TECHNICAL SPECIFICATIONS

TECHNICAL SPECIFICATIONS FOR MICROPROCESSOR BASED 0.2s ACCURACY CLASS STATIC ELECTRONIC TRIVECTOR SPECIAL ENERGY METERS, WITH ABT COMPATIBILITY.

1.         SCOPE          

This specification covers the design, engineering, manufacture, assembly, and testing of CT and VT operated microprocessor based energy meters. The meters shall be 3-Phase 4 wire 0.2s accuracy class Static Electronic Tri-vector energy meters with ABT compatibility.

            It is not the intent to specify completely herein all the details of the hardware, software, communication and design of the system. The material shall, however, conform in all respects to the best standards of engineering, design and workmanship and shall be capable of performing for continuous commercial operation.

2.         APPLICABLE  STANDARDS

The meters shall conform (for testing, performance and accuracy) in all respects the relevant Indian/International standards with latest amendments thereof.

Further, CMRI (Common Meter Reading Instrument) shall conform to CBIP Technical Report No. 111 with latest amendments.

3.         SERVICE CONDITIONS

The meters to be supplied against this specification shall be required to operate satisfactorily, accurately and continuously under the following tropical conditions of hot, humid, dusty, rust and fungus prone environment.

4.         PRINCIPAL PARAMETERS

The energy meters shall be outdoor type connected with the secondary side of out door current and voltage transformers.

5.         TECHNICAL REQUIREMENT:-

5.1       Standard reference voltage (as per relevant IS).

5.2       Voltage range (as per relevant IS)..

5.3       Standard frequency range (as per relevant IS)..

5.4       Standard basic current (as per relevant IS)..

5.5       Accuracy class:-

Interface meter –  .2S

5.6       Starting current & maximum current(as per relevant IS).

5.7       Power factor range(as per relevant IS)..

5.8       Power frequency withstand voltage(as per relevant IS).

5.9       Impulse withstand peak surge 1.2/50 Micro Sec. (as per relevant IS).

5.10     Power consumption (as per relevant IS).

6.         GENERAL AND CONSTRUCTIONAL REQUIREMENTS:

a.         Meters shall be designed and constructed in such a way so as to avoid causing any danger during use and under normal conditions. However the following should be ensured:-

i.          Personnel safety against electric shock

ii.          Personnel safety against effects of excessive temperature

iii.         Protection against spread of fire

iv.         Protection against penetration of solid objects, dust and water in normal working condition.

b.         All the materials and electronic power components used in the manufacture of the meters shall be of highest quality and reputed make to ensure higher reliability, longer life and sustained accuracy.

c.         The meters shall be designed with application of specific integrated circuits. The electronic components shall be mounted on the printed circuit board using latest Surface Mount Technology (SMT).

d.         All insulating materials used in the construction of meters shall be non-hygroscopic, non-aging and of tested quality. All parts that are likely to develop corrosion shall be effectively protected against corrosion by providing suitable protective coating.

e.         The meters shall have an operation indication device such as a blinking LED. The operation indicator shall be visible from the front window.

f.          The front surface of meters once mounted in panel shall conform to the degree of protection IP 51 in the normal working condition of IS: 12063/IEC: 529 for protection against ingress of dust, and moisture.

7.         SEALING OF THE METER:

Proper sealing arrangement shall be provided on the meter to make it tamper proof and to avoid mishandling by un-authorized person. At least two (2) seals on the body, two (2) seals on the terminals block and one seal each on maximum demand resetting device and communication ports shall be provided. Meter base and cover shall be tightened from rear side with at least two nos. unidirectional screws so that meter body could not be opened at site in any case and two nos. firms stickers seals bearing serial no., which should not be repeated shall be provided between meter base and cover.

            A tracking ad recording software for all new seals shall be provided by the manufacturer of the meter so as to track total movement of seals starting from manufacturing, procurement, storage, record keeping, installation, series of inspections, removal and disposal.

            The meter shall be totally sealed and tamper-proof with no possibility of any adjustment at site, except for a restricted clock correction.  The harmonics shall be filtered out while measuring Wh, Var and Varh and only fundamental frequency quantities shall be measured / computed.  Polycarbonate or acrylic seals or plastic seals or holographic seals should be used.  Lead seals should not be used.

