Aricent Electrical Utility Whitepaper

9
ELECTRICAL UTILITY SECONDARY SUBSTATION AUTOMATION

Transcript of Aricent Electrical Utility Whitepaper

ELECTRICAL UTILITY SECONDARY SUBSTATION AUTOMATION

1Electrical Utility Secondary Substation Automation

ELECTRICAL UTILITY SECONDARY SUBSTATION AUTOMATION The Electrical utility industry is going through a difficult evolution

battling issues like balancing high energy demand/consumption

with low energy generation while reducing their carbon footprint.

This has led to modernization of the grid and further proliferation

of smart devices like synchrophasors, sensors, smart meters,

and actuators that provide real-time assessment of power-

system health and control of utility assets like transformers

and capacitor banks.

Of the numerous activities that initiate a smart grid, automating

primary (HV/MV) and secondary (MV/LV) distribution

substations is perhaps the the most challenging activity, with

distribution substations distributed across a vast geography.

In order to introduce optimized automation algorithms into these

distribution substations, utilities use wireless technologies like

WirelessHART, LTE, ZigBee, etc.

Most utilities have automated their primary distribution

substations by using WirelessHART as a wireless sensor network

(WSN) technology between the sensors/actuators and the

automation controller. Even though the technologies used

in the primary substation can be adopted with the activities of

the secondary distribution substation, the secondary substation’s

proximity to residential homes and distributed energy resources

(DER) necessitates defining a secondary substation node (SSN)

that supports orchestration of IEC 61850-based devices as

well as devices supporting ZigBee SEP.

This paper highlights some of the considerations for a SSN as

defined by EU smart energy projects OpenNode and INTEGRIS,

and introduces Aricent’s approach to defining SSN through

our solution accelerators.

IntroductionMany countries across the world are modernizing their power

grids into smart grids in order to increase reliability and energy

efficiency, enable transition to renewable sources of energy,

reduce greenhouse gas emissions, and build a sustainable

economy. Enabling smart grids entails on adding and integrating

many varieties of digital computing and communication

technologies and services with the power-delivery infrastructure.

Bidirectional flows of energy and two-way communication

and control capabilities enable an array of new functionalities

and applications that go well beyond smart meters for homes

and businesses. Smart grids can provide predictive power

information (e.g., meter reading data, charges, and power usage

recommendations) to both utilities and consumers. It can also

diagnose power disturbances and outages to avoid equipment

failure and accidents in generation, transmission, and distribution

within the utility network.

Various standards bodies and national regulatory organizations

are working to define the interoperability of devices used in

smart grids. NIST is one such prominent standards body that

has defined detailed conceptual reference architecture for

smart-grid information networks. NIST’s concept model provides

a high-level, overarching perspective of major relationships

across different domains of power-grid systems like generation,

transmission, distribution, and energy sources, as well as users

with the capability to make decisions and exchange information

with other users. This concept model defines information flow

between different domains and users within the smart grid.

2Electrical Utility Secondary Substation Automation

and breakers), a network that connect all the devices (via wired

Ethernet or wireless connections), and software that receives

input from, and manages, the field devices. Fast and efficient

intercommunication between these devices is achieved

through substation automation system. Advanced distribution

optimization algorithms utilize exchange of information between

the devices and the device that coordinates all substation

devices. An example of this is the acquiring of empty or load

voltage values in order to assess whether they are within the

limits and to acquire medium-voltage distribution line states.

Additional information about the substation, such as door

position, transformer temperature, switch-gear position, and

voltage readings, is also used when making real-time adjustments

for changing loads, generation, and failure conditions within

the distribution system.

Newer microprocessor-based relays and other intelligent devices

provide unprecedented flexibility and rich functionality which,

in turn, provide low-cost monitoring analysis and diagnosis of

electrical faults in the power network. Many newer IEDs provide

optional network interfaces such as distributed network

protocol (DNP) 3.0 or IEC 61850 over transmission control

protocol (TCP)/Internet protocol (IP)/Ethernet.

