Dms Telvent

The Advanced Distribution Management System

The indispensable tool of the Smart Grid era

Telvent utilities group

August 2010

©2010 Telvent. All rights reserved. www.telvent.com/smartgrid | 1.866.537.1091

IntroductionThe Smart Grid era is the result of a shift in focus within the electricity

industry — a shift away from the older, familiar approach of large

power stations and reliance on transmission systems to move bulk

power. Our Smart Grid future is more likely to be focused on smaller

distributed electricity generators, a growth in renewable resources,

eliminating overloads, and reducing peak demand through demand

response options.

In addition to the focus on evolving management of distribution

networks, the electricity consumer is being asked to change long-

standing habits and manage growing appetites for energy. Regulatory

organizations and utilities are trying to cope with this issue all over the

world, blending advanced metering and communications technologies

to bring new options. Dynamic, time of use, and other pricing

alternatives are under consideration to reduce electricity network

congestion and energy costs.

With these changes, the need to more effectively plan, engineer,

and manage the distribution network is a critical requirement. In

addition, there is a rush to implement the core software to support this

responsibility — the advanced distribution management system (DMS).

This paper will provide an overview of the advanced DMS software,

including its diverse, complex portfolio of functionality, as well as its

benefit to the distribution network owner and the energy consumer.

The advanced DMS For more than 40 years, utilities have used the strength and speed

of computers to model electricity networks. For the most part, that

focus has been on transmission networks, and there are many mature

software products on the market that provide strong functionality for

bulk power transmission networks.

Modeling distribution networks is a different, and in many ways, more

complex problem.

The Advanced Distribution Management System

The indispensable tool of the Smart Grid era

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What makes a DMS advanced?

Distribution Management Systems

(DMS) are software applications

with basic capabilities. When a

DMS has advanced functionality —

including volt/VAT control, FLISR

support, advanced forecasting and

planning functions, and others

— that tightly integrates with an

OMS and SCADA, it is considered

to be “advanced.”


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Instead of the need to model static, meshed, and balanced transmission

networks, today’s advanced DMS technology must model radial,

unbalanced distribution networks with rapidly-changing topologies

and demand profiles. Instead of consistent and frequent telemetry

from the transmission network, advanced DMS technology must be

able to coordinate unsynchronized data for management of these

network models. Advanced DMS must also deal with the possibility

of “islanding” portions of the distribution network — creating the

potential for management of multiple and independent distribution

networks.

The advanced DMS must also deal with the evolving use of electricity,

supporting variable, localized demand profiles created by changing

consumption habits, and by new electricity-powered devices such as

battery-powered vehicles and high-tech devices. Further, the advanced

DMS must deal with shifting consumption patterns and customer

demand for higher levels of service for their devices. Not only must

service levels improve, but also the service must be high quality,

including voltage levels that operate within regulatory norms.

The advanced DMS is the tool that enables the power system engineer

and dispatcher to effectively and efficiently engineer, plan and operate

the distribution network. It analyzes unbalanced and dynamically

changing distribution networks in real-time, while providing a study

capability for both backward and forward review to identify options to

improve network reliability while lowering electricity costs.

The advanced DMS is the critical tool for management of the

distribution network, and enables the acquisition of many of the

benefits utilities and consumers expect from their Smart Grid

investments.

The foundation of the advanced DMS At the core of the advanced DMS is the ability to precisely define the

network model, and to process an unbalanced load flow algorithm

based on that model with telemetered data taken from the network.

• The network model

The advanced DMS must be able to represent all aspects of

the distribution network, including a variety of conductor

types, transformers, switches (both manual and motorized),

fuses, and other permanent and temporary devices used


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in distribution system operations. The model must provide

connectivity based on the position of switches, and be able

to determine how individual demand points are connected

to the energy supply.

• The dynamic data

To enable functioning of the advanced DMS load flow

algorithm, it requires data telemetered from the distribution

network. That data is generally made available through

supervisory control and data acquisition (SCADA) systems

and their associated telemetry, through AMI networks, and

from the outage management system (OMS). This manages

the flow of information regarding “lights-out” events on the

distribution network.

The amount of data to be telemetered and stored is

significant and changes frequently, suggesting that great

care must be taken to manage the flow of data to the

advanced DMS — enabling it to process quickly and

efficiently. The data provides a variety of information (e.g.

voltage, current) and device status (e.g. open/closed) to

enable the load flow algorithm to function.

The advanced DMS must also be able to store copies of the

data for future study and training purposes. Historical data

copies can be very helpful in planning for situations that

develop on the network as demand profiles and energy costs

change.

• The unbalanced load flow algorithm

The advanced DMS must have a very fast load flow

algorithm that can solve unbalanced distribution networks

based on data telemetered from the field.

Visualization of advanced DMS results With a complex network model, significant quantities of data (both

telemetered and calculated) and the wide variety of advanced DMS

users (planning and design engineers, operations management,

and distribution system dispatchers, etc.), providing visualization of

advanced DMS results is an important consideration. An advanced

DMS should be able to display network data in a geographic view (e.g.


