a review on distribution automation systems · commercial customer load generally peak in the early...

A Review on Distribution Automation Systems Nandan M Prabhu Electrical and Electronics Engineering KLE M S Sheshagiris College of Engineering and Technology, Belagavi,Karnataka [email protected]

Abstract—Distribution automation system will improve distribution system reliability and security. The main aim is to fast and precise detectionand handling of fault and separating healthy section from fault section and thus reducing outage time. Distribution automation systems are a set of intelligent sensors, processors and communication technologies downstream from a substation that enables an electric power utility to remotely moni-tor and coordinate its distribution assets, and operate these assets in an optimal manner with or without manual intervention. Power Distribution Utili-ties are facing challenges with quality of power as the distribution networks of Indian Power Utility have grown more than double in size and com-plexity in the last 10-15 years as per ministry of power. As a result of population explosion load on the system is increasing day by day. It has resulted in the inefficiency in whole distribution system. Continuance with conventional manual systems is going to prove complex network handling resulting in consumer dissatisfaction at the quality of power and less control on technical and nontechnical losses. The system implemented in this paper de-scribes about operation and control of the equipment connected at the substation and distribution line remotely. The equipment is divided into two types, one type is installed at the substation (SCADA) and the other type is located to the distribution consumers (SMART METER). All the equipment is linked by communication line connected between the substation and the control room, all equipment is controlled and operated remotely to oper-ate and control the distribution system and to communicate each other while sitting in the control room at the sub-station.

Index Terms— Distribution Automation, reliability, Scada, Smart meter,

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1 INTRODUCTIONAs we experienced without electricity, we can’t live at

least for 5 seconds, we are very much dependent on that. Countries with high population like India have very demand for electricity. As per record of National power portal pres-ently India have 350722.48 MW of installed capacity (ther-mal=222927.34 MW, nuclear =6780 MW, hydro =45399.22 MW, res =75055.92 MW) and having actual generation of 3640.25 MU of energy. To transmit this huge power through-out India with 1,49,309 ckt kms of transmission lines at 800 KV, 400 KV, 220 KV, 132 KV, EHVAC and HVDC lines along with 237 substations dated on 5th April 2019. This huge gigan-tic network is operated by POWER GRID CORPORATION OF INDIA LIMITED. “One Nation -One Grid” the whole In-dia is divided into 5 regional grids which are interconnected by HVDC links and are maintained by 34 DISCOMS. Syn-chronisation of all regional grids will help in optimal utiliza-tion of natural resource. The Institute of Electrical and Elec-tronic Engineers (IEEE) has defined DAS as a system that en-ables an electric utility to remotely monitor, coordinate and operate distribution components, in a real-time mode from remote locations [1].

2 ELECTRICAL POWER LOSSES AND THEIR EFFECTS Transmission and distribution system is not ideal so there

will be losses that may be technical or not technical. The technical losses are due to power lost in the conductors (I2*R) due to impedance, transformer losses (iron loss and eddy current loss).

As per the report from ministry of power the total technical losses are nearly 22.5% as per 2018-19 survey, which is very huge compared to our generation. The major loss oc-curs at distribution level which needs lots of development.

Reasons for Technical Losses 1. Lengthy Distribution lines:In rural areas, as the village extends, 11 KV and 415 voltslines are extended over long distances to feed loads over largeareas. So I2R loss will increase.

2. Low Power Factor maintenance:Due to large inductive load in distribution circuits results in apoor power factor. Usually it varies from 0.65 to 0.75. A lowPower Factor contributes towards high distribution losses. Ifthe Power Factor is low, the current drawn will behigh. And the losses will be more.

3. Feeder Phase Current and unbalanced loading conditions:One of the easiest loss savings of the distribution system isbalancing current along three-phase circuits. This is not possi-ble because of single phase loading.

Feeder phase balancing also tends to balance voltage drop among phases giving three-phase customers less voltage unbalance. Equal reading at the substation doesn’t guarantee load is balanced throughout the feeder length.