Distribution Substations and AutomationSubstations in the power grid system are described by their voltage

class and application within a power system. A distribution

substation transfers power from the transmission system to the

distribution system of an area. A typical distribution substation

contains a switch and low-voltage transformer. Many large

cities feature complicated distribution substations containing

both high-voltage switching and low-voltage switching and backup

systems. More typical distribution substations have a switch,

one transformer, and few low-voltage facilities.

Distribution automation (DA) optimizes a utility’s operations

and directly improves the reliability of its distribution power

system. The success or failure of an automation program

hinges on proper selection of equipment and communications

to seamlessly integrate data into the utility control room.

Functions necessary for substation automation and application

are protection, control, measurement, and monitoring.

Typical distribution automation solutions consist of three main

components: an - IED (including reclosers, capacitor controls,

switch controls, faulted circuit indicators, voltage regulators,

Overview of Distribution Domain (Reference: NIST Smart Grid Framework)

Operations

Transmission Substation

Reclosers and Relays

DistributedStorage

CapBank

Customer

N.O. Switch

Sectionalizer

DistributedGeneration

Markets

CL200 2474 JNV JO4

ElxtNet

Control Measure Protect Record Optimize

External Communication Flows Internal Communication Flows Electrical Flows Domain

3Electrical Utility Secondary Substation Automation

substation takes higher priority compared to the secondary

substation automation. However, with increased focus on

power quality in the distribution network and with secondary

substation providing connection points for a wide variety of

loads as well as a growing number of unpredictable renewable

power sources, there is an increased focus on secondary

substation automation. The introduction of distributed

generation in distribution networks requires protection and

control systems that can reliably locate and isolate faults.

With rising demand for electricity, decentralized power

production (rooftop solar panels and household windmills),

and new loads (heat pumps and EVs), utilities, today more

than ever, are looking for ways to enable a smarter, secure

grid that delivers uninterrupted power supply to consumers

at reasonable prices. To achieve this, utilities face various

challenges to keep their substations up and running. Problems

like power outages, costly unplanned maintenance, and rising

operational costs often get in their way and then cascade into

a whole series of problems. Normally, electricity utilities with

SCADA systems have extensive control over transmission-level

equipment, and increasing control over distribution-level

equipment via distribution automation. However, they are

often unable to control smaller entities such as distributed

energy resources (DERs), buildings, or homes.

A micro grid is a cluster of various DERs like solar, wind, fuel

cell, micro-turbine, diesel generator, battery systems, Electrical

Vehicles (EV), etc. With the number of DERs bound to rise quickly,

the ability to monitor these new power inputs into the grid,

balancing grid demand with generation, and coordinating

generation from these micro grids as more generators are

connected to the distribution grid all become increasingly

critical. Seamless two-way communication plays an important

role in the operational and control functions of a micro grid,

such as optimal control, protection, monitoring, metering,

self-healing, etc. Because these DERs may have a grid

interconnection to feed excess power, it is important to

orchestrate their activities with those of the main grid for an

optimal utilization of the micro grid.

