Challenges

• Providing an electrical power model with a grid, generator, transformers, buses, and lumps. The facility utilizes a 711 MW generator on a 24 kV Bus. The Main Step-Up (MSU) transformer grid interconnection operates at a 230 kV voltage. The two auxiliary transformers power two buses on a 4.16 kV system.
• Validating the ETAP model according to plant operating data and understanding the capability of the unit, with all limitations and constraints resulting from the manufacturer's data, climate, power factor, and grid interconnection requirements.
• Defining the true reactive power capability of the unit by using simulation load flow results and historical operating data.
• Analyzing load flows of the system theoretically and by observing real historical data. The North American Generator Forum's validation method, which employed a theoretical analysis approach, provided direction during the process. Mapping all results, measurements, and analyses into D-curve charts to compare theory with practice.
• Using a MOD-025 compliance standard, which defines the method of unit verification for the real and reactive power capability. This testing method is requested by NERC, which is the North American Electric Reliability Corporation.

Selected applications

They chose the ETAP game of software, featuring the Load Flow Software Result Analyzer solution, and ETAP Digital Twin Modeling as the first solution to analyze, calculate, conduct, and visualize the research.

Main Customer Benefits

• The ETAP model fully reflected the reality of the analyzed energy unit. The extended ETAP symbols and behaviors library includes grid, transformers, buses, and looms with specific data. All the electrical parameters provide the opportunity to conduct tests on a wide range of cases.
• In the ETAP model, researchers could consider multiple variations and test behaviors step by step, from the lower value to the higher value. They could test the grid behavior with a voltage in the grid increment of 1%, assuming the correct interconnection was from 98 to 105% which requires running the system at 99%, 100% and then 101% up to 105% grid voltage. They could observe and analyze different reactive capabilities, based on constraints.
• They tested the generator to a minimum MW output of 280, and conducted testing on different interval output generation, such as 380, 480, and 580 MW. The ETAP model is a flexible software that can be used as a standard, but it's also open to specific research.
• They were monitoring the generator MVars, voltage, and power factor, grid MVA, and power factor, and auxiliary bus voltages in dependency of the different system parameters. They utilized ETAP's Loading and Generation categories, along with an efficient Study Wizard, to simplify the research on 80 different load flow cases.
• The results were easily transferred to the Excel D-curve charts.
• They found that the staged testing method by MOD-025 NERC will not identify the true reactive unit capability and limitation of a particular unit. The theoretical approach provides reasonable assurance that the unit capability is satisfactory, as it utilizes historical operating data to minimize the need for stage testing. This approach can support unit modification, such as the need for a main step-up or auxiliary transformer tap change, which can enhance grid reliability and, if needed, provide the required voltage.

Opinions

We utilized power factor control in ETAP and performed ten different iterations of load flows to set the power factor at the grid, as shown here, 93% of the grid and 89% of the terminal. And we mention it in the Excel file, where the D-curve is located.
By Mr. Zia Salami, Senior Management Specialist at CDM Smith