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Squirrel up to No Good – Part 2

1.         Introduction

When you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. …It may be the beginning of knowledge, but you have scarcely in your thoughts advanced to the stage of science.

 - Lord Kelvin (1824—1907)

Variations of the above quote (engraved on the Social Science Building at the University of Chicago), have been attributed to many management professionals, including W. Edwards Deming (who denied it) and Peter Drucker. Indeed, Lord Kelvin probably borrowed it from some earlier scientist. The only reasonable update I have heard is that one should only attempt to manage that which is important to your customers. Power reliability is certainly very important to electric utilities' customers.

The first part of this series (linked below) focused on the history of outage management, and hardware solutions that reduce the number and duration of outages. This paper will focus on metrics, system and software solutions.

2.         Measuring

There are four widely recognized metrics for power reliability. The following definitions were pulled from Pacific Gas And Electric Company's 2017 Annual Electric Reliability Report with some slight edits by the author. [1]

  • System Average Interruption Duration Index (SAIDI): the amount of time in minutes that the average PG&E customer experiences sustained outages (being without power for more than five minutes) in a given year.
  • System Average Interruption Frequency Index (SAIFI): the number of times the average PG&E customer experiences a sustained outage in a given year.
  • Momentary Average Interruption Frequency Index (MAIFI): the number of times the average PG&E customer is interrupted by momentary outages (lasting 5 minutes or less) each year.[2]
  • Customer Average Interruption Duration Index (CAIDI): the average duration of sustained outages. It is determined by taking the total outage minutes for all customer sustained outages (SAIDI) and dividing it by the total number of customer sustained outages (SAIFI).

For the record, PG&E's historical track record for these metrics follow.
Combined Transmission and Distribution Indices (excludes planned and ISO Outages)

Note that the three major PG&E projects that were designed to help measure and manage outages were started and completed per the bullets below. See part 1 for details.

  • Advanced meter infrastructure: started in 2007, completed in 2013
  • Interactive voice response system with speech recognition: started in 2001, completed in 2004
  • Cornerstone project: started in 2010, completed in 2014

3.         Designing
Even before a utility is authorized to proceed with a project, it will spend months to years planning, and preparing proposals for the project. The most powerful planning tool for any utility project is a system model that can incorporate all of the elements of a modern, reliable distribution network (or transmission network for those improvement projects). The model does not stand-alone, but is the central application in a suite of planning applications designed to closely simulate the network being planned, any upgrades and to optimize various aspects of network performance through those upgrades.
There are several leading distribution network simulation and optimization suites. These are briefly described in the subsection below. Since I was employed by Siemens (and a company Siemens acquired) for over twenty years, I am most familiar with their distribution planning suite: PSS®SINCAL. This suite is used by electric utilities in 90 countries, and has applications and features that are competitive with other leading distribution simulation and optimization suites (hereafter: "distribution suites"). Thus I will use this in the second subparagraph below to describe the functions in a major suite.
3.1       Leading Distribution Suites
The following are the leading distribution suites (in alphabetical order, by corporation name), including a brief description of each, the addressed markets, and a link for each. Note that this list is intended to include all suites with (roughly) competitive feature sets that are offered by a competitive firm in the U.S., but it may not be comprehensive.
Cooper Industries, Eaton, CYME: Eaton has a closer relationship with CYME than GE, including a dedicated web site (link below). See the CYME listing for more details.
CYME International T&D, CYME Power Engineering Software: This software is used by Cooper Industries (Eaton) and integrated by GE (see below). On CYME's Website Under their name and primary product area (Power Engineering Software) they have "Now Part of Eaton" in small letters. I could not find any additional details on how close the relationship between CYME and Eaton/Cooper is (acquisition? major investment?) other than it seems to date back to at least 2016. CYME is a Canadian Company located in Saint-Bruno, Québec. The CYME distribution suite appears to be focused on medium to large utilities.
Their distribution suite, CYME Power Engineering Software, offers the following applications. Link to brochure is immediately below.

