Power Application Software 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)

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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.

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PAS Tool Data flow • •

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

RTU Live SCADA Data

Host I/O

Network connectivity models

State Estimator

Power Flow

Short Circuit Analysis

Contingency Analysis

500 280

Power Application Software

PAS Applications Real Time SCADA

Load Forecast

Alarm Processing AGC

SCADA Data Base

CA State Estimator

Rear Projection System

Control Staff Workstations HMI x 8 + 40

SC

Export to Dispatcher Training Simulator

Power Flow Voltage VAR Dispatch

Voltage Security

Security Enhancement

Power Application Software

Fire Wall

Transient Security Export data to Corporate Users

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

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State Estimation Real-Time Network State Estimation - (RTNET) 1. Performs topology processing 2. Estimation the network state Includes busload forecast and transmission loss sensitivities calculation

State Estimator Avon

Z = 100 ohms 1

160

Mersy

300 MW

2 160 400 kV

Σ

• Produce valid topology and real time network solutions for all network apps. • More reliable and more accurate than raw SCADA

395 kV Loads at a bus = 0

When and how often will the State Estimator run?

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

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

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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?

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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

Avon

Z = 100 ohms

Mersy Load

Gen

1

150 300

300 MW

300 MW 2 0 150 400 kV

395 kV

Load

Generation

Power Flow The solution is a MWs and Mvar balance of Load against Generation. Gen Mvar

MW Solved System Generation

Gen MW

Load Mvar

Load MW

Load MVAr

MVAr Load MW

Fixed Instantaneous System Load

Error

Iterations

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

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• 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.

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Contingency Analysis Contingency 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.

400 kV Line Outages Avon – Mersy1 Avon – Mersy Mersy_Rabbit Avon_Illov Illovo_ Mersy

Mustrun Mustrun Mustrun Mustrun Mustrun

400 kV Load Outages Mersy Load 1 Rabbit Load 2 Rabbit Load 3

Mustrun Mustrun Mustrun

Mersy 150 MW

Avon

Rabbit

Load 2

Load 1

Gen

1 450 MW 2

140 MW

250

160 MW 200

Load 3

300 MW 400 kV

397 kV

395 kV

Illovo

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.

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

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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.

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Study Network Sequence Study Network Sequence – The Study Network Sequence is an integrated environment for indepth 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 realtime system, from other study mode functions, or from archive.

Online Dynamic Security • •

VSAT – Voltage Security Assessment Tool TSAT – Transient Stability Assessment Tool

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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

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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

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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

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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

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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 Problem On 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

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Principles of Automatic Generation Control Unit Control System Control Plate Set point

600 580

High

550

Low

Auto/Man

Normal speed is 50 revolutions a second (+/-) Power sent to Transmission

Steam flow Steam flow valve

Turbine CPU

GEN

AGC ERTU

49.875

Memory 12 v

New set point target sent to Generator

HV yard ERTU

CPU Memory 12 v

Instantaneous Output & Hz readings

Dead Bands Hz : 49.85 – 50.15 ACE : +/- 70 Spinning :1000 MW 10 minute : 500 MW

TEMSE AGC Error = Desired - Instantaneous

Questions

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