1.
WHAT IS METER ?
A device which measures, indicates and records certain measurable
quantity.
2.
WHAT IS ENERGY METER ?
A device which measures, indicates and records electrical power
flow (energy) in a specified time between two points.
3.
Pre Requisites of a Meter
Purpose
Futuristic
Reliable
Accurate
:
:
:
:
Catering to Commercial needs
Catering to forceable needs
Repeatability
Good amount of money at stake
Classification of meters
1. Interface Meter :
Installed at interconnecting points between
 Generating company to Inter-state system
 Generating company to Intra-state system
 covered under ABT
2. Consumer Meter :
Electrical utility to consumer not covered under
INTERFACE meters
3. Energy Accounting and Audit Meters :


Used between Gen Stns to different segments of electrical
system determines
Consumption of power
Loss
Our focus is on SEMs which are interface meters
What is Special Energy Meter(SEM)?
SEM is an Application specific Microprocessor
base solid state energy meter. This together with a data
collecting device (DCD) and a local Computer forms a
powerful system of metering and data logging.
This arrangement of metering and data logging
gives a unique method for measurement of all relevant
electrical quantities.
Why metering is required?
ABT, three part tariff :
 Capacity charge (a)
 Energy charge / Scheduled Energy charges (b)
 Adjustment for deviation/ Unscheduled Interchanges (c)
Total payment for the day = a + b (+/-) c
What is Metering?
Meter data handling
Converting meter data into useful information

Feeder wise

Station wise

State wise

Region wise
Its a challenging task for the utilities due to huge volume of data
logged by these meters
Area covered by meters
ISGS
Sub Stations
ICTS
Feeders
Any other drawl or injection points
spread over the state, region and the
country as a whole
Metering Management
Initial/one time activities
 Choose the category of meter
 Selection of meter
 Installation of meters in strategic locations
 Deciding status of meters as Main, Check and Stand-by meters
Periodic/maintenance activities
 Maintaining healthiness
 Periodic checking
 Time correction
 Periodic testing
 Replacement of meter (as and when required)
Regular/routine activities
 Collection of data
 Transmittal of data to a central location for processing
 Processing meter data into useful information
 Archiving final processed data
Features of Special Energy Meter(SEM)
 Works on 3 phase 4 wire principle
 Static meter
 Working voltage of 63.5V
 Accuracy class of 0.2
 Show time stamping
 Measures:



