Overview
It is not always practical to perform detailed EMT studies for every possible scenario. Instead, an effective screening process is required to identify the most critical areas, operating conditions and contingencies where detailed EMT analysis is truly necessary.
To address this challenge, E-Screen was developed as an advanced power system screening platform designed to support and streamline EMT study workflows. E-Screen is primarily used ahead of detailed electromagnetic time-domain simulations to identify:
- Critical network scenarios, including base cases, contingencies, operating conditions, and areas (weak system pockets)
- Critical dynamic devices to be included for EMT studies
- Appropriate study area to be modeled in detailed for EMT studies (boundary selection)
- Sub-Synchronous oscillation risks and their root causes
- Small-signal instability risks and contributing elements
In addition, E-Screen can also be used to generate:
- Frequency-dependent network equivalents (FDNE)
- Harmonic polygons and amplification factors
All of these screening studies are primarily performed using standard power flow data (PSS/E .raw or PSLF .epc). For enhanced screening accuracy, additional inputs — such as dynamic data (.dyr file), frequency response characteristics of black-boxed IBR models (.csv or .txt), and contingency information can also be incorporated.
The primary objective of this screening tool is to use the readily available system data to eliminate the need for predefined study areas or contingencies, thereby reducing the upfront effort required for detailed EMT analysis. This enables evaluation of a very large number of operating conditions and network topology combinations, where all network elements can be considered potential contingencies for systematic screening and ranking of critical cases.
For more information on E-Screen please contact e-tran@electranix.com
E-Screen consists of different modules, incorporating screening matrices designed to streamline and refine the EMT study workflow. The key modules and their associated screening matrices are outlined below.
Single-Frequency Screening
- Network short circuit ratio (NSCR) and interaction factors
- Electrical proximity (Y12)
- Impedance split (Zr)
- Combined short circuit ratio (CSCR)
- Weighted short circuit ratio (WSCR)
Multi-Frequency Screening
- Network frequency scans
- Comparison of frequency scan results based on network sizes and topologies
- Frequency dependant network equivalent (FDNE)
- Harmonic polygon
- Harmonic amplification factor
- Unit interaction factor (UIF) and radiality factor (RF)
Sub-Synchronous (SS) Screening
- SSR analysis: calculations of synchronous machine damping
- SSCI analysis: calculation of net damping at system resonances
- SSFR analysis: calculation of resonance movement across critical frequencies
- Eigenvalue analysis: calculation of unstable modes and participation factors
EMT Study Area (Combined Feature)
This approach utilizes the parameters listed below to define a more accurate and representative study boundary for EMT analyses.
- Interaction factors (from NSCR)
- Electrical proximity (Y12)
- Network frequency profiles
E-Screen utilizes the input data listed below to construct the network admittance matrix representing the entire power system. Depending on the selected screening technique, the admittance matrix is then processed to derive the required screening indices.
For example, in NSCR calculations, the system admittance matrix is first reduced to the Point of Interconnection (POI) buses. The reduced admittance matrix is subsequently inverted to obtain the corresponding impedance matrix. This impedance matrix is then used to calculate interaction factors and NSCR values.
This approach enables utilities, developers, and system operators to prioritize detailed EMT studies more effectively while reducing overall simulation effort. Near real-time identification of weak network areas can also assist operational engineers in enhancing contingency planning and improving overall operational readiness.
Frequently Asked Questions
We update our tools regularly to have the latest PSSE formats supported by E-Screen. Currently versions 26 ,29, 30, 31, 32, 33, 34 and 35 are supported with the latest E-Screen version.
You can send e-mail to the Electranix Corporation at e-tran@electranix.com for all software related updates and support.
The E-Screen program is always under development. Future releases will support negative and zero sequence data in addition to the positive sequence data and will form unbalance network equivalents and frequency scan results. These will include the effects of transformer vector groups, un-transposed transmission lines, negative sequence impedances of black-boxed IBR plants, etc. We also plan to support additional input formats (in addition to the PSS/E. raw format) and frequency dependant transmission line data. If you have any ideas or suggestions for improvements to E-Screen, please send them to us at e-tran@electranix.com.
There are a number of reasons this can occur but the most common issues are study area mismatches and network modifications performed to preserve the stability of EMT simulations (i.e. removal of negative resistances).
Study area mismatches
When a PSCAD network is created using E-TRAN, either a portion of the network or the entire network is translated into PSCAD. Therefore, to obtain comparable results between the two programs, it is recommended to use a consistent study area in both tools (e.g., including the same 5-bus boundary in both E-Screen and E-TRAN/PSCAD).
However, for very large systems, full-network simulations may not be practical in PSCAD due to the computational burden associated with time-domain simulations. In contrast, E-Screen can typically accommodate full-network studies more easily, as it does not perform time-domain calculations.
Network modifications performed to preserve the stability of EMT simulations
EMT simulation programs can experience numerical instability when negative resistances are present in the network model. To ensure robust and stable simulations, both E-TRAN and PSCAD apply specific constraints and corrective measures when such conditions are encountered.
For example, if the conversion of a three-winding transformer to its equivalent star representation results in negative branch resistances, PSCAD will generate an error and prevent the simulation from proceeding. Similarly, if E-TRAN detects a branch or load with a negative resistance, it can automatically modify the resistance value based on user-defined settings available in the Advanced Options page.
These adjustments are intended to produce a numerically stable EMT network model; however, they effectively alter the original network representation. As a result, discrepancies may arise between frequency scan results obtained from E-Screen and those obtained from PSCAD. E-Screen does not require such modifications because it performs frequency-domain calculations rather than time-domain simulations and is therefore not subject to the same numerical stability constraints.
The preferred approach is to address these issues directly in the source network data. For example:
- Generators represented as negative loads in the power flow case should be modeled explicitly as generators.
- Non-physical or inconsistent three-winding transformer parameters should be reviewed and corrected.
- Any network data resulting in negative equivalent resistances should be validated and updated as appropriate.
Once these data quality issues are resolved at the base-case level, frequency scan results produced by E-Screen and PSCAD are expected to exhibit much closer agreement.
For further support contact e-tran@electranix.com.
Get Software Today
For all software quotes contact us today at e-tran@electranix.com
Free Trial
A trial of our suite of software tools are available to try free of charge, if you’d like to request a free trial, please contact e-tran@electeanix.com.
Releases
All minor releases and patches will be available for E-TRAN users holding a software license. Future major releases of E-TRAN will be available at a discounted price to current users.
License Manager
Our software use the Electranix License Manager, which can administer licenses across your network for E-TRAN,E-TRAN Plus and E-SCREEN
Discounts
Discounts may be available for any additional licenses held by the same organization.
E-TRAN for PSS/E users
Electranix has partnered with Siemens/PTI to offer E-TRAN technology integrated with the PSS®E platform. E-Tran (PSS®E-PSCAD Data Conversion Module) and E-Tran Plus for PSS/E (PSS®E-PSCAD Co-Simulation) trial licenses and quotations may be requested through the following form on PSS®E site.