  • Creation and maintenance of distribution network model
  • Per-phase voltage drop and power flow analysis
  • Fault calculations (fault flows and fault voltages)
  • Protective device analysis and coordination
  • Optimal capacitor placement and sizing
  • Load balancing and load allocation/estimation
  • Analyses on balanced or unbalanced three-phase, two-phase and single-phase systems that are operated in radial, looped or meshed configurations.
  • Harmonic analysis
  • Transient stability analysis
  • Arc flash hazards analysis
  • Load flow contingency (N-p)
  • Geographic overlay
  • Reliability assessment
  • Steady state analysis with load profiles
  • Volt/VAR optimization
  • Low-voltage distribution network modeling and analysis
  • Network configuration optimization
  • Single contingency assessment and restoration
  • Substations, sub-networks and secondary grid modeling
  • Cable ampacity calculations
  • Grounding grid design and analysis

Electric Power Research Institute (EPRI), OpenDSS: a freely-available, open-source electrical power system analysis tool used to simulate distribution-level power systems. It supports nearly all frequency domain (sinusoidal steadystate) analyses commonly performed on electric utility power distribution systems.
In addition, it supports many new types of analyses that are designed to meet future needs related to smart grid, grid modernization, and renewable energy research.
OpenDSS appears to be focused on medium to large utilities.
OpenDSS has been used since 1997 in support of various research and consulting projects requiring distribution system analysis. Many of the features found in the program were originally intended to support the analysis of distributed generation interconnected to utility distribution systems and that continues to be a common use.
Since this is an open tool, the site linked below will provide additional links to other resources required to use this simulator. There also appears to be many third-party developers that offer resources for OpenDSS.
OpenDSS has been used for

  • Distribution Planning and Analysis,
  • General Multi-phase AC Circuit Analysis,
  • Analysis of Distributed Generation Interconnections,
  • Annual Load and Generation Simulations,
  • Wind Plant Simulations,
  • Analysis of Unusual Transformer Configurations,
  • Harmonics and Inter-harmonics analysis,
  • Neutral-to-earth Voltage Simulations, and
  • Development of IEEE Test feeder cases.[3]
    The program has several built-in solution modes, including:
  • Snapshot Power Flow
  • Daily Power Flow
  • Yearly Power Flow
  • Harmonics
  • Dynamics
  • Fault-study

