Capacitor Units Research Articles

Bridge capacitor bank design and operation

The concept of a bridge capacitor bank installation was presented in a previous paper (see N.G. Andrei et. al., IEEE Trans. Power Systems, vol.8, no.4, p.1463-70, 1993). This paper discusses design and operation aspects related to the installation of a bridge capacitor bank in a substation. The 138/69 kV bridge capacitor bank installation presented by Andrei et. al. is analyzed. An automatic switching control relay scheme for the same test installation is also discussed. The control scheme takes into account the dual effect a bridge capacitor installation has upon the electrical power system: it generates reactive power on the station 138 kV bus and transfers reactive power from the 69 kV to the 138 kV bus. An unbalance protection scheme preventing the cascading type failure of the capacitor units in the 138/69 kV bridge capacitor bank is also presented. An unbalance protection scheme for high voltage, large MVAr size bridge capacitor banks is also discussed. Simple analytical formulas with practical value to evaluate the magnitude and frequency of the voltage transients generated by the energization of a bridge capacitor bank are presented. Recorded switching transient magnitudes and frequencies are compared with calculated values.

The development of high voltage power capacitor technology in Japan

Unlike other countries, Japan has differed from the normal industrial trend toward using large, tank-type high voltage power capacitors. Recent notable achievements are the development of completely enclosed, compact capacitor banks, which are composed of very large capacitor units. Can-type capacitors have been also manufactured and used in Japan and have been highly developed recently, especially in the field of metallized film capacitors. Described in this report is the development of high voltage capacitor technology, especially of tank-type capacitors. The scale of substations has become larger year by year with the expansion of the Japanese economy. Compact capacitor banks save space but allow unit capacities of main substations to be increased.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Protective system for a high‐power capacitor bank

AbstractA new protection system for capacitor banks in the case of a short‐circuiting accident is described. A pulsed power system composed of many capacitor units and closing switches is well known for producing a controlled pulse current of high power as for the power source of a plasma experimental device, etc. According to the increase of capacity of a bank system, it becomes important to protect the whole bank system from a short‐circuiting accident in a capacitor unit.Although some protective ideas have been proposed, these conventional ideas have not been sufficient to absorb the energy flowing into the failure unit from other normal units. Constructing the new 1‐MJ capacitor bank for a plasma experimental device, a newly conceived protective device is designed. The new protection system can absorb the bank energy and suppress the short‐circuiting current flowing into the failure capacitor units, and overcomes the defect in former protection systems. To confirm the utility of a new protection system, a test of a protection resistor imitating the actual bank circuit was made. The test result showed that absorbable energy for the unit ceramic resistor amounted to 1500 Joule/cc. The new system is adopted to the bank system of the TPE‐1RM15 plasma experimental device.

Discrete VAR optimization in a distribution system using mixed-integer programming with an expert system

A new solution procedure for the discrete VAR optimization of a power distribution system is presented in this paper. In orderto obtain an optimal discrete solution within a reasonable time, a mixed-integer programming method combined with an expert system is proposed to achieve these requirements. The proposed expert system helps the system planning engineers to allocate an appropriate initial feasible solution, and to decide the position of transformer tap settings as well as the number of capacitor units. From three solution stages using the linear programming approach, the expert system approach, and the mixed-integer programming approach, the discrete VAR optimization problem is promptly solved. Numerical simulations of a small-scale system and a practical system are demonstrated with significant results. The results demonstrate the effectiveness and improvement of the proposed method to solve the VAR optimization problem in a power distribution system.

Fuseless capacitor banks

A fuseless capacitor bank construction is described. Before the first fuseless capacitor bank, engineering tests were performed to ensure that the fuseless concept was sound. Testing of faulted units included: continuous current, capacitor switching, and capacitor losses (power factor). Details pertinent to fuseless capacitor bank construction and characteristics of fuseless capacitor banks are discussed. In addition, protective considerations are given, methods for locating a defective capacitor unit are described, and design guidelines are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An algorithm for discrete optimal power flow

This paper presents a new algorithm to solve an optimal power flow problem which can take into consideration the discrete nature of some facilities in power systems. The optimal power flow problem is formulated as a nonlinear mixed-integer programming problem in which the number of transformer taps and the number of shunt capacitor units and reactor units are treated as discrete variables. This paper attempts to solve such a large-scale nonlinar mixed-integer programming problem by some effective programming techniques. The optimization procedure of the algorithm is that the nonlinear mixed-integer programming problem is linearized iteratively and solved by an approximation method for linear mixed-integer programming. A fundamental feature of the algorithm is that it can guarantee a solution which is discrete, feasible and near-optimal. The validity and efficiency of the algorithm is demonstrated by the numerical results of real-scale optimal power flow problems.

