Challenges

• Analyzing and verifying the electrical grid's reliability after planning to add the Waste Heat Recovery plant and an additional separate plant with a 15 MVA generator to the existing cement factory.
• Modeling the strict actual and future powering system. Creating an up-to-date electrical model, including equipment and settings used by the customer. The company's expansion plan increases the fault level and requires additional fault current limiting measures. 
• Carrying out the short-circuit study for the entire cement plant, including the expansion, and designing the whole electrical protection, which is referred to as the application engineering for the new and existing Is-limiters.
• Finding the tripping values for Is-limiters to ensure that no too-high short circuit levels occur and harm the equipment. The limiter should break the line in a strict and accurate moment when the tripping values reach the calculated limit. 
• Finding the correct location for the additional Is-limiter. An advanced calculation tool should be used to confirm that the third Is-limiter will improve system stability and resilience.
• Preparing all the required studies, with consideration of the worst scenarios. Identifying project scenarios in which the peak current fault level exceeds the respective withstand capability of the buses.
• In the design to deliver trustworthy results according to IEC standards.

Selected applications

They chose the ETAP Digital-Twin modeling software, which includes Power System Analysis, Short-Circuit, and other features, to reliably model the grid and microgrid and calculate all protections. ETAP Star Library List includes ABB FCL devices to ease calculations.

ETAP ensures compliance with all needed electrical standards for designing and calculating the protection of the electrical systems used in industry.

Main Customer Benefits

• The ETAP software was used to model the entire distribution system, from high-voltage grid infeed to low-voltage loads. The ETAP analyzing functions provided the results needed for the application engineering process. A highly accurate power system model was created in ETAP based on the ETAP model delivered by the client. This new model has incorporated detailed data provided by the client and is used in the microgrid with all new equipment, PV arrays, inverters, and medium-voltage switchgear.
• They can run the studies and research in one ETAP workspace, to identify in the project operating scenarios configurations in which the fault level exceeds the respective withstand capability of the buses. Engineers can check dependencies between different configurations.  short-circuit settings, protection coordination, and arc flash mitigation settings.
• They created macros that studied 26 different operating scenarios and Is-limiter full locations. Electrical equipment and its settings can be easily changed in the virtual model, managing different scenarios. The user could test these scenarios to find tripping values for every Is-limiter.
• They ran calculations for every scenario. In scenario 18, they found the switchgear's withstand capability, which is 31.5 kA, and a tripping value of 19.3 kA. In scenario 14 (with some generators out of service) they found a tripping value of 12.6 kA. Thank to calculation operating on the ETAP model they could see that the operating scenario while maintaining the same fault location results in a different tripping value.
• They used the ETAP Configuration Manager to understand all possible operating scenarios, fault current flow, and all three Is-limiters' contributions. They investigated every operating scenario, and we looked at all different fault locations where short-circuit faults could potentially occur (every bus in the system). Then, they were able to calculate the tripping value individually for every Is-limiter, and at the end, they selected the smallest tripping value to ensure that the system was properly protected for any given short-circuit location.
• As a conclusion they found that a Fault Current Limiter application engineering is a complex activity highly dependent on the operating scenarios and short-circuit fault location.
• They have to use the ETAP to automate functions and to speed up the fault current limiter application engineering process.

 Opinions

So, this is basically how we determine the tripping value for all fault compliments in the system. We investigate every operating scenario in ETAP, and we look at all different fault locations where short-circuit faults can potentially occur, which is literally every bus in the system. And then for these different configurations, we will then calculate the tripping value individually.  
By Mr. Andreas Peters, Head of Business Development and Solution Marketing, ABB

A circuit breaker typically takes 45 to 120 milliseconds, with relay time, breaking, and arcing time. Compared to that, the electronics of the fault current limiter detect a short circuit current in ultra-fast time in microseconds, and the fault limitation takes five to ten milliseconds. [The FCL was modeled in ETAP library.]
By Mr. Rahul Bhat, Business Development Manager, ABB