Secondary substation automation is used to increase efficiency

of grids. Recently, OpenNode, funded through European

Community’s Seventh Framework Program (FP7/2007-2013),

has begun addressing challenges in increasing efficiency of the

distribution grid through creation of a secondary substation

node (SSN) as an essential component of the smart distribution

grid. This node addresses the functionality required by the

grid to cope with massively distributed embedded systems in

the distribution grid. The SSN allows aggregation of status

monitoring and metering management, as well as running

third-party applications (e.g., advanced grid control algorithms

Until now, many of the sensors used in automation activities

were connected with wires, severely limiting their size and

scope of coverage. Wires and the required conduits are expensive

to install and become fixed installations that are difficult to

change. As a result, many installations find it necessary to

limit the number of sensors simply to control costs, which

restricts the flexibility to adjust these networks to meet new

uses. When not required for critical infrastructure, wired solutions

are often summarily dismissed as being a “luxury.” But with

the growing trend of minimizing technical and commercial

losses by moving from distribution automation to smart

distribution that supports self-healing (i.e., isolation of faults

for faster service restoration) and autonomous restoration,

distributed energy resource deployment, bi-directional flow

of energy and information, enhanced supply security, and

power quality, there is a greater focus on automating the

controller activities in a distribution substation through either

wired or wireless communication technologies.

The use of wireless sensor networks (WSNs) for automation and

monitoring has several benefits over wired systems, including

reduced cost, ease of reconfiguration, and deployment

convenience. There have been significant developments recently

in terms of WSN standardization, with the HART Communication

Foundation and International Society of Automation (ISA)

being particularly influential in the field of wireless industrial

automation systems and ZigBee Alliance in developing ZigBee

wireless standards.

However, WSNs also bring cyber security and privacy challenges

to smart grids. For example, a number of security, privacy, and

reliability issues can appear during electric power delivery.

Competitors can compromise selected nodes and thus fail the

critical mission of supervisory control and data acquisition

(SCADA) systems. Any of these can cripple a grid, resulting in

millions of homes and business establishments losing electrical

power. Security of WSNs is therefore a critical concern when

designing networks for usage within a substation or a mesh

network across substations.

Secondary Distribution Substations and AutomationBased on the voltage handled, a distribution substation is

divided into primary and secondary substations. A secondary

unit substation is typically MV/LV (with input of 1 kV up to 35

kV and output of 1 kV). Principal areas of application include

use in industrial plants, electric power generating stations, and

commercial buildings. With higher voltages involved in the

hierarchy of the network, automation of the primary distribution

4Electrical Utility Secondary Substation Automation

or critical value monitoring like monitoring busbar voltage

and split current across multiple transformers by activating

circuit breakers) that can be dynamically installed during live

operation to enable the controlled shift of grid intelligence

from centralized systems in the utility control center to lower

echelons of the grid hierarchy.

The SSN uses an IEC 61850-based data model that represents

all data points in its canonical tree structure. Thus, all logical

operations in SSN happen solely on the data model, completely

abstracting underlying automation hardware and higher-tier

system architectures. This architecture also proposes to use

IEC 60870-5-104 as standard for exchanging information for

electrical device monitoring and control as the protocol supports

real-time and synchronous data transfer.

The OpenNode requirements specification captures SSN

functional requirements that cover areas related to smart-meter

management and data acquisition, measurement of MV/LV

side of transformer, clock synchronization, fault detection and

isolation, alarm reporting, line restoration (open and close orders

to the MV switches in order to restore the power after an

interruption), auto test, power supply backup management,

fraud detection, autonomous load shedding, manage energy

storage devices, and integration with IEC 61850 procedures

and data model.

Another EU project, INTEGRIS (INTelligent Electrical Grid Sensor

communications), proposes the development of a novel and

flexible ICT infrastructure based on a hybrid Power Line

Communication (PLC) wireless integrated communications

system able to completely and efficiently fulfill the predicted

communications requirements of Smart Electricity Networks

in the future. This includes all-encompassing applications such

as monitoring, operations, customer integration, voltage control,

quality of service control, control of DERS, and asset management

and can enable a variety of improved power system operations,

some of which are to be implemented in field trials that must

prove the validity of the developed ICT infrastructure.