A new delay-line kicker with capacitive loading sandwiches

Abstract The delay-line type of kicker for the in- and ejection into and from cyclic accelerators is the right choice if extremely fast rise and fall times are required. It will be shown that it may be operated at 1 3 of the wave impedance of the pulse generator as compared to the lumped element solution with a corresponding reduction in the pulse voltage [1]. The pulse generator charge voltage will be reduced by a factor of 1.5. However, low wave impedance requires high capacitive loading for which the usual construction of delay-line magnets is prohibitive since is makes use of longitudinal subdivision of the ferritic core of the magnet into a number of individual cells, each cell consisting of a piece of ferrite followed by a capacitive plate connected to the magnet conductor. For decreasing cell length the percentage of longitudinal space occupied by the capacitive plate increases with a corresponding increase in overall length and a decrease in magnetic length. Therefore in practice there exists a lower limit for the cell length and the associated cell inductance. This in turn introduces a lower limit for the wave impedance since the capacitive loading would lead to unacceptable bulky capacitor units. In this article a straightforward modification of the usual design of delay-line kickers will be described with a picture frame ferrite geometry as it is used for lumped element kickers and capacitive loading units being attached to the core like sandwiches. This approach offers a number of advantages compared to the conventional solution.

Minimum area analogue-digital calibration network for high-resolution data convertors

A novel calibration network where the capacitors are determined with reference to the minimum geometry capacitor unit allowed by the technology and follow a non-binary weighting rule to accommodate the large inaccuracies inherent to such small capacitance values is described. This, together with the rather simple digital cell which is associated with the calibration capacitors, and an efficient interconnect strategy, makes it possible to achieve a minimum area calibration network suitable for high-resolution data convenors employing capacitor arrays.

高圧コンデンサ投入時の過渡電流の実態調査

高圧コンデンサ投入時の過渡電流の実態調査

Development of compact 250 kV DC filter for HVDC converter station

As a preliminary step toward the realization of compact converter station equipment for 500 kV HVDC transmission, a prototype of high-reliability, economical, compact 250 kV DC filter equipment is developed and its performance confirmed by a long-term in-service test. The compact dead-tank-type design reduces the installed area and height and the equipment weight to 1/12, 1/3 and 2/3 respectively, of those of the existing design. The size reduction of the capacitor unit is achieved by the use of a wide paper-film dielectric specifically developed for DC filter application and by housing bare capacitor elements in a dead tank and impregnating them with aromatic hydrocarbon oil. For further size reduction, the surge-absorption capacitor is housed in the same tank.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Optimal VAr planning by approximation method for recursive mixed-integer linear programming

The authors propose an algorithm for solving reactive power planning problems. The optimization approach is based on a recursive mixed-integer programming technique using an approximation method. A fundamental feature of this algorithm is that the number of capacitor or reactor units can be treated as a discrete variable in solving large-scale VAr (volt-ampere reactive) planning problems. Numerical results have verified the validity and efficiency of the algorithm. >

Development of Compact Filters for HVDC Converter Station

500 kV large-capacity HVDC transmission is expected in near future in Japan, for which development of reliable, compact and economical equipment is important. As a first step toward this objective, a prototype compact 154-kV 9-Mvar AC double-tuned filter and a prototype compact 125-kV DC filter were developed, which are first kind in the world and are currently under long-term life test. Each filter consists of a capacitor unit and a reactor unit, both dead tank design for ground-level installation. Film-paper mixed dielectric is used for capacitor elements, and polycyclic aromatic hydrocarbon oil as impregnant and for insulation.

Development Of Compact Filters For Hvdc Converter Station

500 kV large-capacity HVDC transmission is expected in near future in Japan, for which development of reliable, compact and economical equipment is important. As a first step toward this objective, a prototype compact 154-kV 9-Mvar AC double-tuned filter and a prototype compact 125-kV DC filter were developed, which are first kind in the world and are currently under long-term life test. Each filter consists of a capacitor unit and a reactor unit, both dead tank design for ground-level installation. Film-paper mixed dielectric is used for capacitor elements, and polycyclic aromatic hydrocarbon oil as impregnant and for insulation.

A mixed integer programme for optimal static capacitor allocation in power systems

A method is presented for the determination of optimal size and location of static capacitor installations in a power system network for maintenance of the bus voltage magnitudes within prescribed limits under highly loaded or outage conditions. The problem is formulated as an optimization problem with the objective function representing the cost of capacitor installations and the constraints represent the reactive power flow equation of the system and the limits on the variations of the tap settings of the tap changing transformers and the generator bus voltages. The generator bus voltage magnitudes are continuously variable and the capacitor units to be installed and the tap settings are treated as discrete or integer variables. By partioning the variables into control and controlled quantities, a number of variables are eliminated from the problem. The problem is then decomposed into two smaller subproblems with integer or continuous variables. These result in the reduction of the computer memory and time requirements.

Series capacitors in power systems

The paper reviews the experience obtained with series-compensated power systems, particularly in Sweden, where internally fused capacitor units and simple system designs have contributed to the the good results. It also introduces new approaches for meeting future demands, e.g., optronic protection and a high-speed flip-flop reinsertion system.

