This information is also significant in helping the users to note and understand the various causes of voltage sag with the aim of attempting to manage voltage sag events when they occur within their jurisdictions. Two main factors are significant in determining whether indeed the impact created by voltage sag occurrence is intense or not. These are strength and time-frame within which the sag occurs, and the sensitivity of the equipment being used. Some of the electronic instruments that are quite susceptible to voltage sag include motor starter contactor; PLCs, control relays, and speed drive controls (Math & Bollen, 2000).
Unfortunately, this information is particularly not with the very end users of most of this equipment. This, therefore, necessitates the implementation of such a research as this particular one so that not only users of this power may be aware, but also the power producers and suppliers alike. At the end of this research, therefore, certain specific outcomes are expected. They serve as the hypotheses for the research. First, it is expected that the findings will point to the fact that voltage sag is brought about by three main causes i.e. faults in the transmission line, starting of the induction motors, and the energizing of the transformer.
The second hypothesis for the research is that some of the solutions to voltage sag problems include the use of electrical and electronics equipment whose tolerance is slightly higher to cushion them from voltage sags, implementing the use of coil hold-in devices mainly to counter the effect of voltage sags on contactors and individual relays, adjusting the power being supplied to the equipment in question, and setting up power conditioning devices (Bollen, 2000). Literature Review Voltage Sag Explained Voltage sag is not necessarily a total lack of power, but a temporary fall in the effective voltage in electronic equipment or the power supply and distribution system that typically occurs usually in a period of less than one minute (Dugan, Mark, Surya, & Wayne, 2003).
It has always been the desire of most utilities to ensure a secure and reliable electric power within their premises. Their desire, however, has always been thwarted by voltage sag is attributed to very many causes that keep varying always. This has been a challenge in the sense that even when users prevent their utilities from a certain cause(s) of voltage sag, there are still other causes that will remain unmitigated at all times which continues to leave them vulnerable (Sankaran, 2002). Causes of Voltage Sag Of the many cause of voltage sag, storms have been reported as the most prevalent causative agent of voltage sag especially in external environments.
According to Dugan, Mark, Surya, & Wayne (2003), when a storm occurs, it leads to several instances of variations in the supply of power to different users. In the course of this, voltage sags also have a higher likelihood of occurring. System faults are also a major cause of voltage sag. According to Math & Bollen (2000), when faults occur, the operations of a power plant and other industrial utilities are interfered with in one way or another. The extent of damage, however, largely depends on whether the fault is symmetrical or asymmetrical.
For a symmetrical fault, the strengths of the resultant voltage sags are of equal magnitude in each phase, while for asymmetrical faults, the resultant voltage sags have magnitudes that are not equal (Dugan, Mark, Surya, & Wayne, 2003). System faults that may lead to voltage sags are such that their magnitudes are largely affected by such factors as the impedance of the fault, the pre-sag voltage level, the manner in which the system is configured, and the type of fault (Bollen, 2000). Starting of induction motors is also a source of voltage sags.
It is indeed a known fact that induction motors are usually balanced at 3 loads (Dugan, Mark, Surya, & Wayne, 2003). This, therefore, makes the voltage sag arising from their starting to be symmetrical in nature.
Read More