Secondary Substation

SSN

Transformer

IEDS Sensors Actuators

Control Centre Other Companies

Retailers

Traders

Power Supplies

Meter Operators

Others

Utility Systems

Technical Systems

Billing Systems

Workforce Management

Business Intelligence

SCADA

GIA

AMM

Millions Thousands One

CriticalInformation

UtilityFinal Customer

Middleware

Device Management

Events Processing

Software Provisioning

Measure Management

Network Supervision and Monitoring

Administration System

Distributed Process Management

GridTopology

Events Measures

Virtual SSN

Ente

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MV-LVSubstation

MV-LVSubstation

HV-MV Substation

Sensor RFID Reader

RFID Tag

PLC CPEPLC HEPLC Repeater

OpenNode and INTEGRIS serve as excellent references for

developing the SSN that will enable automation activities in a

secondary substation utilizing different WSNs (wireless sensor

networks) technologies as well as the DA protocols like IEC

61850 and DNP3.

Source: INTEGRIS

OpenNode overall framework (Source: OpenNode EU project)

5Electrical Utility Secondary Substation Automation

voltage, power factors, and harmonics). This, however, requires

connectivity to distribution management systems with the

intelligence needed to calculate the active power (P) and/or

reactive power (Q) requirements according for the actual situation

and the available P and/or Q in energy storage systems.

As well as implementing proper protection, control, and

monitoring, renewable sources are important. In order to

address this need, ZigBee SEP 2.0 has included a distributed

energy resources function set that provides an interface to

manage DER. Client devices of this function set include intelligent

solar inverters, fuel cells, EV, generation units, and battery

storage systems. Server devices of this function set include

energy management systems that can be part of a secondary

substation node. Servers expose energy transfer control events

called DER Controls (DERC) to client devices e.g., active power

derating setpoint indicating a percentage reduction to be

applied to a DER output. As SEP 2.0 resource representations

are built to be compatible with the IEC Common Information

Model (CIM), there is a greater harmonization among substation

automation standard IEC 61850 and ZigBee.

Secondary Substation Automation and AricentAricent’s SSN Framework is designed to help vendors accelerate

time to market with rapid prototyping and commercialization

of applications necessary for the secondary substation

automation. This framework consists of Aricent Data

Concentrator Application Framework (DCAF) and Aricent

Energy Manager Framework (EMF).

Aricent DCAF provides a Web services-based interface layer

that exposes most common functions related to smart-meter

management (e.g., meter read (ondemand plus periodic),

remote connect/disconnect, alarm management, fraud

detection, and meter administration (including meter registration,

remote software updates, clock synchronization, etc.)). The

framework has been designed in a platform and protocol-

agnostic manner and can be used on both DLMS/COSEM

and other protocols like ANSI C12. Aricent also brings in a

DLMS/COSEM stack on SSN node to connect with smart

meters over PRIME/G3 PLC.

Aricent EMF is an energy management framework that provides

an application environment to develop distribution automation

algorithms. As a first step, Aricent has implemented a demand

response (DR) algorithm wherein it handles events from utility

demand response application server and converts to multiple

ZigBee SEP and HA events. Aricent intends to extend this EMF

to include additional algorithms for secondary substation

automation as well as to enable DER management.

Role of ZigBee in Secondary Substation AutomationAs discussed earlier, use of WSNs based on IEEE 802.15.4

(WirelessHART, ISA 100.11a or ZigBee) are intended for

monitoring and control using analog and digital input/output.

They and they meet the requirements of less power, and also

transmit data a lower rate for automation and monitoring of the

secondary substation. Since WSN-based automation is not new

and there is a large installed base of HART/WirelessHART and

ISA-based automation networks, it is quite natural to select

these technologies for secondary substation automation. At the

same time, ZigBee has evolved as into being WSNs’ cheapest

and easiest solution for controlling and automating small network

devices. Research has shown no significant adverse impact

on the performance of ZigBee by the electromagnetic

environment of the substation and therefore can be used for

automation purposes inside a secondary substation.

All ZigBee networks must have a coordinator to set up the

network, be aware of all its constituent nodes, handle and store

information, act as a repository for security keys, and manage

the information transmitted and received within the network.

