Power Application SoftwarePower Application Software

UPDEA - Workshop UPDEA - Workshop

What are Power Application Tools?

Name as many of the Power Application Tools as you can

Power Application Software (1)– State Estimator (SE)– Operator Load Flow (OLF)– Optimal Power Flow (OPF)– Contingency Analysis (CA)– Short Circuit Analysis (SCA)– Automatic Generation Control (AGC) – Historical Information System (HIS)

Power Application Tools (2)

Power Application Software (2)– SCADA Topology Determination– Plausibility Check of Measurements– Power System Model Adaptation– Power System Security Analysis– Study Base Case Initialisation– Transient Stability Analysis (TSA)– Voltage Stability Analysis (VSA)– Available Transmission Capacity– Complete Model Estimator (CME)– Dynamic Security Assessment (DSA)– Dynamic Stability Analysis

PAS Applications

• The PAS subsystem consists of applications that support :– Real‑time and study mode network analysis– Determining the state of a power system network– Level of security, – How the security and economics of the network might be improved.

• The PAS applications run automatically using data originating from SCADA

• Study applications are run by the operator or planning engineers, to study the effects of changes in the power system.

• Study data can be initialized from a real‑time network solution, or from archive files.

PAS Tool Data flow• Where do the Power Application tools get their data?• What is data path from the substation to the PAS tools

LiveSCADA

Data

StateEstimator

Power Flow

Contingency Analysis

Short Circuit

Analysis

Power Application Software

Network connectivity

models

RTU

Host I/O

500280

PAS Applications

Control Staff WorkstationsHMI x 8 + 40

SCADA Data Base

AGC

AlarmProcessing

Export to Dispatcher

Training Simulator

Export data to

Corporate Users

Fire Wall

Rear Projection System

Power Application Software

State Estimator

Power Flow

SC

SecurityEnhancement

Voltage VAR Dispatch

Voltage Security

Transient Security

CA

Load Forecast

Real Time

SCADA

What are the two primary sub tasks of the State Estimator?

Real‑Time Network State Estimation ‑ (RTNET)

1. Performs topology processing

2. Estimation the network state

Includes busload forecast and transmission loss sensitivities calculation

State Estimation

Instantaneous SCADA values Bus kV, Line MWs and MVAr limit values exceeded

Estimated values based on Kirchoff’s and Ohm’s Laws

State Estimator

Avon

1

2

Mersy

160

160

400 kV 395 kV

Z = 100 ohms

300 MW

Loads at a bus = 0

• Produce valid topology and real time network solutions for all network apps.

• More reliable and more accurate than raw SCADA

When and how often will the State Estimator run?

State Estimation

Runs on a periodic basis, i.e.

• Usually every 5 minutes

• Each time a switching device such as a breaker or isolator changes state

1. What is the output of a State Estimator run ?

2. What is the output used for?

State Estimation

1. RTNET produces an Estimated State of the power system based on SCADA measurements using a least squares fit algorithm.

2. Once RTNET has run to completion the following applications can run:– Power Flow (PWRFLOW)– Optimal Power Flow (OPF)– Contingency Analysis (RTCA)– Dynamic Stability Analysis (VSAT / TSAT)– Voltage VAR Dispatch (VVD)– Short Circuit Analysis (RTSCT)– Security Enhancement Analysis (SENH)

1. What is the purpose of Study Power Flow?

Power Flow• Allows control staff and planners to study the steady-state operation of the

power network under hypothetical and postulated conditions

• Study how the power flows through the network before taking lines out for maintenance and what - if future scenarios

Generation Load

Gen Load

Avon

1

2

Mersy

150

150

400 kV 395 kV

Z = 100 ohms

300 MW300 MW

0

300

Error

Iterations

Power FlowThe solution is a MWs and Mvar balance of Load against Generation.

MW

Fixed

Instantaneous

System Load

MVAr

Load

MVAr

Load

MW

Solved System

Generation

Load

MW

Gen

MW

Gen

Mvar

Load

Mvar

1. How do control staff make changes Study Power Flow?2. How are the results of the study seen?

• Changes to the network topology can be made by changing the status of circuit breakers on one-line diagrams or tabular displays.

• Results of Power Flow analysis can be displayed either on one-line diagrams or in tabular form.

What PAS tool makes recommendations on how to optimise the grid?

Optimal Power Flow

Optimal Power flow ‑

• The primary purpose of optimal power is to provide control staff with network configuration recommendations that will eliminate or reduce violations and/or move the network to a more economical operating state.

• The primary function of OPF is to determine and present optimal, feasible device settings.

• These settings are calculated based on the network model, control model, objective function model, and operating limits.

• The presented control settings should correct (or, if not possible, reduce) any violations of operating limits and optimize the objective function while maintaining feasibility.

Contingency AnalysisContingency Analysis ‑

• Assesses the impact of potential changes in the network, such as equipment outages, on the state of the power system.

