scada for power distribution

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Dr NDR Sarma

SCADA and Distribution Automation

IEEE Hyderabad Section Joint Chapter of PES/IAS Societies

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Generating Plant

Step-up transformers Circuit breakers Transmission System

Transformers in Bulk power substations

Solar or Wind Sources (100KW to 1MW)

Distribution Transformer

Dispersed Storage and generation (DSG)

Voltage Regulator

Capacitor bank

Sub-transmission system

Distribution substation

phase Primary feeders

Three-Battery or Fuel cells,

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Sub-Station Transformer

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Incoming feeders

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Distribution Transformer Location

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Distribution Transformer (1-Ph) Location

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Switch at a DT

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Switch on a 11kV feeder

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Power System connectivity

33 kV lines

220kV Lines

EHV substations

Distribution substations

17.6/220 kV

Sub-station

220/33 kV Sub-station

33/11 kV Sub-station

Industry at 33 kV

11 kV lines (feeders)

Distribution Transformer

11/ 0.4 kV

Industry at 11 kV (Domestic, Commercial, Agricultural)Customers

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Power System in a typical city

EHV Sub-stations

Distribution s/s

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Power System in a typical city

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IT Applications to Power

• Power System Operation and Control

- Power Plant Automation

- Energy Management Systems

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Primary circuits

Generating Plant

One-phase lateral feeder

Voltage Regulator

Capacitor bank

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Primary circuits

Generating Plant

Voltage Regulator

Capacitor bank

( Decision supportTools )

219 kV

248 MW

SCADA and Application Functions

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Levels of Automation

Substation Level Automation

Feeder Level Automation

Customer Level Automation

Voltage Regulator

Capacitor bank

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Function of Distribution Automation System

Remotely monitors the distribution system,

facilitates supervisory control of devices and provides decision support tools to improve the system performance

• SCADA

(Supervisory Control And Data Acquisition)

• Application Functions

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SCADA

How ?

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SCADA Features

Hardware Components

Software Components

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SCADA – Hardware Components

(Voltage : 10 V DC)

Transducer output (011011110011)

A/D Converter output

(Voltage : 10 kV) Field Values

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Remote Terminal Unit (RTU)

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Pole Top RTU

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Remote Terminal Unit (RTU)

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Communication Options

• Wired

• Wireless

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Communication Options - Wired

• Twisted pair cables

• Co-axial cables

• Fiber Optic cables

• PLCC

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Communication Options - Wireless

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Communication Systems - MARS

• Multiple Address Radio System

• Primarily for Data Communication

• Voice Communication possible using a hand set

• Polling interrupted during voice call

• Voice restricted to emergency situations

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Communication Systems - MARS

• Frequency of operation : 800-900/400-512 MHz

• Range : 20-30 Kms

• Half duplex

• Offers data rates up to 9600 Bps

• Very popular for DA application

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Typical Multiple Access Radio Network

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Control Center Architecture

SCADA Host Systems

LAN

MMI 1

MMI 6

Video Projector

Printer Sharer PERIPHERAL

SERVER -2

Time Center

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SCADA – Software Components

• Graphical User Interface

• Logging and Reporting

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SCADA – Software Components(Contd.)

Field Equipment Connectivity

Transducer output (011011110011)

Protocols

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(011011110011)

( Voltage : 11kV) Field Values

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Voltage Regulator

Capacitor bank

Interlocks based on Attributes, values/status

Single, Group, Sequential and Closed Loop Control

Select-Check-Execute, Immediate Execute

Control

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Voltage Regulator

Capacitor bank

Interlocks based on Attributes, values/status

Single, Group, Sequential and Closed Loop Control

Select-Check-Execute, Immediate Execute

Control

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Alarms & Events

Configurable Event Types

Current Alarms Configurable

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Graphical User Interface

Real Time display

Single Line Diagrams,Graphics,Maps

Trends; Real-time and Historic

Alarms; current and Historic

Interface to control field devices

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Automated Mapping and Facilities Management (AM/FM)

• Display of geographical Maps

• Dynamic info on Maps

• Layering, Zooming, Scrolling and Panning

• Historical data on Devices

(From T&D World, Oct 2001)

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Distribution Automation :

