DE446630C - Device for high-voltage systems for displaying the short-circuit between turns of AC devices and machines - Google Patents

Description

GERMAN EMPIRE

ISSUED ON JULY 7, 1927

REICH PATENT OFFICE

PATENT LETTERING

CLASS 74 b GROUP

E33283 VHII ₇₄ B Date of the announcement about the granting of the patent: June 11th ig2j.

Electricity Act Ges. vorm. W. Lahmeyer & Co. in Frankfurt a. M. *).

Device for high-voltage systems to indicate the short-circuit between turns of AC devices and machines.

Addendum to patent 432 837.

Patented in the German Empire on November 5, 1925. The main patent started on April 19, 1925.

Patent specification 432 837 describes a device for high-voltage systems for displaying a shorted turn in alternating current devices and machines described in the series with the equipment to be protected (generators o. The like.) A current transformer set and in parallel to the apparatus to be protected, a voltage transformer set are installed in such a way that the electromotive Powers of the individual phases of their

*) The patent seeker stated as the inventor:

Dr Walter Bütow in Frankfurt a. M.

Size can be compared with each other and by the electromotive forces occurring in them a highly sensitive relay is made to respond, which therefore indicates that a non-zero sum is present. The auxiliary transformer V required in this display device can be omitted if the current transformer set 7 is designed accordingly. In this case it is necessary to specially wind the current transformer. In almost all cases it can be designed as a bushing current transformer, i.e. a converter whose primary winding is either housed in one (single-conductor current transformer, see Dr. G. Keinath, Die Technik der electrical Meßgeräte, 1921, page 295) or in two bushings. In contrast to the normal current transformer, it has to absorb a high magnetizing current and can therefore create air gaps in the active iron. keep. It is easily possible, in addition to the current transformer 7 intended for the interturn fault relay, to slide another one for measuring purposes M and possibly a third one for the overcurrent relay U onto the same bushing, as shown in FIG.

The current transformer set 7 is to be designed so that a voltage on its secondary side equal to the magnitude of the stray voltage of the machine to be protected or of the machine to be protected Apparatus arises when the corresponding current flows through the primary side will. Furthermore, the converter is to be adjusted so that the primary current with the secondary voltage encloses an angle that corresponds to the phase shift between current and stray voltage in the case of the one to be protected Apparatus corresponds.

The current transformer can expediently be designed in such a way that ring-shaped metal sheets receive a cutout. Several such rings are combined into one package, several packages into one current transformer. As Fig. 2 shows, the current transformer can then be calibrated in such a way that the individual packets are shifted against each other. In this way the air gap is changed. The entire circuit diagram that comes into consideration in this additional patent is shown by Abt). 3. The designations in this figure are the same as in Fig. 1 of the main patent. G denotes the generator or the apparatus to be protected, 7 the current transformer set. 6 "the voltage transformer set, Ö the oil switch, A the tripping, M three maximum relays, Z a time relay, R the interturn fault relay, C the capacitor, W a low-voltage transformer set and B the busbars of a direct current source, if the apparatus to be protected G is healthy, it will open The secondary side of the current transformer set 7 generates a voltage which corresponds to the stray voltage or the voltage drops in the apparatus to be protected. Furthermore, a voltage is generated on the secondary side of the voltage transformer set 5 which corresponds to the terminal voltage of the apparatus G to be protected of the voltage transformer set S and the current transformer set "J, the geometric addition or subtraction of terminal voltage and stray voltage (or voltage drop) is formed. In a three-phase system, three voltages of the same magnitude must therefore be obtained, ^{offset from one another by 120 0} and corresponding to the electromotive forces of the individual phases. The sum of these electromotive forces, which is formed in the voltage converter set W , must therefore be zero. The three voltages are compared in that the voltage transformer set W is connected primarily in star, secondarily in open delta. In an open triangle, the current flows back to the converter set W via the capacitor C through the winding fault relay R via the break contact of the timing relay Z.

The capacitor C is used to produce resonance with the inductance of the relay R and the transducer set W in order to eliminate interference caused by harmonics as far as possible. In undisturbed operation, no current can flow in the circuit described last, since there is no unbalance voltage.

