Design parameter based method of partial discharge detection and location in power transformers

Insulation defect detection in time ensures higher operational reliability of power system assets. Power transformers are the most critical unit of power systems both from economical and operational front. Hence it becomes necessary to have knowledge of the actual insulation condition of transformer to increase dependability of the system. The performance and ageing of the transformer insulation is mainly affected by Partial discharges (PD). Proper diagnosis in terms of amplitude and location of partial discharge in a power transformer enables us to predict well in advance, with much confidence, the defect in insulation system, which avoids large catastrophic failures. In this work a 20kVA, 230/50kV single phase core type transformer is used for evaluation of the transfer function-based partial discharge detection and location using modeling of the winding, using design data. The simulation of capturing on-line PD pulses across the bushing tap capacitor is done for various tap positions. Standard PD source model is used to inject PD pulse signal at 10 tap locations in the winding and corresponding response signatures are captured at the bushing tap end (across 1000pF). The equivalent high frequency model of the winding is derived from the design parameters using analytical calculations and simulations in packages such as MAGNET and ANSOFT. The test conditions are simulated using ORCAD-9 and the results are evaluated for location accuracy using design parameter based PD monitoring method.

Design Parameter Based Method of Partial Discharge Detection and Location in Power Transformers

Abstract: Insulation defect detection in time ensures higher operational reliability of power system assets. Power transformers are the most critical unit of power systems both from economical and operational front. Hence it becomes necessary to have knowledge of the actual insulation condition of transformer to increase dependability of the system. The performance and ageing of the transformer insulation is mainly affected by Partial discharges (PD). Proper diagnosis in terms of amplitude and location of partial discharge in a power transformer enables us to predict well in advance, with much confidence, the defect in insulation system, which avoids large catastrophic failures. In this work a 20kVA, 230/50kV single phase core type transformer is used for evaluation of the transfer function-based partial discharge detection and location using modeling of the winding, using design data. The simulation of capturing on-line PD pulses across the bushing tap capacitor is done for various tap positions. Standard PD source model is used to inject PD pulse signal at 10 tap locations in the winding and corresponding response signatures are captured at the bushing tap end (across 1000pF). The equivalent high frequency model of the winding is derived from the design parameters using analytical calculations and simulations in packages such as MAGNET and ANSOFT. The test conditions are simulated using ORCAD-9 and the results are evaluated for location accuracy using design parameter based PD monitoring method

Primary acinic cell carcinoma in an adolescent female

Acinic cell carcinoma (ACC) is a rare, low-grade tumour, accounting for about 17% of all primary salivary gland malignancies in adults. ACC most commonly affects the parotid gland, predominating fifth and sixth decades of life and a female predilection. In the paediatric population, mucoepidermoid carcinoma is the most common parotid malignancy, followed by ACC.We report a case of a 16-year-old female, presenting with a slow-growing right parotid lump. Clinical examination revealed a small right parotid nodule, grade I House-Brackmann score and cervical lymphadenopathy. Radiological investigations revealed a well-circumscribed lobulated lesion in the anterior right parotid gland and reactive lymph nodes. Surgical management included a right partial parotidectomy. Immunohistochemistry was negative for S100, positive with DOG-1 and widespread PAS-D-resistant granules throughout the tumour cells, confirming a diagnosis of ACC.ACC is an important differential diagnosis to consider in salivary gland pathology in the female adolescent patient

The Drying kinetics of Cissus quadrangularis dried in a Fluidized bed dryer

Cissus quadrangularis is an extensively utilized medicinal plant in India which has numerous health benefits. Hence, the drying kinetics of Cissus was studied using fluidized bed dryer to identify suitable drying conditions and to understand moisture removal and its connection to process variables.  The present research aimed to determine a suitable drying model of fluidized bed drying of Cissus quadrangularis Linn., determine the effective moisture diffusivity of the drying process and the activation energy, and investigate the effects of temperatures on the drying kinetics of Cissus. The drying experiments were conducted at three different air temperatures (40, 50 and 60 ºC), bed thickness of 5 cm, constant air velocity of 8 m/s and 0.5-1 cm length Cissus samples. The experimental drying data was fit into thirteen thin layer models and the best model describing the drying of Cissus was selected based on the correlation coefficient (R), root mean square error (RMSE), and reduced chi-square (χ2).  The drying process occurred in a falling rate period for all the drying air temperatures and a constant rate period was not observed. Among all the thirteen models tested, approximation of diffusion was found to explain the thin layer drying behavior of C. quadrangularis accurately. The effective moisture diffusivity for Cissus was in the range of 1.54 - 3.12x 10-10 m2/s  and the activation energy was 30.76 kJ/ mole, respectively.  Hence, fluidized bed drying is more effective for convective drying of Cissus and the drying models are useful for selecting the best operational condition for fluidized bed dryer and design of an equipment