DE1054552B - Arrangement to increase the sensitivity of response counters with a voltage-dependent resistor for surge arresters - Google Patents

Description

GERMAN

Surge arresters are used to determine the number and strength of flashovers with a so-called Response counter provided, which is in series with the surge arrester, between this and earth is connected. Response counters of known design have a voltage-dependent one Resistance to which a heating resistor and a choke coil are connected in parallel. The heating resistor only a small fraction of the leakage current flows through it. He is in a Chamber closed by a membrane, the gas of which heats up and expands in the event of a current surge, the stroke of the membrane being transmitted to a counter. There can also be several, e.g. B. three counters be arranged, which respond to diaphragm strokes of different sizes. With the choke coil, which opposes the very rapid current impulses a high resistance, but for the slowly swelling Wake currents means a much smaller resistance than the voltage-dependent resistance, a well-known electromagnetic impulse meter can be connected in series, which counts the wake. The number and Strength of the flashovers are closed.

In the previous arrangements of response counters, the voltage-dependent one is dimensioned Resistance according to the discharge capacity of the surge arrester for which the device is used is interpreted. By connecting the voltage-dependent resistor and heating resistor in parallel the energy that is available for the three counting stages activated by the membrane is dependent from the voltage drop occurring at the voltage-dependent resistor. The responsiveness of the meter is dependent on this voltage drop for a given mechanical design, the With regard to the protective effect of the arrester, it cannot be increased at will, otherwise the resulting one Residual voltage, which is adapted to the insulation level of the system to be protected, is too high. The response sensitivity is also limited by the mechanical design of the meter, in that this must be robust according to the prevailing operating conditions and the membrane pressures to trigger the first and third counting stage already in a relatively large ratio of about 20: 1000 g, i.e. 1:50, which defines the minimum dimensions of the release mechanism.

The invention relates to an arrangement for increasing the responsiveness of response counters with a voltage-dependent resistor for surge arresters, which is characterized is that the voltage-dependent resistance

arrangement
to increase the response sensitivity of response counters
with a voltage dependent
Resistance for surge arresters

Applicant:
Landis & Gyr AG, Zug (Switzerland)

Representative: Dr.-Ing. A. Schulze, patent attorney, Berlin-Wilmersdorf, Jenaer Str. 13/14

Claimed priority: Switzerland from July 5, 1957

Paul E. Fehr, Zug (Switzerland), has been named as the inventor

at least one also voltage-dependent resistor connected in parallel over at least one spark gap is.

Embodiments of the invention are explained in more detail with reference to the drawing. The drawing shows in

1 shows a basic circuit diagram of a response counter with connected in parallel via a spark gap Resistors, in

Fig. 2 is a current-voltage diagram in

3 shows a basic circuit diagram of a response counter with two spark gaps connected in parallel Resistances.

According to the embodiment of FIG. 1, the response counter, which is connected between a surge arrester 11 of a high-voltage line 12 and earth, contains a voltage-dependent resistor 13 and a heating resistor 14 in a chamber 15 containing a gas or air, the membrane 16 of which depends on the size of the Hubes a counter I or II or III triggers so that the flashovers are counted according to three different strengths. A choke coil and an electromagnet 18 with a counter IV are connected to the resistor 13 in a further parallel circuit, which counts the wake currents in a known manner. According to the invention, three further voltage-dependent resistors 20, 21, 22 are now parallel to the voltage-dependent resistor 13 via a spark gap 19

809 '78Ϊ / 383

Claims (4)

switched, which for purely practical reasons are chosen to be the same strength as the resistor 13. Without these resistors connected in parallel, the resistor 13 would have to be dimensioned for the full leakage current strength of the surge arrester 11, for example 4000 A, and the counter III responds with leakage currents of this strength. At a lower current strength, for example 1000 A, there is a voltage drop which causes the counter II to respond, and at 100 A one to which the counter I still responds. Up to now it has practically not been possible to adjust the counter I to lower leakage currents because the voltage drop quickly becomes too small. Of course, the three resistors 20, 21, 22 can also be replaced by a single equivalent resistor. The dependence of the voltage U on the current / is shown in FIG. 2, and for the above example it follows the curve. If, however, three identical resistors are connected in parallel to resistor 13 via spark gap 19, then all four resistors are dimensioned for a current strength of 1000 A, and as long as there is no flashover at spark gap 19, the voltage follows curve B. It increases even with small ones Current strengths so that at 50A the counter I can respond with certainty. The spark gap is set to this response voltage or higher, so that a voltage according to curve A is formed for higher currents. The voltage dependency is given by the law U = C-K1, and for the counter III at 4000 A where the exponent β has an average value of 0.25 and C is an execution constant. A leakage current of 100 A with four parallel resistors results in a voltage of 100 MUS U-, = C- 2.24 C. With only one resistor, the voltage U2 = C-1000 · 25 = 3.16 C Die for the heating resistor 14 available power is thus compared to previous arrangements in a ratio of 2 r <? 1ftl2 U223.16 "U12.24 c ^ 4000r = 35 40 45 With just one resistor, a voltage Us that is greater than the voltage is achieved at 50 A U1 and C ■ 50ο · 25 = 2.66 C. The response voltage Ui for the counter II at 1000 A is as before U1 = C / IOOOVs5 \ 4 55 = 3.97 C For surge arresters with a very high leakage current, the response sensitivity in are increased in the same way, only it is useful, as shown in Fig. 3, to connect the resistor 20 via a spark gap 23 and the other two resistors 21 and 22 via a further spark gap 24, the first spark gap 23 to the response voltage of the counter I or higher, the second e spark gap 24 is set to the response voltage of meter II or higher. In a practical example for a leakage current of 10,000 A to which the counter III responds, counter I responds to 50 A and counter II to 2500 A. The voltages appearing across the resistor 13 for these three counting stages are approximately 2.66 C for 50 A, 5.95 C for 2500 A and approximately 7.05 C for 10000 A a spark gap, resistors 20, 21j 22 connected in parallel have a smaller constant C than the permanently connected voltage-dependent resistor 13. The power ratio is then increased by the factor -—. Patent claims: 1. Arrangement to increase the sensitivity of response counters with a voltage-dependent resistance for surge arresters, characterized in that the voltage-dependent resistor at least one also voltage-dependent resistor at least one spark gap is connected in parallel. 2. Arrangement according to claim 1, characterized in that the voltage-dependent Resistance three equal, parallel connected resistors connected in parallel via a spark gap are. 3. Arrangement according to claim 1, characterized in that the voltage-dependent Resistance an equal resistance over a first spark gap and two more equal Resistors are connected in parallel via a second spark gap. 4. Arrangement according to claim 1, characterized in that the via a spark gap resistors connected in parallel have a smaller constant than the one that is permanently connected Resistance. 1 sheet of drawings © 809-789 / 383 3.59