DC System Analysis
The DCSDM (Direct Current System Database Model) DC System Analysis Program was developed to address the specific issues associated with existing DC systems in nuclear power plant applications. The program is verified and validated and is available as a safety–related package in compliance with EasyPower’s QA program. Its developers have been audited numerous times by NUPIC and is on the NUPIC qualified supplier’s list.
- Relational database
- Controlled access
- On screen by and checking
- Detailed information maintained for the entire DC system – load data, ratings, cabling, wire numbers, model numbers, etc.
- Reference and comment fields available for all screens
- Automated reports for “hard copy” calculations
- Designed to support “paperless” calculations
- Time dependent load flow analysis (up to 70 steps, down to 0.1 second resolution, up to 200 nodes)
- Handles constant power, constant impedance, and constant current load types
- Battery terminal voltage over time (input to time dependent load flow)
- Battery sizing
- Short circuit calculations
- Component level voltage drop calculations (multiple control paths)
- Complies with IEEE-485 and industry accepted practice
The DCSDM program is developed in Powerbuilder and is designed to interface with the stand-alone and networked versions of Sybase SQL Anywhere. The program uses standard Structured Query Language (SQL) to access a relational database structure through the ODBC. DCSDM’s design ensures that critical plant DC load data are easily stored and managed, and that the program will be scalable and upgradable.
For analysis, the program performs iterative load flow calculations for the DC system throughout the battery discharge cycle and short circuit calculations. The program uses iterative techniques and automatically corrects load currents for calculated voltage at up to 200 nodes. The program allows the use of true time dependent load flow techniques to solve DC networks. Much of the conservatism associated with manual techniques can be removed. The result is less severe load profiles, which translates to more battery margin. Up to 70 different time steps per scenario are allowed for detailed modeling of the battery loading during its discharge cycle. Constant power loads, constant current loads, and constant impedance loads can be modeled at all of the buses. Battery cell sizing and the determination of battery terminal voltage for each minute during discharge is also performed in accordance with the methodology described in IEEE-485. A file of battery discharge characteristic curves is provided that can be edited by the user to add, revise, or delete battery information.
The program also has the capability to work with bus voltage calculations to perform component level voltage drop calculations. This method can be used to calculate the voltage in each potential circuit path to the various components in a DC circuit. It will take into account the other devices that are within the scheme and the effect they have on the voltage drop. The method compensates for the type of device (constant power, current, or impedance) and the calculated voltage at the nearest bus. This provides more accurate (still slightly conservative) calculated voltages at the components, eliminating the excessive conservatism typically found in hand calculations.