Multiple Reignition Research Articles

The ARIANE 5 launcher improvements

After the successful 503 and 504 flights, the way is now open for the operating phase of the new European rocket. But market assessment also establishes the need for improved versions of ARIANE 5. Telecommunication satellites continue to grow in mass, and new missions like launching constellations require versatility of the upper stages (multiple re-ignitions, compatibility with ballistic phases). Moreover, to reduce production costs, a special effort has to be made.

Current-interruption testing of vacuum switching devices

In the international IEC standards for medium and HV switching devices no distinction in test requirements is made between switching devices with different arc-quenching media, like SF/sub 6/, oil and vacuum. This had led to the situation that due to the different technology of arc interruption applied, various aspects of the prescribed test-procedures have a different weight in terms of severity for various types of breakers. Additional test-requirements and interpretations that are specific to vacuum switching devices have been formulated commonly by the joint major test laboratories. In this contribution, the background and practical application of several procedures, now generally adopted by certifying test-laboratories, regarding the peculiarities of vacuum switching devices are elucidated. Because the vacuum switching device has an excellent capability to interrupt current of high frequency, the main part of this contribution will be related to the consequences for test procedures of this aspect that is not encountered in SF/sub 6/ or oil breakers. In particular, the judgment of non-sustained disruptive discharges, multiple re-ignition and virtual current chopping in test-circuits is addressed. Results of a new high-resolution high-frequency current-zero measuring system are presented. This system is able to give insight into the high-frequency arc phenomena in the immediate vicinity of are interruption, and is designed to get more specific information on arc behavior during standard high-power tests.

Overvoltages due to switching off an unloaded transformer with a vacuum circuit breaker

When a vacuum breaker is used to disconnect an unloaded transformer, high overvoltages may result on the secondary side. The phenomena of current chopping and multiple reignitions after contact opening, shortly before current zero, play a significant role in generating these overvoltages, Furthermore, the transient recovery voltage (TRV) is also influenced by virtual current chopping which may lead to fast interruptions and reignitions. The paper reports on a vacuum breaker model implemented in the ATP-EMTP program. Simulations have been performed to determine overvoltages generated by the vacuum breaker, before and after suppression. Network elements were simulated by simplified models of limited complexity.

Overvoltages in secondary circuits of medium-voltage switchgear generated by multiple reignitions of circuit breakers

During switching operations in the high-voltage system, transient voltages and currents occur that can generate overvoltages in the secondary circuits of switchgear. The investigations reported in this article are focused on medium-voltage air-insulated switchgear. The introduced model is able to identify the coupling mechanisms. The coupling via the instrument transformers and the secondary wiring to the electronic equipment is described. At first, the frequency-dependent coupling is explained for each secondary component. These are instrument transformers, the secondary wiring, and the electronic equipment. Then it is shown how to combine these components in order to get a complete description of the interfering mechanisms.

An investigation of transient overvoltage generation when switching high voltage shunt reactors by SF/sub 6/ circuit breaker

The work reported in this paper can be grouped into three categories: empirical investigations; analytical studies; and computer simulations. The studies have identified the causes of high transient overvoltages which are produced when switching high voltage shunt reactors. Laboratory and site testing have shown that multiple reignition is the most likely cause of the high overvoltages. Circuit analysis has been carried out to identify the conditions which lead to multiple reignitions. A computer model has been developed to allow the likelihood of multiple reignitions occurring to be assessed.

Voltage escalation and reignition behavior of vacuum generator circuit breakers during load shedding

This paper focuses on multiple reignitions and voltage escalation that may occur during load shedding when vacuum circuit-breakers are used as generator circuit-breakers. The probability of multiple reignitions and voltage escalation is proportional to the arc angle and is very small. However, repeated reignitions and voltage escalation may be observed in vacuum switching devices after opening operations due to their ability to interrupt HF currents. The transformer side capacitance and the magnitude of the load shedding play a significant role in developing repeated reignitions and voltage escalation when vacuum circuit breakers are used as generator circuit breakers. Of particular concern is the case when a protective capacitor is connected to the system side of the circuit breaker. Although this capacitor reduces the magnitude of the of transient recovery voltage, it decreases the transient frequencies and increases the reignition current that flows through the vacuum circuit breaker after a voltage breakdown. In all the cases under study, the reignition/escalation problems are more severe with the protective capacitor connected to the power system for relative low load shedding at short arc angles. This paper reports on many simulated conditions analyzed by using the Electromagnetic Transient Program (EMTP). Ten generators in the range of 50 through 300 MVA have been considered.

Investigations of multiple reignition phenomena and protection scheme of shunt reactor current interruption in GIS substations

Field measurement and computer analysis concerning 150 MVA shunt reactor current interruptions at a 275 kV gas insulated substation (GIS) were carried out to verify that high-frequency current interruptions can be caused by certain system structures on the circuit breaker power supply side. A shunt reactor current-interrupting test was conducted with phase angle control, which is considered to be the best method for preventing multiple reignitions, using short-circuit test facilities. The possibility of stable reignition-free interruption was confirmed, even when the longest arcing time is preset. >

Prevention of reignition overvoltages by phase‐angle‐controlled switching of a gas circuit breaker at shunt reactor current interruption