- Application Functions

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Operational problems and Potential Applications of DAS

• Fault location, isolation and Service Restoration

• Maintaining good voltage profile

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Application Functions

• Network Reconfiguration

a) Fault localization b) Service Restoration c) Load Balancing

• Integrated Volt-Var Control

• Remote Metering

• Automatic Load Shedding

• Load Management

• Automated Mapping and Facilities Management (AM/FM)

• Trouble Call Management System (TCMS)

• Load Survey and Energy Accounting

1.Ch Narasimha Murthy, KV Raju, A Ramakoteswara Rao, N Balakrishna Reddy, NDR Sarma, P Vani, Sanjay J

Mali, Jhuma Nath, KJ Babu Narayanan, "Gachibowli Distribution Automation", Proceedings, DA/DSM Asia

'96, New Delhi, India, 17-19 Sept 1996, Vol 5, pp 31-40

2 NDR Sarma, "Rapid Growth Leads to System Automation Efforts", Transmission and Distribution World,

Sept, 1997

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Network Reconfiguration - Fault Localization

• Locates faulty section in a radial distribution feeder by operating “Load Break Switches” on a feeder

Remotely controllable Switch

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Remotely controllable Switch on a 11kV feeder

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Remotely controllable Switch on a 11kV feeder

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Network Reconfiguration - Fault Localization

• Localization is faster compared to

manual determination of

faulty section Fault

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• Restores service to non-faulty feeder sections by reconfiguration

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Network Reconfiguration - Service Restoration

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• Fault Identification

• Determination of affected load points

- After isolating the faulted component(s), system would be divided ingroup of connected components

- Loads in the groups with no source points are affected load points

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Network Reconfiguration – Service Restoration

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Network Reconfiguration –

Service Restoration

Loads at nodes 15, 44 and 56 (L7&, L4 and L3) are affected loads for this case

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• Fault Identification

• Determination of affected load points

- After isolating the faulted component (s), system would be divided ingroup of connected components

- Loads in the groups with no source points are affected load points

• Determination of non-restorable affected load points

- No alternate path for an affected load point

- Service restorable to such non-restorable affected load points only after repairing the faults

- Consider the network with all components (except faulted components)

- Check the connectivity

- If connected, service restorable to all components

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• Determination of non-restorable affected load points

- No alternate path for an affected load point

- Service restorable to such non-restorable affected load points only after repairing the faults

- Consider the network with all components (except faulted components)

- Check the connectivity

- If connected, service restorable to all components

- If not connected, network will be divided into different groups

* Type 0 : Does not have affected load points and source points

* Type 1 : Have source points

* Type 2 : Has affected load points but no source points

Loads in Group of Type 2 are non-restorable affected load points !

Network obtained after deleting groups of type 0 and 2

is considered for further analysis

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• Determination of all possible service restoration strategies

- The complete network is reduced to a smaller network by merging

all the connected (except those corresponding to switches in interlocking sequence) together

Network obtained after deleting groups of type 0 and 2

is considered for further analysis

- All ’interesting trees’ of this reduced network correspond to a possible restoration strategy

- Restoration is based on

- satisfaction of current and voltage constraints

- minimum switches

- minimum losses

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Network Reconfiguration –

Service Restoration

Loads at nodes 15, 44 and 56 (L&, L4 and L3) are affected loads for this case

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Network Reconfiguration - Loss Minimization

• Composition and hence consumption patterns of loads on

different feeders are different

• Thus, a particular configuration of the distribution system which is set for minimum loss at a certain instant of time will no longer be a minimum loss configuration at a different instant of time

• This is an important function in Distribution Automation

• Therefore, there is a need to reconfigure the system for loss

minimization when ever there is a change in the loading pattern

on the system

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Network Reconfiguration – Loss Minimization

• Considerations

* Presence of alternate paths

* Operation of LB switches

* Need to have remotely controllable switches

* Reconfiguration for minimum losses

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* Need to have remotely controllable switches

* Reconfiguration for minimum losses

NDR Sarma, KS Prakasa Rao, " A New 0-1 integer Programming Method of Feeder

Reconfiguration for Loss minimization in Distribution Systems", International Journal on

Electric Power Systems Research, Vol 33, 1995, pp 125-131

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How to reconfigure for Loss Minimization ?