4. Load Factor Effect on Losses:Customer consumes different amount of power throughoutthe day and over seasons. Residential customers generally

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draw their highest power demand in the evening hours. Same commercial customer load generally peak in the early after-noon. Load variation is Called load factor and It varies from 0 to 1. Load Factor = Average load in a specified time period / peak load during that time period.

For example, for 30 days month (720 hours) peak Load of the feeder is 10 MW. If the feeder supplied a total en-ergy of 5,000 MWH, the load factor for that month is (5,000 MWh)/ (10MW x 720) =0.69.

Lower power and energy losses are reduced by rais-ing the load factor, which, evens out feeder demand variation throughout the feeder.

5. Switching off transformers:One method of reducing fixed losses is to switch off

transformers in periods of low demand. If two transformers of a certain size are required at a substation during peak periods, only one might be required during times of low demand so that the other transformer might be switched off in order to reduce fixed losses. As transformer with same rating don’t have equal impedance it is not possible to manufacture so their will be a circulating current in between them. This will produce some offsetting increase in variable losses and might affect security and quality of supply as well as the operational condition of the transformer itself. However, these trade-offs will not be explored and optimized unless the cost of losses are taken into account.

Other Reasons for Losses Power theft which is a main problem in India, when we

are surveying a 11 KV line we found that a farmer wasdrawing power from a transformer unofficially, it is diffi-cult to find power theft on a particular feeder when thatis feeding megawatts of power.

Over loading of existing lines to save new line cost. Abnormal operating conditions at which power and dis-

tribution transformers are operated. Low voltages at consumer terminals causing higher

drawl of currents by inductive loads. Poor quality of equipment used in agricultural pumping

in rural areas, cooler air-conditioners and industrial loadsin urban areas.

The long duration of time-consuming to repair the fault do not just disrupt the power supply from customers, but also results in a loss of opportunity for utilities to earn income by delivering electricity. With DAS, it will reduce the outage time by the efficient action and provide power to the healthy sections, which leads to earnings from electricity charges.

3 DISTRIBUTION AUTOMATION Distribution Automation system is very helpful in opera-

tion and maintenance of distribution networks and lower elec-tric service restoration time, reduction in equipment damage,

better availability of system information, remote load control and scheduled power cuts. Remote Control distribution method is proposed to solve the problem. This solution tech-nique is based on the following [2]:

1. TNB system2. Distribution automation system (DAS) development3. Application of RTU and SCADA4. Fault analysis solution5. Usage of communication system

Loop distribution system is the most widely used distribu-tion configuration of any modern system [2]. Example of dis-tribution system automation is shown in figures; the technique used in this research is based on open distribution configura-tion using automation techniques by automatic switching, relays and automatic operation of isolators. The fault identifi-cation, fault location and fault clearing all will be done auto-matically with less time. Steps are shown in figures.

Fig.1. It is a 11kv feeder having 8 load taping named as shown on fig-ure.

Fig.2. Fault occurs between E and F and circuit breaker trips.

Fig.3. Charging each load in sequence and checking for fault which is done through remote switches from substation.

Fig.4. When E and F both charged from RTU circuit breaker trips and with initial load charging results and present compared and algorithm will find out the fault location


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Fig.5. Algorithms will send signals to RTU to trip at junction D and E and it will charge the line from side A. it will also find other way to pow-er up load G and H with network reconfiguration it will find out other way to charge it. All these process will take place within 15 mins.

4 LEVELS OF AUTOMATION 4.1 Sustation level

Fig.6

In India ABB Intelligent Electronic Devices (IEDs) [3] for protection and control are integral parts of the substation automation system. Combined together the SAS and IED lay the foundation for all the higher-level remote functions such as advanced power system management and the monitoring of the condition of the equipment while it is in service. Station level systems are easy to use and to adapt to customer specific requirements. To reducing costs and increasing customer sat-isfaction, which often involves upgrading aging infrastruc-ture? Older protection and control systems can be easily up-graded using ABB’s modular systems. Updating substation automation offers the opportunity to reduce operational and maintenance costs, increasing plant productivity with the aid of enhanced schemes as well as condition monitoring for cir-cuit breakers, power transformers, etc.