AbstractShunt reactors installed at gas‐insulated switchgear substations (GIS‐substations) are switched relatively frequently by large‐capacity gas circuit breakers (GCBs). Surge voltages appear at such switching operations through various mechanisms. Among them, high‐frequency current interruption and subsequent multiple reignition might cause the highest overvoltage and may be harmful to the insulation of the components of the substation.In this paper, shunt reactor current‐interrupting tests are conducted in high‐power laboratory. The existence of critical arcing time above which reignitions never occur is shown through these tests. From this fact, a phase‐angle‐controlled‐interruption system is proposed. With this system, arcing time is set artificially so that reignitions should be prevented. The reliability of this system is confirmed through the reactor current‐interrupting test in the laboratory as well. Afterward the phase‐angle‐controlled‐interruption system is applied to the shunt reactor switching at an actual 275‐kV substation. The switching performance of this system is measured over three months. Reignition‐free interruption is shown to be attained with this system.

Townsend-type breakdown as a criterion for high-frequency vacuum arc interruption at submillimeter gaps

In vacuum circuit breakers, multiple reignitions give rise to HF current arcing ( approximately=500 A; approximately=200 kHz). Due to the small contact distance and the very large current gradient, at every arc-current zero pressures of several tens of millibars can be expected. Very soon thereafter ( approximately=30 ns) this gap is dielectrically stressed by the first component of the restriking voltage ( approximately=10 MHz), originating from parasitic impedances. The combination of the associated high electric field and the relatively high neutral density may cause Townsend-type breakdown, leading to another half-sine of continued arcing. Both dielectric stress and residual neutral density are expressed as a function of di/dt, yielding values of interruptible di/dt as a function of the contact distance with the Townsend breakdown criterion. Comparison with experiments shows fair agreement in the range of di/dt of 100-1000 A/ mu s and distances of 0.1-0.5 mm for two different circuits. >

An electronic method of controlling multiple reignition switching transients in vacuum contactors

An electronic method is described for controlling the contact tip opening of a vacuum contactor in such a way that the probability of transient overvoltages caused by multiple reignitions during load switching is minimized. The multiple reignition transient problem is described, and the electronic hardware utilized to control the vacuum contactor is discussed. Tests of the effectiveness of the system were performed. The test procedure and results of the tests are described. The tests confirmed that control of the tip-opening point on the load current waveform will prevent vacuum contactors from producing multiple reignition transients even under severe conditions such as jogging duty. By varying the tip-opening angle of the contactors under test, a range of arc angles was found in which multiple reignitions did not occur. The test procedure also proved that the electronic control can maintain contactor tip opening in the target band consistently. Other functions that the microprocessor-based electronic control can provide are also discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Low Surge Vacuum Circuit Breakers

Low surge vacuum circuit breakers were developed which used a new electrode material cobalt-silver-selenium alloy. Their chopping current level was below 1.0 A and their high frequency current interruption ability was about 24 Aús. These levels were much lower than those of conventional electrode materials and did not change after load current interruption lifetime and short circuit current interruption tests. From switching tests with motors and no-load transformers, safe operation of these vacuum circuit breakers, without any surge absorber, was confirmed ; the surge level caused by current chopping and the multiple reignition surge level caused by high frequency current interruption were far below the apparatus insulation levels. Furthermore, the new material showed good interruption ability.

Chopping Current and Quenching Capability of Low-Voltage Vacuum Arcs

The chopping current and the quenching capability during switching-off in a vacuum are investigated using Cu/Cr, Mo/Cu, and W/ Cu with added materials of high vapor pressure. Cylindrical contacts of small dimensions (15 mm diameter) with antimony, bismuth, cadmium, and zinc alloyed or added in solid form in holes or slots are used. The chopping current is determined duiing interrupting a 50-Hz current of 45 A. The investigation shows that alloying 2 percent of antimony or 3.7 percent of zinc to W/Cu 70/30 reduces the chopping current to about half of the value of W/Cu 70/30. Adding antimony, bismuth, cadmium, or zinc in solid form leads to a reduction from 6 A to about I A. The quenching capability is investigated in a synthetic test circuit using current injection with switchlng-off currents from 800-2400 A and values of the recovery voltage of 2.7 kV. The interruption properties of W/Cu 70/30 are deteriorated when components of high vapor pressure are added. If the contacts are separated shortly before current zero, multiple reignitions are possible due to the interruption of transient high-frequency currents. For the given circuit conditions, switching with short arcing times and small contact distances shows that multiple reignitions occur with all investigated materials. A dependence between reignition voltage and contact distance is given. Materials with a high vapor pressure generally reduce the reignition voltage.

Measurement and Statistical Simulation of Multiple Reignitions in Vacuum Switches

When the gap length of a vacuum switch at current zero is too small, successive reignitions and extinctions may occur under certain circuit conditions leading to overvoltages. This process of virtual chopping is more likely to happen when the contacts accidentally open shortly before current zero. In order to determine the values of the overvoltage and its probability when opening the contacts randomly, a computer program was developed which simulates the transient recovery voltage (TRV) in a single-phase circuit and determines the highest voltage for each switching operation. The moment of contact opening is simulated by pseudorandom numbers. Input data of the calculation are the circuit parameters, the reignition voltage of the gap versus time after current zero, and its capability of quenching the high-frequency current oscillation occurring after a reignition. These recovery data of the opening gap were determined experimentally for some contact materials using a special switching device in a synthetic test circuit with current injection.