - = -,., __ via the voltage converter29α voltage to a

sa ors. - -. _ The measuring circuit is laid, which closes as follows:

When closed, i.e. include an error- 40

the measuring circuit, the relay 22 is energized and energized the secondary side of the voltage converter 29 α, on the other hand the relay 27. This has both a judge 30 α, relay 31 a, auxiliary contact 35 a, protection-idle and a working contact. In unexcited resistance 36 », line, fault location, earth, state is via the. Break contact one pole of the protective conductor 15, rectifier 30 α, secondary side line 2 connected to the contact of the timing relay 28, 45 of the transformer 29 a. when energized, the same line pole is over

the normally open contact on the shunt release 6 Closing this measuring circuit activates the relay

switched, which thereby responds and excites the self-31a, opens its contact and makes with it

switch 3 opens. Since the entire network is thus voltage-free, the relay 32 α is de-energized. This creates an on _;

The contactors 14 a to 14 d fall off. 50 switch the contactor coil 16 a via the push button switch

If the earth fault is behind this, then ab- 34 a prevents.

If the contactors fall below the earth fault measuring circuit - If there is no fault in the measuring circuit, then it remains broke. As a result, the excitation of the relay 22 is de-energized, and the relay 31 is therefore not α canceled, and this opens its contact, excited. His contact remains closed, and that also switched off by the excitation of the relay 27 55 contactor 14 a can again be manually via the Tastwird. This then closes its break contact. switch 34 α are turned on. This is the supply voltage for the motor. In particularly important branches it is under drive 4 of the automatic switch 3 to the contact of the circumstances desired that this after the return of the Time relay 28 applied. This time relay always runs when there is voltage and switches itself on again immediately. opening of the circuit breaker 3 and indicates after a 60 The circuit of the protection device 17 d is for a certain time, for example after 1 to 2 seconds, such a case is provided.

Switch-on command for the motor drive 4, which The voltage converter 29 feeds two circuits,

Automatic switch 3 closes. the first of which is through the contact of the relay

If the earth fault is between the main switch 3 31 d. the switch 37 and the excitation coil of the relay

and the shooters 18 α to 18 d, the expiry 65 38 closes. If the switch 37 is closed, so

of the timing relay has no effect, since the relays 22 and 27, the relay 38 closes its contact and switches the

remain energized and thus no voltage on the actuating coil 16 d of the contactor 14 d on the mains,

Contact of relay 28 is placed. whereby the contactor is closed and the

The protective devices 17 a to 17 d to the consumer D is connected to voltage. When closed

consumer branches each contain a voltage 7 ° nem switch 37 is therefore for switching on the

Contactor 14 if only the presence of the mains voltage required on its entrance side.

The second of the voltage converter 29 if powered circuit is identical to the measuring circuits of the safety devices 17a, 17 b, 17 c, both of its circuit and its function. The switching elements lying in this circle are therefore designated with the same reference symbols as in the measuring circles of the protective devices 17 a, 17 b, 17 'c .

Test equipment can be arranged at any point in the network, over which each phase can be connected to the protective conductor 15, whereby artificially earth faults can be generated. In this way, the devices 21 and 22 can be checked.

Claims (9)

Patent claims: 1. Circuit arrangement for electrical medium or low voltage distribution systems, in particular for underground networks, for protection against earth faults with an insulation monitoring device directly on or behind the main switch of the network to be protected and earth-fault protection devices for each individual branch, characterized in that in the event of an earth fault in the network to be protected the insulation monitoring device at the beginning of the network switches off the main switch of the network, whereby the switches of the individual branches are opened, and that after return the mains voltage the automatic closing of the switch of the disturbed feeder by its Protective device is blocked. 2. Protection device according to claim 1, characterized by a time relay in the insulation monitoring device, which is within an adjustable .Time period gives a switch-on command for the main switch. 3. Protection circuit according to claim 2, characterized in that the restart command of the timing relay only becomes effective if the earth fault occurs after the branch lines have been switched off is no longer detected by the insulation monitoring device on the main switch. 4. Protection circuit according to claim 3, characterized in that the insulation monitoring device contains a relay (27) which has a normally closed and a normally open contact of which the former acts on the shunt release (6) of the main switch (3) and the latter in the is controlled by the timing relay circuit. 5. Protection circuit according to claim 1, characterized in that the switches for the individual Branches are monitored electrically, with the measurement voltage on the input side of the switch is removed. 6. Protection circuit according to claim 5, characterized in that the protective device of the individual branches through an auxiliary contact of the associated switch on the switched off branches is connected. 7. Protection circuit according to claim 1, characterized in that at branch points of the A switch with protective devices is also provided for each branch line (12, 13) is. 8. Protection circuit according to claim 1, characterized in that a plurality of branches common switch with protective device is superordinate. 9. Protection circuit according to claim 1, characterized in that the protective devices individual Branches are designed in such a way that they can be switched on after the voltage has been restored of the main power switch, switch the feeder switch on again automatically. Considered publications:
German Patent Nos. 434 746, 745 234, 214, 511892. 1 sheet of drawings © 709 657i / 338 8.57