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Transformers are one of the most important and costly components of any power system. Proper monitoring of the health of a transformer is thus inevitable. Online monitoring of partial discharges (PD) is one of the ways by which the risk of catastrophic failure of a power apparatus can be reduced. Common insulation in power transformers are pressboard and oil. Unconventional PD measurement was developed for several decades ago as a form of PD detection system. In these PD measurement systems that are named unconventional method PD is analyzed by indirect features of this phenomenon, which includes electrical, acoustic, UHF, optical, and chemical methods. The main advantage of unconventional method is the ability of this method in order to decrease the amount of signal to noise ratio for on-site or on-line measurement. A study of the correlation between acoustic emission signals generated by PD and electrical PD charges is inevitable. By developing the speed of measuring devices like digital signal processor (DSP) the possibility of evaluation and calculation of acoustic signals in very short time have been increased. The aim of this paper is evaluation of acoustic signals for two different kind of pressboard (new and aged) with two types of sensors (75 kHz and 150 kHz peak frequency) and simulation of Acoustic Emission (AE) signals propagation which are produced due to PD inside a sample transformer tank by using Finite Element Method (FEM). 

Locating the water entries in an oil producer is critical for the success of remedial work, such as acid stimulation and water shut off, to prolong the life of the well and enhance production. Different logging tools are successfully used to obtain this information such as PLT. Practicality of using these logging tools can be limited. A good example of these limitations is a well that cannot flow or sustain flow to surface (dead well). Therefore, in addition to the historical data, previous PLTs, water drive mechanisms for such wells, along with the well performance history, the pressure gradient survey approach is used to come up with best estimate of static OWC in vertical or slightly deviated wellbores. This paper will answer the questions of when, and why conduct a pressure gradient survey and the optimum running procedure by discussing the utilization of the pressure gradient survey as a diagnostic and decision-making tool in a few case histories from the Ghawar filed in Saudi Arabia will be discussed. Introduction Locating oil water contact, OWC, in the wellbore is essential before any well intervention or remedial work such as acid stimulation and water shut-off. The current best tool for such information is the production logging tool, (PLT), which gives the flexibility of seeing both the dynamic, and static OWC, however running the PLT even though it seems as the only tool, is not always a cost-effective way. Therefore, in addition to the historical data, previous PLTs, water drive mechanisms for these wells, and the well performance history. The pressure gradient survey approach is used to come up with the best estimate of the static OWC in vertical or slightly deviated wellbores.

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