8.         MARKING OF METER:

The marking on every meter shall be in accordance with IS 14697/IEC 687. The basic marking on the meter name plate shall be as follows:-

i)          Manufacturer’s name and trade mark.

ii)         Type Designation

iii)         Number of phases and wires

iv)        Serial number

v)         Month & year of manufacture

vi)        Reference voltage/ PT ratio Frequency.

vii)        Rated secondary current of CT (-/1 or -/5 A).

viii)       Principal unit(s) of measurement.

ix)        Meter constant (impulse/kWh).

x)         Class index of meter.

xi)        Text “Property of ……………………..”

xii)        P.O. No. & Date.

xiii)       Guarantee period

9.         CONNECTION DIAGRAM & TERMINAL MARKING:

The connection diagram of the metering module shall be clearly shown  inside portion of the terminal cover and shall be of permanent nature. The meter terminals shall also be marked and this marking should appear in the above diagram. In case any special precautions need to be taken at the time of testing the meter the same may be indicated alongwith the circuit diagram.

10.       M.D. RESETTING:-

10.1.    The meter shall continuously monitor & calculate the average demand in KVA during the Integration period and maximum out of these shall be stored alongwith date & Time in the meter’s memory. The integration period shall be programmable for 15/30/60 minutes on real time basis on block / sliding window principle, that should also be programmable.

10.2     The meter shall also display M.D. reset count. The M.D. resetting should be possible in any of the following ways:-

a.         Automatic reset on a predetermined date & time of the month.

b.         Resetting through a hand held terminal or computer capable of communicating with the meter with password protection.

11.       T.O.D. COMPATIBILITY:-

All the meters shall be compatible with T.O.D. tariff. For T.O.D. tariff meter shall have the provision to define maximum 8 (Eight) T.O.D. registers for different energies.

12.       DISPLAY

12.1     The display shall be L.C.D. type display with Back lit.  Minimum height of the characters shall be 6 mm.

12.2     The three line-to-neutral voltages shall be continuously monitored and in case any of these falls below about 70% the condition shall be suitably indicated and recorded.  The meter shall operate with the power drawn from the VT secondary circuits, without the need for any auxiliary power supply.  Each meter shall have a built in calendar and block, having an accuracy of  6 minutes per year or better.

13.       DATA COMMUNICATION CAPABILITY:

13.1     Each meter shall have an optical port on its front for tapping all data stored in its memory. Portable or hand held data collection devices shall be used for this purpose to serve as the interface between the meters specified above and the local personal computers (PC). The overall intention is to tap the data stored in the meter’s memories once in a month, and transmit the same to a central computer. It shall also be possible to obtain a print out (hard copy) of all data collected from the meters, using the local PC.

13.2     Additionally, the metering system shall have a serial RS232/RS485/USB port for transferring the meter data to a remote location via a suitable communication infrastructure.

13.3     The metering system shall be compatible with suitable Base Computer software .

13.4     All meters of the same model shall be totally identical in all respects except for their unique identification codes. They shall also be totally sealed and tamper proof, with no possibility of any adjustment at site, except for clock correction.

13.5     The meters shall safely withstand the usual fluctuations arising during faults etc.as per IS:14697.  The immunity to external magnetic field shall be strictly as per latest CBIP recommendations.

13.6     The meters shall also withstand without any damage or mal operation, reasonable mechanical shocks, earthquake forces, ambient temperature variations, relative humidity etc. They shall have an IP-51 category dust-tight construction, and shall be capable of satisfactory operation in an outdoor, non-air-conditioned installation.

13.7     The meters shall continue to function, as specified above, in case of failure of one or two phases of VT supply. In case of a complete 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. Any time block contraction or elongation for clock correction shall also be duly accounted for.

14.       REAL TIME CLOCK:-

a)         Each of the meters shall have an independently built-in calendar and clock having an accuracy of ± 5 ppm at 25° C or better. The calendar and clocks shall be correctly set to Indian Standard Time.

b)         The time keeping accuracy of the metering shall be maintained according to the time of load despatch clock, synchronised with RLDC/Generator.

