Author name: Engr. Aneel Kumar

Any numbers of conditions have been the reason for an electrical transformer failure. Statistics show that winding failures most frequently cause transformer faults (ANSI/IEEE, 1985). Insulation deterioration, often the result of moisture, overheating, vibration, voltage surges, and mechanical stress created during transformer through faults, is the major reason for winding failure. Voltage regulating load tap […]

Switching of shunt reactors (and other devices characterized as having small inductive currents such as transformer magnetizing currents, motor starting currents, etc.) can generate high phase-to-ground over-voltages as well as severe recovery voltages, especially on lower voltage equipment such as reactors applied on the tertiary of transformers. Energizing the devices seldom generates high overvoltages, but

SERIES CAPACITOR BANK APPLICATIONS Installation of a series capacitor bank in a transmission line (standard or thyristor controlled) has the potential for increasing the magnitude of phase-to-ground and phase-to-phase switching surge over-voltages due to the trapped charges that can be present on the bank at the instant of line reclosing. In general, surge arresters limit

Surges associated with switching transmission lines (overhead, SF6, or cable) include those that are generated by line energizing, reclosing (three phase and single phase operations), fault initiation, line dropping (de-energizing), fault clearing, etc. During an energizing operation, for example, closing a circuit breaker at the instant of crest system voltage results in a 1 pu

Switching surges occur on power systems as a result of instantaneous changes in the electrical configuration of the system, and such changes are mainly associated with switching operations and fault events. These over-voltages generally have crest magnitudes which range from about 1 per unit to 3 pu for phase-to- ground surges and from about 2.0

A direct stroke is defined as a lightning stroke when it hits either a shield wire, tower, or a phase conductor. An insulator string is stressed by very high voltages caused by a direct stroke. An insulator string can also be stressed by high transient voltages when a lightning stroke hits the nearby ground. An indirect

The level reached by VFT overvoltages originated by disconnector switching or line-to-ground faults inside a GIS is below the BIL of substation and external equipment. However, aging of the insulation of external equipment due to frequent VFT must be considered. TEV is a low energy phenomenon and it is not considered dangerous to humans; the

A) FUSES The most commonly used protective device in a distribution circuit is the fuse. Fuse characteristics vary considerably from one manufacturer to another and the specifics must be obtained from their appropriate literature. Figure 9.28 shows the time-current characteristics which consist of the minimum melt and total clearing curves. FIGURE 9.28 Fuse time-current characteristic.

As can be seen from Fig. 9.33, step distance protection does not offer instantaneous clearing of faults over 100% of the line segment. In most cases this is unacceptable due to system stability considerations. To cover the 10–20% of the line not covered by Zone 1, the information regarding the location of the fault is

The basic requirement for security analysis is to assess the impact of any possible contingency on system performance. For the purpose of setting planning and operating rules that will enable the system to be operated in a secure manner, it is necessary to consider all credible contingencies, different network configurations, and different operating points for