Core specification defines ZigBee’s smart, cost-effective and

energy-efficient mesh network as a self-configuring and self-

healing system of redundant, low-cost, very low-power nodes.

In mesh networks, each wireless node communicates with the

one adjacent to it. In the event of node failure, information

gets automatically rerouted to allow devices to continue

communicating.

Unlike ZigBee-enabled devices, all WirelessHART devices must

have routing capabilities (i.e., no reduced functionality).

WirelessHart networks are self-organizing, with all devices being

treated equally in terms of networking capability, installation,

formation, and expansion. This functionality may be necessary

for primary substations, but is overkill for secondary substations.

To maintain a focus on carbon reduction and effective utilization

of energy resources, it is important to balance energy generation

and demand through well-defined demand response (DR)

systems. Generation can be plagued by factors like fluctuation

(over/under) as well as duration of such fluctuation. These

factors have to be matched with demand-side parameter (e.g.,

under-generation to be managed through DER, over-generation

to be handled through storage, and time variability to be

handled through faster DER/short-term usage. To do this, it is

essential to get the data of the demand side and act on it.

ZigBee enables capture of the information either through

request/response method or last-gasp methods.

More energy sources connected to secondary distribution

networks play an important role in balancing peaks of supply

and demand as well as contributing to supply quality (controlling

6Electrical Utility Secondary Substation Automation

ConclusionAs utilities create their roadmap to build a resilient smart-grid

network, along with providing insight, choice, and control of the

energy usage at the demand side, orchestration of the distributed

generation with the grid network becomes of utmost importance

in maintaining stability of the utility network.

With secondary substation as the perfect position in the grid

network to handle distributed grid management functions

through a substation node that aggregates different

communication technologies to orchestrate activities of the

IED in substation, distributed energy resources, and smart

meters. Aricent, with its expertise in building smart-home

automation frameworks around ZigBee, building data

concentrator products in the substation, building routing

platforms that can work in harsh environments, and enabling

remote controlling of substation networks through backhaul

technologies like LTE and Ethernet, will be a trusted partner

to ODMs/OEMs and utilities that need to build such solutions.

DistributedGeneration,

EVs

DemandResponse,

Load Control

Home EnergyReports,

Web andMobile App

Building Energy ScienceB

ehav

iora

l Sci

ence

Orchestration

Control

Pricing,

Devices,

UtilityPrograms

Choice

Insight

Source: ZigBee Alliance

PRAKASHA M. RAMACHANDRA

is one of the system architects

in the Aricent’s smart energy

practice. He has more than 17

years of experience in architecting

applications & ICT back office

platforms in telecommunication,

media and smart energy domain.

prakasha.ramachandra

@aricent.com

B. VENKAT S. R. SWAMY

Venkat is one of the system

architects in the Aricent’s M2M

and Wireless practice. He has

more than 16 years of experience

in Product Conceptualization,

Architecture and Development in

next Generation Convergent and

wireless technologies and smart

energy domain.

[email protected]

REFERENCES

(1) U.S. NIST, “NIST framework and roadmap for smart grid interoperability standards, release 2. 0,”http://www.nist.gov/smartgrid/upload/NIST_Framework_Release_2-0_corr.pdf

(2) MSA Ghayum, “Comparative Study of Wireless protocols: WiFi, Bluetooth, ZigBee, WirelessHART and ISA SP100, and their Effectiveness in IndustrialAutomation”, University of Texas Master Thesis

(3) Q Shan, et al., “ZigBee Performance in 400 KV Air Insulated Power Substation”, Technological Developments in Education and Automation 2010, pp 15-18

(4) RAP Faria, “A Wireless Sensor Network for Electrical Distribution Substations”, Master Thesis, 2011

(5) M Alberto, et al., “OpenNode: A Smart Secondary Substation Node and its Integration in a Distribution Grid of the Future”, Proceedings of the FederatedConference on Computer Science and Information Systems pp. 1277–1284

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