15.       TAMPER DETECTION FEATURES

15.1     There shall be an appropriate display system by which any attempt of tampering the meter is promptly displayed with date and time tagging. The meter shall have features to detect the occurrence and restoration of, at least, the following common /tamper :-

a)         The meter shall not get damaged or rendered non-functional even if any phase and neutral are interchanged.

b)         The meter shall register energy even when the return path of the load current is not terminated back at the meter and in such a case the circuit shall be completed through the earth.  In case of metallic bodies, the earth terminal shall be brought out and provided on the outside of the case.

c)         The meter shall work correctly irrespective of the phase sequence of supply (only for poly phase).

d)         In the case of 3 Phase 4 wire system, the meter shall keep working even in the presence of any two wires i.e. even in the absence of neutral land any one phase or any two phases.

e)         The registration must occur whether input phase or neutral wires are connected properly or they are interchanged at the input terminals.

f)          The meter shall be factory calibrated and shall be sealed suitably before dispatch.

g)         The meter shall be capable of recording occurrences of a missing potential (only for VT operated meters) and its restoration with date and time of first such occurrence and last restoration along with total number and duration of such occurrences during the above period for all phases.

h)         Additional anti-tampering features including logging of tampers such as current circuit reversal, current circuit short or open and presence of abnormal magnetic field may be provided as per the regulations.

15.2     Last 100 such events in total with date and time shall be stored in the meter memory on first in first out basis.

15.3     There shall be four separate compartments for logging of different type of tampers as follows:

Compartment No.1:

20 events of missing potential

Compartment No.2:

20 events of CT polarity reversal

Compartment No3:

40 events shall be allocated for current/voltage unbalance

Compartment No.4:

20 events of power On/Off

15.4     The logging of various tampers in each compartment should be as under:

a)         Once one or more compartments have become full, the last tamper event pertaining to the same compartment will be entered and the earliest (first one) tamper event should disappear. Thus, in this manner each succeeding tamper event will replace the earliest recorded event, compartment wise. Events of one compartment/category should overwrite the events of their own compartment/ category only.

b)         Tamper count should increase as per occurrence (not restoration) of tamper events. The total No.of tamper counts should also be provided on the meter display as well as at the BCS end.

Tamper data shall be available on meter display as:

Date of first occurrence of tampering.

Time of first occurrence of tampering.

Time of last restoration of tampering.

Date of last restoration to normal condition.

Number of occurrence of tampering events.

16.       HARMONIC MEASUREMENT

16.1     The meter should be capable of measuring fundamental energy as well total energy i.e. fundamental plus harmonics energy. Fundamental energy should be made available on meter display and the same only shall be used for billing purpose.

16.2     The manufacture shall indicate the sampling rate so that it shall be sufficient for the user to determine the accuracy of total energy.

16.3     The values of total energy shall be made available on Data collection device with proper resolution.

17.       SELF DIAGNOSTIC FEATURE

17.1     The meter shall be capable of performing complete self diagnostic check to monitor the circuits for any malfunctioning to ensure integrity of data memory location all the time. The meter shall have indications for unsatisfactory/ nonfunctioning/ malfunctioning of the following:-

a)         Time and date and

b)         All display segments as per the requirement under G 19 of IS 14697.

17.2     The details of malfunctioning of time and date should be recorded in the meter memory. The details of self-diagnostic capability feature should be furnished by the meter manufacturer.

18.       TESTING OF METER:

18.1     Routine and acceptance tests as per IEC:687 IEC 801 & IS 14697 shall be carried out at manufacturer works and the test reports shall be produced to CSEB/licencee before commissioning of the meter: -

i)          A.C. voltage test,

ii)         Insulation resistance test,

iii)         Test on limits of errors,

iv)        Test of meter constant

v)         Test on of starting condition,

vi)        Test of no load condition,

vii)        Repeatability of error test,

viii)       Test of power consumption,

ix)        Vibration test,

x)         Tamper conditions – as per the specification,

xi)        Damp heat cycle test.   

