A new Nomogram Development POM- based tool - Application results in the Idaho Power System. Orlando Ciniglio, IPC Marianna Vaiman, V&R Energy WECC TSS Meeting, Salt Lake City, UT January ,

OUTLINE 1.Some background information 2.What is a Nomogram? 3.Basic Approach 4.Case Studies –  Midpoint West Vs COI  Idaho – NW Vs Limiting element 5.Conclusions 2

Background Information Large GI work prompted need to study interaction between existing path. It was determined that new project could be accommodated on Midpoint West path and not impact existing transfer commitments as long as heavy COI flows N-S were not concurrent. A 90% value for COI (only 10% of the time were COI flows greater than this value) was determined, for the time period of interest, based on historical records It was determined that a Nomogram between these two Paths would help assess the potential interaction. 3

Generic Problem Outline Want to find a Nomogram relation (boundary of operation) between two “Paths” subject to thermal, voltage, flowability and/or stability constraints. –“Paths” can be paths Single Line Generator(s) output Load(s) level –And observing limits in all other paths inside areas of interest By controlling load and generation within pre-specified constraints in the areas of interest. For points at or inside the Nomogram boundaries, system performance is acceptable (marginal at the boundaries) for all credible outages. 4

Generic Problem Outline (Basic Case) 5

Generic Problem Outline (Basic Case – cont) 6

The Concept of a Nomogram Given: –The paths of interest (x & y axes), and By utilizing: –A specified set of generators/loads in pre-defined areas In general, all of the generators/loads in the areas; The generation and loads in the selected areas are allowed to vary within a pre-defined range ( i.e., [Pmax,Pmin], [Lmax,Lmin], for each generator and load in the areas); Determine: –The boundary of operation for simultaneous flows on both paths. Copyright © V&R Energy Systems Research, Inc. All rights reserved. 7

Basic Approach Constraints for Source/Generators: Pmin for the generators (normally set to zero in the power flow cases) need to be adjusted so that the following condition is met: if(MinGenMW = 0, if(MaxGenMW > 0, min ( 0.5*MaxGenMW,MWGen),MinGenMW),MinGenMW) –where if(( condition=true) x,y), means logical statement is evaluated to x if condition is true, and to y otherwise. Establishes [Pmax, Pmin] for generators to that may be adjusted in the process. 8

Basic Approach (cont) Constraints for Sink/Loads: Load min, for each load in the areas of interest is defined as: if(MinLoadMW=0,LDMIN*MIN(MaxLoadMW,MW),MinLoadMW) Where LDMIN is a factor, normally set to 0.8 MW = actual load level Load max, for each load in the areas of interest is defined as: if(MaxLoadMW>0,LDMAX*MaxLoadMW,MaxLoadMW) Where LDMAX is a factor, normally set to 1.15 Establishes [Lmin,Lmax] for loads that may be adjusted in the process 9

How the Nomogram is Constructed in POM? For a Path X flow that is not less than a given value: –Determines the required generation/load adjustments within their limits in the user-defined areas, to cause Path Y to be maximally increased until a violation (voltage/thermal/other path flows/stability) is found. –This will define one point on the nomogram. Changes Path X flow by a given amount, and repeats this process to determine the corresponding Path Y level that can be reached before a violation is found. Computes actual path flow limitations by using available generators/loads, within their user-defined limits Copyright © V&R Energy Systems Research, Inc. All rights reserved. 10

Nomograms vs. Boundary of Operating Region (BOR) Two different computations: –BOR is AC transfer analysis simulation for 2 (or 3) simultaneous transfers –Nomograms is an optimization computation BOR: –Sources and sinks are defined –Changes load/generation in sources and sinks until a violation of monitored constraints occurs –Computes flows on the interfaces (paths) Nomograms: –Selects which combination of generators/loads to adjust and by how much from the specified list –Maximizes the interface (path) Y flow, while keeping interface (path) X greater than a given value, before reaching a violation Copyright © V&R Energy Systems Research, Inc. All rights reserved. 11

Input Data to Build a Nomogram The following information is necessary to build a Nomogram: –A Power Flow Case. –Description of the two paths; flow on one of them is maximized. –Description of other limiting paths with their flows limits. –List of generators/loads that can be adjusted in order to maximize flows on selected paths, as well as their allowed variation range. For example, for generators Pmin/Pmax specified in the base case can be used –Monitored elements (for voltage and thermal constraint monitoring) and limits. –Contingency list. –Solution options (enable/disable control of ULTCs, phase shifters, SVDs, etc.) Copyright © V&R Energy Systems Research, Inc. All rights reserved. 12

Output Files Program outputs results of computations to four files File #1: –The file contains information about the calculation step at which power flow through Path 1 reaches its maximum for a given limit value of power flow through Path 2. –Each record contains three space-delimited fields: Limit value of power flow through Path 2; Step number; Power flow through Path 1 calculated by script BuildNomogramFinal.txt Copyright © V&R Energy Systems Research, Inc. All rights reserved. 13

Output Files (cont.) File #2: –The file contains detailed information about the calculation step at which power flow through Path 1 reaches its maximum for a given limit value of power flow through Path 2. –The file consists of several types of records: The first record contains: –Limit value of power flow through Path 2; –Step number; –Power flow through Path 1 calculated by script BuildNomogramFinal.txt. The second record contains information about particular loads/generators used at calculation step listed in the first record, including bus number, generator/load ID, and the value of real power at this calculation step. The last record contains a list of violations that limit increase in power flow through Path 1. Result for Violation: Midpoint-Hemingway 500kV MW (not in ) Swing Bus MW (not in ) Copyright © V&R Energy Systems Research, Inc. All rights reserved. 14

Output Files (cont.) File #3: –The file contains computation results for all steps at which power flow through Path 1 is computed for a given limit value of power flow through Path 2. –File format is the same as the file format shown above. Program also creates and saves new Power Plow Cases in.epc format for each point on the nomogram: –User defines which point(s)/step(s) to save. Copyright © V&R Energy Systems Research, Inc. All rights reserved. 15

Graphical Output: POM Nomograms Nomograms are built automatically: –In this example, computations are done with a 50 MW step Voltage/Thermal Constraint Not Monitored Voltage Constraint Monitored / Thermal Constraint Not Monitored Copyright © V&R Energy Systems Research, Inc. All rights reserved. 16

Conclusions The process is automated Computes and plots the entire boundary, not just one single point Identifies the mix of generation and loads that should be used to maximize the path flow –Optimization algorithm allows to maximize path flow Copyright © V&R Energy Systems Research, Inc. All rights reserved. 17

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Case Study #1 Want to find a Nomogram relation between Midpoint West and COI (N-S) flows, subject to: –Midpoint – Hemingway < 1500MW –Hemingway – Summer Lake < 1500MW –COI flow >= 1920MW ( North to South). –And observing limits in all other Paths inside areas of interest By controlling load and generation within pre-specified constraints in the areas of interest: –60 Idaho –62 Montana –64 Sierra –65 Pace –40 Northwest –30 PG & E –26 LADWP –73 WAPA R.M. 19

Midpoint West Vs COI 20

COI flows > ~1930MW (10% of the time under light load hours) 21

22 Midpoint West / COI Nomogram (no voltage/no thermal constraints)

Midpoint West / COI Nomogram (voltage/no thermal constraints) 23

24 Midpoint West / COI Nomogram (voltage and thermal constraints)

Questions ? 25