Document 4v9aeBDm5RY7qxnbJakKo1g1V

90f . / A "T -I Tim . \ / v*" Capacitor / \ current Shunt capodror _ Lood Mvct/re s/ current \/ \ i i VX--ii / y-loffrf pewer / \ 1 / \ current / ___ \--i ^Zeroonb \ / | $hunt copoeltor energized with motor when the line twitch Is closed. Keep capotltor size lest than 25% of motor kvo Picture o tteody interchange of current betwoen capacitor and Inductive food. Source supplies only true lood power Capacitors Improve Pf and Cut Costs Growing Demand Expands Barbadoes As hart of Us plant-expansion program to meet growing Fuel will be pulverized bituminous, at times mixed ** demands, the Philadelphia Electric Co is odding two units e small percentage of onthracite. Oil con be burned duris^ in on extension of its existing Borbodoes Station. Present emergency conditions. Fuel Is delivered by roil, plant, housing two turbines and lour boilers developing a large storage yard provided for coal. . totol of 45,000 kw, operates with 300-psig 600-F steam. Superheat control will be effected by portly condeoit^ Standing on the Schuylkill River it is about 15 miles north* saturated steam entering superheater. Boiler and i"r 1 ^ west of Philadelphia. controls and Instruments for each unit will be placed ^ The two new preferred-standard 60,000-kw Westinghouse common board near the unit boiler, but since the ,l*^ turbine-generators will each be supplied 8S0-psig 900-F also serves es o distributing center, the generator *^ steam by a single 600,000 Ib-per-hr dry-bottom Foster Ing end loading will be controlled from a separate Wheeler steam generator. No steam or feedwater connections All five bleed points will be used to feed five closad between units or existing stations will be provided. First deaeration taking place in condenser hotwell. ^ new unit is scheduled to go into service In Feb 1949 and the constructors of the extension for the Philadelphia W second during June 1949. - Co, supplied the obove photo. 122 (784) POWER iftf -Shunt capacitors are used in induitrial plants to improve > power factor, voltage and to ! cut cost of metered energy, i Here's how they do it, also tips on use for best economy By J 1 WILLIAMS Control Station (ng/noor WtttMphowte ffectrlc Cerp Most industrial plants operate ot a power factor less than unity. One prac tical method of improving lagging pf ia the use of o shunt capacitor. When so used it supplies the magnetizing com* ponent of current, which is inherent in *U Inductive equipment As o result leaders, transformers and generating Mfelpment carry only the true power honied by the load. Mum* Capacitor function. Effect pro* 'faced by capacilbrs connected in. shunt ^demonstrated in Fig. 2. Sine func-01 of voltage and current are shown fa * simple distribution circuit. A lar load connected in the system j ** power component of current (hat ig at all times proportional to fa* voltage and in phase with IL The however, contains iron that must Magnetized. This is represented in the circuit by a parallel inductive branch. When line voltage Is applied to the inductive branch, the resulting current / lags behind the applied volt* age beesuee of the electrical inertia of the inductive port of the lood. If o capacitive element whose rating is equal to that of the inductive branch is connected in parallel with the other two elements, the inatanlaneoua current through the capacitive branch ia atwaya exactly equal and opposite to tbe in ductive current. Induciehce end capaci tance, therefore, store ond exchange energy in o way that requires no reac* live current flow In the external circuit. The only current supplied by the gen erator in this example is the powerproducing component, which no one has yet been able to cancel out. Another basic effect produced by con necting ahunt capacitors to a norma! distribution circuit Is an Increase in voltage along the supply Unes. Higher potential results at load points because of interaction between line reactance and shunt capacitance. These two cir cuit elements, considered apart from other impedances ond loads, produce o voltage across the capacitor that is higher thon the voltage (applied to the distribution line. Increased load voltoge leads to develop because a remote ap proach to aeries resonance occurs be tween line reactance and ahunt capael-. tones. This voltage rise is normally offset by the voltage drop associated with the power component of current At light lood the voltage rise may become excessive, resulting in need for switching capacitors ia response to load cycles. Fig.-3 and 4 illustrate one way to analyze voltage rise produced by abont capacitors. Application of ahunt capacitors pro duces Interrelated benefits, hence fol lowing list may overlap In some rospecie: 1. Load pf is improved. 2. Current earned by supply circuits and equipment is reduced or, conversely, more power-producing current can be transmitted over an existing circuit. 3. System losses are reduced. 4. Voltage drop in supply circuits is reduced. 5. Cost of metered electrical energy is reduced. SaltcHag Proper Capacitor. Calcula tion of capacitor sizes is dependent on -whether the unit U to be Installed for correction ol electrical characteristics of the power circuits or for reducing the monthly power bill. Usually it is not difficult to fit a capacitor installation to an existing or proposed lead, to obtain either specified pf or desired voltage increase. A straightforward electric* circuit solution provides required capac itor bank rating. A more detailed study ia usually necessary to establish the right also of o capacitor hank when the application Is primarily to reduce the power bill. Steps of kvar (kllovoU-ampcre-reaothe) demand In the rate schedule must be compared carefully with existing de mands before the most effective correc* * December 1948 (733) I2J