18.2     The meter should be duly calibrated with ESS meter of class 0.1 accuracy or better.

19.       TYPE TESTS:-

19.1     The Energy meter offered shall be fully type tested for the properties / requirement, listed below at independent approved test laboratories as per relevant standards described in this specification. The manufacturer must furnish a complete sets of type test reports along with the bid. These type test must not have been conducted earlier than three years from the date of purchase of meter.

20.       TEST OF INSULATION PROPERTIES:

i)          Impulse voltage Test.

ii)         AC High voltage test.

iii)         Insulation test.

21.       TEST OF ACCURACY REQUIREMENT

i.          Test on limits of error.

ii.          Test on starting condition.

iii.         Test on no load condition.

iv.         Test of ambient temperature influence.

v.         Test of repeatability of error.

vi          Test of influence quantities.

22.       TEST OF ELECTRICAL REQUIREMENT

i.          Test for power consumption.

ii.          Test for influence of supply voltage.

iii.         Test of influence short time over current.

iv.         Test of influence of self‑heating.

v.         Test of influence of heating.

23.       TEST OF ELECTROMAGNETIC COMPATIBILITY

i.          Radio interference measurement.

ii.          Fast transient burst test.

iii.         Test of immunity to electrostatic discharges.

iv.         Test of immunity to electromagnetic HF field.

24.       TEST FOR CLIMATIC INFLUENCES

i.          Dry heat test.

ii.          Cold test.

iii.         Damp heat cyclic test.

iv.         Test for Mechanical Requirements.

v.         Vibration test

vi.         Shock Test

vii.        Spring ‑hammer Test

viii.       Protection against penetration of dust and water.

ix.         Test of resistance to heat and fire.

25.       GUARANTEED TECHNICAL PARTICULARS:

Shall be as per  Schedule –A(i) and A(ii)

26.       DRAWING & TECHNICAL LEAFLETS:

Detailed dimensional drawing alongwith the circuit diagram and detailed technical leaflets showing clearly the quantity of the material used for meters and its constructional features should be available alongwith the meter.

27.       QUANTITIES TO BE MEASURED & FUNCTIONAL REQUIREMENT OF METERS:-

(A)       3-PHASE 4-WIRE 0.2 ACCURACY CLASS ENERGY METERS SUITABLE FOR A.B.T.

27.1     The active energy measurement shall be carried out on 3 phase, 4 wire principle with an accuracy as per class 0.2s of IEC –62053-22 / IS 14697.  The meters shall compute the active energy and load import / active energy and load export from the substation bus bars during each successive 15 minutes block, and store it in its memory.  It shall also display on demand last 15 - minute energy (import / export).   The meter will record in the export or import during 15 minutes time block and not the net drawl, say if meter is connected at CPP, it will record only export of power (ignoring any import of power).  Similarly, if meter is connected to a CPP consumer, it will only record import of power ignoring any export of power.  .

27.2     The M.D. integration period will be 15 minutes by default. However the same should be programmable to 15/30 minutes, the integration will be by default based on the block interval principal with facility to switch over to sliding window principal on demand.

27.3     Meters shall be suitable for working under balanced / unbalanced loads at all power factor as specified in the relevant IS.  The display shall indicate direct values without having to apply any multiplying factor.

27.4     The meter shall continuously compute the average of the RMS values of the three line-to-neutral VT secondary voltage as a percentage of 63.51 V, and display the same on demand. Further, the average frequency of the previous 15 minute block shall also be displayed on demand in Hz.

27.5     The meter shall also compute the reactive power on 3-phase, 4-wire principle, with an accuracy as per relevant standards, and integrate the reactive energy algebraically into two separate registers, one for the period for which the average RMS voltage is 103% or higher, and the other for the period for which the average RMS voltage is below 97.0%. The current reactive power and cumulative reactive energy readings of the two registers shall be displayed on demand.  The readings of the two registers at each midnight shall also be stored in the meter’s memory.

27.6     The reactive energy shall also be stored in four different registers of meter memory as Reactive import while active import, Reactive import while active export, Reactive export while active import, Reactive export while active export. Cumulative energy registers of the same shall be made available on display as well as base computer software (BCS.)

27.7     The meter shall also store the apparent energy (import and export) and cumulative energy registers of the same shall be made available on display as well as BCS.