On the Damage to Metallized Film Capacitors Caused by ElectricalDischarges

High voltage operation of metallized film capacitors leads to electrical spark breakdown in pockets of gas trapped within the sealed capacitor unit. A simple picture of gas discharge processes in the capacitor is used to identify the role played by electric discharges in the deterioration and ultimate failure of capacitors under accelerated life test.

Measurement of the magnitude of internal discharges in power capacitors

An experimental investigation of the effects of internal inductance on the measurement of internal discharges in power capacitors has been carried out. It has been revealed that, for tests on large capacitor units, substantial errors of measurement, loss in sensitivity and deterioration in response characteristics are possible. The error in measurement can be corrected if the self-resonant frequency of the capacitor under test is known. All the effects, can largely be avoided in high-voltage-capacitor units by constructions that avoid low self-resonant frequencies. Such constructions appear to be easier to realise in capacitors rated at 7–10kV than in those rated at 1–1.5kV. In medium-voltage units, the effects are substantial for ratings above 5kV Ar. The feasibility of making discharge tests on capacitor banks by sectionalising the bank, and by in situ tests on pairs of capacitors installed in the bank, has been studied. It is concluded that testing by sectionalising will be impracticable on most sites, but that in situ tests will be possible but laborious.

An Electronic Traffic Counter for Recording Burrow Activity of the Mountain Beaver

Circuit diagram and construction details are given for a small self-contained recording instrument used to study burrow-use patterns of mountain beavers. This recorder, which could be used to study the activities of a variety of burrow-dwelling animals, contains a resistor—capacitor unit operated by a 30-v battery that minimizes the recording of spurious counts. The technique of using the counter in a mountain beaver burrow is described.

A new ionization chamber system for regularly checking x-ray therapy machines.

Regular and Frequent checking of x-ray machines is needed to assure accurate dosage values in therapy. Theoretically, the best solution is to measure the output intensity with a Victoreen or similar dosimeter at least once weekly. Unfortunately, the nature of such instruments and measurements normally prevents delegating this task to a technician, and frequent regular checking appears to be limited to larger hospitals and teaching institutions. A more rugged and inexpensive but still accurate instrument, designed specifically for this purpose, is desirable. Both film and ionization chamber monitoring methods have been discussed in the literature. Film monitoring of x-ray output appears to be of limited promise, because of the considerable technical problems involved and the inherent ambiguity in interpretation of density readings (1). Ionization chamber monitors offer the advantage over Victoreen or similar units that the measuring device is permanently mounted in a reproducible location, eliminating positioning errors (2). While readings of such units are of course responsive to tube housing temperature changes (3), this does not present a serious problem if the test is carried out after a prescribed daily warm-up procedure. Early monitor chamber units, such as the well known Weatherwax design, were of copper, with substantial air volumes. As a result, they produced large enough ionization currents to yield a direct reading on a sensitive panel galvanometer. Unfortunately, most modern x-ray machines can accommodate only small monitor chambers; the reduced current necessitates the use of electronic amplification, with some corresponding operation and maintenance problems. In addition, the indications of commercial monitor chambers are frequently not accurately proportional to roentgen intensity. The system to be described here attempts to overcome some of these problems by special chamber design and the use of a condenser discharge method to measure ionization current instead of an amplifier (Figs. 1 to 3). It consists of three units: an ionization chamber mounted beneath the filter, a portable polystyrene capacitor-electroscope assembly, and a charger unit for the capacitor. In use, the capacitor unit is first charged so that the electroscope (a 0–200 mr self-reading pocket dosimeter) reads 0 mr. It is then plugged across the chamber in the tube housing. The machine is operated at useful factors for a time specified by the physicist at calibration. The resulting “milliroent-gen” reading is a direct measure of the current x-ray output rate. For example, if the reading at calibration was 180 mr, and it is reduced 18 mr to 162 mr, a 90 per cent intensity reading is noted in the daily record and reported to the therapist. Design and Operation Considerations Figure 4 shows the construction of the most recent monitor ionization chamber.

A static voltage differential relay for protection of shunt capacitors

The Bonneville Power Administration (BPA) like other utilities, is converting many of its substations for supervisory control. Visual inspection for blown fuses will be less frequent. This makes it necessary to develop a sensitive relay which will provide automatic protection for the capacitors. This relay has been designed to have enough sensitivity to meet the present protection requirement, that is to prevent consecutive failure of capacitors. It will also provide protection for phaseto- phase and phase-to-ground faults within the capacitors. This relay as it is applied to capacitor protection is known as a differential relay. But this relay is basically an overor undervoltage relay. Therefore, other applications can be made of it when it is applied to other equipment. This relay scheme, as it now stands, has a sensitivity of 0.5%. The Longview tests indicated the sensitivity was 0.4%, a marginal value. Finally, it is hoped that when the reliability of the relay is proved by field tests, further advantages can be derived from it. By relying on its protection against overvoltages, fewer and larger capacitor units may be used to reduce further the cost of a capacitor installation.