Short description CTC V.6.2. Current and temperature calculations of overhead conductors.

Transcription

1 Short description CTC V.6.2 Current and temperature calculations of overhead conductors

2 1 Program features Steady-state current and temperature calculation of overhead conductors with three independent methods. Unsteady-state current and temperature calculation of overhead conductors up to 6 changes of state in serial execution with arbitrary specification of temperature, current load, of period. Graphical display of current-/ temperature function curves within self-defined ranges of temperature or current. Calculation of conductor bundles up to 8 single conductors. Table calculation with Current conductor temperature wind speed ambient temperature as parameters with possibility to compare the calculation methods. Storage of all calculations in compatibility to the database system Microsoft Access. Quick access and storage possibility with defined quick-access-table. Import of input data from defined Excel worksheet and write-back of result data into this Excel sheet. Storage possibility of steady-state input and result data into Excel sheet format for presentations. Printout of calculations, tables and function curves in the languages English and German. Printer preview of all printouts with possibility to store in Bitmap-Format (.bmp) Easy-to-apply and comfortable user interface. Context sensitive Windows-Online-Help 1 Short Description CTC V.6.2

3 2 Program intention, calculation methods and features Steady-state current and temperature calculation By a given maximum conductor temperature, you can calculate a current load, with which the conductor can be operated permanent at any steady weather and ambient condition within ranges close to reality. Exceptions: Rain, snow and frost covered conductor In opposite, by a given maximum steady-state current load and given or measured steady weather and ambient condition you can calculate the temperature of the conductor. These calculations can be done according to three methods: 2.1 Steady-state current and temperature calculation according to CIGRÉ This method is based on section 1 Mathematical Model for evaluation of conductor temperature in the steady state (Normal operation) of the CIGRÉ document 207 Thermal behaviour of overhead conductors published in August 2002 by from the International CIGRÉ Working Group Available under It represents the most current, international applied mathematical model for the calculation of the Steady-state current and temperature calculation of overhead conductors. Further information you will find at the CIGRÉ publication. 2.2 Steady-state current and temperature calculation according to WEBS This method is based on a calculation method according to ALFRED WEBS, published in December 1963 in the German journal Elektrizitätswirtschaft. The method was developed to determine the maximum steady-state current load by a given maximum conductor temperature. Results of this methods are used to define the maximum permissible permanent current load under defined worst-case ambient conditions for the German Standard DIN Steady-state current and temperature calculation according to KIRN This method is based on a calculation method developed at the Short Description CTC V.6.2 2

4 Institute of efficient use of energy, University of Applied Sciences, Karlsruhe, Germany by Prof. Dipl. Ing. Herbert Kirn in cooperation with Badenwerk AG. The method was published in the magazine etz in December 1990 and was furthermore refined in some degree theses of the FH Karlsruhe. It was developed to determine the conductor temperature of conventionally used ACSR conductors within operating overhead line spans for span measurement and sag calculations. A direct comparison between the three independent calculation methods can be done within the program. 2.4 Unsteady-state current and temperature calculation according to CIGRÉ With this calculation method, the time dependent change of the conductor temperature, caused from change of current, can be calculated. You can calculate the period for reaching a given conductor temperature. Also the causal change of current can be calculated, by giving the period and the final conductor temperature. Also the final temperature can be calculated, caused from a given change of current over a distinct period. You can run calculate and display up to 6 changes in time, temperature or current within one step. The calculation is implemented according to Section 2 : Mathematical Model for evaluation of conductor temperature in the unsteady state of the CIGRÉ document 207 Thermal behaviour of overhead conductors published in August 2002 by from the International CIGRÉ Working Group It represents the most modern, international applied mathematical model for the calculation of the Unsteady-Steady-state current and temperature calculation of overhead conductors. Further information you will find at the CIGRÉ publication. 3 Short Description CTC V.6.2

5 2.5 Examples of application cases of the unsteady-state calculation method 1 st application example It can be determined with the help of the unsteady-state calculation, if an overhead conductor line after execution of switching actions in the grid is operated at any time within the permissible temperature range, even maybe the maximum permissible steady-state current load is exceeded for a short time period. 2 th application example A overhead conductor line is in normal steady-state with a current load beneath his maximum permissible steady-state-current. Then it comes to a quick current overload of this line because of multi-failures (line dripping, power plant failure etc.) and in the result, the grid is now no more in the safe n-1 state. Two possibilities to react: Possibility 1: Possibility 2: To protect the line, it will be dropped instantly automatically from the grid. In extreme situation this leads in result to a complete blackout because of following line drippings, see progress of the blackouts USA and Canada at August , and blackout Italy / Swiss at Sept Line drippings and the resulting change-of-states were already simulated in former times with power system analysis tool. The time period at which the conductor line is heated, but still beneath his maximum allowable conductor temperature for these change-of-states was already calculated with the CIGRÉmethod. This time period is usually in the range of minutes, depending on the conductor temperature before the current overload is happening. Within this time period, the overloaded conductor line will be hold in operation. With fast and concerted load shedding the line will be unloaded beneath his current limits before it reaches its temperature limitations. With this, further line dripping will be avoided an the whole transmission grid can be restored to normal operation conditions, the blackout was avoided. Short Description CTC V.6.2 4