4.2 Feeder level

Fig.7

Feeder Automation (FA)[3], encompasses a broad range of applications that help utilities make more efficient use of their distribution feeder systems. For example, utilities can confidently operate closer to the physical limits of their systems with the increase in more robust data for planning, engineering and maintenance, extending equipment useful life. Since FA distribution feeder automation improves re-liable power delivery, in turn it also improves utility cus-tomer satisfaction.

4.3 Customer level / smart meters A smart meter is an electronic device that records con-

sumption of electric energy and communicates the infor-mation to the electricity supplier for monitoring and bill-ing. Smart meters typically record energy hourly or more frequently, and report at least daily [4]. Smart meters en-able two-way communication between the meter and the central system. Communications network may be wireless (WI-FI, GSM), or via fixed wired connections such as power line carrier (PLC) or LAN, OFC etc. If we substitute normal meters by smart meters, we can identify the power theft, and if the customer not pays the bill then remotely, we can disconnect the supply. Online payment, energy monitoring all these can be possible through smart meters. The load factor has been increasing by offering customers “time-of-use” rates which can be set in smart meters. Com-panies use pricing power to influence consumers to shift electric-intensive activities during off-peak times (such as, electric water and space heating, air conditioning, irrigat-ing, and pool filter pumping).Data from these meters can be used to predict the next day load and planning can be done accordingly.it will help the distribution automation system to read the real time power factor, voltage regula-tion at each load centre and improvement can be done.

5 SCADA A SCADA(Supervisory Control and Data Acquisi-

tion ) system for a power distribution application is a typi-cally a PC-based software package. Data is collected from the electrical distribution system, with most of the data originating at substations. In addition to data collection, SCADA systems typically allow commands to be issued from central control and monitoring points to substations. A SCADA system can significantly increase the speed of power restoration following an outage. SCADA-enabled switches and line reclosers can help operators isolate the outage and open adjacent automatic switches to reroute power quickly to unaffected sections all without the need for a line worker to visit the site to perform a lengthy vis-ual inspection, often followed by an educated guess as to the exact nature and location of the problem.

Benefits of Implementing SCADA systems in Electrical


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Distribution automation increases reliability, eliminates the need for manual data collection, alarms enable operators to quickly spot and address problems, operators can use power-ful trending capabilities to detect future problems and analy-sis through various power system load flow studies, provide better routine maintenance of equipment and spot areas for improvement .The main circuit breaker can be controlled by using internet instead of manual control which is possible by the use of RTU and the communication unit with SCADA.

Fig.8

Master Terminal Unit (MTU): Allows operators to view the state of any part of the plant equipment and drives most op-erator interaction with the by alarms. It provides displays of process status information, including alarms and other means.[5] Interfacing / communication: Allows communications equipment from different manufacturers to be connected to-gether. The RS232 or RS-485 interface is designed for the con-nection of two devices.[5] Remote Terminal Unit (RTU): Means a microprocessor to connect data input streams to data output streams. RTU may include a battery or charger circuitry. It is accomplished by using an isolated voltage or current source. In SCADA sys-tem, RTU is a device that collects data, codes the data into a format that is from the master device and implements proc-esses that are directly by the master. RTUs are equipped with input channels for sensing or metering, output channels for control.[5] Intelligent Electronic Devices (IEDs): Includes electronic meters, relays and controls on specific substation equipment. It has the capabilities to support serial communications to a SCADA sever and reports to modern RTU via communication channels. It performs all functions of protection, control, monitoring, metering and communication. SCADA systems used for monitoring and controlling the power. Traditionally, SCADA systems have made use of the Public Switched Net-work (PSN) for monitoring purposes.[5]

6 COMMUNICATIONS FOR DISTRIBUTION AUTOMATION 6.1 Fixed Radio Solutions

Pagers can receive alert signals or short messages from feeder devices or transmit simple on/off commands.