General Electric (CYME): Smallworld is a division of GE that makes geographic information systems (GIS). They also offer many electric utility tools for these system, but these do not include simulation and optimization applications. However they do offer the ability to integrate to CYME Power Engineering Software, listed above.
Operation Technology, Inc., ETAP: ETAP came out of the market for simulation and optimization of electrical distribution networks for large facilities, and is probably a leader in this market. In the last decade or so, they have offered a suite for small to medium electric utilities, etapGRID, and have delivered this suite to a number of utilities in their target market. Applications include network simulation/modeling with Geospatial, Substation & Feeder Diagram, Network Planning & Analysis, Electrical Safety & Protection and Distribution System Optimization.
Siemens PSS®SINCAL: See the next subsection for a detailed description of this distribution suite. Link below is to the brochure:
U.S. Department of Energy, PNNL, GridLAB-D: GridLAB-D was developed with funding from the US DOE Office of Electricity (OE) at Pacific Northwest National Laboratory (PNNL), in collaboration with industry and academia. It is available for Microsoft Windows, macOS and several Linux implementations.[4]
Original work on GridLAB-D was started at PNNL in 2003 under a Laboratory Directed Research and Development project. Starting in 2008 GridLAB-D was made available to the public under an open-source license. US DOE has supported GridLAB-D through both direct funding and funding of projects that support enhancements to the simulation's capabilities.
In 2018 the California Energy Commission awarded several grants to enhance GridLAB-D with the aim to support use in California regions operated by the investor-owned utility ratepayers. The enhancements focus on the California Public Utilities Commission's (CPUC) proceedings related to distributed and renewable energy resource integration, with particular attention to usability, scalability and interoperability.
GridLAB-D™ is a simulation environment that can be integrated with a variety of third-party data management and analysis tools. The core of GridLAB-D™ has an advanced algorithm that simultaneously coordinates the state of millions of independent devices, each of which is described by multiple differential equations. The advantages of this algorithm over traditional finite difference-based simulators are: 1) it handles unusual situations much more accurately; 2) it handles widely disparate time scales, ranging from sub-seconds to many years; and 3) it is very easy to integrate with new modules and third-party systems.[5]
Since GridLAB-D is an open-source tool, it will take some exploration by any potential user to understand whether it is a good fit for their organization. Go through the reference 4 link, and also the link below to start this process. GridLAB-D really does not have a market as such, so it is difficult to say what utilities use it, or how it is used.
3.2       Siemens PSS®SINCAL
PSS®SINCAL is part of a family of power system simulation (PSS) and modeling software (and services) offered by their Power Technology International (PTI) business unit (link below). When I worked for Siemens PSS®SINCAL was limited to distribution network simulation, but now it seems that it also covers transmission-level applications. PTI also offers PSS®E, which has long been one of the most powerful and widely used transmission planning and analysis software suites, and is used by many of the largest regional and national utilities in 140 countries, including some of the largest utilities in the U.S. Siemens also offers a complete range of implementation services and training for all of their PSS software.
The following are functions performed by PSS®SINCAL.
Network model: This model supports all configurations from a simple bus-branch to a full substation model. PSS®SINCAL can run various co-simulations off of a single network model. Network modeling can be done within a simple balanced up to a full four wire system or complete transposed system. Large network model can be simulated with timestamps, variants, scenarios, and can be split into separate models. Modeling of all types of equipment including smart grid data models (see "Protection" and "DER" below). Interactive visualization of network models in schematic, geographic or multi-layer diagrams.
Model management: PSS®SINCAL offers model management solutions that reduce modeling efforts and keep multiple network models up to date from within a single application. Its master database function makes it possible for multiple users to work on a network simultaneously. Special synchronization functions – including conflict management, incremental model update, and network model merge – ensure data consistency.
Load flow: The balanced load flow is an effective tool for calculating operating conditions in electrical networks. This calculation method determines the power flow from the sources – through lines and transformers – to the power consumers. Different kinds of algorithms are available to solve the load flow problem (Current Iteration, Newton Raphson and Admittance Matrix). Unbalanced load flow calculations are enhanced symmetrical load flow calculations. Just as in balanced load flow calculations, the unbalanced load flow calculates the flow of power. In this case, however, the calculations are done for individual phases.
Short circuit calculations: Short circuit calculations are required for assessing the correct ratings for the network (maximum fault currents) and also for protection coordination (minimum fault currents). PSS®SINCAL can calculate one-phase ground faults, two-phase short circuit and ground faults, as well as three-phase short circuits for individual nodes or entire sub-networks. This means the current distribution in the network can be determined for any fault condition. The results of all the calculation can be displayed in the network diagram and on tabular displays. PSS®SINCAL can even provide some results as diagrams (e.g. for voltage curves). All the calculation methods have pre-defined reports to let you document input data and calculation results in detail.
Protection: PSS®SINCAL supports monitoring the management of protection devices and their settings, facilitating protection performance assessments, including stepped-event fault clearance analysis, as well as dynamic fault sequence simulation. It also provides interactive protection coordination with graphical documentation and verifying settings directly within the network model. In addition, the built in protection security assessment module allows for an automated system-wide protection study, as well as the identification and mitigation of critical fault scenarios.
Siemens is acquiring the specialized software company Electrocon International Inc. (EII) to uniquely enhance simulations of power grids and strengthen the company’s electrical digital twin efforts.[6] EII, based in Ann Arbor, MI, develops and markets CAPE (Computer-Aided Protection Engineering) software which focuses on the protection of electricity systems and enables detailed protection modeling for grid analysis and simulations. The CAPE software, designed for transmission and distribution systems in utilities, industry, and infrastructure, will help ensure the safe and reliable operation of large electricity grids. The portfolio and experts of the U.S.-based technology company will complement Siemens’ leading Power System Simulation software suite (PSS®) to more precisely uncover conditions of potential protective device misoperation and resulting avoidable power outages. This capability will be a key feature to integrate renewable energy resources efficiently and to ensure reliable and efficient grid operation.
DER (Distributed Energy Resources): Due to the proliferating deployment of DER on distribution networks, planners need to perform an increasing number of grid interconnection studies. In order to keep up with this trend, both utilities and DER investors need tools that can help them automatically assess the viability of various interconnection proposals. Meaning: what can be economically connected to the grid without compromising the health of the network?
The maximal hosting capacity module within PSS®SINCAL automates different calculation functions (such as load flow, short circuit analysis, protection checks with network adoptions, voltage fluctuations due to DER coming online and offline, etc.)
Additional functions for DER integration include:

  • Time series load flow with grid controllers (voltage, power)
  • Short circuit with defined contributions of generators and converters
  • Harmonic distortion limits according to standards
  • Unbalanced RMS and EMT simulation
  • Standard and vendor-specific dynamic models for wind generators, solar, batteries, SVC, STATCOMs, etc.

