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 foreseen 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 :
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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
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Feeder wise
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Station wise
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State wise
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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
Metering Standards
 Compliance with the relevant standards of Bureau of Indian Standards
(BIS)
 If BIS Standards are not available for a particular equipment or material,
the relevant British Standards (BS), International Electro-technical
Commission (IEC) Standards
 Whenever an international Standard or IEC Standard is followed,
necessary corrections or modifications shall be made for nominal system
frequency, nominal system voltage, ambient temperature, humidity and
other conditions prevailing in India before actual adoption of the said
Standard
 At the time of commissioning, each interface meter shall be tested by the
owner at site for accuracy using standard reference meter of better
accuracy class than the meter under test.
Metering Standards
 All interface meters shall be tested at least once in five years
 The meters may be tested using NABL accredited mobile laboratory or
at any accredited laboratory and recalibrated if required at
manufacturer’s works.
 Active energy Wh  as per class 0.2 S of IEC-687/IEC-62053-22
 Var/Reactive energy  class 2 of IEC-62053-23 or better
 IS standards to be followed w.r.t voltage range, frequency, power factor
range, impulse voltage withstand test, power ferquency withstand
voltage, power consumption etc
Features of Special Energy Meter(SEM)
 Works on 3 phase 4 wire principle
 Static meter
 Working voltage of 63.5V
 Accuracy class of 0.2S
 Show time stamping
 Measures:
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Average frequency
Net active energy transmitted in 15 mins block wise
Daily reactive energy transmitted in high / low voltage
conditions
Features of Special Energy Meter(SEM)
 -ve sign if net Wh export
 Meter continuously integrates and can display on demand the net
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cumulative active energy sent out from the substation bus bars upto that
time.
The cumulative Wh reading at each midnight is stored in the meter’s
memory.
The register moves backwards when active power flows back to
substation bus bars
Meter counts the number of cycles in VT output during each successive
15-minutes block, and divides the same by 900 to arrive at the average
frequency
This is stored in the meter’s memory as a 2-digit code which is arrived at
by subtracting 49 from the average frequency, multiplying by 50 and
neglecting all decimals.
E.g. 49.89 Hz is recorded as 44. In case the average frequency is less
than 49.0 Hz, it is recorded as 00. In case it is 51.0 Hz or higher, it is
recorded as 99.
Features of SEM
 The meter continuously computes the average of the RMS values of the
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three line-to-neutral VT secondary voltages as a percentage of 63.51 V,
and displays the same on demand.
The meter also computes the reactive power (VAR) on 3-phase, 4-wire
principle, with Class 2 accuracy, and integrates the reactive energy
(VARh) algebraically into two separate registers => 103% & <= 97%
When reactive power is being sent out from substation bus bars, VAR
display have a plus sign or no sign and VARh registers move forward
When reactive power flows into the substation busbars, VAR display
have negative sign and VARh registers move backwards.
All 15 minute Wh figures is however be rounded off to the nearest last
decimal but no rounding off for frequency/voltage displays
Features of SEM
 The three line-to-neutral voltage is continuously monitored and in
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case any of these falls below about 70%, a normally flashing lamp
provided on meter’s front become steady.
It go off it all three voltages fall below 70%. The time blocks in
which such a voltage failure occurs/persists is recorded in the meter’s
memory.
The lamp automatically resumes flashing when all VT secondary
voltages are healthy again.
The meters normally operates with the power drawn from the VT
secondary circuits.
The meters are supplied duly fitted with the batteries, which shall not
require to be changed for at least 10 years, as long as total VT supply
interruption does not exceed two years.
The battery mounting is designed to facilitate easy battery
replacement without affecting PCB of the meter
The meters don’t require any separate auxiliary supply for their
operation. All displays may disappear on loss of VT supply.
Features of SEM
 Each meter has a built-in calendar and clock, having an accuracy of 30
seconds per month or better. The calendar and clock are correctly set at
the manufacturer’s works
 Only limited clock adjustment is possible at site, using the DCD.
 When an advance or retard command is given, six subsequent time
blocks is contracted or elongated by ten seconds each. The meter does
not accept another clock correction command for seven days. All clock
corrections are registered in the meter’s memory and suitably shown on
print out of collected data.
