I During emergency situations requiring fast response, a modern interrupter switch in Software

Generating QR Code 2d barcode in Software I During emergency situations requiring fast response, a modern interrupter switch

I A loaded circuit can be dropped inadvertently (through an error or misunderstand-

Because of the no-external-arc feature of most modern interrupter switches, phase conductor spacing can be much less than that established for the older horn-gap switch On the secondary side of the substation there are more feeders and more heavily loaded and longer transmission lines

All of the components in an electrical system are designed to operate at their rated voltages for optimum efficiency and long service An ideal electrical system would provide constant voltage to all customers under all conditions of load Unfortunately, because of the unpredictable dynamics of a practical system, none is ideal Thus, it is necessary to include voltage regulators in the system to correct its performance and keep its voltage reasonably close to an ideal constant There are now at least four different methods for maintaining close to ideal voltage on electric power transmission and distribution systems These include the use of stepvoltage regulators, transformer load-tap changers, fixed and switched capacitors, and static var (volt-amperes reactive) systems (SVS) However, single-phase step-voltage regulators are most frequently used to regulate voltage in electric power distribution systems There are many reasons, both technical and economic, why system voltage should be held close to its intended standard Among them is the fact that overvoltage shortens the life of heating elements in resistive appliances, components in electronic products, and filaments in both incandescent and fluorescent lamps Moreover, overvoltage can damage motor-driven appliances and tools On the other hand, undervoltage increases the time taken for the resistive elements of appliances to heat up while also causing motors to overheat and lose efficiency It will also reduce the performance of electronic products such as computers, radios, and TVs, and dim the illumination from luminaires

Step-type voltage regulators are actually tapped autotransformers that have one winding common to both the primary and secondary circuits The primary (exciter) winding is both magnetically and electrically connected to the secondary (series) winding The series winding is connected in series with the load current Both single-phase and threephase step-voltage regulators are being manufactured They are built in both polemounted and pad-mounted styles A single-phase pad-mounted step-voltage regulator is shown in Fig 3-21 It performs the same function as the traditional overhead-mounted tank-type and substationmounted regulators, with the convenience of pad mounting The unit shown provides regulation in 32 voltage steps of approximately 5 8 percent each for a maximum of 10 percent regulation when used singly or in wye-connected banks These voltage regulators are made in ratings of 7620/7200 and 144 kV for 60Hz systems Their current ratings are from 50 to 548 A Voltage regulation is

FULL METAL BARRIER SEPARATING THE TWO COMPARTMENTS PARKING STAND (2) LIFTING LUGS (2) BUSHING WELLS & INSERTS OR 600-A TERMINATIONS

AUTOMATIC PRESSURE RELIEF DEVICE TAP CHANGER POSITION INDICATOR AND JUNCTION BOX OIL-LEVEL GAUGE LASER-ENGRAVED NAMEPLATES (2)

CONTROL BOX WITH CL-5C CONTROL 1" FILTER PRESS CONNECTION AND FILL PLUG 1" DRAIN VALVE WITH SAMPLER

Figure 3-21

microprocessor-controlled, and the autotransformer core and coil assembly is immersed in insulating oil Pad-mounted voltage regulators are housed in steel enclosures with front access doors that are painted green to blend in with residential surroundings Figure 3-22 is a simplified wiring diagram for a single-phase step-voltage regulator The regulator includes a series winding and a shunt winding that make up the main transformer and a bridging reactor or preventive transformer The series winding is typically rated for 10 percent of the voltage of the shunt winding There are usually eight taps attached to the series winding, and these are wired to segments of a dial switch assembly as individual contacts The voltage difference between these segments is 11 4 percent voltage Contacts on the center-tapped preventive autotransformer are designed to bridge the gap between the dial switch segments to avoid momentary loss of the load Although arcing occurs as the bridge slides, the load is not lost because one contact remains on the segment As a result of this sliding action, load voltage become the average voltage of the taps bridged A reversing switch permits the polarity of the series winding to be reversed with respect to the shunt winding, permitting both plus and minus regulation Both a voltage