DE361029C - Device for protecting electrical systems against overvoltages - Google Patents

Description

GERMAN EMPIRE

ISSUED OCTOBER 9, 1922

REICH S PATENT OFFICE

PATENT LETTERING

-M 361029-CLASS 21c GROUP 61

General Electricity Society in Berlin.

Device for protecting electrical systems against overvoltages. Patented in the German Empire on May 18, 1920.

To isolate electrical systems from damage caused by overvoltages to protect, one arranges parallel to the isolation

come into effect at a certain level, thereby creating an equalization of tension and, if desired, switching off the

Devices, such as spark gaps, ι endangered system or parts thereof, z. B. 5, which cause an overvoltage j of the machines ad the apparatus.

Experience has shown, however, that arrangements of this type are not reliable Protection. Frequently it has even been found to be a new source of overvoltages and actually reduce the safety of the system. The cause of this phenomenon is to be sought in that a certain time is required to break through the spark gap, within which ίο the insulation to be protected is also damaged is, and that also the resulting arc when the breakdown in particular Demolition becomes a source of new surges. To achieve effective protection, both errors in the arrangement must be eliminated together. According to the invention, this is done by, on the one hand, in an known way through homogeneous design of the electric field, artificial Ionization or other means of changing the discharge equipment Time delay of the rollover practically eliminated and, on the other hand, at the same time This spark gap occurring sparks or arcs immediately after the Overlap (bridged with good conductivity and so it can be extinguished immediately without tearing off brings.

Bridging the spark gap also has the advantage that the extensive flame formation that occurs at higher voltages ceases to exist, In particular, if the dampening resistance for the purpose of destruction as quickly as possible the overvoltage energy is chosen to be very small or omitted entirely, an impermissible one Assume scope and lead to damage to the devices. Surge arresters consisting of tips and horns are already available for the same purpose executed with short circuit devices. These arrangements have nothing to do with the subject matter of the invention to do "since through them the protection aimed at by the latter is not achieved, that of the above mentioned phenomena takes into account.

In the 'two illustrated embodiments of the inventive idea acts it is a device for protecting a three-phase generator and the low voltage j voltage side of an associated transformer. ! The generator zero point is grounded. The j Protection device consists of one between earth and the generator terminals, i.e. in parallel to the ziu protective insulation, arranged spark gap, which ibeein the occurrence of a Spanning a certain height with the least possible time delay in the penetrations and should be bridged automatically immediately after responding. When responding The transformer on the high-voltage side is switched off in the spark gap and the generator deenergizes or weakens its field.

In both figures, α denotes the generator, the field winding b of which is excited by the exciter c . Wind, and? which feeds a transformer d with the low-voltage side e and the high-voltage side /. In parallel to the generator to be protected, the spark gap g , specially designed as described, is arranged, the electrodes of which are connected to earth B to limit the current flowing to earth when the voltage crosses over in the circuit diagram according to Fig. 1 in a known manner at resistors h are connected. The ohmic value of the latter is small, in the borderline case, as with the arrangement according to Fig. 2, equal to zero. ■

If one first follows the work process in the embodiment according to Fig. 1, one recognizes that when the spark gap g breaks down, the current flowing to earth directly or with the interposition of a current transformer causes the relay i switched on in the earth line to respond, which causes the closure of a for example caused by the battery k powered Ausläsestkreises. As a result, the main oil switch m is switched off by means of the 'automatic release device I and the de-excitation or field switch-off of the excitation machine c and thus of the generator α is carried out by means of the release device η.

A switch 0 is arranged parallel to the spark gap g and automatically takes effect as soon as the rollover is initiated. The switch 0 then bridges the spark gap in its on position, so that instead of the spark, a metallic connection is created between the spherical electrodes, which causes the spark to extinguish. For the automatic actuation of switch 0 , in the circuit diagram shown in Fig. 1, the triggering element p is switched into the circuit that is closed by the relay i. The relay i remains in its switched-on position, even if the spark gap has already been bridged by metal, since the equalizing current then continues to flow through the relay coil towards the end. Only when the occurred in the plant overvoltage has passed, the relay wind i ineffective and interrupts the k from the current source powered trip circuit, whereby the bypass switch means 0 q wind of the spring accommodated in the Öffenstelkuig. At the same time, the switch η causes the normal excitation of the generator and the fields r of the main switch m when its trip coil is turned off

the involvement of the latter. The restoration of the normal state of the plant takes place automatically after the overvoltage has been eliminated.

While in the arrangement according to Fig. Ι bridging the spark gap in the Way happens that each of the electrodes connected to the three phases with one opposite end electrode connected

ίο wind, the bridging can also be carried out with the same success by simply bridging the three electrodes connected to the three phases or three contacts connected to them. Such an embodiment is shown in Fig. 2. The three with the electrodes g _t, g ", g _s In related contacts g · /, g _2, g _s' turn short-circuited by the switch 0 as soon as the radio link g penetrated and the relay i is excited by the current flowing to earth. This is because the release element p is then made to respond, which in turn releases the pawl for the switch 0 so that the latter assumes the right switch position following the tensile force of the spring q.

The switching arrangement according to Fig. 2 also differs from that according to Fig. 1 in that the switching device causing the field weakening or de-excitation of the excitation machine c is mechanically connected to the bypass switch. If the latter is in the locked position on the left, then the resistor s causing the attenuation of the excitation is short-circuited, while it winds turned on in the field circuit as soon as switch 0 deflects to the right and contacts g _± ', g ₂ ', g ₃ 'of the spark gap electrodes g _± , g ₂ , g _s bridged. In a similar way, the main switch m could also be mechanically coupled to the bridging device 0 , or it could be triggered electrically by an auxiliary switch attached to the bridging switch 0 which closes a tripping circuit With the conduction according to Fig. 2, the switch m is switched off by maximum or reverse current relays t, which are connected to the current transformers ν switched on in the individual phases of the low-voltage side and, if necessary, are provided with time delay devices. The normal state of the system is restored here by repatriation of the Überibrü ckungswitches ο in the starting position by hand and not automatically, as in the embodiment selected in Fig. ι, the main switch m is also switched on again by hand.

Of course, instead of these types of embodiment, other mechanical or electrical precautions for the automatic triggering of the bridging switch when the arcing occurs can be provided, either directly from the current flowing to earth or from the overvoltage occurring between the electrodes of the spark gap g with the interposition of auxiliary devices in Activity are set, and which cause the shutdown of the relevant part of the system or the field weakening of the relevant machine by further mechanical or electrical organs. When designing the switch 0 or the triggering devices and any auxiliary equipment that may be required, care will be taken to keep the time interval from the occurrence of the sparkover to the metallic bridging to a minimum, so that the spark does not have time to form a flame or even to tear off give.

Claims (2)

Patent claims. 1. Device for the protection of electrical Systems against overvoltages, characterized by being homogeneous Design of the electric field, artificial ionization older by other means' to change the discharge phenomena with practically no time delay. The spark gap caused to respond immediately after the response is automatically bridged. 2. Device according to claim 1, characterized in that the bridging device electrically or mechanically with a device for switching off the part of the plant to be protected or for field monitoring of the machine to be protected or both Purposes. 1 sheet of drawings.