27.8     The meters shall be compatible with ABT as well as TOD tariff. For TOD tariff, meter shall have the provision to define maximum 8 TOD registers for different energies & maximum demands.

27.9     The meters shall be able to measure and display parameters like instantaneous phase wise voltages, instantaneous line currents, instantaneous average three phase power factor, average frequency and time.

27.10   Errors shall comply with CBIP recommendations for all power factor angles from 0 to 360 degrees.

27.11   However for reactive power and reactive energy measurement, limits of errors for both active as well as reactive energy in all the four quadrants shall be in accordance to IEC 687 / IEC –62053-22.

27.12   Each meter shall have a test output device (visual) for checking the accuracy of active energy measurement. Further, it shall be possible to switch over the test output device to reactive energy via suitable means.   

27.13   No rounding off to the next higher last decimal shall be done for voltage and frequency displays.

27.14   Each of the metering system shall measure and display on demand the following quantities/parameters on demand for billing purpose essentially

i)          Meter Serial No.

ii)         LCD segment check

iii)         Real Time: HR:MT

iv)        Date  dd/mm/yy

v)       Rising Demand in KVA

vi)        Maximum demand in KW and KVA (export / import)

vii)        Cumulative active energy import

viii)       Cumulative apparent energy import (KVAh)

ix)        Last 15 minutes block average of the active power / load import

x)         Cumulative active energy export

xi)        Cumulative apparent energy export (KVAh)

xii)        Last 15 minutes block average of the active power / load export

xiii)       Instantaneous three phase average power factor with sign/display/legend for lag/lead.

xiv)       Instantaneous Phase Voltage

i) R Phase            ii) Y Phase            iii) B Phase

xv)       Instantaneous Line Currents (Amps)

i) R Phase Line Current   ii) Y Phase Line Current iii) B Phase Line Current

xvi)       Instantaneous Frequency

xvii)      Phase Sequence of voltages (alternatively, this may be provided at MRI/BCS end

xviii)     Instantaneous Active Load in  KW/MW

xix)       Instantaneous Reactive Load in KVAR/MVAR

xx)       Cumulative RKVAH  injection when, average voltage(RMS)>103%Vn

xxi)       Cumulative RKVAH  drawl when ,average voltage(RMS)>103%Vn

xxii)      Cumulative RKVAH  injection when,  average voltage(RMS)  < 97%Vn

xxiii)     Cumulative RKVAH  drawl when , average voltage(RMS) < 97%Vn

xxiv)     Cumulaltive KVArh (lag), when Kwh is import.

xxv)      Cumulaltive KVArh (lead), when Kwh is import.

xxvi)     Cumulaltive KVArh (lag), when Kwh is export.

xxvii)    Cumulaltive KVArh (lead), when Kwh is iexport.

A key pad shall be provided on the meter front for switching on the display and for changing from one indication to the next.

28.       MEMORY:-

Each meter shall have a non-volatile memory in which the following shall be automatically stored.

i.          Active energy import

ii.          Active energy export

iii.         Average frequency for each successive 15-minute block

iv.         Average load (in KW/MW) for each successive 15-minute block for import and export

v.         Reactive Energy Import  (while Active Import/Export)

vi          Cumulative VArh transmittal for voltage high condition, at each midnight, in six digits including one decimal.

vii         Cumulative VArh transmittal for voltage low condition, at each midnight, in six digits including one decimal.

29.       LOAD SURVEY FACILITY:-

29.(A)  It should be possible to store previous at least 35 days every 15 minutes data of energy consumed, demand & Frequency. That is load survey is needed for the demand and energy consumed in every MD integration time cycle (15 min). The demand to be recorded in the load survey shall match with the recorded in DISPLAY PARAMETERS. The demand and energy consumed as discussed shall be recorded separately under energy Import / energy Export within a 15 minutes time block.

29A.1  It should be possible to down load view parameters and load survey data on IBM compatible computers and obtain full details of demand and consumption in statement form and also in graphic form.

29A.2  Meters shall be four Quadrant meter shall be capable of recording active / reactive and apparent energy and also demand in four quadrant.

29A3   Capability of meter to measure fundamental frequency energy and harmonic energy shall be described by the tenderer.

