DE1916951A1 - Electromagnetic relay combined with a current transformer for network protection - Google Patents

Description

Electromagnetic relay combined with a current transformer for the lmetzschutz In the electrical network protection technology normally the protection relays Current transformers with protective cores that have high overcurrent factors connected upstream, to reduce the large primary short-circuit currents to small, easy-to-process secondary currents to step down and to protect the relay against the potential of the high voltage network to isolate. About the damage in the event of a short circuit and the cost of short-circuit resistance To keep as small as possible, protection systems are aimed at, which the primary Jberstrom switch off very quickly; However, this entails quite high manufacturing costs for the otromwandler - protective cores, the protective relays and the circuit breakers.

Due to the subject matter of the invention, it is possible at comparatively to achieve a very quick disconnection of the short-circuit current with little effort. For this purpose, an electromagnetic relay is structurally with the iron core of a Current converter combines that the relay responds from a certain primary overcurrent and thereby the circuit breakers are triggered by means of an auxiliary circuit.

The immediate tripping of circuit breakers by the primary current without a Hilts.st.romkreis is already known, as is the primary trip relay (Main current relay), which are excited directly by the primary current and with ##### an auxiliary voltage can trigger switches. Also as a transformer current release designated operation of switches by the setubdärstrom of current transformers without Interconnection of auxiliary circuits has been known for a long time. What is new, however the structural and magnetically coupled combination of electromagnetic relays Current transformers, the various advantages explained in more detail below compared to has the types mentioned.

If the core of a current transformer is not saturated, the magnetic flux almost exclusively in iron, while in saturated iron the The river partly also takes its way through the air in the vicinity of the iron core.

This effect can be achieved through a suitable shape of the iron core reinforce, for example, by a magnetic shunt that creates an air gap contains.

The air gap can now structurally with the armature of an electromagnetic Relays are connected. At normal operating current, the core is generally not yet saturated, and the magnetic flux practically does not run over the magnetic one Shunt, since the magnetic conductivity of the shunt due to the air gap is much smaller than that of the unsaturated core. with a saturated core as a result of the primary short-circuit current, the magnetic conductivity of the core is reduced but much smaller, and part of the magnetic flux that is then increased anyway flows via the shunt, which attracts the armature of the relay attached there will.

The start of saturation of a current transformer core is at the nominal burden around n times the nominal current, where n is the overcurrent factor. While protective cores generally have to have high overcurrent factors (e.g. n - 20 or 400) and thus Make large material and space required, are in the invention At the core mostly small overcurrent factors (e.g. n = 3) are expedient, which are not large Require effort.

It is even possible to use this core as a measuring core at the same time, as it is well known that the cores should have small overcurrent numbers for measurement purposes. By the size of the burden, if necessary through additional burdens, can be the actual The overcurrent factor can be changed from the outside as required for the response of the with the current transformer core combined relay is appropriate.

For example, the trip coil can be connected to the relay via an auxiliary circuit of the circuit breaker can be connected to without time delay through intermediary Relay circuits immediately switch off a short-circuit current in the network. A special A protective core in addition to the measuring core is therefore no longer required for this purpose. With a fully displaced short-circuit current, the relay according to the invention is special respond quickly because the current transformer core is in the short-circuit current due to the direct current element saturates very quickly. Albeit the connected circuit breaker very much responds quickly, it can be achieved that in addition to the thermal effect of the The short-circuit forces, which are particularly large in the case of full displacement, also apply to the short-circuit current can be kept small.

Figure 1 shows an embodiment of the inventive concept.

kit 1 is the core, with 2 the primary conductor, with 3 the secondary winding and with 4 the main insulation of a schematically sketched bushing current transformer marked. On the head is a magnetic shunt 5 with an air gap a (I mean that is monitored by the armature 6 of an electromagnetic relay. The contact member of a closer 7 is attached to the armature. During normal operation the compression spring 8 keeps the contacts open.

Depending on the dimensions of the magnetic circuit and the size the burden 9, the contacts are closed from a certain overcurrent. To a If necessary, you can avoid fluttering the contacts due to the alternating magnetic field short-circuit windings are attached in the circuit of the magnetic shunt.

A second way of realizing the invention is shown in FIG 2 outlined. The numbers 1, 3, 4 and 9 have the same meaning as in Figure 1. 10 is the multi-turn winding of the winding current transformer.

As an anchor and at the same time as contact elements of the electromagnetic Relay, an encapsulated inert gas magnetic switch 11 is provided here, which often also called Reed or HERKON (protected name). The contact flags off Soft magnetic material are mostly used to protect against corrosion and pollution melted in a glass tube filled with a protective gas; through this the contacts are particularly reliable. Such hlagnetschalters can also placed under Isolierol or cast in resin.

