DE1260600B - Device for limiting overcurrents - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

HOIh

H02h

German class: 21c-68/50

Number: 1 260 600

File number: L 52661 VIII b / 21 c

Filing date: January 24, 1966

Open date: February 8, 1968

Patent 1,227,129 relates to a device for limiting overcurrents, in particular at the Coupling point of high-voltage alternating current networks, as well as equalizing currents between them Networks in the event of a short circuit in one of these networks or in the event of a step outside, with one in the connection Series connection of two reactances, an inductance and a capacitance, is inserted, which are different Sign and have about the same size in normal operation, so that the resonance frequency this series resonant circuit corresponds approximately to the mains frequency, being parallel to the capacitor an iron-closed saturable inductor with only its copper resistance is connected and with the saturable choke coil an additional ohmic resistance is in series, which is at saturation the throttle predominantly determines the resulting conductance of the arrangement.

It is already the use of a series resonant circuit to limit the current in AC networks and known at the coupling point of two networks, in which the capacitor is operated by a relay Switch is bridged in the event of a short circuit. When normal conditions return, a Time delay, the bridging is canceled again. Since mechanical switches with the well-known Time delay are used, this device does not fulfill the task of the main patent, to lock off the dynamic current peak value.

Another known device for limiting short-circuit currents in AC lines also consists of a capacitance and an inductance connected in series, which have a resonance form a coordinated resonant circuit. In the event of an overcurrent, the capacity is determined by a spark gap, a gas discharge arrester or other gas discharge vessels bridged. Because of this Sudden response of the shunt leads to an extremely hard short-term switching action, which is very undesirable at higher powers in AC networks. Besides, it still is today associated with very great difficulty, if not impossible, such elements as spark gaps and gas discharge arrester for bridging one of the reactances in the event of a short circuit for the desired performance range achievable with the present application.

Another device for the protection of overcurrent-sensitive Consumers such as B. of devices with silicon rectifiers or transistors, also consists of a device adapted to resonance to limit overcurrents

Addendum to the patent: 1 227 129

Applicant:

Licentia Patent-Verwaltungs-G. m. b. H.,

6000 Frankfurt, Theodor-Stern-Kai 1

Named as inventor:

Dr.-Ing. Hans Becker, 6100 Darmstadt

Series resonant circuit which has a negligible resistance in nominal operation, with for Capacitance a saturable choke with as little loss as possible is connected in parallel, its inductance as a result Overcurrent saturated state oscillations of higher frequency for the purpose of reloading the Capacitor executes, so that the flowing current is pushed down below the rated current. Tipping process and rapid reloading, which this arrangement uses to limit the current, practically exclude their use at higher power in high-voltage systems. Also because of the Harmonic feedback due to the strongly distorted current curves is the arrangement in network operation not portable.

Only one device according to patent 1,227,129 meets the requirements with an economical design of the elements for high and extra high voltage networks with regard to voltage and power range valid requirements. Static electromagnetic machines, such as transformers and reactors, and capacitors can be produced in any required and desired design. In particular, they are arcing Switching devices such as spark gaps, surge arresters and circuit breakers for Switching on the capacitor shunt avoided. The former have the disadvantage that they go through the extremely powerful arcs would be subject to severe wear, provided that they could even be manufactured economically for the required performance range. the Circuit breakers, on the other hand, have an un-

809 507/497

Claims (1)