Portability: Application with standardized interfaces for easy data import and export, allowing users to maintain a variety of data sets in a single system. The use of open or commercial databases permits direct data exchange with other systems (e.g., GIS, SCADA, ERP, MDMS, Asset Management). Model management is based on standard databases (i.e., Microsoft® Access®, ORACLE®, SQL Server, SQLite). Modern user interface with interactive internet visualizations of network models in schematic, geographic, or multilayer diagrams. Programming can be done with standard scripting languages such as VBA, VBS, C++, .Net, Python™ and Java via COM.
Contingency analysis and restoration of service modules: PSS®SINCAL offers the following functions:

  • Automatic user-configured contingency creation
  • Ability to save and recreate any contingency individually
  • Probabilistic contingencies
  • Contingency creation from restoration of supply results
  • Substation and node outages with restoration
  • Free user-defined outages and restoration scenarios
  • Automatic corrective actions according to user-given rules with different strategies (support of fault location, isolation, and service restoration (FLISR))
  • Event-based post-fault actions
  • Fast contingency screening and ranking to find the most critical outages in large system
  • Automatic definition of outages and recovery actions
  • Several contingency comparison modes
  • Interactive result monitor including graphical representation
  • High speed solution due to parallel processing

Optimal branching modules: PSS®SINCAL offers the following functions:

  • Optimization of tie open point positions subject to loss minimization and / or improvement of system reliability
  • Consideration of load flow constraints
  • Support of balanced and unbalanced systems
  • Enhanced reporting features and graphical visualization

Compensation Optimization: PSS®SINCAL offers the following functions:

  • Determination of optimal locations, types, phase technology and sizes of capacitors or shunts due to power factor needs
  • Economic assessment considering costs of losses against installation costs
  • Placement of available equipment
  • Various methods including heuristic approach

Volt/VAR Optimization: PSS®SINCAL offers the following functions:

  • Optimize feeder voltages and losses with load variations (e.g., min / max values or operation points)
  • Combine and place capacitors automatically at all locations
  • Different methods including heuristic approach
  • Determine transformer and capacitor set points
  • Compare the optimized results in spreadsheets and diagrams before and after

Load Balancing: PSS®SINCAL offers the following functions:

  • Reduction in unbalances at transformer or unbalances in feeder
  • Automatic reconnection of node and branch elements or whole feeders per phase
  • Generic optimization algorithms

Load Allocation (Trim) / Transformer Tap Optimization: PSS®SINCAL offers the following functions:

  • Supporting meter elements for scaling at any network position
  • Radial and meshed systems
  • Successive meters with different parameter sets and directional information including voltage, current, power
  • Balanced and unbalanced networks
  • Load and generator scaling on provided meter values including DER
  • Meters' support profiles
  • Loads can support whole feeder with transformer information and voltage drops under different conditions
  • Load flow solution fits to minimal and maximal network states
  • Optimization of transformer tap positions of outgoing feeders to keep the voltage in an optimal range for min and max consumption
  • Color representation in single line diagram
  • Voltage diagrams for feeders with min and max voltages

Optimal Power Flow: Optimizes the grid by minimizing network losses by optimal equipment set points
Multiple Faults: All type of faults and interruptions at bus bars or branches with user-definable distances.
Arc-Flash Hazard: Arc-Flash calculation in accordance with IEEE-1584. Other functions include:

  • NFPA 70E-2012 and BGI / GUV-I 5188
  • Support of empirical formulae ranging from 208V to 15 kV
  • Theoretical model for any voltage and every type of equipment
  • User-defined protection devices
  • Several options for incident energy calculation (meshed systems)
  • Calculation of arcing-current energy
  • Automated preparation of arc flash labels with flash protection boundary, PPE category and work permits

Other applications and functions are available. I tried to include most of the ones that are important for distribution utilities above. Go through the link below for a complete description.
Also the link below is to the primary web site for PSS®SINCAL. This has many useful links. If you scroll to the bottom, there are links to other application brochures.


[2] PG&E’s outage reporting tools were originally designed to track momentary outages as defined in D96-09-045. Under CPUC Decision 16-01-008 (link below), this method of tracking momentary outages corresponds to the MAIFIE definition contained in the IEEE Guide for Electric Power Distribution Reliability Indices (IEEE 1366 standard), which counts multiple outage interruptions that occur close to each other in time as a single momentary outage event. This metric is equal to the total number of customer momentary interruption events divided by the total number of customers served and does not include the events immediately preceding a sustained interruption.

[4] Wikipedia article on GridLAB-D,

[5] GridLAB-D Home Page,

[6] Siemens Press Release, "Siemens strengthens digital twin efforts with U.S. grid protection software acquisition", October 3, 2018,

John Benson's picture

Thank John for the Post!

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