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Metering & Data Processing. 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.

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A device which measures, indicates and records certain measurable quantity.


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 : Catering to Commercial needs

Futuristic : Catering to forceable needs

Reliable : Repeatability

Accurate : Good amount of money at stake

classification of meters
Classification of meters
  • Interface Meter :

Installed at interconnecting points between

    • Generating company to Inter-state system
    • Generating company to Intra-state system
    • covered under ABT

2. ConsumerMeter :

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
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

Reason of metering


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
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
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 parameters of SEM

Display Parameter Indication Display format

Meter identification code A NP1234A

Date (day, date, month, year) d dd-mm-yy

Time (hour, min, sec) t hh:mm:ss

Cumulative Wh reading c xxxx.x Wh

Reactive Power Pr xxx:x VAr

Average freq. of previous block F xx:xx

Net Wh transmittal-previous block E xx:xx

Average % voltage U xx:xx

Voltage high VArh register reading H xxxx:x VArh

Voltage low VArh register reading L xxxx:x VArh

Real time indication rtC Fit

Low battery indication 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 meters1
Location of Meters

Philosophy of installation

  • For GENERATING Stations

Out going feeders



400 KV BUS





location of meters2
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




220 KV BUS

for inter state lines

Location of Meters







For Inter-state lines.





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
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 Var – Low Date
  • NP–4201–A 63895.0 97845.8 74358.6 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
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.

DCD with Optical Cord

Optical port in SEM

data collection through rs 485
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

Processing, Checking &

Validation of SEM data

data processing of sem data
Data processing of SEM data
  • Raw data is sent to RLDCs every week by Tuesday noon from 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
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


  • Net bus check of substations using Kirchhoff’s


Checks are also carried out to ascertain time drift in the meters with reference to Master meter.