3 4 provide an avoidable time delay to which it corresponds approximately to the mains frequency for the resonant circuit, Set task, even the dynamically effective, with a closed-iron current amplitude parallel to the capacitor of the short-circuit current, sene saturable inductor is connected and where make unsuitable. Only the magnetic switching element with the saturable choke coil is an additional one in the form of the saturation choke, the saturation and 5 ohm resistance of which is in series, the saturation of the thus switching function by increasing the short-throttle the resulting conductance of the facility circuit-current-dependent voltage drop itself is largely determined, according to patent 1,227,129 can meet the requirements. is sufficient if according to the invention after removal of the The reactance of this choke is the ohmic resistance when the short circuit is not disrupted saturated state in the normal current range ent- io is designed so that it is shunted to the corresponding high, so that the capacitance with the main capacitor chokes a considerable amount for the duration of the recovery time a non-disturbed series resonant circuit bil borrowed assumes a higher value. det. If the voltage drop across the condensate, the increase in the total resistance is Sator as a result of an increase in the current, for example by switching on a corresponding one If the limit value is correct, the inductor core is reached in 15 partial resistance. Saturation and its inductive resistance are reduced. This connection is expediently carried out in themselves. the way that a corresponding partial resistance As a result of the now effective essentially ohmic normally bridged by a switching element and see shunt to the capacitor is the contact element for the duration of the recovery time the excess hen resonance disturbed and the resonant circuit has a 20 bridging interrupted. compared to before by many times larger A particularly low-inertia and easy to betäresultierenden resistance, so that the current is effectively limited in tigendes fast switching element for the connection of the connecting line. As an additional resistance for the duration of the recovery limiting current, that is to say as the maximum value of the continuous time, for example in the form of two short-circuit currents, controllable valves connected in anti-parallel can be
coupling a value can be achieved that can be close to the nominal value according to the drawing parallel to the series current. capacitor, which in normal operation with the inductive Now the voltage drop across the resistor and vity X _{L form} the balanced series resonant circuit so that the voltage stresses of the individual det, switched circuit consists of a choke X _s elements, the greater the greater the ohmic 30 (saturation choke) and the series connection of two resistors. Higher voltage drops mean resistances .R ₁ and R ₂ . The resistor R ₁ is known to be stronger insulation and higher cost. always turned on and provides the short circuit case, the most economical solution is achieved when required minimum resistance. The Widerfür is a given degree of limitation of the smallest standing R _2, with a shift member 5 Bridges. After possible resistance is used. When the short-circuit has ended, this switch is opened If the short-circuit is now removed and the resistance R _ges = R ₁ + R ₂ which is now present hears the short-circuit current on _s , the device returns to in, causing a short recovery time. After the return of the consequence of their inertia not immediately in the normal-to-limit clutch in the normal state, stand back but it remains, however, the switch S is closed again. _{Since the inventory R 2,} which is reduced compared to the short-circuit case, is approximately the same order of magnitude as R _{1, it} should have a certain time, the recovery time, in which it is only briefly (approximately 100 msec) in its high-resistance state. During this time tet is and during this time only about the nominal current flows via the parallel circuit to X _c, a current from which flows via the resistor, results in about the Neiinstrom.es of the coupling for the counter magnitude. This was R ₁ , and switch S was no costs, the smaller the negative 45% of the total costs, the greater the recovery time. A level R is the smaller the load impedance (depending on the application, it is particularly recommended when the short circuit has ended) and the smaller its cos φ is. Coupling for a nominal impedance with poor In order to design a cos ψ as quickly as possible after the short circuit.
to restore orderly network operations, the Recovery time should be as short as possible. To do this, a large 50 claims would be: Resistance .R required ₅ which, however, makes the 1. Device for limiting overcurrent Claims in the event of a short circuit increase and the men, especially at the coupling point of Coupling becomes uneconomical. Thus, one would be high-voltage alternating current networks, as well as from forced to compromise between the two balancing flows between these networks in the other contradicting demands with accession 55 short-circuit in one of these networks or with confessions in one or the other tion to close. Series connection of two reactances, A simultaneous fulfillment of both requirements, an inductance and a capacitance, inserted is used in a device to limit excess current, which has different signs and normal currents, especially at the coupling point of 60 "operated about the same size, so that the High-voltage alternating current networks, as well as from the resonance frequency of this series resonant circuit DC currents between these networks roughly correspond to the network frequency, with parallel Ultimate event in one of these networks or in the event of an exit to the capacitor, an iron-closed saturation event, wherein a series circuit bare choke coil is connected in the connection and wherein with of two reactances, an inductance and an additional 65 saturable inductor a capacitance is inserted, the different series ohm resistance is in series, which at saturation sign and in normal operation about the same size of the throttle the resulting conductance of the influence, so that the resonance frequency predominantly determines this serial direction, according to the patent 1227129, characterized in that after eliminating the fault of the short circuit the ohmic resistor is designed so that it is shunted to the capacitor for the Duration of the recovery time assumes a considerably higher value. 2. Device according to claim 1, characterized in that to increase the value of the Resistance a brief connection of a corresponding partial resistance takes place. 3. Device according to claim 1 or 2, characterized in that a corresponding one Partial resistance normally bridged by a switching element and the switching element for the Duration of the recovery time interrupts the bridging. 4. Device according to one of claims 1 to 3, characterized in that two antiparallel-connected controllable valves are provided as bridging switching element . 1 sheet of drawings 809 507/497 1.68 © Bundesdruckerei Berlin