29A.4  Necessary software for various programmable features as discussed above in the meter and also necessary window based software for the IBM compatible computer to obtain various details as discussed above and additional any shall be provided by the supplier.  The software shall include provision for load survey graphic presentation and other reports generation in BCS from the data collected from the meter through meter reading instruments.

29(B)   BRIEF OF FUNCTIONAL REQUIREMENT / GUIDELINES OF SPECIAL ENERGY METER (AS PER CEA GUIDELINES):-

i)          The meter must perform four quadrant measurement.  The interface meters suitable for ABT shall be static type, composite meters, as self-contained devices for measurement of active and reactive energy, and certain other parameters as described in the following paragraphs.  The meters shall be suitable for being connected directly to voltage x-mers (VTs) having a rated secondary line-to-line voltage of 110V and to current x-mers (CTs) having rated secondary current of 1A (Model-A:3 element 4 wire or Model C:2 element, 3 wire) or 5A (Model-B:3 element 4 wire or Model D:2 element, 3 wire).  The reference frequency shall be 50 Hz.

            The active energy (Wh) measurement shall be carried out on 3-phase 4-wire principle with accuracy as per class 0.2S of IEC-687/IEC-62053-22.

            The Var and reactive energy measurement shall also be on 3-phase 4-wire principle with accuracy as per class 0.2 of IEC-62053-22 or better.

ii)         There shall be provision for self-check and diagnosis at regular intervals.  The meter shall have indication for unsatisfactory functioning of the following:

-           Time and calendar

-           Real time clock battery

-           All display parameters

-           Non-volatile memory.

iii)         There shall be programmable facility to restrict access with three level passwords.

iv)        On any programme change the meter shall reset itself to zero and the previous in- formation shall be stored in the non-volatile memory.

v)         There shall be provision for access to the meter by a computer (desktop, PC or laptop) and remote reading or data storage via communication system.

vi)        The meter shall log the time and date of all programme changes in a billing period.

vii)        The meters shall be essentially static tri-vector meters. 

viii)       The meters shall have following facilities:

a)         Communication: compatible with RS 485 or RS 232  port..

b)         Load survey capability.

c)         Missing potential indication in case of failure of potential at the meter incoming terminal.

d)         Provision for tele-metering using common protocol.

e)         Provision for collection of data by meter reading instrument (MRI).

f)          Provision for time synchronizing facility from external clock.  Provision for correcting real time by MRI.

g)         Sliding integration window/block integration.

h)         Real time clock.

i)          Non volatile memory for 35 days.

j)          Test output device in the form of a pulse indicator accessible from the front and capable of being monitored by suitable testing equipment.

ix)        Transformers / transducers required for their functioning shall be in-built in the meters.  Necessary isolation and / or suppression shall also be built-in for protecting the meters from surges and voltage spikes that occur in the VT and CT circuits of extra high voltage switchyards.

x)         The active energy (Wh) measurement shall be carried out on 3-phase, 4-wire principle, with an accuracy specified in the regulation.  The meter shall display on demand the export / import energy during 15 minutes block.

xi)        Further the meter shall continuously integrate and display on demand the export/import cumulative active energy sent out / in from / to the S/S bus bars up to that time in export and import register.  The cumulative energy reading at each midnight shall be stores in the meters memory in respective registers.  There shall be separate register for export and import.

xii)        The meter shall count the number of cycles in VT output during each successive 15 minutes block and divide the same by 900 to arrive at the average frequency (truncated to second place of decimal).  This shall be stored in the meter’s memory.  The average frequency of the previous 15 minutes block shall also be displayed on demand in hertz.   

xiii)       The meter shall continuously compute the average of the Root Mean Square (RMS) values of the three line to neutral VT secondary voltage as a percentage of 63.51V and display the same on demand.

xiv)       The meter shall also compute the reactive power (VAR) on 3-phase 4-wire principle within the accuracy and integrate reactive energy (VARh) as below in following registers :-

Above 103% voltage : Reactive energy import & export.

Below 97% voltage : Reactive energy  import & export.

