Thermal Analysis of Cable Sealing Ends
A general analytical method for thermal analysis of high-voltate oil-filled cable sealing ends is presented. Oil flow within the conductor oil duct, longitudinal heat flow through the conductor and conductor losses variation with temperature are taken into consideration. The method is successfully applied for a sealing end of a 300 kV, 2000 mm2 integral sheath cooled oil-filled cable. A companion paper where cable joints are analyzed, is referenced.
STEADY STATE TEMpERAluRE DISTRIBUTION OF HIGH VOLTA(X BUSHINGS-ANAIYSIS AND MEASUREMENTS
M Constant in the general differential equation, 'C A ccanputer program is developed to perform the thermal analysis of the temperature distribution of the conductor in a high voltage bushing under steady state conditions. A thermal circuit for an element of length dx of the conductor is analyzed and a differential equation representing the thermal performance is obtained. In the present method the solution of the temperature differential equation can be obtained without any prior measurenwts of the conductor temperature. The analysis is applied to a 69 kV airto-air bushing with one end imnersed in oil as well as to an exprimntal bushing. Good agreement between the predicted and the measured tesnperature distribution is obtained. The locations of the hot spots inside the conductor, under different loading conditions, have been calculated with good accuracy. In order to reduce the hot spots, a new evaporative cmlingmthcd is applied to both bushings. The conductor thermal analysis has been mdified to include the cooling effect. The tenperature profile along the conductor, with cooling is predicted theoretically. Good agreemnt with the measured values is obtained. Mn Constant of part n of the conductor, 'C MI Constant in the general temperature equation, 'C Mln Constant of part n, 'C N n Nu Nusselt nunher Rf Film thermal resistance for surface to oil convection, 'c m/w R, Effective thermal resistance of liquid saturated wick material, 'C matt Rm Effective thermal resistance between solid surface and anbient, 'C m/watt R& Radial thermal resistance of dielectric i, 'C mflatt Rtl Total radial thermal resistance from conductor to ambient through the bushing condenser, *C m/Watt Tbtal number of axial parts of the bushing system An index of different parts of the bushing A Constant in the general temperature equation, 'C Ta Ambient temperature, 'C A, Conductor cross section area, Tc Conductor teqerature, 'C Afi Constant of part n, 'C Tcn Conductor tesnperature of part n, *C A, surfacearea, m2 Ts Bushing surface teqerature, *C a0 Constant in the general differential equation Tsv Saturated vapor temperature, 'C a0n Constant of part n of the conductor a2 Constant in the general differential equation Wc Generated heat in the conductor per unit length, Watt/m azn Constant of part n of the conductor Wdi Dielectric loss in dielectric i per Unit length, B constant in the general temperature equation, 'C Watt/m constant of part n, 'C
Wireless temperature logging technology for the fishing industry
A system for autonomous temperature logging of fish catches is described. The system is completely wireless and is comprised of a number of loggers, in individual fish boxes, and a base station, assigned to a particular trawler. The temperature of the fish is monitored by the loggers, which contain a thermistor and RF transmitter circuitry. The data is sent at fixed intervals (usually 5 minutes) to the base station. Through a GSM modem, the base station communicates the collected data to the shore where a server uploads the temperature-time information to a database. The database and controlling software are completely Web-based and can be accessed by an Internet-enabled PC, laptop or PDA. This allows remote initiation and control of the system, in addition to querying of the database. To date, successful trials have been conducted for salmon, mackerel and whelk fishing off the Irish coast.