 Each meter has a unique identification code, which is marked
permanently on its front, as well as in its memory.
Features of SEM
 Identification code:: NP-four digit running serial number-A OR B 
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e.g. NP-6060-A
“A” for Model-A, and “B”, for the use with CT secondaries of 1 A and 5
A respectively.
A touch key or push button is provided on the meter front for switching
on the display and for changing from one indication to the next
Each meter has an optical port on its front for tapping all data stored in
its memory
Each meter is provided with a RS-485 port on one of it’s sides, from
where all the data stored in the meter’s memory can also be tapped.
Data stored in the meter’s memories is tapped once a week from any of
the two ports mentioned above and transmitted to RLDCs by e_mail
generally
Meters are totally sealed and tamper proof, with no possibility of any
adjustment at site, except for clock correction.
Features of SEM
 Meters continue to function for the remaining healthy phase(s), in
case one or two phases of VT supply fails with recording of a
lower reading corresponding to number of phases under outage
 In case of a complete VT supply failure, the computation of
average frequency shall be done only for the period during which
the VT supply was available in the 15-minute block
SEM Technical Specifications
 Standard
: IEC-687 / IEC-62053-22
 Accuracy Class
: 0.2S
 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.
Data stored in a SEM
Each meter has a non-volatile memory in which the following is
automatically stored:
i) Average frequency for each successive 15-minute block, as a 2-digit
code
ii) Net Wh transmittal during each successive 15-minute block, upto
second decimal, with plus/minus sign
iii) Cumulative Wh transmittal at each midnight, in six digits including
one decimal
iv) Cumulative VARh transmittal for voltage high condition, at each
midnight in six digits including one decimal
v) Cumulative VARh transmittal for voltage low condition, at each
midnight, in six digits including one decimal
vi) Date and time blocks of failure of VT supply on any phase, as a
star (*) mark
The meters store all the above listed data in their memories for a
period of ten (10) days
Data older than ten (10) days get erased automatically.
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.
Testing of SEMs-general norms
 On-site functional checking and rough testing of accuracy are
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being carried out for all meters once a year by the CTU
Full testing for accuracy for every meter is being carried out by
the CTU at an accredited laboratory once every five (5) yrs. with
meter of higher accuracy class
The constituents/agencies may depute one authorized
representative to witness the tests.
Normally no re-calibration is required.
In case a meter is found to violate any of its accuracy , functional
requirements during the above periodic accuracy checks, the same
is replaced by CTU by a duly tested/certified meter, and the
defective meter is sent back to the manufacturer for appropriate
recalibration and re-certification
Fictituous meters
 Fictituous meters(FICTMTRS) are a combination of METERS treated as
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a single entity. e.g.
(i) Total drawal of an SEB
(ii) Total relief from a generating station
(iii) Total transaction of energy between two regions.
FICTMTRS used to simplify the calculation process
Every fictitious meter is basically summation of certain no of Real
meters.
E.g. (FK-92) = +(FK-08) +(FK-09) +(FK-10) +(FK-11)+(FK-12) +(FK13) +(FK-17) +(FK-15) +(FK-16)
i.e FK92 represents TOT FSTPP Gen = sum of all real main meters
installed in all the outgoing feeders from FSTPP
Such FICTMTRS are incorporated vide a .cfg file where the above
formulae are listed in format readable by the software code
Metering arrangement-Typical view-TSTPP-I
Pairs.Dat File
 This file gives the LOC-ID of main meter and standby meter and the
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permitted pair tolerance for each pair.
Main meters are those which are connected on 400 kV side of ICT or
generator side of power station or sending end of inter state lines
The standby/check meters are on the other end
Standby meters are connected in reverse polarity so that sum of both
MWh is zero in ideal condition. Suppose
E.g. the power flow is from main meter to standby meter, the main meter
gives a +ve value and standby meter gives a –ve value and vice versa.
Tolerance value in MWh for a 15 min block in +ve direction & -ve
direction is given in this PAIRS.DAT, depending upon transformer /Line
losses & CT/PT errors
The given tolerance value towards +ve side is called X value.
The tolerance value towards –ve side is called Y value.
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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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.
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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.