If, however, a shorted turn of phase occurs in a protected ¹ QQ apparatus G, so the electromotive force of this phase must be made smaller. The geometric addition or subtraction of terminal voltage and stray voltage, however, results in an electromotive force in the diseased phase that is smaller than the electromotive forces in the healthy phases. In addition, the phase shift between the three voltages will deviate ^{from 120 0.} It is produced on the secondary side of the voltage transformer set W Unsymmetriespannung which causes a current through the capacitor C, the Windungsschlußrelais R and the normally closed contact of the time-'relais Z flows, is brought whereby the relay R to the response.

The relay R attracts its armature, thereby the normally open contact controlled by this armature is switched on, and a current can be drawn from the direct current busbar B via the normally open contact of the relay R ₃

Fall flap Fw and the tripping coil A of the oil switch Ö flow back to the other pole of the direct current source B. Thereby, the oil ö switch is thrown, so that the sick apparatus is separated from the busbars. The drop flap Fw indicates that the interturn fault relay R has responded. It may be necessary to block the interturn fault relay R using an overcurrent relay. This is particularly the case with generators whose reactance changes unevenly in the event of non-three-phase short circuits. Blocking is also necessary if it is not possible to design the current transformer set / in such a way that the secondary voltage remains proportional to the primary current intensity. In Fig. 3, three more current transformers are therefore provided that work on the maximum relay M. If * o one of these maximum relay M responds, a normally open contact is closed so that from one pole of the DC power source B, a current to the other pole of the DC source flows back B through the now closed working contact and the timing relay Z. The timing relay Z now attracts its armature and interrupts the above-mentioned break contact in the circuit of the interturn fault relay R. After a certain, adjustable time, the timing relay Z closes a working contact, so that a current from one pole of the direct current source B via the working contact, the drop flap Fm and the trip coil A to the other pole of the direct current source B can flow. Now the apparatus to be protected is switched off by the overcurrent relay M , and after a much longer time than by the winding- fault relay R, since a time graduation must be made in the control centers and substations in order to ensure the most perfect operation possible. The drop flap Fm indicates that in this case the tripping has been switched off by an overcurrent. It is mentioned above that the stray voltage is either to be added or subtracted from the terminal voltage in order to obtain the electromotive force of the apparatus G to be protected. In the case of generators, for example, the terminal voltage and the stray voltage can be added to form the electromotive force, while in the case of motors, the geometric difference between the terminal voltage and the stray voltage is to be formed.

For transformers, the device described above is used unchanged on the secondary side of the transformer. In Fig. 3 the secondary side of the transformer would be designated with G in this case. The no-load current of the transformer is neglected, which is acceptable in most cases. A current transformer set J can also be arranged on both the primary and the secondary side, with the no-load current of the transformer being taken into account. In this case, two converter sets J ₁ and J _{2 are obtained} . Secondarily, they are both connected in series and operate on a transducer set W, as shown in Fig. 4, so that only one relay is required.

The diagram in Fig. 4 shows how the arrangement works. Of the For the sake of simplicity, first a transformer with the transformation ratio will be used ι: ι accepted.

Let: V ₁ the primary voltage applied, E ₁ the primary electromotive force, E ₂ the secondary electromotive force, V _sl the primary stray voltage, V _s2 the secondary stray voltage, V ₂ the secondary terminal voltage, J ₀ the no-load current, J ₂ the secondary Load current, 7 ' ₂ the secondary load current, transfers to the primary side, J ₁ the entire primary current.

The diagram recorded in single-phase initially applies to single-phase alternating current, but then also to each phase of a multi-conductor system. As can be seen from the circuit diagrams, the phase voltage of the converter set W is applied to the short-circuit relay R , so that the diagram applies to all cases.