Average frequency
Net active energy transmitted in 15 mins block wise
Daily reactive energy transmitted in high / low voltage
conditions
SEM Technical Specifications
 Standard
: IEC-687 / IEC-62053-22
 Accuracy Class
: 0.2
 Interface (Compatible with DCD) : With RS 485
 Reference Voltage(Vref)
: 110V.(P-P)
 Rated Current
: 5A or 1A.
 Operating Voltage
: +20% to -30% of Vref.
 Operating Current
: 0.2% to 200% of Rated current
Types of SEM
SEMs are of following two types :
A-TYPE : Connected to VT having rated secondary line-line
voltage of 110V and CT having rated
secondary current of 1A.
B-TYPE: Connected to VT having rated secondary line-line
voltage of 110V and CT having rated secondary
current of 5A.
It operates with power drawn from the secondary
circuits and no auxiliary power supply required.
Operating section of (SEM)
a) Analog Section: High precision Current transformer and
voltage transformer step down input currents and voltages
which are fed to an Analog to Digital converter.
b) Digital Section: A powerful microprocessor controls the
Analog and Digital sections. Analog to Digital converters are
fed from high precision instrument transformers. The Digital
samples from Analog to Digital converter are used to process
the metering data. The sampling rate is 3000 samples per
second which gives the meter an exceptional accuracy and
results.
c) Power supply Section: A switch mode power supply
(SMPs) unit supplies power to the meter’s internal circuit.
Display parameters of SEM
Display Parameter
Indication
Meter identification code
A
Date (day, date, month, year)
d
Time (hour, min, sec)
t
Cumulative Wh reading
c
Reactive Power
Pr
Average freq. of previous block
F
Net Wh transmittal-previous block
E
Average % voltage
U
Voltage high VArh register reading H
Voltage low VArh register reading
L
Real time indication
Low battery indication
Display format
NP1234A
dd-mm-yy
hh:mm:ss
xxxx.x Wh
xxx:x VAr
xx:xx
xx:xx
xx:xx
xxxx:x VArh
xxxx:x VArh
rtC Fit
Low Bat
Classification of SEMs
 Main Meter : means a meter, which would primarily be
used for accounting and billing of electricity.
 Check Meter : means a meter, which shall be connected to
the same core of CT and PT to which main meter is
connected and shall be used for accounting and billing of
electricity in case of failure of main meter.
 Standby Meter : means a meter connected to CT and VT,
other than those used for main meter and check meter and
shall be used for accounting and billing of electricity in case
of failure of both main meter and check meter;
Location of Meters
Location
Main meter
Check meter
Standby meter
Generating System
On all outgoing
feeders
On all outgoing
feeders
HV side of GT
HV side of Station
Aux. Transformers
Transmission
System
At one end of the
line between the
S/Ss of the same
licensee and at the
both ends of the
line between S/Ss
of two different
licensees. Meters at
both ends shall be
considered as main
meter.
There shall be no
separate standby
meter. Meter
installed at other
ends of the lines in
case two different
licensees shall
work as standby
meter.
ICT
HV side of ICT
LV side of ICT
Location of Meters
Philosophy of installation
• For GENERATING Stations
Out going feeders
CHECK METER
MAIN METER
400 KV BUS
STAND BY
METER
GENERATOR
STN
TRANSFORMER
Location of Meters
 For ICTS
Main meter is provided on EHV side of ICT and stand by
meter on LV side of ICT.
400 KV BUS
MAIN METER
ICT
STAND BY METER
220 KV BUS
Location of Meters
•
For Inter-state lines.
SEB-A
SEB-B
A
B
MAIN
METER
STAND BY METER
MAIN METER
STAND BY METER
Location of Meters
 Metering arrangement for POWERGRID
lines.
On POWERGRID lines, unless an end is regional energy
accounting point, an Energy Meter is provided only at one
end of each line. The readings recorded by these meters are
being used for information and analysis only, and not for
the energy accounting purposes.
Measurement principle of SEM
Net Wh Transmittal during each successive 15-min time block up to
second decimal, with plus/minus sign.
Cumulative Wh transmittal at each midnight in 6-digits including one
decimal
It works in real time with the help of an in-built clock.
Average frequency of 15 mins block as 2 digit code ( 00 to 99 )
Actual freq = 49 + ( 2digit code / 50 )
e.g. If, SEM shows 2 digit code of 55 as frequency code,
The actual frequency = 49 + (55 / 50)
= 50.1 Hz
Cumulative VARh transmittal for high voltage condition at each midnight
( V > 103% of Rated Voltage)
Cumulative VARh transmittal for low voltage condition at each midnight
(V < 97% of rated Voltage)
Data for Time blocks of failure of VT supply on any phase has a star mark
as prefix.
Special Energy Meter (SEM)
Each meter has an optical port to access data stored in its memory.
Hand held data collection device (DCD) are used as an interface
between the meters and the PC
Meters can store 10 days data. Data downloaded in coded form
(*.MRI, *.DAT) and is converted to Text file (*.NPC) through
software SMARTGRID/ VINCOM.
Each day data, is of the following form
Meter no
Watt hr Var – High
NP–4201–A 63895.0
97845.8
Var – Low
74358.6
Date
12 – 10 - 07
Meter no is of nine character starting with NP and A or B at the
end indicates the type of CT used.
Any voltage problem is indicated by a star “*” mark preceding the
energy data.
Data Collecting Device (DCD)
DCD is a hand held terminal, capable of
communicating with SEM as also with PC. Both
communication requires suitable software at both
DCD and SEM
 Features:
 Battery operated
 It has a key board / pad
 LCD display screen
 Communication slot
SEM data collection through DCD
Conventional data collection method for past 12 years.
Optical port in SEM
DCD with Optical Cord
Data collection through RS-485
What is RS-485?
 Two wire connectivity (having ground) between meter
and PC.
 Enables automatic data downloading from all the meters
in a location to a local PC.
No need of DCD
Connection Diagram : RS 485
Special Energy Meter
RS 232
D+
D-
Substation PC
RS 232 to RS 485
Converter
Data processing of SEM data
 Raw data is sent to RLDCs every week by Tuesday noon from

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




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sites through e-mail.
Raw data is converted to text files.
All text files are appended to a single text file.
Korba end SEM is used as master frequency meter.
Actual energy is calculated by a software as per configured
fictitious meter.
Daily Output MWh pertaining to drawal/injection/IR exchange
is created.
Daily Regional output file for the week period is created.
Regional loss is calculated after processing.
RLDCs send processed SEM data to respective RPCs.
Data checking & Validation
Identification of any metering error can be done through three
broad categories of checks.



End1- End 2 (using pair check)
Net bus check of Generators using Kirchhoff’s
law.
Net bus check of substations using Kirchhoff’s
law.
Checks are also carried out to ascertain time drift in the meters
with reference to Master meter.