Reactive energy import when active energy import

Reactive energy import when active energy export

xv)       Each meter shall have a test output device (visual) for checking the accuracy of active energy (Wh) measurement.  The preferred pulsing rate is twenty per Wh and four for 1A and 5A CT respectively.  It shall be possible to couple this device to suitable testing equipment also.

xvi)       The accuracy of the meter shall not be affected by harmonics circulating in the system of magnitudes within permissible limits stipulated by CEA grid Standards and Regulations.  The meter shall indicate and record the total resultant quantities of fundamental frequency and harmonics or alternatively the meter shall record fundamental frequency quantities and harmonics related quantities (such as MWh, MVAh and MVARh) separately.

xvii)      The meters shall normally operate with the power drawn from the VT secondary circuits.  The total burden imposed by a meter for measurement and operation shall not exceed 10 VA on any of the phases.  An automatic back up to continue operation of the meter’s calendar clock, and for retaining all data in its memory, shall be provided through a long life battery, which shall be capable of supplying the required power for at least two years.  The meters shall be 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 meters shall not require any separate auxiliary supply for their operation.  All displays may disappear on loss of VT supply.

xviii)     Each meter shall have a built calendar and clock having an accuracy of one  minute per year or better .The calendar and clock shall be correctly set at the manufacture’s works. The date (day-month-year) and  time (hour-min-sec) shall be displayed on the meter front (when VT supply has been connected), on demand. Only limited clock adjustment shall be possible at site, using the Data Collection Device (DCD). When an advance or retard command is given, six subsequent time blocks shall be contracted or elongated by ten seconds each. The meter shall not accept another clock correction command for seven days. All clock correction shall be registered in the meter’s memory and suitably shown on print out of collected data.

xix)       Each meter shall have a unique identification code, which shall be marked permanently on its front, as well as in its memory.

xx)       Each meter shall have at least one nine (9) – character, nine-segment electronic display, for indication of the various parameters (one at a time), on demand.

xxi)       A touch key or push button shall be provide on the meter front or switching on the display and or changing from one indication to the next. The display shall switch off automatically about one minute after the last operation of touch key/push button. When the display is switched on, the parameter last displayed shall be displayed again, duly updated..

xxii)      The three line-to-neutral voltages shall be continuously monitored, and in case any of these falls below 70%, the condition shall be suitably indicated and recorded.  The meter shall operate with the power drawn from the VT secondary circuits, without the need for any auxiliary power supply.  Each meter shall have a built-in calendar and clock, having an accuracy of 30 seconds per month or better.

xxiii)     In case of installation of check meter also, this should be identical to main meter and should be connected in same core of CT & PT.

xxiv)     Each meter shall have an optical port on its front or tapping all data stores in its memory.  Portable or hand held data collection devices shall also be separately provided or this purpose, one for each substation, to serve as the interface between the meters specified above and the local personal computers (PC).  The overall intention is to tap the data stored in the meter’s memories once in a month and transmit the same to a remote central computer using communication links, through the local PC.  It shall also be possible to obtain a print out (hard copy) of all data collected from the meters using the local PC.

xxv)      The whole system shall be such as to provide a print out (both from the local PC, and from remote central computer) in an easily understandable / self-explanatory format.

xxvi)     All meters of the same model shall be totally identical in all respects except for their unique identification codes.  They shall also be totally sealed and tamper proof, with no possibility of any adjustment at site, except for clock correction.

xxvii)    The meters shall also withstand without any damage for mal-operation reasonable mechanical shocks, earthquake forces, ambient temperature variations from –20°C to 55°C, relative humidity etc.  They shall have an IP-51 category dust tight construction, and shall be capable of satisfactory operation in an indoor, non-air conditioned installation.

xxviii)   The harmonics shall be filtered out while measuring Wh, VAR and VARh and only fundamental frequency quantities shall be measured / computed.

xxix)     Portable / hand-held data collection devices (DCD) shall be tailor-made for tapping al data stored in a meter’s memory and faithfully transferring it to the local PC.  Each device shall at least comprise of the following:-

-           A lead with optical head or coupling it to the meter;

-           A lead or plugging it to a personal computer;

-           A internal battery for powering the devices;

-           A case for safely carrying it about.

-           A battery charger.

            The total arrangement shall be such that one (1) operator can carry out the whole operation himself, in about 5 minutes per meter.