Implementation of Online ABT monitoring SystemIn The Tata Power Co. Ltd. Mumbai

S. G. Patki, S. C. Dhapre, S. G. Joshi, S. A. Wangade

Introduction

TATA Power Company is the largest private sector

utility in the field of generation, transmission and

distribution of electricity. It owns and operates

thermal generating stations at Trombay in

Mumbai,Jojobera in Jharkhand, and Belgaum in

Karnataka with combined installed capacity of 1858

MW. It has also set up hydro generating plants at

Bhira,Bhivpuri and Khopoli in the Raigad district of

Maharashtra with combined installed capacity of 480

MW.TPC is responsible for distribution of electricity

in Mumbai and has set up extensive transmission

and distribution network in its Mumbai operations.

TPC network is interconnected with MSETCL at

Trombay,Kalwa & Borivli. In addition to the above

interconnecting points, TPC has provided several 22

KV outlets to MSETCL from its receiving stations at

Kalyan, Ambarnath, Salsette, Kolshet and Panvel.

MSETCL partly caters to the loads in above areas

by wheeling power through 22 KV outlets provided

by TPC. Also, some direct customers of MSETCL

are fed through TPC network in Saki and Khopoli

area. Thus, in all there are about 24 metering points

between MSETCL and TPC at different geographic

locations spread over a distance of 100 KM. Static,

HT Trivector meters with TOD features are installed

at these metering points. The meters are jointly read

every month to arrive at the net interchange

between TPC and MSETCL during the month in

each TOD slot.

Need for change in metering scheme

In May, 2004 TPC decided to supply power to

utilities outside Maharashtra, as per availability,

using transmission network of MSETCL. In view of

ABT tariff being applicable for such transactions,

TPC was required to monitor net interchange with

MSETCL on fifteen-minute basis and also provide

schedule of power Sale on fifteen-minute time slot

basis, in advance. Existing TOD tariff would

continue to apply for normal power transactions

between TPC and MSETCL.

Existing TOD meters were not suitable for this

application and it was necessary to install new

meters. Also, it was decided to install a scheme for

remote communication with the meters and monitor

the net exchange between TPC and MSETCL on a

real time basis to avoid excessive unscheduled

interchange during periods of wheeling.

Procurement of meters and software

The salient points included in the specifications for

meters and on line monitoring software were

1. The meters should be compatible for TOD as well

as ABT.

2.Meter should have two independent auxiliary

supplies, one DC and one AC for better reliability.

3.Meter should be suitable for remote

communication on a real time basis.

4.On line monitoring software should be capable of

collecting and collating data from all the connected

meters on a real time basis and compute net

exchange between MSETCL and TPC once in a

minute.

5. On line monitoring System should provide user-

friendly screens for continuous monitoring of net

exchange.

6. Monitoring screen should change the color when

unscheduled interchange is resulting into net loss to

TPC.

7.Communication failure should be annunciated

immediately.

8. It should be possible to prepare daily schedule

and e-mail or FAX the same to RLDC.

9. System should generate user defined MIS reports

such as monthly UI report highlighting periods of

high-unscheduled interchange.

TPC procured new meters compatible with ABT as

well as TOD along with on line monitoring software

in May-2004. New meters were installed in series

with the existing TVMs.The server and software

installation at Trombay along with necessary set up

for remote communication was completed in

November-2004.

Installation of Communication network.

As the metering points were geographically spread,

getting data at a central location on real time basis

was a challenging task and required very reliable

communication network. Out of the total 24 metering

points, only 13 points were measuring significant

interchange of power with MSETCL. Remaining 11

metering points were located in consumer premises

and the combined consumption recorded by them

was insignificant. It was therefore decided to include

only 13 major metering points in the on line-

monitoring scheme.

Out of these 13 major metering points,

connectivity to TPC’s own Fiber optic network was

available for only 8 metering points located in TPC

receiving stations at Salsette, Kolshet, Saki, Kalyan

and Trombay. Three metering points located at

Kalwa and Borivli stations of MSETCL and two

points located at Ambernath substation of TPC did

not have FOP connectivity and required some other

media to establish communication with the Server.

Depending on the availability of communication

media & geographical location, following

communication configurations were chosen.

1.Leased Telephone Line was used for Meters at

Kalwa as FOP network was not available here.

2.Combination of Leased telephone line and TPC

Fiber network was chosen for the meter at Borivali

since nearest available FOP network point was

about 2 Km away from the meter. The data is

transferred up to FOP point using leased line and

further transfer of data to the server is through FOP.

3.Two meters at Trombay were connected directly

to the Data Acquisition Server (DAS) using copper

cables, as they were located very close to the server

room.

4.TPC Fiber network was chosen for six meters

located at Salsette, Kalyan, Saki & Kolshet.

5.TPC Microwave system was used for two meters

at Ambernath as FOP network and leased line was

not available. The meter data is transferred directly

to server through MW system.

As some of the metering installations are in 220kV /

100 kV switchyards, it was decided to use

armoured, shielded, four pair, CAT-5 cables for data

communication to avoid electro-magnetic

interference. To optimize the usage of fiber

channels, it was decided to form a Data-Bus at

Salsette for all the meters connected to FOP

network.