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maps), a schematic view, and in single-line diagrams. Further, the end-

user should be able to easily manage the level of information displayed

in these views.

Individual utilities have developed different means to view their

network information over time, and the advanced DMS must be

flexible enough to support the format desired by the utility. Done

correctly, the advanced DMS will be able to drive full-scale power

network projections in system operations centers, both at dispatcher

workstations and projected on larger screens to inform those in the

control center or elsewhere.

State estimation — ensuring the accuracy of advanced DMS results One dictionary defines state estimation as “a branch of probability

and statistics concerned with deriving information about properties of

random variables, stochastic processes, and systems based on observed

samples.” In power networks, state estimation takes observable data

from the field and derives a model of what is actually happening, by

processing the data to identify bad readings or to estimate missing

data.

The quality of data telemetered from various points on the distribution

network is typically imperfect. Problems in devices or in the

telecommunications networks associated with those devices suggest

that prior to conducting an advanced analysis, the data must be pre-

processed to eliminate bad data points, estimate non-telemetered

points, and resolve any issues with “time skew” for unsynchronized

telemetry systems.

The tool that performs this quality analysis is known as state estimation,

a critical feature of the advanced DMS. To trust the results of the

analytical software, the inputs must be quality checked, and either

adjusted or eliminated to avoid bad results.

Advanced DMS analytical functionality The advanced DMS has functionality that supports several functional

areas:

• Operations planning and analysis, loss minimization

One of the primary uses for the advanced DMS is the real-

time analysis that enables optimization of the distribution

network. The advanced DMS continually runs real-time


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analysis, identifying problems and suggesting approaches to

better balance load, suggest switching to minimize losses,

and identify other potential and real problems, as well as

likely solutions.

The advanced DMS enables utilities to reduce energy waste

on their distribution networks through a more detailed

understanding of losses — and through reconfiguration and

network optimization — to minimize those losses.

• Supporting outage management activities

The advanced DMS provides analytical support to ensure

that outage causes are identified and resolved more quickly.

Integrated with an OMS, it provides a “next generation”

level of functionality, which that can use to improve network

reliability.

The advanced DMS has a strong level of functionality around

fault location, identification, and service restoration (FLISR).

The FLISR functionality already present at most utilities is

enhanced with the advanced DMS’s ability to locate faults

(based on telemetry and analysis) and to provide ranked

switching options to a dispatcher (e.g. prioritization based

on connected load, connected customers, etc.) based on

the dynamic state of the network. The advanced DMS can

extend the capability of traditional self-healing network

automation by allowing it to operate on the as-switched

network model in any arbitrary configuration.

Because the advanced DMS maintains information about

the as-switched state of the network, it facilitates and

automates the creation of switching orders, for planned

and unplanned work that dispatchers or field operators can

execute according to traditional procedures, or which can be

executed automatically in the presence of field automation.

This can all be accomplished while managing tagging

functionality as needed, and ensuring that the state of the

network is well represented at all times — including the

incorporation of temporary elements that may be used to

support outage restoration.


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• Volt/VAR Control

The volt/VAR control functionality contained in the advanced

DMS enables utilities to ensure power quality in all parts

of the distribution network. It also provides a transparent

approach to demand response that utilities can exercise

without any need or expectation of customer involvement.

To this end, volt/VAR management supported by the

advanced DMS enhances overall network stability and

reliability.

Performing analysis and control for volt/VAR optimization

on a distribution network may require additional field

telemetry and control. It may also require the identification

of feeder segments where additional capital infrastructure

investments may be needed to enable the creation of a

more “level” voltage profile. The strengthening of the

distribution network for maximum use of advanced DMS

functionality may therefore require additional time and

capital expenditures for the utility.

Demand response Demand response is a key function that drives utilities to Smart Grid

programs and to the implementation of advanced DMS software. The

complex world of demand response suggests many options can be

exercised to reduce demand in the face of increasing demand, and the

potential of surging costs and network instability. The advanced DMS

understands that there are multiple approaches to demand response,

and the software can direct the implementation of demand response

options that are created by Smart Grid programs.

Some demand response actions depend on customers to react on

their own. Utilities and governments routinely request for electricity

consumers to change their consumption patterns when supply is

short. Regulators can also create rate structures that encourage similar

conduct through normal attention to energy costs. However, since

these approaches do not provide sufficient reduction, additional

demand response options are provided, and the advanced DMS can

support the prioritized application of these options.


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In general, the available options fit into three categories, which are

listed in order of customer impact (lowest to highest):

1. Conservation voltage management (CVR) — also

known as Distribution System Demand Response

(DSDR)

This functionality utilizes volt/VAR management functionality

to reduce demand through reduced voltage on the

distribution network. The voltage reduction (usually

between 3 percent and 7 percent) results in reduction

in the power delivered by a similar amount, all without

customer awareness. Further, voltage management can be

accomplished on a feeder or feeder segment basis to resolve

a local overload (perhaps as a result of electric vehicles or

other infrequent demand anomalies) instead of on a system-

wide basis. This surgical use of demand response and its

lack of impact on customers is often the critical reason to

implement an advanced DMS.