• There are several methods in the literature

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0-1 Integer Programming Method

• Elements 12, 23 and 16 are initially open

• Node 6 can be switched to Ckt 2 or node 14 can be switched to ckt 1

• Node 9 can be switched to Ckt 3 or node 23 can be switched to ckt 1

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• Nodes 6,9,14 and 23 can be associated with variables X6, X9, X14, and X23

• These variables are 0-1 integer variables

• X6= 1 implies that node 6 is connected to ckt 1 and X6= 0 implies that

node 6 is NOT connected to ckt 1 but connected to ckt 2

• Thus the values of X6 and X14 will decide whether node 6 is to be

switched on to ckt 2 or node 14 is to be switched on to ckt 1

• It is important to see that each node is connected to any one circuit,

i.e., both cannot be zero simultaneously

X6 + X14 ≥ 1

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• Current in element 1 can be written as

• Power loss in element 1 can be written as

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• Power loss in element 1 can be written as

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General Form for loss in element 1

General Form for loss in element i

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Loss Function for Circuit 1 is obtained by taking summation over all elements in the circuit

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Power loss functions

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Total loss function for the entire system

This function has to be minimized subject to

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Network Reconfiguration - Load Balancing

• Composition and hence consumption patterns of loads on different feeders are different

• To distribute loads among transformers/feeders

• Remote control of switches for reconfiguration

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Load Balancing - Illustration

* To distribute loads among transformers/feeders

* Remote control of switches for reconfiguration

• Considerations

NDR Sarma, P.S Nagendra Rao, V.C Prasad and KS Prakasa Rao, "A New and Efficient Method of

Feeder Reconfiguration for Load Balancing in Distribution Systems", Proceedings of 59th American

Power Conference, Chicago, USA, April, 1997

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Why Distribution Automation ?

Benefits

- Tangible

- Intangible

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Tangible Benefits

Substation Automation

Feeder Automation

Customer interface Automation

Reduction in O&M Costs of LTC

• Deferment of additional feeders

• Effective utilization of existing feeders

Reduction in O&M Costs of:

• Regular Meter Reading

• Reprogramming of Meters

• Service Connect/Disconnect

• Processing of Customer Claims

Reduction in O&M Costs for:

• Routine Relay Testing

• Relay Setting

• Routine Data Collection

• Non-Routine Data Collection

• Data Analysis

• Testing of Data Logging Devices

• Repair of Data Logging Devices

Increased Revenue Due to:

• Loss Reduction due to Feeder Reconfiguration

• Loss Reduction due to Capacitor Banks Automation

• Faster Service Restoration

Reduction in Capital Expenditure

Increased Revenue Due to:

• Reduction of System Peak Load

• Tamper Detection to Reduce Electricity Theft

• Reduced Payments for Customer Claims

• Fault Location and Isolation

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Summary of cost/benefit Analysis Results (done in 1991)

based on tangible benefits

Substation Automation

Feeder Automation

Customer interface Automation

Details of the area : 32,000 customers with electric and gas meters with a mix of 53 % residential,

8 % commercial 37% industrial and 2% agricultural.

Peak demand : 124 MW Area served by three major substations (230/21 kV, 115/12 kV, 60/12 kV) with 13 primary feeders circuits (eleven 12kV and two 21kV) in the area David L Brown, et al., “Prospects For Distribution Automation at Pacific Gas & Electric

Company”, IEEE Transactions on Power Delivery, Vol 6, No 4, October 1991, pp 1946-1954.

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Feeder Automation

Customer interface Automation

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• Technology Development Project supported by

DoE, Govt of India

• Involves all aspects of DA

Specifications, Design and Development, Implementation

1.Ch Narasimha Murthy, KV Raju, A Ramakoteswara Rao, N Balakrishna Reddy, NDR Sarma, P Vani, Sanjay J

Mali, Jhuma Nath, KJ Babu Narayanan, "Gachibowli Distribution Automation", Proceedings, DA/DSM Asia

'96, New Delhi, India, 17-19 Sept 1996, Vol 5, pp 31-40

2 NDR Sarma, "Rapid Growth Leads to System Automation Efforts", Transmission and Distribution World,

Sept, 1997

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