A study of the effects of full three-phase representation in power system analysis

The effects of unbalances caused by untrasposed EHV transmission lines and unbalanced loads in power system analysis have been thoroughly analyzed and determined;In the steady-state analysis, it is concluded that three-phase representation of the system is necessary and the unbalance analysis needs to be performed at least once under specific system conditions to ensure a safe and normal operation of the system. The newly developed method is proved to be an efficient approach to be used in this type of analysis;In the electromagnetic transient analysis, it is concluded that untransposed transmission lines have no significant impact on the transient overvoltages caused by single line-to-ground fault clearing and, therefore, may be represented fully transposed. It is noted, on the other hand, that unbalanced loads can affect the transients and must be included in the analysis. It has been shown, however, that balanced initial conditions may be used to represent the network and the loads in the system

Primary mucin-producing urothelial-type adenocarcinoma of the prostatic urethra diagnosed on TURP: a case report and review of literature

Mucin-producing urothelial-type adenocarcinoma of the prostatic urethra is extremely rare. These lesions must be differentiated from other mucinous tumors including mucin-producing prostatic adenocarcinoma and metastases from either colonic or bladder primaries. We report here a case of urothelial-type adenocarcinoma arising from the prostatic urethra. The patient is an 81 year-old man with a history of pT1 urothelial cell carcinoma of the bladder status post trans-urethral resection of bladder tumor (TURBT) who initially presented with irritative lower urinary tract symptoms and mucosuria refractory to Flomax and finasteride. A shared decision was made for the patient to undergo trans-urethral resection of prostate (TURP). At the time of surgery, a papillary tumor emanating from the prostatic urethra was found and no urothelial lesions were noted in the bladder. Pathology of the resected prostatic chips revealed an invasive adenocarcinoma with intestinal-type differentiation that stained positive for CK7, CK20, and villin, but negative for PSA, PSAP, uroplakin, and CDX-2. Colonoscopy was normal and CT scan did not show any evidence of colonic lesions nor visceral or lymph node metastases. Thus, the patient was diagnosed with a primary urothelial-type adenocarcinoma of the prostatic urethra. Herein we review the literature regarding this unusual entity, and discuss the differential diagnosis, immunohistochemistry, and the importance of correctly identifying this rare tumor

A novel approach to Extended System Frequency Response Model for Complex Power Systems (ESFR)

This paper presents a practical medium-order multi-machine Extended System Frequency Response (ESFR) model that is applicable for the frequency study of large, complex power systems or an island portion due to sudden load disturbances or generator outages. The ESFR model is a simplification of the real system and can be used to capture the essential system dynamics behaviour, commonly associated with high-capacity hydro generation and thermal generating units. Classification of power system generations and developing an equivalent unit for each class is proposed by the first step of this two-step method. The above components are put together in a composite frame, which takes into consideration all significant characteristics and factors related to the frequency response of the system. The IEEE standard model with the best performance for each element has been selected via a comparative analysis in single-machine and multi-machine environments. The second step aims to equalize the effective parameters numerically and comprises two sub-steps. The first sub-step identifies the parameters with considerable impacts on the frequency response of the components via sensitivity analysis. The second sub-step involves extensive comparative studies to find the best formulas for determining the equivalent value of the effective parameters. The graphical interface of an advanced power system software with a user-friendly simulation environment was used for the analysis. The results show that the current approach is capable in terms of accuracy and practicality to capture the diversity of the generating resources in modern power systems

A study of the effects of full three-phase representation in power system analysis

The effects of unbalances caused by untrasposed EHV transmission lines and unbalanced loads in power system analysis have been thoroughly analyzed and determined;In the steady-state analysis, it is concluded that three-phase representation of the system is necessary and the unbalance analysis needs to be performed at least once under specific system conditions to ensure a safe and normal operation of the system. The newly developed method is proved to be an efficient approach to be used in this type of analysis;In the electromagnetic transient analysis, it is concluded that untransposed transmission lines have no significant impact on the transient overvoltages caused by single line-to-ground fault clearing and, therefore, may be represented fully transposed. It is noted, on the other hand, that unbalanced loads can affect the transients and must be included in the analysis. It has been shown, however, that balanced initial conditions may be used to represent the network and the loads in the system.</p

Climatic Design Principles of Underground Spaces Using CFD Simulation

Iranians used wind catchers to achieve harmony between a structure and the environment and guarantee the environmental comfort of the indoor areas. Wind catchers were the symbols of Persian architecture and with introduction of modern technologies, these traditional elements became obsolete. Rapid population and traffic lead to use underground spaces in cities. This paper proves the ability of wind-catchers to provide natural ventilation in underground spaces based on climatic parameters. Simulation was conducted in complete computational fluid dynamics package to simulate wind in underground space. Results demonstrate that in specific climate condition, wind-catchers could provide natural ventilation for underground space