Under the influence of the imposed primary voltage, the no-load current J ₀ , which causes the electromotive forces Ij ₁ and E _{2, arises in the primary winding of the transformer.} This .. no-load current creates a voltage drop in the primary winding, so that the electromotive force S ₁ must be smaller than the primary terminal voltage V ₁ . If the transformer is subjected to a secondary load, namely by the current denoted by J ₂ in the diagram, a corresponding current 7 ' _{2 must} arise on the primary side. By geometrically adding the latter to the no-load _{current / 0} , one obtains the actually flowing primary current J ₁ , which causes the voltage drop V _sl on the primary side of the transformer. Likewise, the voltage drop F ₅₂ arises on the secondary side G of the same due to the load current J ₂ . The primary electromotive force becomes smaller as a result of the primary stray voltage F ₅₁ , as can be seen from the diagram, and the secondary terminal voltage is reduced by the secondary stray voltage. If now the current transformer sets J ₁ , / "are designed so that

wherein the set of current transformers J ₁ a primary current J ₁ corresponds to a secondary terminal voltage equal to the primary stray voltage V _sl, and when further the current transformer set J ₂ is formed so that the load current J ₂ as primary current of the current transformer set J ₂ is a secondary terminal voltage V ₂ arises at the current transformer set, which is equal to the secondary stray voltage V ₅₂ , the conditions are met that the primary terminal voltages V _{1 are} formed ^{by the voltage transformer set 5 1} and the two current transformer sets J ₁ and J _2. In the case of the transformer, however, the primary terminal voltage V _{x is to be} regarded as an imposed electromotive force. The sum of these imposed electromotive forces (or primary terminal voltages) must be zero. Accordingly, a voltage in the open triangle and thus a current in the interturn fault relay R can only occur at the converter set W if there is a fault in the transformer. It should also be noted that a distinction must be made between the electromotive force of the transformer, which is designated in the diagram with E _x and B ₂ , and the forced electromotive force, which is equal to the terminal voltage V _x .

It is now also possible, instead of the imposed electromotive forces, to simulate primary terminal voltages V _x ) and the electromotive forces E ₁ or E _{2 of} the transformer. For example, with a circuit according to Fig. * 3, if the primary side of the transformer is designated by G , the primary electromotive force JS _{1 of} the transformer is obtained at the transformer set W. If the secondary side of the transformer is denoted by G in Fig. 3, the secondary electromotive force E _{2 of} the transformer is obtained at the transformer set W. You can now compare the voltages that arise at the two converter sets W on the primary and the secondary side of the converter in a further set of transducers. The sum of the voltages must then be zero again. If the idle current J _{0 of} the transformer is neglected, the two stray voltages V ₃₁ and V _s2 on the primary and secondary side of the transformer can be combined to form a single stray voltage V _s and, as noted above, a single set of current transformers J can be used . In this case, only the secondary side of the transformer has to be switched according to Fig. 3, with G denoting the secondary side of the transformer.

The previous considerations apply, as mentioned above, for the case that the transmission ratio of the transformer is 1: 1. The same diagram applies, however even if the transformation ratio is different and accordingly for the voltage converters is taken into account for any translations (see e.g. Dr. G. Kittler and Dr. J. W. Petersen »Allgemeine Elektrotechnik «, 2nd volume, Stuttgart 1909, page 480 or page 498).

Claims (4)

Patent claims: 1. Device for high-voltage systems for displaying the short-circuit between turns of AC devices and machines according to Patent 432 837, characterized in that the voltage generated in the current transformer (J) is added directly to the secondary voltage of the voltage transformer (S) in that the current transformer (J ) has a special type of winding and absorbs a high magnetizing current through air gaps in the active iron. 2. Device according to claims, characterized in that the bushing current transformer from annular sheet metal. packages that are provided with a cutout, and that by twisting A comparison of the current transformer (J) is achieved by individual packages. 3. Apparatus according to claim 1 and 2, characterized in that the interturn fault relay (R) indicating the differences in the electromotive forces in the individual phases operates via contacts which are dependent on overcurrent relays (M). 4. Apparatus according to claim 1 and 2, characterized in that a current transformer set (J ₁ , J ₂ ) is attached to the high-voltage and low-voltage side of the transformer, so that the no-load _{current (J 0} ) of the transformer is taken into account in the protection. 1 sheet of drawings.