2. Direct load control

Most utilities have implemented some form of direct load

demand response, generally through radio-controlled devices

located on water heaters, air conditioners and pool pumps.

Using this form of demand response, utilities can turn off

these devices for a short period of time (perhaps 15 to 20

minutes) to reduce demand on the distribution network. The

direct load programs already in place rotate the “turn-offs”

around the service territory to reduce customer impact. Since

there is some amount of customer impact, while minimal,

utilities must generally ask customers to “opt-in” to such a

program, and often trade a rate advantage or discount to

customers who choose the program.

Direct load control will continue to increase in complexity

with the evolution of home area network (HAN) technology

and the continued roll-out of AMI systems. The advanced

DMS is designed for integration with these end-of-network

systems, supporting direct load control by identifying

appropriate feeders segments and timing in a prioritized

manner.


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3. Load interruption/islanding

When other demand response options fail, utilities

disconnect some demand to maintain the ability to serve the

rest. Again, most utilities have “opt-in” programs for such

interruption, including interruptible rates that are supported

by regulators and governments. However, depending on

the nature of the overload and danger to the health of

the distribution network, utilities may have to exercise

interruption options with little or no advance notice — even

to customers who have not elected this option. Once again,

the advanced DMS makes recommendations and prioritizes

options for utility dispatchers to enable decision making in

situations where it is unavoidable.

Distributed generation The Smart Grid was initially intended to support the addition of

environmentally-renewable energy resources to the distribution

network, including wind, solar, biomass, and others. However,

managing a distribution network with hundreds or thousands of

potential energy sources requires an advanced DMS.

The advanced DMS can help maintain the balance needed to reliably

operate a diverse supply environment in the face of dynamic changes in

demand and in the topology of the distribution network.

As distributed generation becomes more prominent, distribution

networks may tend to become small “islands” of energy that can

operate while connected to the rest of the distribution network. They

may also operate independently as a “micro-grid” in a disconnected

manner. The advanced DMS can manage the network through these

operating approaches, optimizing it for losses, reliability, or cost of

operation, while maintaining a secure distribution network.

• Distribution network planning and demand forecasting

Since utilities must take a forward look in planning their

distribution networks, the advanced DMS must provide

functionality to enable planning and budgeting for

maintenance of reliability and quality of service. Advanced

planning functionality must start with demand forecasts

for the time frames required. The advanced DMS includes

demand forecasting (short, medium, and long-term)

contributing to the planning process.


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Dispatcher training simulatorIn addition to the diverse real-time and off-line analytical functionality

contained in the advanced DMS, it is also possible to take a “snapshot”

of the distribution network — including the network model and

associated telemetry. This snapshot can then be used to train

distribution system dispatchers. The advanced DMS can also support

the storage of past forecasted models.

To be effective, the dispatcher training simulator must also have the

ability to move through time (typical demand and supply changes),

with events that can be programmed by an instructor. In this manner,

the simulator enables training cases based on experience or in advance

of anticipated events.

SummaryThe advanced DMS is an indispensable tool of the Smart Grid era.

Starting with the foundation of a fast, unbalanced load flow engine

and the ability to validate data via state estimation, the advanced

DMS provides complete functionality to help utilities optimize their

distribution networks. The software also provides dispatchers,

engineers, and others who operate and manage the network with easy

network visualization.

The advanced DMS includes significant functionality to manage

outages and perform FLISR operations. It also has the tools to support

volt/VAR optimization, which enables voltage-based demand response

functionality (DSDR), the form of demand response that has the least

impact on customers. The software supports distributed generation,

enabling the utility to grow and accommodate the renewable

generation expected of the Smart Grid era, while optimizing the

network for reliable service.

Lastly, the advanced DMS supports short, medium and longer term

planning, and also enables the capture of “cases” to support the

training of dispatchers who operate the distribution network.

Advanced DMS — the indispensable tool of the Smart Grid era.

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The concept of the virtual power plant

Virtual power plants (VPP) come

from a utility’s ability to dispatch

(set appropriate output levels) an

amount of power that exists in the

form of distributed generation and

demand response, instead of as a

physical power plant.

Using a variety of demand

response approaches (e.g.

direct load control, volt/AVR

management, etc.) and distributed

energy resources (e.g. energy

storage, renewable generation,

etc.), a utility can create a profile

of a virtual power plant, and use

it in its energy dispatch algorithms

when balancing demand and

supply.

This also requires critical analytics

and controls, such as those

provided by the advanced DMS —

using SCADA, DMS, and other tools

as needed — to create the VPP

and the forward operational plan

a utility would expect in a power

plant environment.

The advanced DMS is the tool that

enables the VPP concept.

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