In Figure 2, a magnetic shunt is created with an air gap formed that the iron core has a groove-shaped recess 12 on the outside, about the the magnetic switch is arranged. As the current carrying capacity of the magnetic switch is limited, e.g. B. to 3 A, if necessary, several such contacts connected in parallel or relays with stronger switching capacity connected downstream.

The constant interruption of the circuit due to the fluttering of the Magnetic switch - contacts in the alternating magnetic field can, if necessary, be eliminated by z. B. two contacts are connected in parallel, of which one contact is in a magnetic circuit with a short-circuit winding. This ensures that the two magnetic switches as a result of a phase shift the exciting magnetic fields are never open at the same time.

Instead of the two different types of magnetic shunts In Figures 1 and 2, other constructive solutions are possible to get this out The magnetic stray field emerging from the core under strong excitation changes to electromagnetic Let the relay work. Except for the two types of electromagnetic that have been drawn Relays other designs are also possible to implement the invention.

If you have an electromagnetic relay without magnetic coupling to the core as known only structurally combined with the current transformer to the to use the main insulation of the current transformer for the relay at the same time, then with a suitable design of the relay this is caused by the magnetic field of the primary conductor triggered. However, this design has the disadvantage that the response current is high the respective arrangement of the primary conductor and the material conductor during assembly of the current transformer becomes dependent. With the magnetic coupling to the current transformer core on the other hand, the magnetic field acting on the relay is largely independent of the external routing of the conductors; if necessary, the current transformer core is provided for this purpose As is well known, compensation windings or screens to maintain the external field influence to reduce the measurement accuracy.

In addition, the magnetic coupling allows the Response current due to the change in the current transformer burden, which in general between 25 * and 100% of the nominal burden may be varied without affecting the error limits of the converter are exceeded.

The well-known kink in the magnetization characteristic increases in the combination according to the invention, the triggering magnetic field when entering Saturation abruptly, whereby the adjustment current strength with a particularly small tolerance can be set. This is another advantage of the invention built relay opposite the tripping by the proportional with the overcurrent rising magnetic fold of the primary conductor.

As a current transformer to achieve sufficient measuring performance and accuracy Designed as a winding transformer with several primary windings for small rated currents it is guaranteed that bclsk attaching a relay according to the invention to ..ia.n Such current transformers can also be used with small short-circuit currents on request a Can cause the relay to respond instead of the usual excitation of distance protection relays via a protective current transformer with a rotating armature relay, which has the shortest command time of about 30 to 100 ms, the excitation can take place immediately according to the fflinvention -, In the case of magnetic switches, the shortest command time is around 2 to 5 ms can be reduced.

Several relays can be used for staggered overcurrent detection attach to a current transformer core with different response currents.

Distance and differential protection devices can in their mode of operation are disturbed when the protective cores as a result of the DC link in the short-circuit current temporarily go into saturation. If you build the described ones on these protective cores Relay on, then information can be sent to the saturation that has occurred give the protective device to stabilize their operation.

By arranging the relay according to the invention on different Setting a network is a remote message about the course of the short-circuit current and an automatic switch-off of the short-circuit-prone power supply is possible.

For the ferrimessage it can be useful to connect the relay with a Holding winding: and to be provided with holding contacts, so that by means of an auxiliary voltage after switching off the primary overcurrent, the relay contacts tn the response position being held.

Finally, through the specified current transformer-relay combination the overdrive of a fault recorder. switched on and after the end of the short-circuit current be switched off again.

From the application examples described above, which are further supplemented could be, it can be seen that by the invention in a simple manner and a number of tasks in the field of network protection technology with a very short response time is to be solved, which so far only with greater effort and with longer command times were to be fulfilled.

Considered publications: 1 ¢ German patents and utility models - auxiliary application "Kippschwingungsgedämfter voltage converter" file number P 1901612.7 H02h 21 d 3 2 filing date January 14, 1969 2. Petry, H .: nStrom- und voltage converter für Schnell - Netzschutz "Zeitschrift" Elektriz it ätswirtschaft " 3. Petry, H .: "Short circuit, displayed in medium-voltage networks" magazine "Elektrotechnik" 51 t (1969) 13 to 20

Claims (3)

Claims 1. Electromagnetic combined with a current transformer Relay for zetzschutz, characterized in that the armature or armatures of the relay be placed near the iron core of the current transformer in the Neise that due to the magnetic field in the vicinity of the primary overcurrent magnetically strong energized Zisenkernes on the anchor or anchor a force is exerted and thereby contact members are actuated. 2. Electromagnetic relay combined with a current transformer for the network protection according to claim 1, characterized in that the anchor or anchor of the relay bridge the air gap of a magnetized shunt, which is called Part of the iron core of the current transformer is formed. 3. Rit a current transformer Combined electromagnetic relay for iQetzscnutz according to claims 1 and 2, characterized by dal3 as Armature and, at the same time, one or more encapsulated protection devices as contact elements of the relay - Magnetic switches (reed contacts) are used.