• The application runs in the real time and study environments.

Mersy

Gen Load 1

Avon

1

2

250

400 kV 397 kV

150 MW

200 450 MW

Load 3

300 MW

160 MW

395 kV

Rabbit

Load 2

140 MW

Illovo

400 kV Line OutagesAvon – Mersy1 MustrunAvon – Mersy MustrunMersy_Rabbit MustrunAvon_Illov MustrunIllovo_ Mersy Mustrun

400 kV Load OutagesMersy Load 1 MustrunRabbit Load 2 MustrunRabbit Load 3 Mustrun

Outage Scheduler • Outage Scheduler –

– The Outage Scheduler provides the capability to schedule equipment outages or derations.

– The outage schedules are used by the study applications to study system conditions at a particular time, taking into account the necessary topological or rating changes.

Security Enhancement

• Security Enhancement ‑

– A set of optimization algorithms that recommend operator actions for moving the system to the most secure and efficient operating point given the specified constraints. It includes Constrained Dispatch, Contingency Planning, and Preventive Action.

– The application runs in the real‑time and study environments.

Voltage‑Var DispatchVoltage‑Var Dispatch –– Runs as part of the real‑time sequence. – Recommends reactive/voltage control changes to minimize MW losses,

or to correct voltage violations.

Voltage‑Var Dispatch

• Voltage-Var Dispatch (VVD) is a real-time version of the study Optimal Power Flow application.

• It runs as part of the real-time network sequence, uses only reactive power and voltage controls, and is initialized from the results of the state estimator.

• If the state estimator found voltage violations, VVD will attempt to correct the violations with minimal reactive power control changes.

• If no voltage violations were found, then VVD will attempt to minimize MW losses using reactive power controls.

• Resulting control change recommendations are presented to the dispatcher as advisory recommendations.

Short Circuit Analysis• Short Circuit Analysis –

– Calculates short circuit currents that result from specified faults.

– The Short Circuit analysis program requires a set of fault definitions in the FAULTS database before execution can begin.

Study Network SequenceStudy Network Sequence ‑

– The Study Network Sequence is an integrated environment for in-depth studies.

– It includes Economic Dispatch, Power Flow, Optimal Power Flow, and Contingency Analysis functions that can run in sequence.

– The Study Network Sequence is initialized either from the real-time system, from other study mode functions, or from archive.

Online Dynamic Security

• VSAT– Voltage Security Assessment Tool

• TSAT– Transient Stability Assessment Tool

VSAT Purpose

• VSAT is a tool to assess power system voltage stability • It allows the user to specify multiple scenarios on the network to analyze • Inputs are power flow data, contingency definitions, security limits, transfer

definitions.• The outputs are MW transfer limits, critical contingencies, PV curves

VSAT Features

• Part of an automatic run sequence to cater for changing loads• High speed analysis on a dedicated server • Event driven such as change of system state (equipment failure, generator

redispatch)• Manual such as on instruction from an operator• Transfer limit or base-case security analysis using the following criteria:

– Voltage stability margin– Voltage decline– Reactive power reserves– Thermal overloads

TSAT Purpose• TSAT is a tool to assess power system transient stability • It allows full time-domain simulations of large, complex power systems• Inputs

– Powerflow data– Contingency definitions– Transfer definitions– Security criteria– Analysis and solution options

• Outputs– Transient stability index– Damping Index– Voltage duration index– Frequency duration index– Relay margin index

TSAT Features

• Quick screening of contingencies, in order to minimize number of contingencies to be analyzed in detail

• Security analysis using the following criteria:– Transient stability– Damping– Transient voltage– Transient frequency– Relay margins

VSAT and TSAT Uses

• Helping the operator in deciding whether or not to run a power station in Emergency Level 1 due to its impact on the transfer limit

• Deciding on the next worst contingency that could lead to a voltage collapse during an outage and the amount of load that must be shed to mitigate this after implementation of all remedial measures.

• Determining safe generation limits due to an outage of a line at a power station

State Estimator ProblemOn Load – caring MWs and Mvars

Off Load – caring Mars only

Problem:• Due to the way in which the topology model is evaluated, the line was seen

to be in service • It was carrying Mvars only and thus deemed to be in service even though

the breaker was open.• Lesson – add logic that can differentiate between open lines and Mvar only

states

TurbineTurbine

Steam flow

Normal speed is50 revolutionsa second (+/-)

GENGEN49.875

Power sent to Transmission

Auto/Man

Set point

550

600

580High

Low

ControlPlate

Unit Control System

Dead BandsHz : 49.85 – 50.15ACE : +/- 70

Spinning :1000 MW10 minute : 500 MW

Steam flow valve

Principles of Automatic Generation Control

TEMSE AGC

HV yardERTUCPU

12 v

Memory

Instantaneous Output & Hz readings

Error = Desired - Instantaneous

AGCERTUCPU

12 v

Memory

New set point target sent to Generator

Questions