ABT Meters

1. The meter is designed to keep last minute data in

memory, which is then fetched by the server in a

cyclic manner from all the connected meters.

2.The meter works on a serial RS-232

communication principle with a baud rate of 1200

bps.The protocol used for communication is

designed to be proprietary for data security.

3. To establish online monitoring with 13 meters at

maximum interval of 58 seconds, it was necessary

to virtually extend their optical ports to the server.

This was achieved by installing some special

devices called Net Box (NB-Repeaters) & Data

Communication Unit (DCU-Amplifiers) at both meter

and server end. (Refer to fig.02)

4. As the data from connected meters was to be

integrated every minute for arriving at net

interchange, it was absolutely essential to have time

synchronization between server and all the

connected meters. A GPS clock was connected to

the server, which in turn synchronizes individual

meter clocks with Server periodically and ensures

time synchronization.

Problems during commissioning

1. During communication trials, it was observed that

indigenous RJ-45 & RJ-11 connectors used for

terminations on NBs, DCUs & Modems were not

getting latched properly resulting into loose contact

and frequent communication failure. Imported

connectors were then used to overcome this

problem.

2.The data bus formed at Salsette for six meters

was intermittently failing to communicate.

Investigations revealed that the leased line modem

used at Borivli and Kalwa were introducing an extra

character in the data string, which was causing CRC

failure & pulling the entire data bus down. To

overcome this problem, a different make MODEM

and DCU was connected at Borivli.

3. The leased line at Kalwa was found to be

unreliable & communication used to fail frequently. It

was then decided to use TPC Microwave network

instead of leased line.

4.Microwave communication was found to be more

reliable than the leased line. However, due to

external Radio Frequency Interference (RFI),

occasional failure was observed on microwave

channels also.

On line monitoring Software:

1.Online monitoring scheme works on client-server

architecture. The data acquisition server collects &

stores data of each meter & the client machine

provides online monitoring screens & user-defined

reports.

2.Oracle is used for data base management & SQL

is used for Server-Client communication on LAN.

The server IP is defined in the database.

3. Network configuration is done in Server machine

through client machine.

4.The client machine configuration contains Meter

master data (Meter Sr. no, Meter ID’s Multiplication

Factor, etc.) Installation master data, details of

Generating station, Virtual meter definitions and

their master data, frequency steps, scheduling etc.

4.The software was initially designed to provide two

on line monitoring screens.

a) Online UI monitoring screen

b) Online graphical screen.

Toggling between the two screens was found to be

cumbersome by our Load dispatch staff.. The

software was modified to merge the two screens

into a single screen, named “Online UI, & graphical

screen.” (Ref fig 1)

This screen provided load dispatcher the following

data on a minute-to-minute basis

a) Schedule and average frequency of current

interval b) Block time c) Last minute interchange d)

Interchange since start of block e) Prorated

interchange at the end of the block f) Desired

interchange to avoid unscheduled interchange .g) UI

in MW h)Loss or Gain in Rupees i) Alarms.

5.Software was designed for Generating stations

and hence only export scheduling was possible.

However, to meet increasing demand of Mumbai

city, TPC was required to procure peak power from

other utilities and thus import scheduling became

necessary. This feature was added later.

Conclusion.

1. Experience of TPC so far is that FOP network is

the most reliable communication media for such

critical schemes. It was therefore decided to extend

FOP network to all the metering points.

2.If communication with one meter fails, it is not

possible to generate UI report for this period. It

should be possible to collect meter data manually

and input the same in Integration software so that UI

report is available for entire month irrespective of

communication failures.

3.It should be possible to convert Integration

software data and reports in EXCEL format and

export the same. This will help the user to generate

other MIS reports.

4. The load survey data, frozen readings, tamper

events etc registered by connected meters are not

captured by the Integration software. This feature

should be available with Integration software.

5. Separate communication channel is required to

collect billing data from connected meters using

meter reading software. It is desirable to obtain this

data through the same communication channels

used by Integration software to avoid duplication of

network.

Figure-1

On line monitoring screen on client machine.

Figure- 2

TPC Microwave Network

Ambernath

Kalyan

LAN

Saki

Kolsheth

Salsette TPC Borivali

MSETCL Borivali Leased Line Leased Line 100kV Trombay

100kV Kalwa

220kV Trombay 220kV Kalwa

ABT Online monitoring Network

ABT Meter-1

ABT Meter-2

ABT Meter-3

ABT Meter-4

ABT Meter-5

ABT Meter-6

ABT Meter-10

ABT Meter-11

ABT Meter-12

ABT Meter-13

NB

NB

NB

NB

NB

NB

NB

NB

NB

NB

ModemDCU

DCU

DCU

DCU

FOX - 20

FOX - 20

FOX - 20

FOX - 20

ABT Meter-9

LLM

LLM

FOX - 20

FOX - 20

FOX - 20

FOX - 20

NBR

NBR

NBR

NBR

DCU FOX–U SAL

FOX– U LDD STAR

S DAS

DCU

STAR

S

Client

GPS

MW

Modem

MW

DCU

NBR

DCU

NBR

LLM

LLM

ABT Meter-7 NB DCU

FOX - 20 NBR

ABT Meter-8 NB