Licensed radio can be used with a variety of methods and configurations in the Very High Frequency (VHF) and Ultra High Frequency (UHF) spectrums.

Cellular carriers and the economies of scale provided by millions of subscribers have made cellular technology an at-tractive option for DA. One drawback for utilities is the possi-ble lack of certain service options and even basic coverage in some rural markets. Satellite communication is an excellent “gap filler” technology for hard-to-reach areas. New service offerings have the following characteristics:

Bandwidth of 30 to 100 kbps; Latency of 2 to 8 seconds (longer latency for some ser-

vice offerings); Availability from most locations Satellite technology is not recommended for widespread use in DA applications. This is primarily due to the high cost of in-stalling the required facilities and the high ongoing monthly expenses.[6]

6.1 Power Line Communications In powerline communications, the high-voltage pri-

mary distribution wires act as the communications me-dium. System-wide implementation of power line commu-nication facilities requires a major financial investment and commitment that usually cannot be justified solely for DA purposes. However, many utilities have already deployed power line communication systems for handling automatic metering, and DA systems can make use of this existing infrastructure.[6]

7 EFFECTS OF DISTRIBUTION AUTOMATION ON

DISTRIBUTION SYSTEM RELIABILITY When a fault occurs at the system, customers affected

by the failure of supply. Then repair crews went to the fault area. They began trip circuit breakers along the distri-bution lines to find the fault sections. After that, through the proper switching actions, the faulted section was iso-lated and the power service was restored for other healthy sections of the network. This whole process will took for nearly 1 day it may depend on length of line so until that customer has to run his own generator for supply or he should suffer from power cut.

When a failure occurred in distribution system, this scheme worked on each feeder. The logical actions were formed by detecting the variation of fault current and voltage. Then the fault records, location and isolation of faulted feeder sections can be realized automatically after the coordination of reclosers and sectionalizers, and finally achieving the non-fault zones’ power supply in distribution system through network reorganization. As a result, repair crews can be sent


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directly to the faulted area and carrying out precise fault loca-tion and repair activities. As a result, the network returns to its normal status.

The whole process shortens fault handling time.

8. CONCLUSIONElectric power utilities worldwide are increasingly adopt-

ing the computer aided monitoring, control and management of electric power distribution system to provide better ser-vices to electric consumers. There was number of general, interesting research challenges are emerged from this auto-matic distribution for fault detection and restoration. Thus, the literature survey organised in the power system, how to distribute the power without any interruption and how to rectify the fault with immediate effect and restore the system with normal load. Apart from the challenges mentioned, a number of other opportunities are available with MAS tech-nology for distribution automation. A Multi-Agent System (MAS) technology is developed for some kind of application including power system restoration. Because it can be imple-mented in the updated communication, Intelligent Agents are promoted for easy and speed fault detection, isolation and restoration.

REFERENCES [1] Smarter Fault Location, Isolation, and Service Restoration using Inte-

grated Distribution Management Systems and Distribution Automa-tion, A. Jayantilal, Senior Member, IEEE C. A. McCarthy, Member, IEEE.

[2] Electrical Distribution Automation System for Low Voltage (LV)System. Musse Mohamud Ahmed, Member, IEEE

[3] https://new.abb.com/water/automation-and-scada. [4] https://en.wikipedia.org/wiki/Smart_meter [5] PLC & SCADA based distribution and substation automa-

tion S Angayarkanni1, L Aruna2, R Aswini3, C Deepa4, JKowsalya5

[6] https://www.elp.com/articles/powergrid_international/print/volume-12/issue-4/features/communications-for-distribution-automation.html


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a review on distribution automation systems · commercial customer load generally peak in the early...

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